Scientific Highlights - 2007

General Areas of Research

Since its establishment, GSCC-CMMI has been a leading research institution in the identification, development, and application of specialized biological products, called monoclonal antibodies, which are selected proteins made by the body as part of the immune response, especially to attack and neutralize infectious organisms. The antibodies can be made against target molecules, or receptors, expressed in higher amounts by cancer cells as compared to their normal counterparts. This quantitative difference has enabled these antibodies to differentiate cancer cells from normal ones, thus being selective delivery agents for cytotoxic agents, such as radiation and chemotherapy. In addition, these antibodies have been shown to be anticancer agents by themselves, causing control of cancer growth and even killing cancer cells by a variety of mechanisms, some immunological and others involving interference with the function of the receptor molecules targeted by these antibodies.

GSCC-CMMI scientists, under the leadership of Dr. David M. Goldenberg, have been involved in not only developing new and different antibodies against different cancers, but also in studying how they function, alone or as carriers of isotopes or drugs, and how they can be reengineered to improve their efficacy and reduce toxicity and immunogenicity. Not all antibodies are alike, even when they are made against the same cancer target, since there are various components and protein sequences of different parts of antibodies, and this results in differences in binding to the target, retention in the body, etc. Our scientists study all of these aspects as part of the knowledge needed to advance these new agents to clinical trials.

GSCC-CMMI not only performs this early, fundamental research on antibodies and antibody conjugates (with isotopes and drugs), but it also collaborates with many other researchers and physicians in both the U.S. and foreign countries to translate this research into clinical applications. Past clinical trials at our center have involved the evaluation of new antibodies in patients with lymphomas and with cancers of the colon-rectum, pancreas, ovary, and thyroid. Collaborative preclinical and clinical studies are now underway in cancers of the kidney, colon-rectum, thyroid, lung, and prostate, as well as lymphomas and myelomas, with researchers as close as NY Hospital-Cornell Medical Center in NYC, and as far away as Melbourne, Australia. This international cooperation results in sharing of new knowledge by joint meetings and conference, training young investigators at our center (for example, from France, Germany, and The Netherlands). GSCC-CMMI also organizes an International Conference on Cancer Therapy with Antibodies and Immunoconjugates every two years, and has published the proceedings of this meeting, attended by about 200 scientists and physicians from around the world, in prestigious cancer journals. This meeting has been supported both by industry, the National Cancer Institute, and the New Jersey Commission on Cancer Research. GSCC-CMMI scientists are very prolific in publishing their work and findings in the most prominent cancer journals, including Cancer Research, Clinical Cancer Research, International Journal of Cancer, Blood, and Journal of Nuclear Medicine, as well as invited chapters in books and reviews in major journals.

Specific Topics

Pancreatic Cancer. Pancreatic cancer is an insidious disease with a particularly high mortality rate. In large measure, this is due to the location of the pancreas in the retroperitoneum, where the tumor can grow in a silent fashion. Symptoms that might suggest the patient seek medical assistance are usually not evident until an advanced stage of tumor growth, and even at this point in time, the clinical presentation can be vague and representative of varying pathologies. Combined with the fact that at present, there are no effective means for treatment of this disease, patient outcomes are generally poor; 5-year survival is less than 5%. However, if detected early when the cancer is still restricted to the pancreas, treatment by surgical resection, with or without chemo- and radiation-therapy, can improve 5-year survival to roughly 25%; yet even this statistic is not very encouraging. Consequently, considerable effort has been placed on finding new methods to detect pancreatic cancer at an early stage of tumor growth before becoming invasive. Dr. David V. Gold previously developed a monoclonal antibody, PAM4, which may provide for early detection, diagnosis, imaging, and therapy of this disease. The antibody is reactive with a target-antigen present in greater than 90% of pancreatic cancers, and yet is not found in normal pancreas or other normal organs. Together with other GSCC investigators, Dr. Gold is now developing a novel PAM4-based antibody construct called TF10, to target imaging and/or therapeutic materials to the sites of tumor growth. Recent preclinical studies have demonstrated a vastly superior imaging of pancreatic cancer achieved with TF10-pretargeting such that we are ready to bring this reagent to clinical trials, first in a population of patients with confirmed pancreatic cancer and then, if successful, in a population of patients with symptoms that are suggestive of pancreatic cancer. Dr. Gold's work is supported in part by individual grants from the National Cancer Institute.

