Our foundation funded two exciting projects in 2011. The first was in support of Dr. Ronald Levy, Professor and Chief, Division of Oncology at Stanford University. Ron and team are applying his successful research in the use of monoclonal antibody technology for the treatment of B cell lymphomas to now target an enhancement to this approach for HER2 breast cancer. Ron’s prior work led to the development of rituxamab, which has become the standard of care for B cell lymphomas, saving many lives since its creation.
The second project helped launch an entirely new approach to clinical trials of recently developed and promising new drugs. The trial is known as I-SPY 2 (www.ispy2.org) and its goal is to bring the latest drugs to patients with early stage or newly discovered breast cancer The value of this is twofold as it will allow access to these treatments as a new patient begins the fight with their disease, while also more effectively measuring the impact of these drugs by treating a patient prior to a tumor’s surgical removal. By reversing the traditional order of therapy in this fashion, the efficacy of a new drug can be seen far more readily in the actual tumor’s response to treatment. Spearheaded by Dr. Laura Esserman, Professor of Surgery and Radiology from the University of California at San Francisco, leading cancer centers from across the United States will launch the I-SPY 2 trial this year. Nadia’s Gift is funding this program for the Mayo Clinic in Rochester, Minnesota.
- Grants made in 2010
- A Potential Link to a New Therapeutic Strategy
- Targeting an Essential Growth Mechanism of Breast Cancer Cells
- A Follow-on Grant to Inducing “Senescence” in Breast Cancer Tumor
- Grants made in 2009
- Inducing “Senescence” in Breast Cancer Tumor Cells
- Targeting breast cancer stem cells via stem cell-specific resistance and survival mechanisms
- A Novel Vaccine for Metastatic Breast Cancer
A Potential Link to a New Therapeutic Strategy
Dr. Lawrence Recht
Professor of Neurology & Clinical Neurosciences
Judah Folkman, cancer researcher and physician, contended in the early 1970’s that cancers could not grow without blood vessels to feed them. This process is called angiogenesis. Since his discovery, cancer biologists have sought to better understand the molecules that are involved in helping blood vessels grow and feed tumors. Using Folkman’s ideas led to the development of “antiangiogenic” treatments, such as Avastin, that prevent the growth of blood vessels that feed cancer cells. This approach revolutionized the field of cancer therapeutics.
It is generally believed that the driving force underlying the process of making new blood vessels is “hypoxia”, defined as a lack of oxygen. Without oxygen, cells cannot survive. Scientists have learned that lowering the levels of oxygen in tissue causes an increase in molecules that release factors that promote angiogenesis (blood vessel growth).
It is not clear why no one has, as yet, attempted to link the process of angiogenesis with the equally important process of cancer metabolism. Metabolism can be defined as the way in which cells make the necessary energy (usually in the form of sugar or glucose) to survive. For maximal metabolism in the human body, cells require ample blood flow to receive their crucial supply of oxygen.
Because cancer cells are dividing rapidly, they should benefit from getting as much energy from sugar (glucose) as possible. However, cancer cells for some reason choose not to process glucose in this way, instead bypassing the part of the cell (mitochondria) that usually processes sugar most efficiently to make energy. Cancer cells choose this much less efficient shortcut, even when oxygen is plentiful, in complete opposition to how normal cells flourish.
This paradoxical situation, which was noted over eighty years ago by Otto Warburg, occurs in all cancers and results in the environment becoming overloaded with acid molecules (since the shortcut results in the production of lactic acid). Why a rapidly proliferating tissue such as cancer cells, that should require as much energy as possible, would choose such an inefficient and toxic method of energy production remains a mystery.
Based on the unique clinical responses of cancers to molecules such as Avastin which block blood vessel growth, I and my colleagues have proposed a highly novel hypothesis in which blocking angiogenesis results in a marked change in the cancer’s metabolism. The change forces the cells to use their mitochondria to make glucose which paradoxically, will markedly slow the cancer process. I have denoted this process as the “Warburg-Folkman” effect.
My collaborators and I believe that forced mitochondrial utilization in the production of glucose puts the cancer at a disadvantage and makes it at least for some interval, extremely vulnerable to further insults such as chemotherapy. By linking blood flow and energy metabolism, our hypothesis suggests a myriad of possible new paths for cancer therapies.
