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.

Enrollment Completed in Phase 2 ALLSTAR Cardiac Clinical Trial


Capricor Therapeutics Inc. has announced the completion of patient enrollment in their Phase 2 ALLSTAR clinical trial.  ALLSTAR stands for ALLogeneic Heart STem Cells to Achieve Myocardial Regeneration, and this trial will test Capricor’s CAP-1002 product in patients suffering from cardiac dysfunction following a heart attack.

CAP-1002 cells are cardiosphere derived cells (CDCs) that were isolated from donors.  This investigational therapy is an off-the-shelf “ready to use” cardiac cell therapy that comes from donor heart tissue.  CAP-1002 cells are made to be directly infused into a patient’s coronary artery during a catheterization procedure.

These CDCs were tested in the CADUCEUS clinical trial, in which they were shown to decrease scar size and increase viable heart tissue when implanted into the hearts of heart attack patients.  One-year follow-up examinations of these confirmed the earlier results.

ALLSTAR will study a population similar to the one in the CADUCEUS study (patients who had experienced a heart attack 30-90 days earlier), except that ALLSTAR will treat patients 91-365 days after suffering a heart attack.  The extension of the patient pool was to see if the indication window for CAD-1002 could be extended.

The Capricor CEO Linda Marbàn said, “With the last patient in ALLSTAR having been dosed on September 30, we expect to report top-line 12-month primary efficacy outcome results in the fourth quarter of 2017.”

ALLSTAR is being sponsored by Capricor and is led by Drs. Timothy Henry and Rajendra Makkar of the Cedars-Sinai Heart Institute.  The trial is being conducted at approximately 25-40 sites across the U.S.

The Phase I portion of the trial was funded in part by the National Institutes of Health and completed enrollment in December 2013, and the Phase II portion of the trial is supported in large part by the California Institute for Regenerative Medicine (CIRM).

Positive Results from Mesoblast’s Phase 2 Trial of Cell Therapy in Diabetic Kidney Disease


Mesoblast Limited has announced results from its Phase 2 clinical Trial that evaluated their Mesenchymal Precursor Cell (MPC) product, known as MPC-300-IV, in patients who suffer from diabetic kidney disease. In short, their cell product was shown to be both safe and effective. The results of their trial were published in the peer-reviewed journal EBioMedicine.  Researchers from the University of Melbourne, Epworth Medical Centre and Monash Medical Centre in Australia participated in this study.

The paper describes a randomized, placebo-controlled, and dose-escalation study that administered to patients with type 2 diabetic nephropathy either a single intravenous infusion of MPC-300-IV or a placebo.

All patients suffered from moderate to severe renal impairment (stage 3b-4 chronic kidney disease for those who are interested).  All patients were taking standard pharmacological agents that are typically prescribed to patients with diabetic nephropathy.  Such drugs include angiotensin-converting enzyme inhibitors (e.g., lisinopril, captopril, ramipril, enalapril, fosinopril, ect.) or angiotensin II receptor blockers (e.g., irbesartan, telmisartan, losartan, valsartan, candesartan, etc.).  A total of 30 patients were randomized to receive either a single infusion of 150 million MPCs, or 300 million MPCs, or saline control in addition to maximal therapy.

Since this was a phase 2 clinical trial, the objectives of the study were to evaluate the safety of this treatment and to examine the efficacy of MPC-300-IV treatment on renal function.  For kidney function, a physiological parameter called the “glomerular filtration rate” or GFR is a crucial indicator of kidney health.  The GFR essentially indicates how well the individual functional units within the kidney, known as “nephrons,” are working.  The GFR indicates how well the blood is filtered by the kidneys, which is one way to measure remaining kidney function.  The decline or change in glomerular filtration rate (GFR) is thought to be an adequate indicator of kidney function, according to the 2012 joint workshop held by the United States Food and Drug Administration and the National Kidney Foundation.

nephronanatomy

Diabetic nephropathy is an important disease for global health, since it is the single leading cause of end-stage kidney disease.  Diabetic nephropathy accounts for almost half of all end-stage kidney disease cases in the United States and over 40% of new patients entering dialysis treatment.  For example, there are almost 2 million cases of moderate to severe diabetic nephropathy in 2013.

