Gamida Cell Announces First Patient with Sickle Cell Disease Transplanted in Phase 1/2 Study of CordIn™ as the Sole Graft Source


An Israeli regenerative therapy company called Gamida Cell specializes in cellular and immune therapies to treat cancer and rare (“orphan”) genetic diseases. Gamida Cell’s main product is called NiCord, which provides patients who need new blood-making stem cells in their bone marrow an alternative to a bone marrow transplant. NiCord is umbilical cord blood that has been expanded in culture. In clinical trials to date, NiCord has rapidly engrafted into patients and the clinical outcomes of NiCord transplantation seem to be comparable to transplantation of peripheral blood.

Gamida Cell’s two products, NiCord and CordIn, as well as some other products under development utilize the company’s proprietary NAM platform technology to expand umbilical cord cells. The NAM platform technology has the remarkable capacity to preserve and enhance the functionality of hematopoietic stem cells from umbilical cord blood. CordIn is an experimental therapy for those rare non-malignant diseases in which bone marrow transplantation is the only currently available cure.

Gamida Cell has recently announced that the first patient with sickle cell disease (SCD) has been transplanted with their CordIn product.  Mark Walters, MD, Director of the Blood and Marrow Transplantation (BMT) Program is the Principal Investigator of this clinical trial. The patient received their transplant at UCSF Benioff Children’s Hospital Oakland.

CordIn, as previously mentioned, is an experimental therapy for rare non-malignant diseases, including hemoglobinopathies such as Sickel Cell Disease and thalassemia, bone marrow failure syndromes such as aplastic anemia, genetic metabolic diseases and refractory autoimmune diseases. CordIn potentially addresses a presently unmet medical need.

“The successful enrollment and transplantation of our first SCD patient with CordIn as a single graft marks an important milestone in our clinical development program. We are eager to demonstrate the potential of CordIn as a transplantation solution to cure SCD and to broaden accessibility to patients with rare genetic diseases in need of bone marrow transplantation,” said Gamida Cell CEO Dr. Yael Margolin. “In the first Phase 1/2 study with SCD, the expanded graft was transplanted along with a non-manipulated umbilical cord blood unit in a double graft configuration. In the second phase 1/2 study we updated the protocol from our first Phase 1/2 study so that patients would be transplanted with CordIn as a standalone graft, which is expanded from one full umbilical cord blood unit and enriched with stem cells using the company’s proprietary NAM technology.”

Somewhere in the vicinity of 100,000 patients in the U.S suffer from SCD; and around 200,000 patients suffer from thalassemia, globally. The financial burden of treating these patients over their lifetime is estimated at $8-9M. Bone marrow transplantation is the only clinically established cure for SCD, but only a few hundred SCD patients have actually received a bone marrow transplant in the last ten years, since most patients were not successful in finding a suitable match. Unrelated cord blood could be available for most of the patients eligible for transplantation, but, unfortunately, the rate of successful engraftment of un-expanded cord blood in these patients is low. Therefore, cord blood is usually not considered for SCD patients. Without a transplant, these patients suffer from very high morbidity and low quality of life.

Eight patients with SCD were transplanted in the first Phase 1/2 study performed in a double graft configuration. This study is still ongoing. Preliminary data from the first study will be summarized and published later this year. A Phase 1/2 of CordIn for the treatment of patients with aplastic anemia will commence later this year.

Umbilical Cord Blood Mesenchymal Stem Cells do Not Cause Tumors in Rigorous Tests


Human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) have the ability to self-renew and also can differentiate into a wide range of cell types. However, many clinicians and scientists fear that even these very useful cells might cause tumors.

To that end, Moon and colleagues from the Korean Institute of Toxicology have rigorously tested the tendency for hUBC-MSCs to cause tumors. They used a large battery of tests in living organisms and in culture. hUCB-MSCs were compared to MRC-5 and HeLa cells. MRC-5 cells are known to have no ability to cause tumors and HeLa cells have a robust ability to form tumors, and therefore, constitute negative and positive controls,

To evaluate the ability of cells to cause tumors, Moon and others examined the tendency of these cells to grow without being attached to a substratum. This is a hallmark of tumor cells and is called “anchorage-independent growth” (AIG). To assess AIG, the cells were grown in soft agar, which is a standard assay for AIG. hUCB-MSCs and MRC-5 cells formed few colonies in soft agar, but HeLa cells formed a greater number of larger colonies. This indicated that hUCB-MSCs and MRC-5 cells do not show AIG, a common trait of tumorigenic cells.

The next assay implanted these cells into live laboratory animals. hUCB-MSCs were implanted as a underneath the skin of BALB/c-nu mice (nasty creatures – they bite). All the mice implanted with hUCB-MSCs and NRC-5 cells showed any sign of tumors. Both gross and microscopic examination failed reveal any tumors. However, all mice transplanted with HeLa cells developed tumors that were clearly derived from the implanted cells.

These experiments, though somewhat mundane, rigorously demonstrate that hUCB-MSCs do not exhibit tumorigenic potential. This provides further evidence of these cells clinical applications.

The paper appeared in Toxicol Res. 2016 Jul;32(3):251-8. doi: 10.5487/TR.2016.32.3.251.

Gamida Cell Phase 3 Study Design Outline Approved by FDA and EMA


Gamida Cell, a cell therapy company based in Jerusalem, Israel, has reached agreements with the US Food and Drug Administration (USFDA) and the European Medicines Agency (EMA) with regards to a Phase III study design outline for testing their NiCord product. NiCord is a blood cancer treatment derived from a single umbilical cord blood until expanded in culture and enriched with stem cells by means of the company’s proprietary NAM technology.

Gamida Cell is moving forward now with plans to commence an international, multi-center, Phase III study of NiCord in 2016. Phase I/II data of 15 patients are expected in the fourth quarter of 2015. NiCord is in development as an experimental treatment for various types of blood cancers including Acute Myeloid Leukemia (AML), Acute Lymphoblastic Leukemia (ALL), Myelodysplastic Syndrome (MDS), and Chronic Myelogenous Leukemia (CML).

NiCord® is derived from a single cord blood unit which has been expanded in culture and enriched with stem cells using Gamida Cell’s proprietary NAM technology. NAM technology proceeds from the observation that nicotinamide, a form of vitamin B3, inhibits the loss of functionality that usually occurs during the culture process of umbilical cord blood stem cells, when added to the culture medium. Pre-clinical studies have also shown that the expanded cell grafts manufactured using NAM technology demonstrate improved functionality following infusion in a living animal. These stem cells show improved movement, home to the bone marrow, and show higher rates of engraftment, or durable retention in the bone marrow. Based on these results, Gamida Cell is currently testing in clinical trials (in patients) cells expanded in culture with the NAM platform to determine their safety and effectiveness as a treatment for blood cancers, sickle-cell anemia and thalassemia. NiCord is intended to fill the crucial clinical need for a treatment for the vast majority of blood cancer patients indicated for bone marrow transplantation, with insufficient treatment options. This segment has a multi-billion dollar market potential.

“The FDA and EMA feedback is a major regulatory milestone for NiCord. NiCord is a life-saving therapy intended to provide a successful treatment for the large number of blood cancer patients who do not have a family related matched donor. Gamida Cell is dedicated to changing the paradigm in transplantation by bringing this therapy to market as soon as possible,” said Dr. Yael Margolin, president and CEO of Gamida Cell.

