Using Light to Guide T Lymphocytes to Attack Tumors


Solid tumors have a whole bag of tricks to avoid the immune system. Fortunately, new therapies aim at these strategies to sensitize the patient’s immune system to the tumor. A new study from the University of Rochester Medical Center laboratory has discovered a simple, practical way that uses light and optics to turn killer immune cells to the tumors.

The lead author of this study, Minsoo Kim, Ph.D., works as a professor of Microbiology and Immunology, and is also an investigator at the Wilmot Cancer Institute. This work from Kim’s laboratory were published in the online journal Nature Communications. Kim described the method devised in his laboratory as similar to “sending light on a spy mission to track down cancer cells.”

A new therapy for treating hard-to-crack cancers is called immunotherapy. Immunotherapy does not utilize radiation or chemotherapy, but instructs the patient’s T lymphocytes to attack the cancerous cells. For example, CAR T-cell therapy removes the patient’s T cells, grows them in the laboratory, genetically engineers them to recognize, attack and kill the cancer, and then reintroduces these cells back into the patient. This is one type of immunotherapy. While this ingenuous technique shows remarkable promise, the immune system can overreact or under-react sometimes. Also, slippery cancers can find ways to hide from marauding T cells. Likewise, aggressive tumors often have mechanisms by which they suppress the immune system and surround themselves with a kind of “no-go” zone that prevents any immune cells from coming near the tumor. These immunosuppressive microenvironments that surround the malignant tumor keeps T cells out.

While it is true that T cells can be engineered to be more efficient killers, unleashing such supercharged T cells into the body can produce a tempest of toxicities. Is there a safer way?

Kim and his colleagues tried to find a kinder, gentler way to crack the tumor. They used a two-prong approach. First, Kim and others discovered that light-sensitive molecules could effectively guide T cells toward tumors. Kim and his coworkers even discovered that a molecule from algae called “channelrhodopsin” (CatCh) that is light-sensitive, could be introduced into immune cells by genetically engineering them with viruses. This technology is so novel that the university’s technology transfer office has filed for patent protection on the invention. Secondly, Kim collaborated with University of Rochester optics and photonics experts to design a Light Emitting Diode (LED) chip that could be implanted and shine light on the tumor.

Next, the Kim group fitted their mice with a small battery pack that sent a wireless signal to the implanted LED chip. When the ears of the mice were implanted with aggressive melanoma cells taken from a patient, the chip remotely shines light on the implanted tumor and surrounding areas. The light-guided T cells ran headlong to the tumor, ignoring the no-go zone where they killed the implanted tumor.

Even more interestingly, the LED chip with the battery pack were used in many control mice and no toxic side effects were observed. In the tumor-implanted mice, the light-guided T cells completely destroyed the implanted melanoma was destroyed without dangerous side effects.

In the future, Kim wants to determine if the wireless LED signal can deliver light to tumors deep within the body instead only on the surface. Also, can light shined into deep areas of the body still guide the T cells to the tumor to attack the tumor.

Kim cautiously emphasized that while his discovery is exciting, it is only meant to be combined with immunotherapy to make it safer, more effective, and traceable. Perhaps with additional improvements, Kim’s optical method might allow doctors to see, in real-time, if cancer therapies are reaching their target. Currently when patients receive immunotherapy, they must wait for several weeks and then have imaging scans to determine if the treatment worked.

“The beauty of our approach is that it’s highly flexible, non-toxic, and focused on activating T cells to do their jobs,” Kim said.

Hitting Acute Myeloid Leukemia Where It Hurts


Research teams from Massachusetts General Hospital and the Harvard Stem Cell Institute have teamed up to devise a new strategy for treating acute myeloid leukemia (AML). This new strategy is an outgrowth of new findings by these research groups that have identified an enzyme that plays a central role in the onset of AML.

