Blood Cancer

Coding Dimension ID: 
287
Coding Dimension path name: 
Cancer / Blood

Derivation and Characterization of Cancer Stem Cells from Human ES Cells

Funding Type: 
SEED Grant
Grant Number: 
RS1-00228
ICOC Funds Committed: 
$642 500
Disease Focus: 
Blood Cancer
Cancer
Stem Cell Use: 
Cancer Stem Cell
Embryonic Stem Cell
Cell Line Generation: 
Cancer Stem Cell
oldStatus: 
Closed
Public Abstract: 
Cancer is the leading cause of death for people younger than 85 (1). High cancer mortality rates underscore the need for more sensitive diagnostic techniques as well as therapies that selectively target cells responsible for cancer propagation (1) Compelling studies suggest that human cancer stem cells (CSC) arise from aberrantly self-renewing tissue specific stem or progenitor cells and are responsible for cancer propagation and therapeutic resistance (2-9). Although the majority of current cancer therapies eradicate rapidly dividing cells within the tumor, the rare CSC population may be quiescent and then reactivate resulting in disease progression and relapse (2-9). We recently demonstrated that CSC are involved in progression of chronic phase chronic myelogenous leukemia (CML), a disease that has been the subject of many landmark discoveries in cancer research(19-30), to a more aggressive and therapeutically recalcitrant myeloid blast crisis (BC) phase. These CSC share the same cell surface markers as granulocyte-macrophage progenitors (GMP) but have aberrantly gained the capacity to self-renew as a result of activation of the Wnt/-catenin stem cell self-renewal pathway (4). Because human embryonic stem cells (hESC) have robust self-renewal capacity and can provide a potentially limitless source of tissue specific stem and progenitor cells in vitro, they represent an ideal model system for generating and characterizing human CSC (10-18). Thus, hESC cell research harbors tremendous potential for developing life-saving therapy for patients with cancer by providing a platform to rapidly and rationally test new therapies that specifically target CSC (2-18). To provide a robust model system for screening novel anti-CSC therapies, we propose to generate and characterize CSC from hESC (10-18). We will investigate the role of genes that are essential for initiation of CML such as BCR-ABL and additional mutations such as b-catenin implicated in CSC propagation (19-30). The efficacy of specific Wnt/b-catenin antagonists at inhibiting BCR-ABL+ human ES cell self-renewal, survival and proliferation alone and in combination with potent BCR-ABL antagonists will be assessed in sensitive in vitro and in vivo assays with the ultimate aim of developing highly active anti-CSC therapy that may halt cancer progression and obviate therapeutic resistance (4,31).
Statement of Benefit to California: 
The research outlined in this proposal represents a unique opportunity for collaborations between investigators from disparate disciplines to use human embryonic stem cells to challenge an existing paradigm namely that leukemic blasts are responsible for progression of chronic myelogenous leukemia (CML) rather than leukemic stem cells (LSC). Current clinical diagnostic tests are not sufficiently sensitive to predict timing of progression for all patients with CML nor are they adequate for determining the type of therapeutic intervention required. Moreover, the primary therapy for CML, Abl kinase inhibition, was shown to be cardiotoxic when given long-term at high doses. Furthermore, amplification of BCR-ABL is not the sole event that occurs during CML progression to blast crisis. Identification and inhibition of molecular mutations responsible for the generation of LSC in CML blood and/or marrow may prevent progression to blast crisis (BC) and would represent an innovative, effective form of CML therapy. Modeling of LSC responsible for CML progression in human embryonic stem cells could have a significant impact on our understanding of the pathophysiology of CML, provide novel diagnostic and therapeutic modalities and improve the quality and possibly quantity of life of patients with CML. By using BCR-ABL transduced human embryonic stem cells, we will rigorously evaluate the LSC hypothesis and as a consequence, the additional molecular events required for progression to blast crisis CML. The ultimate aims of this grant are to develop more sensitive methods to predict leukemic progression and to identify novel molecular therapeutic targets through the development of LSC models using human embryonic stem cells. We aim to provide a robust, reproducible system for testing novel anti-LSC compounds alone and in combination in order to expedite the development of novel therapeutic agents for anti-LSC clinical trials at {REDACTED}. Not only may the translational research performed in the context of this grant speed the delivery of innovative anti-LSC therapies for Californians with leukemia, it will help to train California’s future R&D workforce in addition to developing leaders in translational medicine. This grant will provide the personnel working on the project with a clear view of the importance of their research to cancer therapy and a better perspective on future career opportunities in California.