“The positive regulatory feedback confirms that Gamida Cell’s NiCord program is on a clear path to approval both in the U.S. and EU. We look forward to continuing the development of this very important product in cooperation with sites of excellence in cord blood transplantation worldwide,” said Dr. David Snyder, V.P. of Clinical Development and Regulatory Affairs at Gamida Cell.

The Phase III study will be a randomized, controlled study of approximately 120 patients. It will compare the outcomes of patients transplanted with NiCord to those of patients transplanted with un-manipulated umbilical cord blood.

 

Umbilical Cord Blood and Bone Marrow Transplants in Myelodysplastic Syndrome


Myelodysplasia syndrome (MDS) killed my mother. Therefore, this paper caught my eye.

This paper describes a multicenter study from Argentina that examined children with MDS. MDS affects the blood cell-producing stem cells in the bone marrow so that these cells make immature red blood cells that do not properly carry oxygen to tissues. The rogue stem cells produce droves and droves of these immature cells that overpopulate the bone marrow and crowd out the normal bone marrow stem cells. Patients with MDS suffer shortness of breath, weakness and fatigue, mental lapses, and other symptoms of anemia.  They also must rely on blood transfusions in order to keep them alive. Bone marrow transplants or umbilical cord transplants can cure MDS patients.

In this study, Ana Basquiera, from the Hospital Privado Centro Médico de Córdoba, Argentina, and her colleagues evaluated the overall survival, disease-free survival (DFS), non-relapse mortality (NRM) and relapse incidence in MDS children who underwent bone marrow and umbilical cord transplants. These children received these transplants in six different clinical throughout Argentina. All in all, 54 transplants were conducted in 52 patients. The mean age of these patients was 9 years old (range: 2–19), and 35 of the patients were males.

Several different types of MDS were seen in these patients, but all of them were not treatable by other means. Because MDS often precedes leukemia, seven (13%) patients at the time of the transplant transformed to acute myeloid leukemia (AML) and the diagnosis of two other patients also worsened.

All patients had their own bone marrow wiped out by means of a “conditioning regimen.” These are drugs that destroy the bone marrow stem cells of the patient and leave them without the means of make their own red blood cells or immune cells. Patients must then receive high doses of antibiotics and anti-fungal drugs while their bone marrow is repopulated. As you can guess, this is a nasty, dangerous procedure.

Of these patients, 63% received bone marrow stem cells, 26% stem cells from peripheral blood, and 11% umbilical cord blood. Five-year disease-free survival and overall survival were 50% and 55% respectively; and for patients with juvenile myelomonocytic leukemia, 57% and 67% respectively.

Cumulative incidence of non-relapse mortality and relapse were 27% and 21% respectively. Statistical analyses of the data from these treatments showed that patients who had received umbilical cord blood (HR 4.07; P = 0.025) and were younger than nine years old tended to have a lower overall survival rate. Also, younger patients who experienced graft-versus-host disease (GVHD), in which the engrafted immune cells begin to attack the tissues of the patient, had a higher rate of non-relapse mortality (no real surprise there).

Thus, more than half of the patients achieved long-term overall survival. The mortality and relapse rates were rather high, however, and it is possible that less toxic conditioning regimens or more intensive prevention of GVHD could lead to better results in some children. Until such procedures are make available, such mortality rates will probably remain high, even though the procedure does potentially cure the patients of MDS.  Thus this remains a “high risk, big pay-off” procedure.

This was published in Pediatric Blood and Cancer.

Engineered Neural Stem Cells Deliver Anti-Cancer Drug to the Brain


Irinotecan is an anticancer drug that was approved for use in 1996. It is a modified version of the plant alkaloid camptothecin, and even though it shows significant activity against brain tumors in culture, but in a living body, this drug poorly penetrates the blood-brain barrier. Therefore irinotecan usually does not accumulate to appreciable levels in the brain and is typically not used to treat brain tumors.

That could change, however, if a new strategy published in paper by Marianne Metz and her colleagues from the laboratory of Karen Aboody at the Beckman Research Institute at the City of Hope in Duarte, California, in collaboration with colleagues from several other laboratories.

In this paper, Metz and her co-workers genetically engineered neural stem cells to express enzymes called “carboxylesterases.” These carboxyesterase enzymes convert irinotecan, which is an inactive metabolite, to the active form, which is known as “SN-38.” The efficient conversion of irinotecan to SN-38 in the brain greatly accelerates the therapeutic activity of this drug in the brain. Also, the constant conversion of irinotecan to another molecule accelerates the transport of irinotecan past the blood brain barrier.

To test this strategy. Metz and others grew the engineered neural stem cells in culture and measured their ability to make carboxylesterases in culture, and their ability to convert irinotecan into SN-38 in culture.  In both cases, the engineered neural stem cells made a boat-load of carboxylesterase and converted irinotecan into SN-38 in spades.  More importantly, the genetically engineered neural stem cells behaved exactly as they did before, which shows that the genetic manipulation of these cells did not change their properties.

Next, Metz others tested the ability of the engineered neural stem cells to kill human brain tumor cells in culture in the presence of irinotecan.  Once again, the genetically engineered neural stem cells effectively killed human brain tumor cells in culture in a irinotecan-concentration-dependent manner.  When these genetically engineered neural stem cells were injected into the brains of mice with brain tumors, intravenous administration of irinotecan produced high levels of SN-38 in the brain.  This shows that these cells have the capacity to increase the production of SN-38 in the brain.

This strategy is similar to other strategies that been used in various clinical trials, but because neural stem cells have a tendency to move into brain tumor tissue and surround it, they represent an efficient and effective way to deliver anticancer drugs to brain tumors.  Also, since the particular neural stem cell line used in this experiment (HB1.F3.CD) does not cause tumors and is also not recognized as foreign by the immune system, it is a particularly attractive stem cell line for such an anti-tumor strategy.

Preventing the Rejection of Embryonic Stem Cell Derivatives – Take Two


Yesterday I blogged about the paper from Yang Xu’s group that used genetically engineered embryonic stem cells to make adult cell types that were not rejected by the immune systems of mice with humanized immune systems. I would like to say a bit more about this paper before I leave it be.

First of all, Xu and his colleagues engineered the cells to express the cell-surface protein PD-L1, which stands for programmed cell death ligand 1 (also known as CD274), and another protein called CTLA4-Ig. The combination of these two proteins tends to make these cells invisible to the immune system for all practical intents and purposes.

PD-L1, however, is used by tumor cells to evade detection by the immune system. For example, increased expression of PD-L1 is highly correlated with the aggressiveness of the cancer. One particular experiment examined 196 tumor specimens that had been extracted from patients with renal cell carcinoma (kidney tumors). In these tumor samples, high expression of PD-L1 was positively associated with increased tumor aggressiveness and a those patients that had higher expression of PD-L1 have a 4.5-fold increased risk of death (see Thompson RH, et al., Proc Natl Acad Sci USA 101 (49): 17174–9). In patients with cancer of the ovaries, those tumors with higher PD-L1 expression had a significantly poorer prognosis than those with lower PD-L1 expression. The more PD-L1 these tumors expressed, the fewer tumor-hunting T cells (CD8+ T cells) were present (see Hamanishi J, and others, Proc Natl Acad Sci USA 104 (9): 3360–5).

So the Xu paper proposes that we introduce genetically engineered cells, which are already at risk for mutations in the first place, into the body, that constitutively express PD-L1, a protein known to be highly expressed in the most aggressive and lethal tumors. Does this sound like a good idea?