During blood cell development in the bone marrow, hematopoietic stem cells divide to produce daughters cells, one of which remains a stem cells and the other of which becomes a progenitor cell. The progenitor cells can either differentiate toward the lymphoid lineage, in which it will become either a B-lymphocyte, T-lymphocyte, or a Natural Killer cell, or a myeloid precursor that can give rise to neutrophils, megakarocytes (that produce platelets), monocytes, eosinophils, or red blood cells. However, the means by which myeloid cells are formed in the bone marrow of AML patients is abnormal, and the myeloid precursor cells do not differentiate into a specific white blood cells, but, instead, remain immature and proliferate and crowd out and suppress the development of normal blood cells.

David Scadden, MD, director of the MGH Center for Regenerative Medicine (MGH-CRM), co-director of the Harvard Stem Cell Institute (HSCI), and senior author of this Cell paper, had this to say about AML: “AML is a devastating form of cancer; the five-year survival rate is only 30 percent, and it is even worse for the older patients who have a higher risk of developing the disease.” Dr. Scadden continued: “New therapies for AML are extremely limited – we are still using the protocols developed back in the 1970s – so we desperately need to find new treatments.”

What genetic changes cause these developmental abnormalities that lead to AML? As it turns out, a wide range of genetic changes occur in AML (see Medinger M, Lengerke C, Passweg J. Cancer Genomics Proteomics. 2016 09-10;13(5):317-29; and Prada-Arismendy J, Arroyave JC, Röthlisberger S. Blood Rev. 2016 Sep 2. pii: S0268-960X(16)30060-1). In this paper, however, the authors proposed that the effects on differentiation had to transition through a few shared events. Using a method created by lead author David Sykes of the MGH-CRM and HSCI, the team discovered that a single dysfunctional point in the developmental pathway common to most forms of AML that could be a treatment target.

Previous studies had demonstrated that expression of the HoxA9 transcription factor, a transcription factor that must be inactivated during normal myeloid cell differentiation, is actually quite active in the myeloid precursors of 70 percent of patients with AML.  Unfortunately, no inhibitors of HoxA9 have been identified to date.  Therefore, Scadden and others used a different, albeit freaking ingenious, approach to screen small molecules that were potential Hox9A inhibitors based not on their interaction with a particular molecular target but on whether they could overcome the differentiation blockade characteristic of AML cells.

First, they induced HoxA9 overexpression in cultured mouse myeloid cells to design a cellular model of AML.  They also genetically engineered these cultured cells to glow green once they differentiated into the mature white blood cell types.  These groups screened more than 330,000 small molecules to find which would produce the green signal in the cultured cells.  The green glow indicated that the HoxA9-induced differentiation blockade had been effectively overcome. Only these 330,000 compounds, only 12 induced terminal differentiation of these cells, but 11 of then acted by suppressing a metabolic enzyme called DHODH.  DHODH, or dihydroorotate dehydrogenase, is a biosynthetic an enzyme that is a member of the pyrimidine biosynthesis pathway, which catalyzes the oxidation of dihydroorotate to orotate.

dhodh

This is a shocking discovery because the DHODH enzyme is not known to play any significant role in myeloid differentiation.  Corroboratory experiments demonstrated that inhibition of DHODH effectively induced differentiation in both mouse and human AML cells.

The next obvious step would be to use known inhibitors of DHODH in mice with AML.  They were able to identify a dosing schedule that reduced levels of leukemic cells and prolonged survival that caused none of the adverse effects of normal chemotherapy.  Even though six weeks of treatment with DHODH inhibitors did not prevent eventual relapse, treatment for up to 10 weeks seemed to have led to long-term remission of AML.  This remission included reduction of the leukemia stem cells that can lead to relapse.  Similar results were observed in mice into which human leukemia cells had been implanted.

“Drug companies tend to be skeptical of the kind of functional screening we used to identify DHODH as a target, because it can be complicated and imprecise. We think that with modern tools, we may be able to improve target identification, so applying this approach to a broader range of cancers may be justified,” says Scadden, who is chair and professor of Stem Cell and Regenerative Biology and Jordan Professor of Medicine at Harvard University. Additional investigation of the mechanism underlying DHODH inhibition should allow development of protocols for human clinical trials.

Scadden noted that this manuscript describes six years of work and, also, is a true reflection of the collaborative nature of science in pursuit of clinically relevant therapies.