Multiple Myeloma and Lymphoma. Dr. Rhona Stein is directing her research efforts towards the development of approaches for using monoclonal antibodies to optimum advantage as therapeutic agents for the treatment of cancers. In collaboration with Dr. David Goldenberg, she is concentrating on the use of unlabeled or naked antibodies for the treatment of hematologic malignancies including non-Hodgkin's lymphomas and multiple myeloma, as well as evaluation of combined modality treatments to assess whether monoclonal antibodies can enhance the efficacy of chemotherapy. Dr. Stein recently showed the effectiveness of milatuzumab, an antibody that targets the cell surface protein CD74, in preclinical animal models of human multiple myeloma and non-Hodgkin's lymphoma. Combination of milatuzumab with chemotherapeutic drugs (bortezomib, doxorubicin, dexamethasone, and lenalidomide) led to significantly increased efficacy compared to the agents given singly in laboratory tests. Milatuzumab also shows considerable promise as a drug immunoconjugate. A doxorubicin conjugate of milatuzumab yielded long-term survival in the majority of mice bearing human non-Hodgkin's lymphomas and multiple myeloma. Moreover, studies comparing milatuzumab to antibodies targeting the cell surface protein, CD20, such as rituximab (which is currently in widespread clinical use), demonstrated that activity is augmented when anti-CD74 and anti-CD20 monoclonal antibodies are combined. These preclinical studies have demonstrated that milatuzumab is an effective therapeutic agent that may be of significant value for treatment of B-cell malignancies, such as lymphoma and multiple myeloma, when used alone or in combination with other known therapeutics for these diseases. Milatuzumab is currently in clinical evaluation for therapy of multiple myeloma, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia. Reports of these studies have been presented by Drs. Stein and Goldenberg at the 2007 annual meetings of the American Society of Hematology and the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, a joint meeting of the American Association for Cancer Research, National Cancer Institute, and the European Organization for Research and Treatment of Cancer. This work is being funded under a program project grant from the National Cancer Institute. This grant also includes collaborative studies with Dr. Mitchell Smith at the Fox Chase Cancer Center and Dr. Myron Czuczman at Roswell Park Cancer Institute, in which we are cooperatively studying methods and antibody combinations for the improved therapy of lymphomas.

Novel Antibody-Based Methods for Imaging and Treatment of Cancer. Dr. Robert M. Sharkey, working together with Dr. Habibe Karacay, is focusing on a novel technique capable of delivering compounds selectively to tumors. This method, called pretargeting, uses a specialized antibody prepared by molecular engineering, a bispecific antibody because it can bind not only to tumor cells, but to a small, synthetic compound. The bispecific antibody is first targeted to a tumor, and then the small compound carrying a radionuclide is given. This pretargeting method has been shown to be a more sensitive and specific method for detecting tumors than the more commonly used nuclear imaging methods, and was the subject of an article published by the GSCC team in Nature Medicine. Pretargeting can also be used to target radiation selectively to tumors for improved therapy. Drs. Sharkey and Karacay have expanded their preclinical investigations to include lymphoma and pancreatic cancers, both projects being supported by NCI awards. Dr. Karacay has initiated new studies with investigators at Vanderbilt University and the New Jersey Institute of Technology for pretargeting nanoparticles. On the clinical front, Dr. Sharkey was awarded a grant from the National Cancer Institute to fund the initiation of therapy studies in patients with gastrointestinal cancers, in collaboration with clinical investigators at the Lombardi Comprehensive Cancer Center at Georgetown University in Washington, DC. Dr. Sharkey is working closely with investigators in the Netherlands, France, and Germany to develop clinical trials that will evaluate therapy of gastrointestinal and lung cancers, as well as imaging studies in gastrointestinal cancers. New grant support is being sought to initiate clinical studies in collaboration with Mount Sinai Medical Center in New York City for the treatment of pancreatic cancer.