The difficulty with getting traction for any revolutionary theory is that hard scientific proof is needed. This means we need to demonstrate that cancers start using their mitochondria after being exposed to agents such as Avastin. Although this seems simple, until recently there was no way to assess cell metabolism in the live animal subject. At Stanford, a cutting edge technology is being developed that will overcome this obstacle and allow us to use MRI technology to follow the fate of glucose in the animal subject.
We have partnered with the scientists who have developed this specialized MRI technology and have agreed to go forward with a defining experiment. This experiment will involve following the fate of a molecule involved in glucose metabolism—pyruvate—that has been labeled so as to be detectable by MRI. This molecule can be taken up by the cancer cells and then used for energy just like glucose. We predict that cancer cells will bypass their mitochondria and break this molecule down into lactate. After administering Avastin, however, we predict that more of this pyruvate will be converted to the molecule bicarbonate, indicating it has been processed by the mitochondria. Affirming the validity of this hypothesis about how cancer cells are nourished and grow in animals will therefore allow us to design experiments in the clinic for new cancer treatment therapies.
Return to topRoel Nusse, PHD, Professor & Chairman
Department of Developmental Biology
Stanford University School of Medicine
An essential hallmark of cancer cells is their ability to divide without limits. Normal cells become stationary and specialized to generate form and function of tissue; but cancer cells keep on proliferating, thereby forming a lethal threat. Interestingly however, normal organs do contain a minor population of cells that also have the potential to divide without limits. These are the stem cells, the cells that are precursors to specialized cells. In contrast to cancer cells however, the proliferation of normal cells is under tight control. While they can divide forever, they only do so when there is demand for more cells, such as after tissue damage. In that sense, cancer cells differ from stem cells, as they escape this type of control. What causes this behavior? Can we understand the mechanisms by which cells become independent to outside cues? This ability to proliferate forever has been termed self-renewal, because the cells make exact copies of themselves rather than becoming different. Because self-renewal is such an important property of cancer cells, there is great interest in understanding its mechanism and by doing so, we might be able to interfere with tumor cell growth.
The aim of this project is to identify the molecular mechanisms that confer self-renewing behavior to breast cancer cells, with the ultimate goal of interfering with their function and therefore with the growth of cancer cells. Based on this hypothesis, we intend to examine the connections between cancer and stem cells using an approach based on animal models and extended to human cancers. More specifically, we will explore data obtained in our lab that show that so-called Wnt growth factors are essential for the self-renewal of normal mammary stem cells, implying that these factors also promote the self-renewal of breast cancer stem cells. Wnt proteins are important stem cell factors for which we have unique expertise. There are several molecules known that inhibit Wnt signals and we will test to what extent these molecules interfere with cancer stem cell growth.
This work may lead to a new way to interfere in the proliferation of breast cancer cells and therefore to therapeutic intervention. Our research will also use novel cell culture methods to study the proliferation of breast cells. These cell culture methods will be important in designing screens for new drugs that interfere with the growth of cells.
Return to topBeverly Mitchell, MD
George E. Becker, Professor of Medicine
The initial project in the Mitchell lab, funded by Nadia’s Gift, was based on observations in cultured breast cancer cell lines. Notably, a drug that depleted GTP, a building block of RNA and DNA, caused these cells to undergo what we term “senescence” or irreversible cell cycle arrest. These cells are unable to grow when given fresh medium or put into an animal. Thus, they are functionally inert and one of the objectives of cancer chemotherapy is to induce this kind of senescence in tumors in patients. The drug that was used in tissue culture has also been used in patients with blood cancers in a recent clinical trial in which the Mitchell lab participated. It was a trial to evaluate possible toxicity and we learned that the drug was not toxic in humans at doses that greatly exceeded what is necessary to inhibit its target enzyme.