Pancreatic Cancers Treated Better By Breaking Up Scar Tissue


Despite advances in cancer treatment, tumors of the pancreas remain among the most difficult to treat. To date, pancreatic cancers remain largely resistant to immune-based therapies, despite the successes of immunotherapies in treating lung cancers and melanomas.

A new study from Washington University School of Medicine in St. Louis that was published in the journal Nature Medicine, has shown that immunotherapy against pancreatic cancer can shrink these tumors if they are given in combination with drugs that break up the fibrous scar tissue in these tumors.

Physicians at Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital are using the strength of these data to conduct a phase 1 clinical trial in patients with advanced pancreatic cancer. This clinical trial will test the safety of this drug combination when given alongside standard chemotherapy.

“Pancreatic tumors are notoriously unresponsive to both conventional chemotherapy and newer forms of immunotherapeutics,” said senior author David G. DeNardo, PhD, an assistant professor of medicine. “We suspect that the fibrous environment of the tumor that is typical of pancreatic cancer may be responsible for the poor response to immune therapies that have been effective in other types of cancer.”

Pancreatic cancers are unusual among cancers since they characteristically consist of large swaths of scar tissue. These balls of fibrous tissue that surround the tumor create a protective environment for cancer cells. These scar tissue-based capsules prevent the immune system accessing the tumor cells and also limit the exposure of these tumors to chemotherapies that have been administered through the bloodstream. DeNardo and his colleagues used a mouse model of pancreatic cancer to determine if disrupting these fibrous capsules could sensitize pancreatic tumors to chemotherapy regimens.

Pancreatic tumors are surrounded by a protective "nest" made of fibrotic scar tissue and the cells that manufacture it (red). A new study demonstrates that disrupting this fibrous tissue makes immune therapy and chemotherapy more effective in attacking tumors of the pancreas. (Image: DeNardo Lab)
Pancreatic tumors are surrounded by a protective “nest” made of fibrotic scar tissue and the cells that manufacture it (red). A new study demonstrates that disrupting this fibrous tissue makes immune therapy and chemotherapy more effective in attacking tumors of the pancreas. (Image: DeNardo Lab)

“Proteins called focal adhesion kinases are known to be involved in the formation of fibrous tissue in many diseases, not just cancer,” DeNardo said. “So we hypothesized that blocking this pathway might diminish fibrosis and immunosuppression in pancreatic cancer.”

Focal adhesion kinase (FAK) is a protein (encoded by the PTKs gene) that controls cell adhesion and cell motility. Inhibiting FAK activity in breast cancer cells makes them less likely to spread to other organs (see Chan, K.T., et al. 2009. J. Cell Biol. doi:10.1083/jcb.200809110). Small molecules have been designed that can readily inhibit FAK, and DeNardo and his colleagues used FAK inhibitors against pancreatic cancer in combination with immunotherapy.

Focal Adhesion Kinase

In their mouse study, an investigational FAK inhibitor was administered to mice in combination with a clinically approved immune therapy that activates the patient’s own T-cells so that they can effectively attack tumor cells.

Mice that had pancreatic cancer survived no longer than two months when given either a FAK inhibitor or immune therapy alone. If the FAK inhibitors were added to standard chemotherapy, the tumor response improved over chemotherapy alone. However, the three-drug combination that consisted of FAK inhibitors, immune therapy and chemotherapy, displayed the best outcomes in laboratory studies and more than tripled survival times in some mice. Some were still alive without evidence of progressing disease at six months after treatment and beyond.

The success of this mouse study provided a strong rationale for testing this drug combination in patients with advanced pancreatic cancer, according to oncologist Andrea Wang-Gillam, MD, PhD, an associate professor of medicine, who was involved with this research.

“This trial is one of about a dozen we are conducting specifically for pancreatic cancer at Washington University,” she said. “We hope to improve outcomes for these patients, especially since survival with metastatic pancreatic cancer is typically only six months to a year. The advantage of our three-pronged approach is that we are attacking the cancer in multiple ways, breaking up the fibers of the tumor microenvironment so that more immune cells and more of the chemotherapy drug can attack the tumor.”