Progress Report: 
  • SEED Grant Research Summary
  • Compelling studies suggest that cancer stem cells (CSC) arise from primitive self-renewing progenitor cells. Although many cancer therapies target rapidly dividing cells, CSC may be quiescent i.e. asleep resulting in therapeutic resistance. Recently, we demonstrated that CSC drive progression of chronic phase (CP) chronic myeloid leukemia (CML), a subject of many landmark cancer research discoveries, to a therapeutically recalcitrant myeloid blast crisis (BC) phase. CML CSC share cell surface markers with granulocyte-macrophage progenitors (GMP) and have amplified expression of the CML fusion gene, BCR-ABL. In addition, they aberrantly gain self-renewal capacity, in part, as a result Wnt/β-catenin activation. Because human embryonic stem cells (hESC) have robust regenerative capacity and can provide a potentially limitless source of tissue specific progenitor cells in vitro, they represent an ideal model system for generating and characterizing human CSC. The main goals of this research were to generate CSC from hESC to provide an experimentally amenable platform to expedite the development of sensitive diagnostics that predict progression and combined modality anti-CSC therapy.
  • To this end, we tested whether BCR-ABL expression in hESC is sufficient to induce changes characteristic of CML stem cells. Unlike mouse ESC, introduction of a novel lentiviral BCR-ABL vector into hESC did not drive myeloid differentiation nor did it induce stromal independence in vitro underscoring key differences between mouse and human hESC and the importance of in vivo models. Notably, Hues16 cells had a higher propensity to differentiate into CD34+ cells than other hESC lines particularly in AGM co-cultures and thus, were used in subsequent in vivo experiments. Moreover, this SEED grant funded Yosuke Minami in Professor Jean Wang’s lab to create a unique CML blast crisis mouse model typified by GMP expansion and resistance to a BCR-ABL inhibitor, imatinib (Minami et al, PNAS 2008;105:17967-72). In addition, a bioluminescent humanized model of blast crisis CML was created based on transplantation of GMP from patient blood into immune deficient mice (RAG2-/-gc-/-). Cells were tagged with firefly luciferase that emits a bioluminescent signal so that leukemic transplantation efficiency could be tracked in vivo (IVIS). As few as 1,000 human blast crisis CML GMP could transplant leukemia in immune deficient mice thereby providing an important model for studying the molecular events that contribute to leukemic transformation (Abrahamsson et al, PNAS 2009;106:3925-9).
  • In the second aim, we hypothesized that BCR-ABL is sufficient for generating CML from self-renewing stem cells. In these studies, Hues16 cells differentiated into CD34+ cells were lentivirally transduced with BCR-ABL leading to sustained BCR-ABL engraftment in 50% of transplanted mice. Chronic phase CD34+ cells derived from CML blood were less efficient at sustaining CML engraftment (7%) suggesting that hESC derived CD34+ cells have higher self-renewal potential and are similar to advanced phase CML progenitors.
  • Thirdly, we hypothesized that BCR-ABL was necessary but not sufficient for progression to blast crisis. Introduction of lentiviral activated beta-catenin or shRNA to GSK3beta, together with BCR-ABL did not enhance BCR-ABL engraftment compared with BCR-ABL transduction of hESC alone. These studies suggested that hESC may already have sufficient self-renewal capacity to sustain the malignant CML clone and are molecularly comparable to advanced CML progenitors that behave like CSC. In addition, through extensive cDNA sequencing of human blast crisis CML progenitors, we found that 57% of samples harbored a misspliced form of GSK3beta that promoted tumor production and could serve as a novel prognostic marker in CML clinical trials (Abrahamsson et al, PNAS 2009;106:3925-9).
  • In the final aim, we hypothesized that CML CSC are not eliminated by BCR-ABL inhibitors alone and that combined modality therapy will be required. In collaborative research involving in vitro analysis of imatinib resistant CML progenitors and more recently in a humanized mouse model of blast crisis CML, we found that dasatinib, a potent BCR-ABL inhibitor, is necessary but not sufficient for CSC eradication. Discovery of a GSK3beta deregulation, a negative regulator of both beta-catenin and sonic hedgehog (Shh) pathways (Zhang et al, Nature 2009), led us to disover that Shh combined with BCR-ABL inhibition abrogated CSC driven tumor formation (manuscript in preparation) providing the impetus for an upcoming Pfizer sponsored Shh inhibitor clinical trial for refractory hematologic malignancies.