We now propose to test the effects of this drug on human breast tumors initiated from breast cancer stem cells, which will be implanted in mice. If we can replicate the effects of the drug on tumors in an experimental animal, it would go a long way towards positioning the drug for further testing in solid tumors such as metastatic breast cancer. We will collaborate with Dr. Max Diehn, also a recipient of a seed grant from Nadia’s Gift. Dr. Diehn will isolate breast cancer stem cells by sorting them into very pure populations. He will then inject them into the mammary fat pads of immunodeficient mice that will accept human tumor cells. We will treat the mice with the drug by mouth twice a day for two weeks at increasing time intervals after the tumor cells are implanted. We will look for inhibition of tumor growth when tumors are both small and at later stages of tumor development, using all the safeguards to insure that the mice do not experience discomfort (i.e. we do not let the tumors get very large). We will analyze the tumors for whether the drug is hitting its target, whether the tumor cells are undergoing senescence or cell death, and whether we can understand the precise biochemical mechanism by which the drug is acting. These experiments, although conceptually simple, would be carried out over the next year.
If we find that the drug induces the same effects in primary human breast cancer cells implanted in mice as it does in culture, we would strongly advocate that the drug go into Phase II trials for metastatic breast cancer. If we get to that point, we would also analyze its effects on circulating tumor cells which can be isolated from small amounts of peripheral blood by new techniques developed at Stanford. We have a huge advantage in that the drug has already been tested in humans and shown to be safe.
Return to topBeverly Mitchell, MD
The ideal objective in cancer therapy is to achieve selective killing of the tumor cells without inhibiting the survival of normal tissues. Increasing evidence suggests that, in addition to killing, causing cancer cells to “senesce” or age will reduce tumor growth and prevent metastasis. Our laboratory has been working with breast cancer cell lines that grow in an unregulated fashion. There is a protein called nucleostemin that is expressed at high levels in breast cancers and other tumors. Nucleostemin regulates a critical cell survival protein called p53. We have found that inhibitors of the synthesis of specific nucleotides that are important for tumor and normal cell growth cause nucleostemin to be degraded. The disappearance of nucleostemin is associated with increases in p53 and, in breast cancer cells, this increase is associated with “senescence” instead of cell death. This means that the tumor cells, instead of being disbursed randomly in a tissue culture plate, form ducts that look like normal ductal cells in the breast. They also stop growing.
This observation has the potential to be taken on to a clinical study after validation in a mouse tumor model. We will first use breast cancer cells that are derived from human tumors and grown in the immunodeficient mice. We will treat mice with inhibitors of nucleotide synthesis and examine the human breast cancer cells for specific evidence of senescence. We will also look at effects of these inhibitors on nucleostemin and p53 levels, as well as on metastasis and survival. If we can reproduce the effects that we see in cultured cells in the mouse model, we would then take this approach into a clinical trial in refractory breast cancer. Inhibitors of nucleotide synthesis have been approved for use in other clinical settings and a clinical trial would be based on demonstrating efficacy in the mouse model.
Return to topMax, Diehn, MD/PhD
A growing body of evidence indicates that cancer stem cells (CSCs) co-opt defense and survival mechanisms found in normal stem cells in order to resist commonly used cancer treatments such as chemotherapy and radiotherapy. Our lab is interested in studying these resistance mechanisms and in developing methods to overcoming them in the clinic. In particular, we are interested in two stem cell resistance/survival mechanisms. The first involves defenses against reactive oxygen species (ROS), which are highly reactive chemical species that can injure a cell’s genetic material. We and others have shown that normal stem cells protect their genomes by generating low levels of ROS and by expressing enhanced ROS defenses. Recently, we have published data indicating that this also appears to be true for breast cancer stem cells. This observation carries important implications for the treatment of breast cancer patients, since radiotherapy and many forms of chemotherapy kill cancer cells through the induction of ROS. Along these lines, we have shown that interference with ROS defenses in CSCs sensitizes them to ionizing radiation in vitro. We next plan to evaluate if inhibition of ROS defenses in CSCs could be a viable strategy for sensitizing CSCs in the clinic. Specifically, using a murine breast cancer model we will test if L-S, R-Buthionine Sulfoximine (BSO), a drug that depletes ROS defenses, can radiosensitize tumors and deplete CSCs in vivo. BSO has been safely given to human subjects in the past, and if these studies are positive, we plan to develop a clinical protocol testing the efficacy of combined treatment with radiation and BSO in human breast cancer patients.