New Gene Therapy Treatment Stops Deadly Brain Cancer in its Tracks


Brain cancers called Diffuse Intrinsic Pontine Gliomas (DIPGs) are often a death sentence. These aggressive, fast-growing, drug-resistant tumors are deadly and they originate from glial cells in the brain.

However a recent report published in the journal Cancer Cell details an experimental gene therapy that stops DIPGs in their tracks. This study included researchers from several different institutions, but was led by scientists at Cincinnati Children’s Hospital Medical Center. The study examined human cancer cells and a mouse model of DIPG.

DIPGs seem to require a gene called Olig2 (which encodes a transcription factor) to grow and survive. The majority of gliomas express the protein encoded by the Olig2 gene and removing this gene halts tumor growth and liquidating Olig2-producing cells inhibits tumor formation. This collaborative team designed a technique scientists found a way to use a gene therapy to shut down Olig2 expression.

“We find that elimination of dividing Olig2-expressing cells blocks initiation and progression of glioma in animal models and further show that Olig2 is the molecular arbiter of genetic adaptability that makes high-grade gliomas aggressive and treatment resistant,” said Qing Richard Lu, PhD, lead investigator and scientific director of the Brain Tumor Center at Cincinnati Children’s. “By finding a way to inhibit Olig2 in tumor forming cells, we were able to change the tumor cells’ makeup and sensitize them to targeted molecular treatment. This suggests a proof of principle for stratified therapy in distinct subtypes of malignant gliomas.”

DIPGs originate from supporting brain cells called oligodendrocytes. Oligodendrocytes make the insulation that surrounds the axons of various nerves in the central nervous system. Olig2 expression appears at the early stages of brain cell development, and is also present in the early-stage dividing and replicating cells in tumors. Olig2 also participates in the transformation of normal oligodendrocyte progenitor cells (OPCs) into cancer cells that divide uncontrollably. Olig2 also facilitates the adaptability of gliomas that helps them evade chemotherapeutic regimens. Indeed, clinically speaking, DIPGs may initially respond to chemotherapeutic agents, but they tend to quickly adapt to these drugs and develop high-levels of resistance to them.

Lu and his colleagues and collaborators eliminated Olig2-positive dividing cells from DIPG tumors that were still in the early stages of tumor formation. Lu and his colleagues used an ingenious technique to remove Oligo2 expression: by genetically engineering a herpes simplex virus-based vector, they delivered a suicide gene (Thymidine kinase) into replicating Olig2-positive cancer cells. Since herpes simplex viruses (HSVs) have the ability to grow in neurons that do not divide a great deal, the HSV-vectors are well suited to this purpose. After infecting the early DIPG cells with the HSV vectors, they administered an anti-herpes drug already in clinical use, ganciclovir (GCV), which kills any cells that have the thymidine kinase gene. The Olig2-deleted tumors were not able to grow.

In follow-up work, Lu and his colleagues observed a fascinating fate for the Olig2- tumors. These cells differentiated into astrocyte-like cells that continued to form tumors, but expressed the epidermal growth factor receptor (EGFR) gene at high levels. EGFR is an effective target for several chemotherapy drugs. In repeated tests in mouse models, Olig2 inhibition consistently transformed the glioma-forming cells into EGFR-expressing astrocyte-like cells. Then these tumors were treated with an EGFR-targeted chemotherapy drug called gefitinib. These treatments stopped the growth of new tumor cells and tumor expansion.

According to Dr. Lu, with additional testing, verification, and, of course, refinement, this experimental therapy that he and his colleagues have designed, could help prevent the recurrence of brain cancer in patients who have undergone initial rounds of successful treatment. Lu also added that these new treatments would probably be used in combination with other existing therapies like radiation, surgery, other chemotherapies and targeted molecular treatments.