Development of Therapeutic Antibodies Targeting Human Acute Myeloid Leukemia Stem Cells

Funding Type: 
Disease Team Research I
Grant Number: 
DR1-01485
ICOC Funds Committed: 
$19 999 996
Disease Focus: 
Blood Cancer
Cancer
Collaborative Funder: 
UK
Stem Cell Use: 
Cancer Stem Cell
Cell Line Generation: 
Cancer Stem Cell
oldStatus: 
Active
Public Abstract: 
Acute myeloid leukemia (AML) is a cancer of the blood and bone marrow that is rapidly fatal within months if untreated. Even with aggressive treatment, including chemotherapy and bone marrow transplantation, five-year overall survival rates range between 30-40%. Evidence indicates that not all cells in this cancer are the same, and that there is a rare population of leukemia stem cells (LSC) that are responsible for maintaining the disease. Thus, in order to cure this cancer, all LSC must be eliminated, while at the same time sparing the normal blood forming stem cells in the bone marrow. We propose to develop therapeutic antibodies directed against surface markers present in much larger amounts on LSC than on the surface of normal blood forming stem cells. We recently identified and validated several such protein markers including CD47, which we determined contributes to leukemia development by blocking the ingestion and removal of leukemia cells by immune system cells called macrophages. In this way, CD47 acts as a “don’t eat me” signal on LSC. Moreover, we determined that monoclonal antibodies (mAbs) directed against CD47, able to block its interaction with macrophages, mask the “don’t eat me” signal resulting in ingestion and elimination of leukemia in mouse pre-clinical models. We propose a combination of clinical studies, basic research, and pre-clinical development to prepare a therapeutic antibody directed against CD47 and/or other LSC-specific proteins for Initial New Drug (IND) filing with the FDA, and then a Phase I clinical trial to be conducted at {REDACTED} and in the Collaborative Funding Partner country. In collaboration with the pioneering Collaborative Funding Partner country AML Working Group, we will track expression of the LSC proteins in patient samples and correlate with clinical outcomes. This will allow us to identify particular LSC proteins that must be targeted to achieve cure, thereby prioritizing candidate therapeutic antibodies for clinical development. Concurrently, we will conduct basic research and pre-clinical development to prepare these candidates. Basic research during years 1 and 2 will focus on the characterization of anti-CD47 mAb efficacy, investigation of mAb targeting of additional LSC molecules, and determination of efficacy in combinations with anti-CD47. Pre-clinical development during years 1 and 2 will focus on blocking anti-CD47 mAbs, including antibody humanization and large animal model pharmacologic and toxicity studies. Similar studies will be conducted with the most promising antibodies resulting from our basic research. During years 3-4, we will proceed with GMP grade production of the best candidate, followed by efficacy testing in mouse models and large animal models. Finally, in year 4, we will prepare an IND filing with the FDA/MHRA and develop a Phase I clinical trial with this antibody for the treatment of AML. Ultimately, therapeutic antibodies specifically targeting AML LSC offer the possibility of less toxicity with the potential for cure.
Statement of Benefit to California: 
Acute myeloid leukemia (AML) is an aggressive malignancy of the bone marrow with nearly 13,000 new diagnoses annually in the US and 2,200 in the Collaborative Funding Partner country. Current standard of care for medically fit patients consists of several cycles of high dose chemotherapy, and often includes allogeneic hematopoietic cell transplantation. Even with these aggressive treatments, which cause significant morbidity and mortality, relapse is common and the five-year overall survival is 30-40%, but <10% in patients with relapsed or refractory disease or in the majority of AML patients who are over age 65. The goal of this research proposal is to prepare therapeutic antibodies directed against AML stem cell-specific antigens for IND filing with the FDA and a Phase I clinical trial. There are several potential benefits of this research for California: (1) most importantly, this research has the potential to revolutionize current clinical practice and provide a targeted therapy for AML that offers the possibility of less toxicity with the potential for cure; (2) this research will directly contribute to the California economy by funding a contract manufacturing organization to generate and produce GMP-grade clinical antibody, by employing several individuals who will be essential for the conduct of these studies, and through the purchase of equipment and reagents from California vendors; (3) additional clinical and economic benefits for California will derive from the potential application of clinical agents developed here to a number of other human cancers and cancer stem cells; (4) our animal models indicate that a significant fraction of patients with fatal AML can be cured, resulting in savings on their clinical care plus their return as productive contributors to the California economy; (5) if our therapeutic antibodies show clinical benefit in AML, they will be commercialized, and under CIRM policy, profits derived from treating insured patients and lower cost therapies for uninsured patients, would enrich the state and the lives of its citizens; (6) finally, this research has the potential to maintain California as the national and world-wide leader in stem cell technology.