With respect to CTLA4-Ig, this is a cell-bound version of a drug that has been approved as an anti-transplantation rejection drug called Belatacept (Nulojix), made by Bristol-Myers-Squibb. Since this is a cell-bound version of this protein, it will almost certainly not have the systemic effects of Belatacept, and if the cells manage to release a certain amount of soluble CTLA4-Ig, it is likely to be very little and have no biological effect.

Therefore, this strategy, while interesting, does come with its own share of risks and caveats.

Regenerating Injured Kidneys with Exosomes from Human Umbilical Cord Mesenchymal Stem Cells


Zhou Y, Xu H, Xu W, Wang B, Wu H, Tao Y, Zhang B, Wang M, Mao F, Yan Y, Gao S, Gu H, Zhu W, Qian H: Exosomes released by human umbilical cord mesenchymal stem cells protect against cisplatin-induced renal oxidative stress and apoptosis in vivo and in vitro. Stem Cell Res Ther 2013, 4:34.

Ying Zhou and colleagues from Jiangsi University have provided helpful insights into how adult stem cell populations – in particular, mesenchymal stem cells (MSCs) isolated from human umbilical cord (hucMSCs) – are able to regulate tissue repair and regeneration. Adult stem cells, including MSCs from different sources, confer regenerative effects in animal models of disease and tissue injury. Many of these cells are also in phase I and II trials for limb ischemia, congestive heart failure, and acute myocardial infarction (Syed BA, Evans JB. Nat Rev Drug Discov 2013, 12:185–186).

Despite the documented healing capabilities of MSCs, in many cases, even though the implanted stem cells produce genuine, reproducible therapeutic effects, the presence of the transplanted stem cells in the regenerating tissue is not observed. These observations suggest that the predominant therapeutic effect of stem cells is conferred through the release of therapeutic factors. In fact, conditioned media from adult stem cell populations are able to improve ischemic damage to kidney and heart, which confirms the presence of factors released by stem cells in mediating tissue regeneration after injury (van Koppen A, et al., PLoS One 2012, 7:e38746; Timmers L, et al., Stem Cell Res 2007, 1:129–137). Additionally, the secretion of factors such as interleukin-10 (IL-10), indoleamine 2,3-dioxygenase (IDO), interleukin-1 receptor antagonist (IL-1Ra), transforming growth factor-beta 1 (TGF-β1), prostaglandin E2 (PGE2), and tumor necrosis factor-alpha-stimulated gene/protein 6 (TSG-6) has been implicated in conferring the anti-inflammatory effects of stem cells (Pittenger M: Cell Stem Cell 2009, 5:8–10). These observations cohere with the positive clinical effects of MSCs in treating Crohn’s disease and graft-versus-host disease (Caplan AI, Correa D. Cell Stem Cell 2011, 9:11–15).

Another stem cell population called muscle-derived stem/progenitor cells, which are related to MSCs, can also extend the life span of mice that have the equivalent of an aging disease called progeria. These muscle-derived stem/progenitor cells work through a paracrine mechanism (i.e. the release of locally acting substances from cells; see Lavasani M, et al., Nat Commun 2012, 3:608). However, it is unclear what factors released by functional stem cells are important for facilitating tissue regeneration after injury, disease, or aging and the precise mechanism through which these factors exert their effects. Recently, several groups have demonstrated the potent therapeutic activity of small vesicles called exosomes that are released by stem cells (Gatti S, et al., Nephrol Dial Transplant 2011, 26:1474–1483; Bruno S, et al., PLoS One 2012, 7:e33115; Lai RC, et al., Regen Med 2013, 8:197–209; Lee C, et al., Circulation 2012, 126:2601–2611; Li T, et al., Stem Cells Dev 2013, 22:845–854). Exosomes are a type of membrane vesicle with a diameter of 30 to 100 nm released by most cell types, including stem cells. They are formed by the inverse budding of the multivesicular bodies and are released from cells upon fusion of multivesicular bodies with the cell membrane (Stoorvogel W, et al., Traffic 2002, 3:321–330).

Exosomes are distinct from larger vesicles, termed ectosomes, which are released by shedding from the cell membrane. The protein content of exosomes depends on the cells that release them, but they tend to be enriched in certain molecules, including adhesion molecules, membrane trafficking molecules, cytoskeleton molecules, heat-shock proteins, cytoplasmic enzymes, and signal transduction proteins. Importantly, exosomes also contain functional mRNA and microRNA molecules. The role of exosomes in vivo is hypothesized to be for cell-to-cell communication, transferring proteins and RNAs between cells both locally and at a distance.

To examine the regenerative effects of MSCs derived from human umbilical cord, Zhou and colleagues used a rat model of acute kidney toxicity induced by treatment with the anti-cancer drug cisplatin. After treatment with cisplatin, rats show increases in blood urea nitrogen and creatinine levels (a sign of kidney dysfunction) and increases in apoptosis, necrosis, and oxidative stress in the kidney. If exosomes purified from hucMSCs, termed hucMSC-ex are injected underneath the renal capsule into the kidney, these indices of acute kidney injury decrease. In cell culture, huc-MSC-exs promote proliferation of rat renal tubular epithelial cells in culture. These results suggest that hucMSC-exs can reduce oxidative stress and programmed cell death, and promote proliferation. What is not clear is how these exosomes pull this off. Zhou and colleagues provide evidence that hucMSC-ex can reduce levels of the pro-death protein Bax and increase the pro-survival Bcl-2 protein levels in the kidney to increase cell survival and stimulate Erk1/2 to increase cell proliferation.

Another research group has reported roles for miRNAs and antioxidant proteins contained in stem cell-derived exosomes for repair of damaged renal and cardiac tissue (Cantaluppi V, et al., Kidney Int 2012, 82:412–427). In addition, MSC exosome-mediated delivery of glycolytic enzymes (the pathway that degrades sugar) to complement the ATP deficit in ischemic tissues was recently reported to play an important role in repairing the ischemic heart (Lai RC, et al., Stem Cell Res 2010, 4:214–222). Clearly, stem cell exosomes contain many factors, including proteins and microRNAs that can contribute to improving the pathology of damaged tissues.

The significance of the results of Zhou and colleagues and others is that stem cells may not need to be used clinically to treat diseased or injured tissue directly. Instead, exosomes released from the stem cells, which can be rapidly isolated by centrifugation, could be administered easily without the safety concerns of aberrant stem cell differentiation, transformation, or recognition by the immune system. Also, given that human umbilical cord exosomes are therapeutic in a rat model of acute kidney injury, it is likely that stem cell exosomes from a donor (allogeneic exosomes) would be effective in clinical studies without side effects.

These are fabulously interesting results, but Zhou and colleagues have also succeeded in raising several important questions. For example: What are the key pathways targeted by stem cell exosomes to regenerate injured renal and cardiac tissue? Are other tissues as susceptible to the therapeutic effects of stem cell exosomes? Do all stem cells release similar therapeutic vesicles, or do certain stem cells release vesicles targeting only specific tissue and regulate tissue-specific pathways? How can the therapeutic activity of stem cell exosomes be increased? What is the best source of therapeutic stem cell exosomes?

Despite these important remaining questions, the demonstration that hucMSCderived exosomes block oxidative stress, prevent cell death, and increase cell proliferation in the kidney makes stem cell-derived exosomes an attractive therapeutic alternative to stem cell transplantation.

See Dorronsoro and Robbins: Regenerating the injured kidney with human umbilical cord mesenchymal stem cell-derived exosomes. Stem Cell Research & Therapy 2013 4:39.