Combination therapy with radiolabeled and unlabeled antibodies. Both unconjugated antibodies to CD20 and radiolabeled antibodies to CD20 have been approved for therapy of B-cell lymphomas. Since they act by different mechanisms, it would probably be an advantage to combine agents of this type. However, the unconjugated antibody will inhibit the binding of a radiolabeled antibody to the same antigen, so the combination should optimally use a radiolabeled antibody to a different antigen. Drs. Jules Mattes and David Goldenberg selected CD22 as the other target, since radiolabeled anti-CD22 previously was shown to be an effective agent, alone, in patients. This was combined with an unlabeled anti-CD20 antibody. The radiolabel used was 90-yttrium, which emits high-energy beta particles that are suitable to treat large tumor masses. In an animal model, this combination produced markedly improved therapy compared to either agent alone, with the majority of mice being cured. Large, rapidly growing tumors were treated effectively. This approach may be applicable to the clinic not only for B-cell lymphoma but also for other tumor types.

Effect of cross-linking antigens on the surface of tumor cells. It was reported by investigators at GSCC and other institutions that cross-linking of antigens on the surface of tumor cells, by antibodies or other agents, can induce the death of those cells. This probably occurs via apoptosis, a biochemical process that results in the death of the cell. Dr. Jules Mattes has further examined this effect, using antibodies and other novel antibody-derived cross-linking agents. He was interested not only in the induction of apoptosis, but also in the induction of antibody internalization into the cell, which could be useful for delivering toxic agents. Using lymphoma target cells, there was apoptosis induction with certain cell lines, but only at a relatively low level. Antibody internalization was also induced to a small extent. The major effect of cross-linking was that it greatly reduced the dissociation of the antibody from the cell, meaning that the antibody was retained on the cell surface for a much longer period. Prolonged retention would be expected to increase the therapeutic effect of the antibody, so this information may be useful in the development of antibodies for clinical use.

Angiogenesis and Metastasis. Dr. Alice Taylor has continued her investigation of the role of Placenta Growth Factor (PlGF) in the pathology of cancer. Previously, her laboratory showed that PlGF enhanced formation of the new blood vessels essential for tumor growth. In addition, Dr. Taylor found that PlGF stimulates tumor cell motility and invasive activity, which are characteristic of metastasizing cancer cells. In ongoing experiments, she is determining which cellular machinery PlGF 'turns on' to produce this metastatic behavior. In addition, Dr. Taylor is pursuing the further development of small proteins that block P1GF and similar growth factors. She used the small proteins to treat mice bearing a human lymphoma. The treatment increased the proportion of surviving mice (33% survival in controls, vs. 67% survival in treated) and prolonged the time until the first death from 7 weeks to 12 weeks. Mice with human breast cancers implanted in their mammary glands, rather than under the skin, were also treated with the PlGF-blocking proteins. The treatment inhibited lung metastases by 82% and the primary breast tumors were 19% smaller than controls. Dr. Taylor is investigating the exact way that the PlGF-blocker affects cancer cells and the tumor environment, so that this new category of drugs can be brought to clinical trials soon.

Chemotherapy: Resistance and Enhancement. Cancer is usually treated by the use of drugs and/or radiation therapy. Unfortunately, most of the time these treatments will fail because the tumor is sufficiently resistant so that dose limiting adverse side effects are reached before a cancer-killing level of therapy can be achieved. At the present time, gemcitabine (GEM) is considered the front-line, drug of choice for treatment of advanced pancreatic cancer. Although this agent can provide palliation of disease symptoms, it has not demonstrated a significant survival advantage. Dr. David Modrak has observed that in vitro, pancreatic cancer cells respond to increasing doses of GEM by undergoing apoptosis, a form of cellular suicide, or programmed cell death. However, even at GEM concentrations as high as 100-times the generally accepted dose, a significant fraction of cells do not undergo apoptosis, but instead, are induced to enter a senescence-like phenotype. Senescence is characterized by cell cycle arrest and biologic inactivity. However, senescent cells are still viable and, in vivo, may represent a population of cells from which the tumor could re-grow. Reducing the number of senescent cells after chemotherapy will likely reduce the number of tumor "stem" cells and the production of necessary growth factors. Dr. Modrak has discovered that a deficiency in a lipid known to be involved with signaling apoptosis can lead to accumulation of these senescent cells after chemotherapy. Recent studies have demonstrated that by addition of specific lipids at non-toxic levels in the culture media, pancreatic cancer cells, which normally undergo senescence when treated with GEM, preferentially enter into apoptosis. Studies in mice bearing human pancreatic tumors have confirmed the initial cell culture studies and, importantly, have provided evidence that this procedure does not increase toxicity. These studies provide hope that translation to clinical trials will provide significantly improved survival for patients treated with chemotherapy.