Progress Report: 
  • Our program is focused on producing new therapeutic candidates to prolong remission and potentially cure highly lethal cancers where patients have few alternative treatment options. We have selected Acute Myelogenous Leukemia (AML) as the initial clinical indication for evaluating our novel therapeutics, but anticipate a full development program encompassing many other types of solid tumor cancers.
  • Our strategy is to develop an antibody that binds to and eliminates the cancer-forming stem cells in leukemia and other solid tumors. While current cancer treatments (e.g. surgery, chemotherapy, radiation) will frequently get rid of the bulk of the tumor, they rarely touch the tiny number of cancer stem cells that actually re-generate the masses of cancer cells that have been eliminated. When the latter occurs, the patient is described as having a relapse, leading to a disease recurrence with poor prognosis. Our strategy is to eliminate the small number of cancer-regenerating stem cells by targeting cell membrane proteins expressed by these cells.
  • We have discovered that many cancer cells coat themselves with a protein called CD47 that prevents them from being eaten and disposed of by the patient’s blood cells. In this context, CD47 can be considered a ‘don’t eat me’ signal that protects the cancer cells from being phagocytosed i.e. ‘eaten’. The antibody we are developing binds to and covers the ‘don’t eat me’ CD47 protein, so that the patient’s blood cells are now able to ‘eat’ the cancer cells by standard physiological responses, and eliminate them from the body.
  • Developing an antibody such as this for use in humans requires many steps to evaluate it is safe, while at the same ensuring it targets and eliminates the cancer forming stem cells. The antibody must also ‘look’ like a human antibody, or else the patient will ‘see’ it as a foreign protein and reject it. To achieve these criteria, we have made humanized antibodies that bind to human CD47. We have shown that the antibodies eliminate cancer cells in two ways: (i) blood cells from healthy humans rapidly “ate” and killed leukemia cells collected from separate cancer patients when the anti-human CD47 antibody was added to a mixture of both cell types in a research laboratory test tube; (ii) the anti-human CD47 antibody eliminates human leukemia cells collected from patients, then transferred into special immunodeficient mice which are unable to eliminate the human tumor cells themselves. In these experiments, the treated mice remained free of the human leukemia cells for many weeks post-treatment, and could be regarded as being cured of malignancy.
  • To show the antibodies were safe, we administered to regular mice large amounts of a comparable anti-mouse CD47 antibody on a daily basis for a period of many months. No adverse effects were noted. Unfortunately our antibody to human CD47 did not bind to mouse CD47, so it’s safety could not be evaluated directly in mice. Since the anti-human CD47 antibody does bind to non-human primate CD47, safety studies for our candidate therapeutic need to be conducted in non-human primates. These studies have been initiated and are in progress. Following administration of the anti-human CD47 antibodies, the non-human primates will be monitored for clinical blood pathology, which, as in humans, provides information about major organ function as well as blood cell function in these animals.
  • The next step after identifying an antibody with strong anti-cancer activity, but one that can be safely administered to non-human primates without causing any toxic effects, is to make large amounts of the antibody for use in humans. Any therapeutic candidate that will be administered to humans must be made according to highly regulated procedures that produce an agent that is extremely “clean”, meaning free of viruses, other infectious agents, bacterial products, and other contaminating proteins. This type of production work can only be performed in special facilities that have the equipment and experience for this type of clinical manufacturing. We have contracted such an organization to manufacture clinical grade anti-human CD47 antibodies. This organization has commenced the lengthy process of making anti-CD47 antibody that can be administered to humans with cancer. It will take another 18 months to complete the process of manufacturing clinical grade material in sufficient quantities to run a Phase I clinical trial in patients with Acute Myelogenous Leukemia.
  • Our program is focused on producing new therapeutic candidates to prolong remission and potentially cure highly lethal cancers where patients have few alternative treatment options. Our strategy is to develop an antibody that will eliminate the cancer stem cells which are the source of the disease, and responsible for the disease recurrence that can occur months-to-years following the remission achieved with initial clinical treatment. The cancer stem cells are a small proportion of the total cancer cell burden, and they appear to be resistant to the standard treatments of chemotherapy and radiation therapy. Therefore new therapeutic approaches are needed to eliminate them.