Radio Interview About my New Book


I was interviewed by the campus radio station (89.3 The Message) about my recently published book, The Stem Cell Epistles,

Stem Cell Epistles

It has been archived here. Enjoy.

Stem Cell-Conventional Treatment Combo Offers New Hope in Fighting Deadly Brain Cancer


A new type of treatment that combines neural stem cells with conventional cancer fighting therapies shows promise in animal studies for the most common and deadliest form of adult brain cancer — glioblastoma multiforme (GBM). The details are revealed in a groundbreaking study led by Maciej Lesniak, M.D., that appeared in the journal STEM CELLS Translational Medicine.

“In this work, we describe a highly innovative gene therapy approach, which is being developed along with the NIH and the FDA. Specifically, our group has developed an allogeneic neural stem cell line that is a carrier for a virus that can selectively infect and break down cancer cells,” explained Dr. Lesniak, the University of Chicago’s director of neurosurgical oncology and neuro-oncology research at the Brain Tumor Center.

The stem cell line used is a neural stem cell line called HB1.F3 NSC. The US Food and Drug Administration has recently approved this cell line for use in a phase I human clinical trial.

Glioblastoma multiforme remains fatal despite intensive treatment with surgery, radiation and chemotherapy. Cancer-killing viruses have been used in clinical trials to treat those tumors that resist treatment with other therapies and infiltrate throughout the brain. Unfortunately, according to Lesniak, this therapy was subject to some “major drawbacks.”

“When you inject a virus into a tumor alone (without a carrier, like NSC), the virus stays at the site of the injection, and does not spread. Moreover, our immune system clears it. By using NSCs, we can achieve a widespread distribution of the virus throughout the tumor mass, since the NSC travel. Also, they act like a stealth fighter, hiding the virus from the immune system.” Lesniak and his co-workers used NSCs loaded with a novel oncolytic adenovirus. This virus selectively targets glioblastoma multiforme in combination with chemo-radiotherapy. Using this strategy, Lesniak’s team was able to overcome the limitations associated with anticancer viral therapies.

Using mice that had glioblastoma multiforme, the research team showed that their neural stem cell line, which is derived from human fetal cells, significantly increased the median survival time of the mice beyond conventional treatments alone. The addition of chemo-radiotherapy further enhanced the benefits of this novel stem cell-based gene therapy approach.

“Our study argues in favor of using stem cells for delivery of oncolytic viruses along with multimodal chemo-radiotherapy for the treatment of patients with glioblastoma multiforme, and this is something that we believe warrants further clinical investigation,” Dr. Lesniak concluded.

Lesniak’s team is completing final FDA-directed studies. He expects to start a human clinical trial, in which a novel oncolytic virus will be delivered via NSCs to patients with newly diagnosed glioblastoma multiforme, early in 2014.

Treatment of glioblastoma multiforme depends on novel therapies,” said Anthony Atala, M.D., Editor of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine. “This study establishes that a combination of conventional and gene therapies may be most effective and suggests a protocol for a future clinical investigation.”

How Stem Cells Maintain Skin


Professor Kim Jensen from BRIC, University of Copenhagen and Cambridge University has used careful mapping studies to challenge current ideas of how the skin renews itself.

Skin is a rather complex organ system that consists of many cell types and structures. Skin includes proliferating cells in the stratum germanitivum, differentiating cells in the upper layers of the epidermis, hair cells, fat, sensory neurons, Langerhans cells, and sweat and sebaceous glands.

Jensen explained, “Until now, the belief was that the skin’s stem cells were organized in a strict hierarchy with a primitive stem cells type at the top of the hierarchy, and that this cell gave rise to all other cell types of the skin. However, our results show that there are differentiated levels of stem cells and that it is their close micro-environment that determines whether they make hair follicles, fat- or sweat glands.”

Jensen’s work completes what was a “stem cell puzzle.” As Jensen put it, “our data complete what is already known about the skin and its maintenance. Researchers have until now tried to fit their results into the old model for skin maintenance. However, the results give much more meaning when we relate them to the new model that our research purposes.”

To give an example of what Jensen is talking about, over-proliferation of skin cells can initiate skin cancer, but the stem cells of the skin that help maintain the integrity of the skin will lack any detectable genetic changes. According to Jensen, the reason these stem cells lack detectable genetic changes in that they do not take part in over-proliferation.

To demonstrate this, Jensen used a unique technique to label skin cells. They made a mouse strain that expresses a glowing protein from the control region of the Lrig1 gene. The Lrig1 gene is expressed in all proliferating skin stem cell populations. Therefore, making a mouse strain in which all cells expressing Lrig1 also express a glowing protein is a sure-fire way to label the skin stem cell populations.

Jensen and his cohorts used several experimental strategies. First, they simply mapped out the glowing cells in the skin. Jensen and his colleagues discovered that the skin contains several stem cell populations that reside in distinct compartments.  These different compartmentalized skin stem cells contributed to specific tissues and their domains did not over lap.

Basic RGB

 

When the mice were wounded, the proliferating stem cells freely crossed over into each other’s domains and helped heal and remake structures that they normally would not make.  This shows that upon wounding, the stem cells compartment boundaries break down as the stem cells proliferate to recreate the compartments that might have been lost as a result of wounding.  Therefore, Jensen’s work shows that Lrig1 marks stem cells in the epidermis, and that these stem cells have a unique lineage potential.  Secondly, the epidermis is maintained in discrete compartments by these multiple stem cell populations.  These stem cell populations largely keep to themselves and do not invade other compartments.  Therefore, stem cell compartmentalization underlies maintenance of the tissue complexity of the skin and not “hierarchy.”  This simply means that where the stem cells live is far more important to skin stem cell function than who their parents were.  Finally, wounding alters stem cell fate and break down the boundaries.

Wounding does more than that.  When Jensen and his colleagues made a mouse with an activated form of the ras gene that was expressed in skin, the skin showed no signs of tumor formation.  This is odd, since activating mutations in ras are extremely common in human and mouse tumors and cultured cells with activated ras mutations grow like cancer cells.  However, if the skin of these mice with the activated ras gene in their skin is wounded, then tumors form.  Therefore, wounding not only breaks down the compartments in which stem cells reside, it also potentiates cancer formation.

Jensen said of his results, “Our research will now take two directions.  We will establish mathematical models for organ maintenance in order to measure what stem cells are doing in the skin.  Also, we will expand our investigations in cancer initiation, hoping for results that can contribute to cancer diagnostics and improved treatment.”

Using Sleeping Stem Cells to Treat Aggressive Leukemias


British scientists have discovered that aggressive forms of leukemia (blood cancers) do not displace normal stem cells from the bone marrow, but instead, put them to sleep. If the normal stem cells are asleep, it implies that they can be awakened. This offers a new treatment strategy for acute myeloid leukemia or AML.

This work comes from researchers at Queen Mary, University of London with the support of Cancer Research UK’s London Research Institute.

In the United Kingdom, approximately 2,500 people are diagnosed with AML each year. The disease strikes young and old patients and the majority of patients die from AML.

In healthy patients, the bone marrow contains hematopoietic stem cells (HSCs) that divide to form either a common myeloid precursor (CMP) or a common lymphoid precursor (CLP) that differentiate into various kinds of white blood cells or red blood cells or lymphocytes. Individuals afflicted with AML, however, have bone marrow invaded by leukemic myeloid blood cells. Since red blood cells are derived from the myeloid lineage, AML causes red blood cell deficiencies (anemia), and the patient becomes tired, and is at risk for excessive bleeding. AML patients are also more vulnerable to infection those white blood cells that fight infections are not properly formed.