Lu and his team will continue their research with other human cell lines and “humanized” mouse models of high-grade glioma. Such mouse models use genetically engineered mice that can grow brain tumors derived from the tumor cells of specific human patients. These tumor cells come from the tumors of patients whose families have donated biopsied tumor samples for research. This allows researchers to test different targeted drugs in their therapeutic protocol that may best match the genetic makeup of tumors from specific individuals.

The entire research team cautions the experimental therapeutic approach they describe will require extensive additional research. Therefore, this type of treatment is years away from possible clinical testing. Having said that, Lu said the data are a significant research breakthrough, since this study identifies a definite weakness in these stubborn cancers that almost always relapse and kill the patients who get them.

Pancreatic Cancer Stem Cells Could Be “Suffocated” by an Anti-Diabetic Drug


A new study by researchers from Queen Mary University of London’s Barts Cancer Institute and the Spanish National Cancer Research Centre (CNIO) in Madrid shows that pancreatic cancer stem cells (PancSCs) are very dependent on oxygen-based metabolism, and can be “suffocated” with a drug that is already in use to treat diabetes.

Cancer cells typically rely on glycolysis; a metabolic pathway that degrades glucose without using oxygen. However, it turns out that not all cancer cells are alike when it comes to their metabolism.

PancSCs use another metabolic process called oxidative phosphorylation or OXPHOS to completely oxidize glucose all the way to carbon dioxide and water. OXPHOS uses large quantities of oxygen and occurs in the mitochondria. However, this is precisely the process that is inhibited by the anti-diabetic drug, metformin.

Ever crafty, some PancSCs manage to adapt to such a treatment by varying their metabolism, and this leads to a recurrence of the cancer. However, this English/Spanish team thinks that they have discovered a way to prevent such resistance and compel all PancSCs to keep using OXPHOS. This new discovery might open the door to new treatments that stop cancer stem cells using oxygen and prevent cancers from returning after conventional treatments. A clinical trial is planned for later next year.

Dr Patricia Sancho, first author of the research paper, said: “We might be able to exploit this reliance on oxygen by targeting the stem cells with drugs that are already available, killing the cancer by cutting off its energy supply. In the long-term, this could mean that pancreatic cancer patients have more treatment options available to them, including a reduced risk of recurrence following surgery and other treatments.”

PancSCs become resistant to metformin by suppressing a protein called MYC and increasing the activity of a protein called PGC-1α. However, this resistance mechanism of PancSCs can be abolished if a drug called menadione is given. Menadione increases the amount of reactive oxygen species in mitochondria. Additionally, resistance to metformin can be prevented or even reversed if the MYC protein is inhibited by genetic or pharmacological means. Therefore, the specific metabolic features of pancreatic Cancer Stem Cells are amendable to therapeutic intervention and can provide the basis for developing more effective therapies to combat this lethal cancer.

Pancreatic cancer is still one of the most difficult cancer types to treat. It rarely causes symptoms early on and does not usually trigger diagnosis until its later and more advanced stages. Unfortunately, many patients do not live longer than a year after being diagnosed. These cancers are also becoming more common due to obesity, which increases the patient’s risk for metabolic syndrome and diabetes, which are pancreatic cancer risk factors. Limited treatment options and a failure to improve survival rates mean that finding new treatment strategies is a priority.

PancSCs could be an important but as yet overlooked piece of this puzzle, since they compose only a small proportion of the tumor. PancSCs also have the potential to make new tumors, even if all the other cells are killed, and are prone to spreading around the body (metastasis). Therefore killing these PancSCs is a better way to treat such dangerous cancers.

Bone Marrow Pretreatment with Hypomethylating Agents Improves Progression-Free Survival in Leumemia Patients


When patients have certain types of leukemia, they can be cured if they receive a bone marrow transplant from a healthy donor. The immune cells from the donated bone marrow will then attack the cancer cells vigorously, and the leukemia will slip into remission.

Such a strategy is called an “allogeneic bone marrow transplant,” and it is an effective way to treat some types of leukemia. However, this technique is risky and it usually involves some patient-related mortality. The problem is getting the transplanted cells to survive.