  • In year 2 of the CIRM award, we have continued to develop a clinical-grade antibody that will eliminate the cancer stem cells in Acute Myelogenous Leukemia (AML). We have identified several antibodies that cause human leukemia cells to be eaten and destroyed by healthy human white blood cells when tested in cell culture experiments. These antibodies bind to a protein called CD47 that is present on the outer surface of human leukemia cells. The anti-CD47 antibodies can eliminate leukemia growing in mice injected with AML cells obtained from patients. We have now extensively characterized the properties of our panel of anti-CD47 antibodies, and have identified the lead candidate to progress though the process of drug development. There are several steps in this process, which takes 18-24 months to fully execute. In the last 12 months, we have focused on the following steps:
  • (i) ‘Humanization’ of the antibody: The antibody needs to be optimized so that it looks like a normal human protein that the patient’s immune system will not eliminate because it appears ‘foreign’ to them.
  • (ii) Large scale production of the antibody: To make sufficient quantities of the antibody to complete the culture and animal model experiments required to progress to clinical safety trials with patients, we have contracted with a highly experienced manufacturing facility capable of such large-scale production. We have successfully transferred our antibody to them, and they have inserted it into a proprietary expression cell that will produce large amounts of the protein. This process is managed through weekly interactions with this contract lab. They send us small amounts of the material from each step of their manufacturing process and we test it in our models to ensure the antibody they are preparing retains its anti-cancer properties throughout production.
  • (iii) Pre-clinical safety studies: The antibody must be tested extensively in animals to ensure it does not cause serious limiting damage to any of the normal healthy tissues in the recipient. We have spent much of the last 12 months performing these types of safety experiments. The antibody has been administered to both mice and non-human primates and we have evaluated their overall health status, as well as analyzing their blood cells, blood enzyme levels, and urine, for up to 28 days. We have also collected samples of their organs and tissues to evaluate for abnormalities. Thus far, these assessments have appeared normal except for the development of a mild anemia a few days after the initial antibody injection. Subsequent experiments indicate that this anemia can be managed with existing approved clinical strategies
  • (iv) Determination of optimal dose: We have used mice injected with human cancer cells from AML patients, and determined how much antibody must be injected into these mice to produce a blood level that destroys the leukemia cells. This relationship between antibody dose and anti-cancer activity in the mouse cancer model enables us to estimate the dose to administer to patients.
  • Hematologic tumors and many solid tumors are propagated by a subset of cells called cancer stem cells. These cells appear to be resistant to the standard cancer treatments of chemotherapy and radiation therapy, and therefore new therapeutic approaches are needed to eliminate them. We have developed a monoclonal antibody (anti-CD47 antibody) that recognizes and causes elimination of these cancer stem cells and other cells in the cancer, but not normal blood-forming stem cells or blood cells. Cancer stem cells regularly produce a cell surface ‘invisibility cloak’ called CD47, a ‘don’t eat me signal’ for cells of the native immune system. Anti-CD47 antibody counters the ‘cloak, allowing the patient’s natural immune system eating cells, called macrophages, to eliminate the cancer stem cells.
  • As discussed in our two-year report, we optimized our anti-CD47 antibody so that it looks like a normal human protein that the patient’s immune system will not eliminate because it appears ‘foreign’. In this third year of the grant, we initiated the pre-clinical development of this humanized antibody, and assigned the antibody the development name of Hu5F9. Our major accomplishments in the third year of our grant are as follows:
  • (i) In addition to the hematological malignancies we have studied in previous years, we have now demonstrated the Hu5F9 is effective at inhibiting the growth and spread throughout the body [metastasis] of a large panel of human solid tumors, including breast, bladder, colon, ovarian, glioblastoma [a very aggressive brain cancer], leiomyosarcoma, head & neck squamous cell carcinoma, and multiple myeloma.
  • (ii) We have performed extensive studies optimizing the production and purification of Hu5F9 to standards compatible with use in humans, including that it is sterile, free of contaminating viruses, microorganisms, and bacterial products. We will commence manufacturing of Hu5F under highly regulated sterile conditions to produce what is known as GMP material, suitable for use in humans.