HSC differentiation2

David Taussig from the Barts Center Institute at Queen Mary, University of London said that the widely accepted explanation for these symptoms is that the cancerous stem cells displace or destroy the normal HSCs.

However, Taussig and his colleagues have found in bone marrow samples from mice and humans with AML contain plenty of normal HSCs. Thus, AML is not destroying or displacing the HSCs. Instead, the cancerous stem cells appear to be turning them off so that they cannot form HSCs. If Taussig and his coworkers and collaborators had determine how these leukemic myeloid blood cells are shutting off the normal HSCs, they might be able to design treatments to turn them back on.

Such a treatment strategy would increase the survival of AML patients. Only 40% of younger patients are cured of AML, and the cure rate for older patients in much lower. Current treatments that include chemotherapy and bone marrow transplants are not terribly successful with older patients.

Taussig’s group examined the levels of HSCs in the bone marrow of mice that had been transplanted with human leukemic myeloid cells from AML patients. They discovered that the numbers of HSCs stayed the same, but these same HSCs failed to transition through the developmental stages that result in the formation of new blood cells. When Taussig and his group examined bone marrow from 16 human AML patients, they discovered a very similar result.

Even though AML treatment has come a long way in the last ten years, there is still an urgent need for more effective treatments to improve long-term survival. This present study greatly advances our understanding of what’s going on in the bone marrow of AML patients. The future challenge is to turn this knowledge into treatments.

Under normal circumstances, stress on the body will boost HSC activity. For example, when the patient hemorrhages, the HSCs kick into action to produce more red blood cells that were lost during the bleed. However, the cancer cells in the bone marrow are somehow over-riding this compensatory mechanism and the next phase of this research will determine exactly how they do it.

Using Human Induced Pluripotent Stem Cells to Study Diamond Blackfan Anemia


Diamond-Blackfan Anemia or DBA results from mutations in a gene on chromosome 19 (in most cases). Mutations in the ribosomal protein S19 affects the ability of blood cells to make protein and causes low numbers of red blood cells. DBA patients are dependent on blood transfusions, but some are cured, to some extent at least, by bone marrow transplants. Unfortunately, some DBA patients have severe side effects from bone marrow transplants, which means that bone marrow transplants are not a panacea for all DBA patients.

Fortunately, Michell J. Weiss and his colleagues at the Children’s Hospital of the Philadelphia (CHOP) have used human induced pluripotent stem cells (iPSCs) to study DBA at the molecular level and even develop the beginnings of a cure for DBA patients. Weiss collaborated with Monica Bessler, Philip Mason, and Deborah French, all of whom work at CHOP.

Remember that red blood cells are made inside the bone marrow of the patient by hematopoietic stem cells (HSCs). HSCs divide to renew themselves, and to produce a daughter cell that will differentiate into one of several different types of blood cells. As a kind of gee-wiz number, a healthy adult person will produce approximately 10[11]–10[12] (100 billion to 1 trillion) new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation.

In DBA patients, the bone marrow is empty of red blood cells. In order to get a better idea why, Weiss and his team isolated fibroblasts from the skin of DBA patients, and used genetic engineering techniques to convert them into iPSCs. When Weiss and his group tried to differentiate these iPSCs derived from DBA patients into red blood cells, they were not able to make normal red blood cells. However, Weiss and his colleagues used different genetic engineering techniques to fix the mutation in these iPSCs. After fixing the mutation, these cells could be differentiated into red blood cells. This experiment showed that it is possible to repair a patient’s defective cells.

This is a proof-of-principle experiment and there are many hurdles to overcome before this type of experiment can be done in the clinic to DBA patients. However, these iPSCs can play a vital role in deciphering some of the mysteries surrounding this disease. For example, two family members may have exactly the same mutation, but only one of them shows the disease whereas the other does not. Since iPSCs are specific to the patient from whom they were made, Weiss and his group hope to compare the molecular differences between them and understand the difference in expression of this disease.

Also, these cells offer a long-lasting model system for testing new drugs or gene modifications that may offer new treatments that are personalized to individual patients.

Weiss and his research group used this same technology to test drugs for the often aggressive childhood leukemia, JMML or Juvenile Myelomonocytic Leukemia. Once again, iPSCs were made from JMML patients and differentiated into myeloid cells, which divided uncontrollably just as the original myeloid cells from JMML patients.

Weiss and his colleagues used these cells to test two drugs, both of which are active against JMML. One of them is an inhibitor of the MEK kinase that was quite active against these cells. This illustrates how iPSCs can be used to test personalized treatment regimes for patients.

The stem cell core facility at CHOP is also in the process of making iPCS lines for several inherited diseases: dyskeratosis congenita, congenital dyserythropoietic anemia, thrombocytopenia absent radii, Glanzmann’s thrombasthenia, and Hermansku-Pudlak syndrome.

The even longer term goal is the use these lines to specifically study the behavior of such cells in culture and under certain conditions, test various drugs on them, and to develop treatment strategies on them as well.

RNA Molecule Protects Stem Cells During Inflammation


During inflammation and infection, bone marrow stem cells that make blood cells (so-called hematopoietic stem cells or HSCs) and progenitor cells are stimulated to proliferate and differentiate into mature immune cells. This especially the case for cells of the so-called “myeloid lineage.

Hematopoietic Stem Cells (HSCs) are able to differentiate into cells of two primary lineages, lymphoid and myeloid. Cells of the myeloid lineage develop during the process of myelopoiesis and include Granulocytes, Monocytes, Megakaryocytes, and Dendritic Cells. Circulating Erythrocytes and Platelets also develop from myeloid progenitor cells.

Hematopoiesis from Multipotent Stem Cell

Repeated infections and inflammation can deplete these cell populations, which leads to serious blood conditions and increased incidence of cancer.

A research team from the California Institute of Technology, led by Nobel Prize winner, David Baltimore, has discovered a small RNA molecule called microRNA-146a (miR-146a) that acts as a safety valve to protect HSCs during chronic inflammation. These findings also suggest that deficiencies for miR-146a might contribute to blood cancers and bone marrow failure.

Baltimore and his colleagues bred mice that lacked miR146a. MicroRNAs are very short RNA molecules (around 22 base pairs long) that regulate the activities of other genes. They control the expression of genes at the transcriptional and post-transcriptional level. In the case of miR146a(-) mice, whenever these mice were subjected to chronic inflammation, the total number and quality of their HSCs declined steadily. In contrast, miR-146a(+) mice were better able to maintain their levels of HSCs despite long-term inflammation.

The lead author of this work, Jimmy Zhao, said, “This mouse with genetic deletion of miR146a is a wonderful model with which to understand chronic inflammation-driven tumor formation and hematopoietic stem cell biology during chronic inflammation.”

Zhao also noted the surprising result that the deletion of one microRNA could cause such a profound and dramatic pathology. This underscores the critical and indispensable function of miR-146a in protecting the quality and longevity of HSCs. This work also establishes the connection between chronic inflammation and bone marrow failure and diseases of the blood.

Even more exciting is the prospect of synthesizing anti-inflammatory drugs that could treat blood disorders. In fact, it is possible that artificially synthesized miR146a might be an effective treatment if small RNAs can be effectively delivered to specific cells.

Zhao also noted the close resemblance that this mouse model has to the blood disorder human myelodysplastic syndrome or MDS. MDS is a form of pre-leukemia that causes severe anemia and a dependence on blood transfusions. MDS usually leads to acute myeloid leukemia. Further study of Zhao and Baltimore’s miR146a(-) mouse might lead to a better understanding of MDS and potential new treatments for MDS.