Circadian Rhythms Impact upon Cancer Treatment and Prevention. In collaboration with Dr. Rosaleen Blumenthal, Dr. Jack Burton has continued this work that shows that the timing of administration of many drugs used in cancer treatment affects both their side effects and efficacy. This circadian effect was previously shown for multiple chemotherapy drugs, and later Dr. Blumenthal showed similar effects with anti-tumor antibodies. Subsequent studies in collaboration with Dr. Burton showed that certain arthritis drugs, Cox-2 inhibitors, have anti-cancer activity in an animal model of breast cancer that can be enhanced by administering it at the right time of day. Also, its side effects could be substantially reduced with this approach. Later studies by their groups showed strong circadian effects of the nutritional agents, selenium, vitamin D, and curcumin (the active ingredient of the spice turmeric) in an animal model of prostate cancer. All three of these agents have shown promise for the prevention of three of the most common cancers: breast, prostate and colon. To better evaluate the potential benefits of circadian timing with these nutritional agents, Drs. Burton and Blumenthal have conducted initial studies in another animal model, in which prostate cancer develops gradually and spontaneously, as it does in patients. This work is being funded under a grant awarded by the National Cancer Institute. Another laboratory initiative they are pursuing has shown that a new class of agents called PPARgamma antagonists have significant anti-cancer activity alone and in combination with chemotherapy and antibody-based treatment.

Adjuvant Radioimmunotherapy of Colorectal Cancer Patients Following Resection of Liver Metastases. In a collaboration with the Department of Surgery at the University of Goettingen in Germany, Dr. David Goldenberg has coauthored an article in the September 2007 issue of the Annals of Surgical Oncology, which showed that using a radiolabeled antibody against carcinoembryonic antigen (CEA), given after complete resection of liver metastases of colorectal cancer, showed a median survival of 58 months versus 31 months for controls who did not receive the radiolabeled antibody (based on a follow-up period of 91 months). This is the first study of a survival advantage for radioimmunotherapy, a method pioneered by Dr. Goldenberg and his colleagues at GSCC, in the management of an advanced cancer. The German surgeons are now organizing a multicenter trial to study this new method at various German hospitals and university centers.

Improved Detection and Diagnosis of Rectal and Colon Cancers. Dr. David Goldenberg is participating in a study at the University of Goettingen, Germany, under support by the German Research Society (DFG), for developing and applying some new methods for the improved detection of rectal cancer by diagnostic imaging methods. This is a clinical study involving the surgeons and nuclear medicine physicians in Goettingen, who were awarded a multi-project grant to improve the management of rectal cancer. In yet another collaboration, Drs. Goldenberg and Sharkey are working with a group of scientists and physicians at the University of Nijmegen, The Netherlands, in applying diagnostic imaging methods being studied at GSCC for the diagnosis and detection of colonic cancers, and have jointly submitted a paper for the forthcoming Society of Nuclear Medicine meetings to present this work.

Twelfth Conference of Cancer Therapy with Antibodies and Immunoconjugates. Under the Chairmanship of Dr. Goldenberg, this international conference (supported by the National Cancer Institute, the New Jersey Department of Health and Senior Services, and several pharmaceutical companies) has been occurring biennially in New Jersey, attracting scientists and clinicians from the USA and about 15 foreign countries. The proceedings of the Eleventh Conference were published in the September 15, 2007 issue of Clinical Cancer Research. The next conference scheduled for October 16-18, 2008 will be held at the Sheraton Parsippany Hotel.