A new study from the University of Texas MD Anderson Cancer Center in Houston, Texas has examined over eighty patients who have received allogeneic bone marrow grafts for chronic myelomonocytic leukemia (CMML). Stefan O. Ciurea and his colleagues have identified a new pre-treatment that seems to decrease the degree of tumor relapse.  Their study was published in the Biology of Blood and Bone Marrow Transplantation.

83 consecutive patients with some form of CMML received an allogeneic bone marrow transplants between April 1991 and December 2013 were examined in detail. They asked if pre-treatment of the bone marrow stem cells with chemicals called “hypomethylating agents” before transplant improved progression-free survival.

Seventy-eight patients received “induction treatment” before transplant, 37 received hypomethylating agents and 41 received cytotoxic chemotherapy. Patients treated with a hypomethylating agent had a significantly lower cumulative incidence of relapse at 3 years post-transplant (22%) than those treated with other agents (35%; p=0.03). However, the transplant-related mortality 1 year post-transplant did not significantly differ between these groups (27% and 30%, respectively; p=0.84). The lower relapse rate resulted in a significantly higher 3-year progression-free survival rate in patients treated with a hypomethylating agent (43%) than in those treated with other agents (27%; p=0.04).

This study supports the use of hypomethylating agents before allogeneic stem cell transplantation for patients with CMML to achieve remission and improve progression-free survival of patients. Of course future studies are needed to confirm these findings, but they suggest that pretreating bone marrow stem cells with hypomethylating agents prior to transplanting them will beef the cells up and help them life longer to fight tumors.

Biomaterial Sponge-Like Impant Traps Spreading Cancer Cells


Prof Lonnie Shea, from the Department of Biomedical Engineering at the University of Michigan and his team have designed a small sponge-like implant that has the ability to mop up cancer cells as they move through the body. This device has been tested in mice, but there is hope that the device could act as an early warning system in patients, alerting doctors to cancer spread. The sponge-like implant also seemed to stop rogue cancer cells from reaching other areas where they could establish the growth of new tumors. Shea and others published their findings in the journal Nature Communications.

According to Cancer Research UK, nine in 10 cancer deaths are caused by the disease-spreading to other areas of the body. Stopping the spread of cancer cells, or metastasis, is one of the ways to prevent cancers from becoming worse. Complicating this venture is the fact that cancer cells that circulate in the bloodstream are rare and difficult to detect.

Shea’s device is about 5mm or 0.2 inches in diameter and made of a “biomaterial” already approved for use in medical devices. So far, this implant has so far been tested in mice with breast cancer. Implantation experiments showed that it can be placed either in the abdominal fat or under the skin and that it tended to suck up cancer cells that had started to circulate in the body.

Cancer Cell Trapping Implants

The implant mimicked a process known as chemoattraction in which cells that have broken free from a tumor are attracted to other areas in the body by immune cells. Shea and others found that these immune cells are drawn to the implant where they “set up shop.” This is actually a natural reaction to any foreign body, and the presence of the immune cells also attracts the cancer cells to the implant.

Initially, Shea and others labeled cancer cells with fluorescent proteins that caused them to glow under certain lights, which allowed them to be easily spotted. However, they eventually went on to use a special imaging technique that can distinguish between cancerous and normal cells. They discovered that they could definitively detect cancer cells that had been caught within the implant.

Unexpectedly, when they measured cancer cells that had spread in mice with and without the implant, they showed that the implant not only captured circulating cancer cells, but it also reduced the numbers of cancer cells present at other sites in the body.

Shea, said that he and his team were planning the first clinical trials in humans fairly soon: “We need to see if metastatic cells will show up in the implant in humans like they did in the mice, and if it’s a safe procedure and that we can use the same imaging to detect cancer cells.”

Shea and his coworkers are continuing their work in animals to determine what the outcomes if the spread of the cancer spread was detected at a very early stage, which is something that is presently not yet fully understood.

Lucy Holmes, Cancer Research UK’s science information manager, said: “We urgently need new ways to stop cancer in its tracks. So far this implant approach has only been tested in mice, but it’s encouraging to see these results, which could one day play a role in stopping cancer spread in patients.”