The second stem cell resistance mechanism which we plan to study involves targeting self-renewal and pro-survival pathways to CSCs. Self-renewal is the process by which normal and malignant stem cells divide to produce more stem cells. In unpublished work we have identified a gene expression signature shared by CSCs and normal stem cells which contains genes linked to stem cell self-renewal and survival. We have already shown that inhibition of one of the genes in this signature, Stat3, significantly limits CSC survival. We next wish to functionally screen the remaining targets in the CSC self-renewal/survival signature to determine which could serve as useful clinical targets. First, we will assess the importance of these genes to CSC survival in vitro and then we will test the positive candidates in vivo using murine models of breast cancer. For a number of these targets, drugs are already clinically available and are being used for non-oncologic indications, potentially allowing rapid development of clinical protocols if pre-clinical experiments indicate activity against CSCs. We plan to develop at least one clinical protocol for breast cancer patients using the most promising candidate that comes out of our screen.
Return to topEllie Guardino, MD, PhD
There is ample evidence that women who develop breast cancer have defects in their immune system, suggesting that they lack the normal immune “surveillance” that is an important safeguard against cancer. These same immune deficiencies may explain why breast cancer so often recurs following early treatment. Thus, a rational approach for breast cancer therapy and prevention is to develop a vaccine that will boost or “educate” the immune system to recognize and destroy breast cancer cells before they metastasize.
The proposed clinical study uses a novel gene therapy that delivers a viral vaccine called MVA-BN-HER2 to treat patients with HER2 positive metastatic breast cancer. Preliminary data from previous studies in the laboratory showed that a tumor associated antigen for breast cancer (HER2) can be isolated and targeted with immune therapies. Proof of concept was achieved when a humanized anti-HERE2 antibody was developed that demonstrated clinical benefit in humans. The goal of this current study is to produce data to further support the concept that patients who receive HER2 vaccination can overcome tolerance to breast tumors and generate HER2-specific immune response that correlates positively with clinical benefit. This trial will provide a platform for development of other immune vaccines in HER2 negative breast cancer and may eventually lead to the development of a vaccine to prevent breast cancer in patients with increased risk of developing the disease.
Dr. Guardino will recruit patients to participate in this trial who have HER2 positive metastatic breast cancer and who have stable disease following chemotherapy. Patients may be on biologic therapy such as trastuzumab or lapatinib. After baseline imagining studies and blood work are performed, patients will receive MVA-BN-HER2 breast cancer vaccine every three weeks for a total of three doses. They will be monitored for side effects and tested for signs of therapeutic response. Study investigators will specifically test for appropriate changes in the immune system that suggest positive immune response and clinicians will follow up with imaging studies to look for breast cancer recurrence.
Stanford has developed state-of-the-art technologies to study specialized immune cells, like B cells and T cells. In collaboration with leading immunologists at Stanford and other institutions, Dr. Guardino and her collaborators hope to identify the limitations of the immune system that result in breast cancer development and recurrence and to validate methods that will demonstrate the vaccine’s ability to overcome these limitations. If successful, this vaccine could be a major advancement in the treatment of the 25%-30% of breast cancers considered most aggressive and could eventually be adapted for use in other subtypes of breast cancer. The Stanford Cancer Center is uniquely positioned to accelerate the development of vaccines and immune therapies to treat breast cancer. Immunologists are conducting clinical immunotherapy and vaccine studies in a number of other diseases and have established protocols for evaluating immune responses in blood-related cancers and other solid tumors. For example, anti-DC20 antibody was developed in the laboratory of Dr. Ron Levy and vaccines are being studied as a possible curative treatment for patients with lymphoma. Researchers are also employing methods that use specialized immune cells, called dendritic cells, which present a target molecule to immune cells that can track down and destroy specific molecular targets linked to cancer. These and other studies are providing important clues to the potential of vaccine therapy and will help inform Stanford’s methodology for current and future vaccines directed at breast cancer.
Over the next several years, Dr. Guardino will enlist the best and brightest Stanford faculty to join her novel breast cancer research program, which will include clinical trials for new vaccines and other promising therapies. Eventually, Stanford’s breast cancer research program will require new facilities with advanced equipment to scale up vaccine production as well as personnel to carry out experimental protocols. As these efforts intensify, faculty will rely to an even greater extent on the generosity of concerned and committed individuals in the community to guarantee that physician-scientists like Dr. Guardino have the resources they need to translate lifesaving discoveries to patients who need them.
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