David Baltimore, senior author of this paper, said, “This study speaks of the importance of keeping chronic inflammation in check and provides a good rationale for broad use of safer and more effective anti-inflammatory molecules. If we can understand what cell types and proteins are critically important in chronic-inflammation-driven tumor formation and stem cell exhaustion, we can potentially design better and safer drugs to intervene.”

See Jimmy L Zhao, Dinesh S Rao, Ryan M O’Connell, Yvette Garcia-Flores, David Baltimore. MicroRNA-146a acts as a guardian of the quality and longevity of hematopoietic stem cells in mice.  DOI: http://dx.doi.org/10.7554/eLife.00537Published May 21, 2013.  Cite as eLife 2013;2:e00537.

Postscript: This paper is especially meaningful to me because my mother died of MDS. The fact that a better model system for MDS has been established is an essential first step in finding a treatment for this killer disease.

What Does Breast Cancer Have to Do With Skin Stem Cells?


BRCA1 is a gene that plays a huge role in breast cancer. Particular mutations in BRCA1 predispose women increased risks of breast cancer cervical, uterine, pancreatic, and colon cancer and men to increased risks of pancreatic cancer, testicular cancer, and early-onset prostate cancer.

BRCA1 encodes a protein that helps repair damage to chromosomes. When this protein product does not function properly, cells cannot properly repair acquired chromosomal damage, and they die or become transformed into cancer cells.

What does this have to do with stem cells? A study led by Cédric Blanpain from the Université libre de Bruxelles showed that BRCA1 is critical for the maintenance of hair follicle stem cells.

Peggy Sotiropoulou and her colleagues in Blanpain’s laboratory showed that when BRCA1 is deleted, hair follicle cells how very high levels of DNA damage and cell death. This accumulated DNA damaged drives the follicle stem cells to divide furiously until they burn themselves out. This is in contrast to the other stem cell populations in the skin, particularly those in the sebaceous glands and epidermis, which are maintained and seem unaffected by deletion of BRCA1.

Sotiropoulou said of these results: “We were very surprised to see that distinct types of cells residing within the same tissue may exhibit such profoundly different responses to the deletion of the same crucial gene for DNA repair.”

This work provides some of the first clues about how DNA repair mechanisms in different types of adult stem cells are employed at different stages of stem cells activation. Blanpain and his group is determining if other stem cells in the body are also affected by the loss of BRCA1. These results might elucidate why mutations in BRCA1 causes cancer in the breast and ovaries, but not in other tissues.

Engineered T Cells Help a Child Get Rid of Leukemia


Pediatric oncologists from The Children’s Hospital of Pennsylvania (CHOP) and collaborating scientists from the University of Pennsylvania (UPenn) have used genetic engineering techniques to reprogram T lymphocytes from a young cancer patient’s blood. This reprogramming drove the T cells to attack the child’s leukemia, and, to date, has completely cured the child of leukemia.

Stephan Grupp, a pediatric oncologist from CHOP, is part of a clinical trial that tests cell therapy for adult chronic lymphocytic leukemia (CLL). CLL is the most common type of leukemia in adults and usually occurs during or after middle age and only rarely occurs in children.

As regular readers of this blog are aware, the bone marrow contains a stem cell population called hematopoietic stem cells. While this stem cell population is not a homogeneous one, these stem cells divide to renew themselves and replenish all the blood cells that we lose each day. When the hematopoietic stem cells divide, they renew themselves and give rise to either a myeloid or lymphoid progenitor cells. Myeloid progenitors differentiate into one of three types of mature blood cells: 1) red blood cells, which carry oxygen and the other substances to all tissues in the body; 2) white blood cells that fight infection and disease; 3) platelets that form blood clots to stop bleeding. Lymphoid progenitors become lymphoblast cells which then differentiate to become one of three cell types: 1) B lymphocytes, which make antibodies to fight infection; 2) T lymphocytes that help B lymphocytes to make antibodies to fight infection; 3) natural killer cells that attack cancer cells and viruses.

Hematopoietic stem cells

CHOP’s Stephen Grupp and Carl June, of the Perelman School of Medicine at the Univ. of Pennsylvania, lead this research group. Together, they have presented new data at the American Society of Hematology annual meeting in Atlanta that shows nine of 12 patients with advanced leukemias in the clinical trial, including two children, who responded to treatment with their newly engineered cells. This treatment strategy uses an engineered T lymphocyte that Grupp and June call “CTL019 cells.” By reprogramming the T cells to specifically attack this aggressive form of leukemia, some of these patients showed a complete remission of their leukemias.

Of the nine patients who responded to CTL019 treatment, one was a 7-year-old patient who suffered from acute lymphoblastic leukemia (ALL). Grupp and Penn colleagues adapted their treatment to combat ALL, which is the most common type of childhood leukemia and the most common childhood cancer. Although physicians cure roughly 85 percent of ALL cases, the remaining 15 percent of such cases stubbornly resist treatment.

Grupp’s research builds on his ongoing collaboration with scientists from UPenn. These UPenn researchers developed modified T cells as a treatment for B-cell leukemias. T cells are at the center of the immune response. T lymphocytes recognize and attack invading foreign invaders, but cancer cells slip under their surveillance net because they are so similar to normal cells. CAR T cells, which stands for “chimeric antigen receptor T cells” are engineered to specifically detect and target cancerous B cells. Since the B cells are the cancerous cells in the case of certain leukemias, such as ALL and CLL, CAR T cells can purge the body of these cancers rather effectively.

On the surface of B cells is a protein called CD19. By raising high-affinity antibodies to CD19 and then physically attaching those antibodies to T cells, UPenn researchers invented a kind of guided missile that detects and destroys B cells and B-cell leukemias.

When Grupp and his crew used CLT019 in his pediatric patients, they found that the engineered T cell was very active, but it caused an undesirable side effect called cytokine release syndrome. The child became very ill and was admitted to the intensive care unit. However, Grupp and his team counteracted these toxic side effects by using two 2 drugs that suppress the immune response and these thwarted the overactive immune response and rapidly relieved the child’s treatment-related symptoms. An added bonus was that these drugs had no effect on the engineered T cells, which still destroyed leukemia cells until the cows came home. These results were so effective, that this clinical approach is now being successfully incorporated into CTL019 treatments for adults as well.

The CHOP/UPenn team reported on early results of this clinical trial in adult chronic lymphocytic leukemia (CLL) patients in August of 2011. In their seven-year-old patient, they engineered her own T cells to attack her aggressive form of childhood leukemia. Without this treatment, she faced grim prospects once her cancer relapsed after conventional treatment. However, with this innovative CTL019 experimental therapy, the bioengineered T cells multiplied rapidly in her body and destroyed the leukemia cells. After her CTL019 treatment, the child’s doctors found that she had no evidence of cancer.

According to Grupp: “These engineered T cells have proven to be active in B cell leukemia in adults. We are excited to see that the CTL019 approach may be effective in untreatable cases of pediatric ALL as well. Our hope is that these results will lead to widely available treatments for high-risk B cell leukemia and lymphoma, and perhaps other cancers in the future.”

Susan Rheingold, one of the leaders in the Children’s Hospital program for children with relapsed leukemia added: “This type of pioneering research addresses the importance of timing when considering experimental therapies for relapsed patients. To ensure newly relapsed patients with refractory leukemia meet criteria for options like CTL019, we must begin exploring these innovative approaches earlier than ever before. Having the conversation with families earlier provides them more treatment options to offer the best possible outcome.”