Diabetic nephropathy can even occur in patients whose diabetes is well controlled – those patients who manage to keep their blood glucose levels at a reasonable level.  In the case of diabetic nephropathy, chronic infiltration of the kidneys by inflammatory monocytes that secrete pro-inflammatory cytokines causes endothelial dysfunction and fibrosis in the kidney.

Staging of chronic kidney disease (CKD) is based on GFR levels.  GFR decline typically defines the progression to kidney failure (for example, stage 5, GFR<15ml/min/1.73m2).  The current standard of care (renin-angiotensin system inhibition with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers) only delays the progression to kidney failure by 16-25%, which leaves a large residual risk for end-stage kidney disease.  For patients with end-stage kidney disease, the only treatment option is renal replacement (dialysis or kidney transplantation), which incurs high medical costs and substantial disruptions to a normal lifestyle.  Due to a severe shortage of kidneys, in 2012 approximately 92,000 persons in the United States died while on the transplant list.  For those on dialysis, the mortality rate is high with an approximately 40% fatality rate within two years.

The main results of this clinical trial were that the safety profile for MPC-300-IV treatment was similar to placebo.  There were no treatment-related adverse events.  Secondly, patients who received a single MPC infusion at either dose had improved renal function compared to placebo, as defined by preservation or improvement in GFR 12 weeks after treatment.  Third, the rate of decline in estimated GFR at 12 weeks was significantly reduced in those patients who received a single dose of 150 million MPCs relative to the placebo group (p=0.05).  Finally, there was a trend toward more pronounced treatment effects relative to placebo in a pre-specified subgroup of patients whose GFRs were lower than 30 ml/min/1.73m2 at baseline (p=0.07).  In other words, the worse the patients were at the start of the trial, the better they responded to the treatment.

The lead author of this publication, Dr David Packham, Associate Professor in the Department of Medicine at the University of Melbourne and Director of the Melbourne Renal Research Group, said: “The efficacy signal observed with respect to preservation or improvement in GFR is exciting, especially given that this trial was not powered to show statistical significance. Patients receiving a single infusion of MPC-300-IV showed no evidence of developing an immune response to the administered cells, suggesting that repeat administration is feasible and may in the longer term be able to halt or even reverse progressive chronic kidney disease. I hope that this very promising investigational therapy will be advanced to rigorous Phase 3 clinical trials to test this hypothesis as soon as possible.”

Patients who received s single IV infusion of MPC-300-IV cells showed no evidence of developing an immune response to the administered cells.  This suggests that repeated administration of MPCs is feasible and might even have the ability to halt, or even reverse progressive chronic kidney disease.

Packham and his colleagues hope that this cell-based therapy can be advanced to a rigorous Phase 3 clinical trial to further test this treatment.

Stem Cell Therapy Might Improve Brain Function of Traumatic Brains Injury Patients


Accidents happen and sometimes really bad accidents happen; especially if they injure your head.  Traumatic brain injuries or TBIs can result from automobile accidents, explosions or other events that result from severe blows to the head.  TBIs  an adversely affect a patient and his/her family for long periods of time.  TBI patients can experience cognitive deficits that prevent them from thinking or speaking straight, and sensory deficits that prevent them from seeing, hearing or smelling properly.  Psychological problems can also result.  Essentially, TBIs represent a major challenge for modern medicine.

According to data from the Centers for Disease Control (CDC), 1.7 million Americans suffer from TBIs each year (of varying severity).  Of these, 275,000 are hospitalized for their injuries and approximately 52,000 of these patients die from their injuries.  In fact, TBIs contribute to one-third of all injury-related deaths in the United States each year.  More than 6.5 million patients are burdened by the deleterious effects of TBIs, and this leads to an economic burden of approximately $60 billion each year.

Currently, treatments for TBI are few and far between.  Neurosurgeons can use surgery to repair damaged blood vessels and tissues, and diminish swelling in the brain.  Beyond these rather invasive techniques, the options for clinicians are poor.

A new study by Charles S. Cox, professor of Pediatric Surgery and co-director of the Memorial Hermann Red Duke Trauma Institute, and his colleagues suggest that stem cell treatments might benefit TBI patients.  The results of this study were published in the journal Stem Cells.