  • (iii) Another step to show Hu5F9 is safe to administer to humans is to administer it to experimental animals and observe its effects. We have demonstrated that Hu5F9 is safe and well tolerated when administered to experimental animals. Notably, no major abnormalities are detected when blood levels of the drug are maintained in the potentially therapeutic range for an extended duration of time.
  • (iv) We have initiated discussions with the FDA regarding the readiness of our program for initiating clinical trials, which we anticipate to start in the first quarter of 2014. To prepare for these trials we have established a collaboration between the Stanford Cancer Institute and the University of Oxford in the United Kingdom, currently our partners in this CIRM-funded program.
  • To our knowledge, CD47 is the first common target in all human cancers, one which has a known function that enables cancers to grow and spread, and one which we have successfully targeted for cancer therapy. Our studies show that Hu5F9 is a first-in-class therapeutic candidate that offers cancer treatment a totally new mechanism of enabling the patient’s immune system to remove cancer stem cells and their metastases.

Development of Highly Active Anti-Leukemia Stem Cell Therapy (HALT)

Funding Type: 
Disease Team Research I
Grant Number: 
DR1-01430
ICOC Funds Committed: 
$19 999 826
Disease Focus: 
Blood Cancer
Cancer
Collaborative Funder: 
Canada
Stem Cell Use: 
Cancer Stem Cell
oldStatus: 
Active
Public Abstract: 
Leukemias are cancers of the blood forming cells that afflict both children and adults. Many drugs have been developed to treat leukemias and related diseases. These drugs are often effective when first given, but in many cases of adult leukemia, the disease returns in a form that is not curable, causing disability and eventual death. During the last few years, scientists have discovered that some leukemia cells possess stem cell properties that make them more potent in promoting leukemia growth and resistance to common types of treatment. These are called leukemia stem cells (LSC). More than in other cancers, scientists also understand the exact molecular changes in the blood forming cells that cause leukemias, but it has been very difficult to translate the scientific results into new and effective treatments. The main difficulty has been the failure of existing drugs to eliminate the small numbers of LSC that persist in patients, despite therapy, and that continue to grow, spread, invade and kill normal cells. In fact, the models used for drug development in the pharmaceutical industry have not been designed to detect drugs or drug combinations capable of destroying the LSC. Drugs against LSC may already exist, or could be simple to make, but there has not been an easy way to identify these drugs. Recently, physicians and scientists at universities and research institutes have developed tools to isolate and to analyze LSC donated by patients. By studying the LSC, the physicians and scientists have identified the molecules that these cells need to survive. The experimental results strongly suggest that it will eventually be possible to destroy LSC with drugs or drug combinations, with minimal damage to most normal cells. Now we need to translate the new knowledge into practical treatments. The CIRM Leukemia Team is composed of highly experienced scientists and physicians who first discovered LSC for many types of leukemia and who have developed the LSC systems to test drugs. The investigators in the Team have identified drug candidates from the vigorous California pharmaceutical industry, who have already performed expensive pharmacology and toxicology studies, but who lack the cells and model systems to assess a drug’s ability to eliminate leukemia stem cells. This Team includes experts in drug development, who have previously been successful in quickly bringing a new leukemia drug to clinical trials. The supported interactive group of physicians and scientists in California and the Collaborative Funding Partner country has the resources to introduce into the clinic, within four years, new drugs for leukemias that may also represent more effective therapies for other cancers for the benefit of our citizens.
Statement of Benefit to California: 
Thousands of adults and children in California are afflicted with leukemia and related diseases. Although tremendous gains have been made in the treatment of childhood leukemia, 50% of adults diagnosed with leukemia will die of their disease. Current therapies can cost tens of thousands of dollars per year per patient, and do not cure the disease. For the health of the citizens of California, both physical and financial, we need to find a cure for these devastating illnesses. What has held up progress toward a cure? Compelling evidence indicates that the leukemias are not curable because available drugs do not destroy small numbers of multi-drug resistant leukemia stem cells. A team approach is necessary to find a cure for leukemia, which leverages the expertise in academia and industry. Pharmaceutical and biotech companies have developed drugs that inhibit pathways known to be involved in leukemia stem cell survival and growth, but are using them for unrelated indications. In addition, they do not have the expertise to determine whether the inhibitors will kill leukemia stem cells. The Leukemia Team possesses stem cell expertise and has developed state of the art systems to determine whether drugs will eradicate leukemia stem cells. They have also have access to technologies that may allow them to identify patients who will respond to the treatment. The development plan established by the Leukemia Disease Team will also serve as a model for the clinical development of drugs against solid tumor stem cells, which are not as well understood. In summary, the benefits to the citizens of California from the CIRM disease specific grant in leukemia are: (1) direct benefit to the thousands of leukemia patients (2) financial savings due to definitive treatments that eliminate the need for costly maintenance therapies
Progress Report: 
  • Development of Highly Active Leukemia Therapy (HALT)
  • Leukemias are cancers of the blood forming cells that affect both children and adults. Although major advances have been made in the treatment of leukemias, many patients still succumb to the disease. In these patients, the leukemias may progress despite therapy because they harbor primitive malignant stem-like cells that are resistant to most drugs. This CIRM disease specific grant aims to develop a combination of highly active anti-leukemic therapy (HALT) that can destroy the drug-resistant cancer stem-like cells, without severely harming normal cells.