In August 2012, the biotechnology company Novartis acquired exclusive rights from UPenn to CART-19, the therapy that was the subject of this clinical trial and which is now known as CTL019.

A New Blood Vessel-Generating Stem Cell Discovered With Therapeutic Potential


The laboratory of Petri Salven at the University of Helsinki, Helsinki, Finland, has discovered a new type of stem cell that play a decisive role in the growth of new blood vessels. These stem cells are found in the walls of blood vessels and if protocols are developed to isolated these stem cells, they might very well provide news ways to treat cardiovascular diseases, cancer and many other diseases.

The growth of new blood vessels is known angiogenesis. Angiogenesis is required for the repair of damaged tissues or organs. A downside of angiogenesis is that tumors often secrete angiogenic factors that induce the circulatory system to remodel itself so that new blood vessels grow into the tumor and feed it so that it can grow faster. Thus angiogenesis research tries to promote the growth of new blood vessels when they are needed and inhibit angiogenesis when it is unwanted.

Several drugs that inhibit angiogenesis have been introduced as adjuvant cancer treatments. For example, the drug bevacizumab (Avastin) is a monoclonal antibody that specifically recognizes and binds to an angiogenic factor known as vascular endothelial growth factor or VEGF. When VEGF receptors on the surface of normal endothelial cells. When VEGF binds to receptors on the surfaces of endothelial cells, a signal is sent within those cells that initiate the growth and survival of new blood vessels. Bevacizumab binds tightly to VEGF, which prevents it from binding and activating the VEGF receptor.

Other angiogenesis inhibitors include sorafenib (Nexavar) and sunitinib (Sutent), which are small molecular inhibitors of the receptors that bind the angiogenic factors and the downstream targets of those receptors. Unfortunately, the present crop of angiogenesis inhibitors are not all that effective under certain conditions and they are also extremely expensive and have some very undesirable side effects.

Professor Salven has studied angiogenesis for some time, and his research has focused on the endothelial cells that compose blood vessels. Where do these cells come from and how can we make more or less of them as needed?

A long-standing assumption by scientists in the angiogenesis field was that new endothelial cells came from stem cells found in the bond marrow. This assumption makes sense since there are several stem cell populations in bone marrow that express blood vessel markers and can form blood vessels in culture. However, in 2008, Salven’s group published a paper that demonstrated that new endothelial cells could not come from bone marrow stem cells (see Purhonen S, et al., (2008). Proc Natl Acad Sci U S A. 105(18): 6620-5). Therefore, the mystery remained – from where do new endothelial cells come?

Salven has recently solved this conundrum in his recent paper that appeared in PLoS Biology. According to Salven, “We succeeded in isolating endothelial cells with a high rate of division in the blood vessels of mice. We found that these same cells in human blood vessels and blood vessels growing in malignant tumors in humans. These cells are known as vascular endothelial stem cells, abbreviated VESC. In a cell culture, one such cell is able to produce tends of millions of new blood vessels wall cells.”

Slaven continued: “Our study found that these important stem cells can be found as single cells among the ordinary endothelial cells in blood vessel walls. When the process of angiogenesis is launched, these cells begin to produce new blood vessel wall cells.”

Salven’s colleagues have tested the effects of these new endothelial cells in mice. A particular mouse strain that carries a mutation in the c-kit gene was examined in these experiments. The c-kit gene encodes a cell surface protein called CD117, which is a vital element in the cells that form blood vessels. IN these c-kit mutant mice, new growth of new blood vessels was very poor and the growth of malignant tumors was also quite poor. However, if new stem cells from animals that did not possess a mutation in the c-kit gene were implanted into these mutant mice, blood vessels quickly formed.

As previously mentioned, the cell surface protein CD117 does seem to mark VESCs, but other cells other than VESCs have CD117 on their surfaces. Therefore, isolating all CD177-expression cells only enriches preparations for VESCs; it does not isolate VESCs. Presently, Salven and his group are searching for better surface molecules that can be used to more effectively isolated VESCs from surrounding tissue. If this isolation succeeds, then it will be possible to isolated and propagate VESCs from patients with cardiovascular diseases and expand them in culture for therapeutic purposes.

Another potentially fertile field of research is to find a way to inhibit the activity of VESCs to prevent tumors from remodeling the circulatory system. By cutting of their blood supply, tumors will not only grow slower, but also not spread nearly as quickly.

See: Fang S, Wei J, Pentinmikko N, Leinonen H, Salven P (2012) Generation of Functional Blood Vessels from a Single c-kit+ Adult Vascular Endothelial Stem Cell. PLoS Biol 10(10): e1001407. doi:10.1371/journal.pbio.1001407

Rapamycin Prevents Side Effects Of Radiation Therapy By Protecting Stem Cells


Radiation therapy is very heavily used to treat many different types of cancer. Unfortunately, radiation damages normal cells and tissues and can have horrible side effects that debilitate patients. However, a class of drugs known as inhibitors of mTOR, which stands for mammalian target of rapamycin, can prevent the tissue damage normally caused by radiation. These drugs protect against radiation-induced damage by protecting normal stem cells. Since these stem cells help repair the damaged tissues, these drugs speed recovery and improve outcomes. These results come from a preclinical study published in the September issue of the journal Cell Stem Cell.

The senior author of this study, J. Silvio Gutking of the National Institute of Dental and Craniofacial Research, made this comment about his study: “We can exploit the emerging findings for the development of new preventive strategies and more effective treatment option for patients suffering this devastating disease.”

After undergoing radiation therapy, cancer patients often suffer from a painful condition called mucositis. Mucositis is characterized by the swelling of tissues in the mouth, and this swelling can prevent patients from drinking and the pain of this condition drives them to heavily rely on narcotic pain killers. Mucositis and other types of radiation-induced tissue damage are induced by depletion of stem cells capable of repairing damaged tissue.

In their study, Gutkind and his team discovered that an mTOR inhibitor called rapamycin protects stem cells extracted from the mouths of healthy individuals against radiation-induced damage. Fortuitously, rapamycin does not convey the same protections to cancer cells. The drug extended the lifespans of normal stem cells and allowed them to grow after irradiation. Rapamycin exerted its protective effects by preventing the accumulation of harmful molecules called reactive oxygen species (ROS). Also mice that received rapamycin during radiation treatment did not develop mucositis.

Rapamycin is already approved by the Food and Drug Administration and is currently under investigation in clinical trials as a cancer prevention agent and a potential treatment of various kinds of cancer. These novel findings could have immediate and important implications for a many different cancer patients.

According to Gutkind: “Mucositis prevention would have a remarkable impact on the quality of life and recovery of cancer patients and at the same time would reduce the cost of treatment. Our study provides the basis for further testing in humans, and we hope that these findings can be translated rapidly into the clinic.”

Abnormal Blood Stem Cells are the Cause of Leukemia


Cancer is, to a large degree, a disease of stem cells. When stem cells acquire particular mutations, they lose their controls on cell division and begin to divide uncontrollably. Several different studies have established that several types of cancers result from abnormal stem cells. Blood cancers, for example, form when stem cells accrue rare genetic mutations, according a new study. This discovery overturns the traditional view that blood cancers can originate from any blood cell, and it could conceivably help to prevent relapses in leukemia patients.