This study enrolled 25 TBI patients.  Five of them received no treatment and served as controls, but the remaining 20 received gradually increasing dosages of their own bone marrow stem cells.  The harvesting, processing and infusion of the bone marrow cells occurred within 48 hours of injury.  Functional and cognitive results were measured with standard tests and brain imaging with magnetic resonance imaging and diffusion tensor imaging.

This work is an extension of extensive preclinical work done by Cox and his coworkers in laboratory animals and a phase I study that established that such stem cell transplantation are safe for human patients.  The implanted stem cells seem to quell brain inflammation and lessen the damage to the brain by the TBI.

Despite the fact that those TBI patients who received the stem cell treatments had greater degrees of brain damage, the treatment group showed better structural preservation of the brain and better functional outcomes than the control group.  Of particular interest was the decrease in indicators of inflammation as a result of the bone marrow cell-based infusions.

Cox said of this trial, “The data derived from this trial moves beyond just testing safety of this approach.”  He continued:  “We now have a hint of a treatment effect that mirrors our pre-clinical work, and were are now pursuing this approach in a phase IIb clinical trial sponsored by the Joint Warfighter Program within the US Army Medical Research Acquisition Activity, as well as our ongoing phase IIb pediatric severe TBI clinical trial; both using the same autonomous cell therapy.”

This an exciting study, but it is a small study.  While the safety of this procedure has been established, the precise dosage and long-term benefits will require further examination.  However it is a fine start to what may become the flowering of new strategies to treat TBI patients.

Targeting EGFL6 Protein Halts Growth and Spread of Ovarian Cancer


Dr. Ronald J. Buckanovich, professor of hematology/oncology and gynecologic oncology at the University of Michigan Medical School, and his colleagues have identified a protein that help ovarian cancer cells multiply and spread to other organs.  When he and his coworkers inhibited this protein with an antibody they were able to stop the spread of ovarian cancer cold.

The EGFL6 or epidermal growth factor like 6 precursor protein, which is also known as MAEG, maps to human Xp22 chromosome.  The EGFL6 protein is expressed primarily in fetal tissues and during early development (see Yeung G., et al., (1999) Genomics 62, 304307; and Buchner G., et al., (2000) Genomics 65, 1623).  The expression of MAEG has also been detected in several tissues, including the dermis of the trunk, hair follicles, and the mesenchyme of the cranio-facial region (see Buchner G., and others, (2000) Mech. Dev. 98, 179182).  EGFL6 protein has been proposed as a possible biomarker in ovarian cancer (Buckanovich R. J., and others, (2007) J. Clin. Oncol. 25, 852861).

In this paper, which appeared in Cancer Research, Buckanovich and others amplified the expression of EGFL6 in ovarian cancer cells.  Increased EGFL6 expression stimulated cancer growth some two-three times.  This effect was observed in cultured ovarian cancer cells and in a mouse model of ovarian cancer.  Conversely, elimination of EGFL6 greatly reduced ovarian cancer growth, decreasing the rate of growth some four-fold.

EGFL6 specifically acts in cancer stem cells.  To review, in tumors, not all cancer cells are the same.  Inside malignant tumors or even among circulating cancerous cells (as in the case of leukemia) there are usually a variety of different types of cancer cells.  The stem cell theory of cancer proposes that among cancerous cells, a small population among them act as stem cells that reproduce themselves and sustain the cancer.  Cancer stem cells, therefore, are like normal stem cells that renew and sustain our organs and tissues.  Therefore, cancer cells that are not stem cells can certainly adversely affect health, but they cannot sustain the cancer long-term.  Therefore, cancer stem cells fuel the growth and spread of cancers and also are often resistant to chemotherapy and radiation treatments.

Further experiments by Buckanovich and his colleagues showed that EGFL6 cause cancer stem cells to divide asymmetrically so that the one of the daughter cells remains a cancer stem cell while the other daughter cell is a cancer cell that can affect the patient but cannot sustain the cancer. This asymmetric cell division also generates a good deal of diversity among cancer cells.

Buckanovich noted: “What this means is that the stem cell population remains stable.  But the daughter cells, which can have a burst of growth, multiply, and allow the cancer to grow.”.