  • During the current year of support, substantial progress has been made in achieving this goal. The CIRM investigators have shown that two different drugs that inhibit different proteins in leukemia stem cells can sensitize them to chemotherapeutic agents, and block their ability to self-renew. The CIRM investigators have also demonstrated that two different antibodies against molecules on the surface of the leukemia cells can inhibit their survival in both test tube experiments and in mouse models.
  • Extensive experiments are underway to confirm these promising results. The results will enable the planning and implementation of potentially transforming clinical trials in leukemia patients, during the period of CIRM grant support.
  • During the past 12 months, our disease team has made further progress in
  • the development of stem cell targeted treatment for chronic lymphocytic
  • leukemias and other leukemias. Stem cells express some molecules on the
  • surface that are different from the corresponding molecules on adult
  • cells. The ROR1 molecule is highly expressed by malignant cells from
  • patients with chronic lymphocytic leukemia, as well as by progenitor cells
  • from other forms of leukemia and lymphoma. It is not expressed by normal
  • adult cells. With the support of the CIRM Disease Team grant, the
  • cooperating investigators have prepared monoclonal antibodies against the
  • ROR1 molecule, that are potent and specific. In animal models, the
  • antibodies can retard leukemia growth and spread. Unlike other anti-cancer
  • drugs, the new antibodies are not toxic for normal bone marrow cells.
  • Thus, they can potentiate the action of other agents used for the
  • treatment of leukemia.
  • The disease team is now focused on the pre-clinical development, safety
  • testing, and scale-up manufacturing of our new, promising agents, in
  • preparation for their introduction into the clinic.
  • During the past 12 months, our disease team has made further progress in
  • the development of stem cell targeted treatment for chronic lymphocytic
  • leukemias and other leukemias. Stem cells express some molecules on the
  • surface that are different from the corresponding molecules on adult
  • cells. The ROR1 molecule is highly expressed by malignant cells from
  • patients with chronic lymphocytic leukemia, as well as by progenitor cells
  • from other forms of leukemia and lymphoma. It is not expressed by normal
  • adult cells. With the support of the CIRM Disease Team grant, the
  • cooperating investigators have prepared a humanized monoclonal antibody against the
  • ROR1 molecule, that is potent and specific. In animal models, the
  • antibodies can retard leukemia growth and spread. Unlike other anti-cancer
  • drugs, the new antibodies are not toxic for normal bone marrow cells.
  • Thus, they can potentiate the action of other agents used for the
  • treatment of leukemia.
  • The disease team is now focused on the pre-clinical development, safety
  • testing, and scale-up manufacturing of our new, promising agents, in
  • preparation for their introduction into the clinic.
  • During the past 12 months, our disease team has made further progress in
  • the development of stem cell targeted treatment for chronic lymphocytic
  • leukemias and other leukemias. Stem cells express some molecules on the
  • surface that are different from the corresponding molecules on adult
  • cells. The ROR1 molecule is highly expressed by malignant cells from
  • patients with chronic lymphocytic leukemia, as well as by progenitor cells
  • from other forms of leukemia and lymphoma. It is not expressed by normal
  • adult cells. With the support of the CIRM Disease Team grant, the
  • cooperating investigators have prepared a humanized monoclonal antibody against the
  • ROR1 molecule, that is potent and specific. In animal models, the
  • antibodies can retard leukemia growth and spread.
  • The disease team has now finalized the pre-clinical development, safety
  • testing, and scale-up manufacturing of our new, promising agent, in
  • preparation for their introduction into the clinic.

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