Stanford University researchers have identified the origins of leukemia. They used so-called “next-generation sequencing” techniques and various other methods to identify rare, pre-cancerous, blood stem cells in six individuals with acute myeloid leukemia. After identifying these pre-cancerous cells, they compared the genetic sequences from the pre-cancerous blood stem cells to the sequences of the same chromosomal regions from the patients’ leukemia-plagued stem cells. This analysis revealed the exact order of rare mutations that blood stem cells accrued in order to become cancerous.

Stanford hematologist Ravi Majeti, co-lead author of the study, commented: “I’m surprised that we identified the clonal hierarchy that led to leukemia in five of the six cases. I didn’t think we’d find that amount of evidence of pre-leukemia stem cells.”

Scientists have suspected for the last few decades that cancer stem cells, and in particular leukemia stem cells, lead to cancer. In 2005, a Stanford pathologist named Irving Weissman added a twist to this idea when he proposed that normal blood stem cells become cancerous stem cells by accumulating rare mutations. Weissman’s hypothesis suggested that leukemia originated in blood stem cells. Weissman’s hypothesis makes sense of a simple fact; blood stem cells live much longer than regular blood cells, which only live up to a few weeks at most. A few weeks is simply not enough time, to acquire the number of rare mutations necessary to become cancerous. Since blood stem cells are capable of self-renewal, they survive in the body throughout the lifetime of an organism. Unfortunately, such a hypothesis, despite its great explanatory power, is very difficult to directly test, and, therefore, has remained controversial.

The best way to test Weissman’s hypothesis is to identify the protein-coding mutations in several acute myeloid leukemias, and then isolate and analyze the rare, pre-cancerous stem cells to determine which, of the leukemia mutations were present in those pre-cancerous stem cells.

In addition to their sequencing approach, this team also used high-throughput flow cytometry to identify markers specific to a patient’s healthy blood cell-making stem cells versus their leukemia stem cells in order to isolate the very rare populations of pre-cancerous stem cells.

These techniques were pioneered by Thomas Snyder, who is a chief scientist at ImmuMetrix and co-lead author of this paper. Snyder worked as a post-doctoral researcher in the laboratory of Stanford bioengineer Stephen Quake when this he collaborated on this study. Together, Quake and Snyder developed those techniques to sort and study the genomes of each individual cell. “It is only when you can look at a single cell and determine its genotype that you can conclusively show the early stages in the evolution of the cancer,” said Snyder.

Umbilical Cord Stem Cells and Cancer


The umbilical cord blood stem cells have been used to treat cancer patients whose bone marrow tissues have been wiped out by radiation or chemotherapeutic treatments. Several clinical trials have addresses the capacity of umbilical cord blood to reconstitute the bone marrow of cancer patients.

The first set of clinical trials have examined the use of umbilical cord blood in children. Gluckman and her colleagues reported the use of umbilical cord blood to treat children who had suffered from a variety of blood maladies. 74 patients were treated with umbilical cord blood. 63% of the patients survived one year after the procedure, and the rate of graft-versus-host disease (GVHD) was only 9%. Now this study showed that umbilical cord blood could be used to reconstitute the bone marrow, but how well does it work compared to bone marrow transplants?

To answer this question, Rocha and his colleagues compared kids who had received umbilical cord blood transplants with those who had received bone marrow transplants. 113 cord blood transplant patients were compared to 2052 bone marrow transplant recipients. In this study, the umbilical cord blood recipients took longer to have their bone marrow reconstituted, but the rate of graft-versus-host disease was lower. The survival rate of the two groups three years after the procedure was also about the same (64% for the umbilical cord blood recipients and 66% for the bone marrow recipients). Thus, umbilical cord blood seemed to work as well as bone marrow when it came to reconstituting the bone marrow.

Since the rates of GVH disease were so low, could umbilical cord blood that was not properly tissue matched to the recipient also work? The answer was yes. Once again Gluckman and her colleagues showed that the rate of GVH disease was rather low, and the rate of recovery in a group of 65 patients was quite high (87%). Such a treatment with unmatched bone marrow would be a disaster, since GVH disease would almost certainly result from such a treatment. The results of Gluckman’s small study were confirmed by a much larger study by Rubinstein and others in 1998.

Can cord blood be used to treat adults with similar maladies? Clinical studies have confirmed that the answer is yes. Survival rates from a host of clinical trials have ranged from 15%-70%, but clearly adults can benefit from umbilical cord blood transplantations. Once again, the rates of GVH disease were lower in umbilical cord blood recipients when compared to bone marrow recipients, but once again, the time required for bone marrow recovery was greater.

In Minnesota, Wagner and his colleagues pioneered the use of “double umbilical cord blood grafts” in which umbilical cord blood is taken from two different babies to treat an adult patient. This overcomes the limited volume and cell numbers in an umbilical collection from a single donor. These are only used for patients who are very ill, but studies have shown that patients who have received double umbilical cord blood grafts have a ten-fold lower decrease in the risk of relapse of blood cancers.

Thus over the past two decades, umbilical cord blood transplants have become rather attractive sources of material to reconstitute bone marrow. Although low cell numbers are still a chronic problem with them, the ability to culture and expand these cells in culture may give a new life to this useful treatment.

Targeting Breast Cancers with Neural Stem Cells


Singapore scientists, in particular researchers at the Institute of Bioengineering and Nanotechnology (IBN) showed that engineered neural stem cells can target and kill breast cancers.

In this study, workers in the laboratory of Shu Wang used mouse induced pluripotent stem cells (iPSCs) and differentiated them into neural stem cells (NSCs). They then engineered the NSCs to express a viral gene called thymidine kinase. Thymidine kinase comes from Herpes viruses, and this is particular gene that is not found in human cells. Therefore it is a target for anti-herpes virus drugs. By using an insect virus called “baculovirus,” Wang and his colleagues introduced thymidine kinase into NSCs. The use of baculovirus makes the NSCs safer for clinical use, since, being an insect virus, it does not grow in human cells, but can introduce genes into them.

By placing the herpes thymidine kinase gene into NSCs, it makes from susceptible to antiherpes drugs. For example, ganciclovir (Cytovene), is phosphorylated by thymidine kinase, and this molecule is quite toxic to cells. Contact between the engineered NSCs and cancer cells, would cause transfer of the toxic molecule to the cancer cells, which would kill cancer cells too. However, this begs the question: Can NSCs home to the tumor and target it?

In order to test the ability of NSCs to target and treat breast cancers, Wu’s group injected NSCs loaded with the suicide gene mice afflicted with breast tumors. Then they treated the mice with ganciclovir. Dual-colored whole body imaging was used to track the distribution and migration of the engineered NSCs.

Imaging showed that the NSCs homed in on the breast tumors in the mice, and accumulated in various organs that were infiltrated by the cancer cells. The survival of the tumor-bearing mice was prolonged from 34 days to 39 days. These data demonstrate that iPS-derived NSCs are able to effectively seek out and inhibit tumor growth and proliferation.

According to Dr Shu Wang, “We have demonstrated that tumor-targeting neural stem cells may be derived from human iPS cells, and that these cells may be used in combination with a therapeutic gene to cripple tumor growth. This is a significant finding for stem cell-based cancer therapy, and we will continue to improve and optimize our neural stem cell system by preventing any unwanted activation of the therapeutic gene in non-tumor regions and minimizing possible side effects.”

Professor Jackie. Y. Ying, IBN Executive Director, said, “IBN’s expertise in generating human stem cells from iPS cells and our novel use of insect virus carriers for gene delivery have paved the way for the development of innovative stem cell-based therapies. With their two-pronged attack on tumors using genetically engineered neural stem cells, our researchers have discovered a promising alternative to conventional cancer treatment.