EGFL6 does more than just promote cancer cell proliferation.  EGFL6 is also a promoter of cancer stem cell migration.  When blood vessels were engineered to express EGFL6, tumor metastasis (spread) was even more robust.

Treatment of tumor-afflicted mice with an antibody that specifically binds to EGFL6 and inactivates it caused a 35% reduction in cancer stem cells and significantly reduced overall tumor growth.  Additionally, the antibody also prevented tumor metastasis.

Buckanovich thinks that targeting EGFL6 might be a potential therapy for women with stage 3 ovarian cancer.  Such a treatment might control the growth and spread of ovarian cancers.

Dr. Buckanovich added: “The bigger implication is for women at high risk of ovarian cancer.  These patients could be treated before cancer develops, potentially blocking cancer from developing or preventing it from spreading.  If cancer did develop, it could be diagnosed at an early stage, which would improve patient outcomes.”.

The next step for Buckanovich and his colleagues is developing an antibody that can properly work in human cancer patients.

Patient-Specific Heart Muscle Cells Before the Baby Is Born


Prenatal ultrasound scans can detect congenital heart defects (CHDs) before birth. Some 1% of all children born per year have some kind of CHD. Most of these children will require some kind of rather invasive, albeit life-saving surgery but an estimated 25% of these children will die before their first birthday. This underscores the need for netter therapies of children with CHDs.

To that end, Shaun Kunisaka from C.S. Mott Children’s Hospital in Ann Arbor, Michigan and his colleagues have used induced pluripotent stem cell (iPSC) technology to make patient-specific heart muscle cells in culture from the baby’s amniotic fluid cells. Because these cells can be generated in less than 16 weeks, and because the amniotic fluid can be harvested at about 20-weeks gestation, this procedure can potentially provide large quantities of heart muscle cells before the baby is born.

In this paper, which was published in Stem Cells Translational Medicine, Kunisaki and others collected 8-10 milliliter samples of amniotic fluid at 20 weeks gestation from two pregnant women who provided written consent for their amniocentesis procedures. The amniotic fluid cells from these small samples were expanded in culture, and between passages 3 and 5, cells were selected for mesenchymal stem cell properties. These amniotic fluid mesenchymal stem cells were then infected with genetically engineered non-integrating Sendai viruses that caused transient expression of the Oct4, Sox2, Klf4, and c-Myc genes in these cells. The transient expression of these four genes drove the cells to dedifferentiate into iPSCs that were then grown and then differentiated into heart muscle cells, using well-worked out protocols that have become rather standard in the field.

Not only were the amniotic fluid mesenchymal stem cells very well reprogrammed into iPSCs, but these iPSCs also could be reliably differentiated into cardiomyocytes (heart muscle cells, that is) that had no detectable signs of the transgenes that were used to reprogram them, and, also, had normal karyotypes. Karyotypes are spreads of a cell’s chromosomes, and the chromosome spreads of these reprogrammed cells were normal.

As to what kinds of heart muscle cells were made, these cells showed the usual types of calcium cycling common to heart muscle cells. These cells also beat faster when they were stimulated with epinephrine-like molecules (isoproterenol in this case). Interestingly, the heart muscle cells were a mixed population of ventricular cells that form the large, lower chambers of the heart, atrial cells, that form the small, upper chambers of the heart, and pacemaker cells that spontaneously form their own signals to beat.

This paper demonstrated that second-trimester human amniotic fluid cells can be reliably reprogrammed into iPSCs that can be reliably differentiated into heart muscle cells that are free of reprogramming factors. This approach does have the potential to produce patient-specific, therapeutic-grade heart muscle cells for treatment before the child is even born.

Some caveats do exist. The use of the Sendai virus means that cells have to be passaged several times to rid them of the viral DNA sequences. Also, to make these clinical-grade cells, all animal produces in their production must be removed. Tremendous advances have been made in this regard to date, but those advancements would have to be applied to this procedure in order to make cells under Good Manufacturing Practices (GMP) standards that are required for clinical-grade materials. Finally, neither of these mothers had children who were diagnosed with a CHD. Deriving heart muscle cells from children diagnosed with a CHD and showing that such cells had the ability to improve the function of the heart of such children is the true test of whether or not this procedure might work in the clinic.