Robert DiPaola, MD, professor of medicine, UMDNJ-Robert Wood Johnson Medical School; co-director, prostate cancer program, The Cancer Institute of New Jersey (CINJ); executive director, Dean and Betty Gallo Prostate Cancer Center

Vaccine therapies have become attractive for translational study in prostate cancer. The development of immune therapies for prostate cancer includes the study of viral, dendritic, DNA, peptide and carbohydrate vaccines, which have promising results in initial studies. Viral vaccines are particularly promising, since they mimic natural infection and can induce potent immune responses. Replicating and non-replicating members of the poxvirus family have been widely studied for expression of tumor antigens and other immunomodulatory genes, such as cytokines and co-stimulatory molecules. A large number of tumor-associated antigens are available for insertion into viral vectors for future development. In this regard, our team — and other investigators — have completed initial studies of a smallpox virus containing the gene sequence for prostate specific antigen (PSA) in patients with prostate cancer. For example, an Eastern Cooperative Oncology Group (ECOG) study demonstrated safety and efficacy in patients with PSA progression after local therapy for prostate cancer (Kaufman H, DiPaola RS, et al. J Clin Oncol. 2004 Jun 1; 22(11):2122-32). The safety of a second generation PSA vaccine was recently tested with three additional co-stimulatory molecules (called TRICOM) along with the gene sequence for PSA in the viral vector (DiPaola et al. Proceedings of the American Association for Cancer Research 45:1035 Abs#4485, 2004). Based on these initial data, we proposed and have received approval from the ECOG and the NCI to begin a phase III study of the optimized smallpox vaccine with PSA, TRICOM and the addition of GM-CSF, an additional growth factor that has been demonstrated to enhance immune responses. The study is titled “a phase III study of PSA vaccine in androgen refractory PSA progression with absence of metastatic disease and GM-CSF,” or PARADIGM. This phase III national study will determine the true benefit of a vaccine in prostate cancer and is planned to begin in 2006.

Targeting Apoptosis
In addition to the translational studies of new immune paradigms on a national level, we have been studying methods to improve standard chemotherapy in prostate cancer by targeting apoptosis, the regulated pathway of tumor cell death. Advanced prostate cancer is only temporarily controlled by hormonal therapy or chemotherapy. The current standard chemotherapy is the agent docetaxel, which has been demonstrated to improve survival in men with advanced hormone resistant prostate cancer (HRPC). Despite initial benefit in many patients, docetaxel has improved the median survival by only 2.5 months, promoting efforts to discover agents that will overcome the molecular mechanisms of resistance that develop to docetaxel. To overcome tumor resistance, we used an epithelial cell line model developed in the laboratory of Eileen White, PhD, a resident faculty member of the Center for Advanced Biotechnology and Medicine, a joint program of UMDNJ and Rutgers University, to dissect out mechanisms of resistance such as mutations in p53 and overexpression of the anti-apoptotic protein bcl-2. In an attempt to sensitize these cells to taxol, a cousin of docetaxel, we found that 13-cis retinoic acid and alpha interferon (CRA/IFN) reduced the expression of bcl-2 and are capable of overcoming resistance. We hypothesized that drugs which could overcome bcl-2 mediated resistance would improve chemotherapy response or duration of response in the clinic. We then translated these results to the clinic in a series of clinical trials with funding from the National Cancer Institute (DiPaola, R.S., et al. Clin Cancer Research, 3:1999-2004, 1997; DiPaola et al. J Clin Oncol 17:2213-2218, 1999; Thalasila, DiPaola, et al. Cancer Chemother Pharmacol, 52: 119-124, 2003). Recently, a phase II randomized study with CRA/IFN with taxol was accepted as a national trial. Initial results demonstrated that CRA/IFN was able to reduce bcl-2 expression in the blood of patients (Elsayed, DiPaola, R. S. et al. Proceedings of the American Society of Clinical Oncology 23:431 (4707), 2004).

Based on these studies with CRA/IFN combined with taxol, we have now obtained funding through the Department of Defense to complete studies with CRA/IFN combined with docetaxel. We hypothesized that CRA/IFN will improve the response rate, or duration of response, of docetaxel in patients with HRPC. These studies are nearing completion at CINJ. Within the same scientific theme of understanding mechanisms of resistance to docetaxel chemotherapy and developing strategies to overcome such resistance, we have also studied additional agents that affect tumor cells resistant to taxol and docetaxel. One of these agents, epothilone, was studied in our laboratory and was found to potentially occur by different mechanisms of resistance compared to taxol (Ioffe, DiPaola, et al. The Prostate. 2004 Nov 1;61(3):243). We are currently completing a trial with epothilone in patients with prostate cancer that progressed despite treatment with docetaxel. This study is being conducted by ECOG supported through NCI.

We have also tried to overcome tumor resistance to chemotherapy by treating patients earlier in their course, prior to the development of resistance mechanisms. Some of these studies have already been published and are being used to support further study of agents in early prostate cancer (DiPaola et al. Cancer. Oct 15; 92(8):2065-71, 2001; Rao, DiPaola et al. The Prostate, 61:2004; Kumar, DiPaola et al. J. Clin Oncol, 2004; Goodin, DiPaola et al. J. Clin Oncol May 20, 2005). Other ongoing clinical trials of earlier agents include a prevention study of calcitriol, a vitamin D derivative, in patients with prostatic intraepithelial neoplasia, a marker of high risk for prostate cancer; this study is based on laboratory studies in mouse models conducted in the laboratory of Cory Abate-Shen, PhD, co-director of the prostate program at CINJ.

Tarketing Metabolism
We have also published preliminary data that supports a novel approach targeting metabolism to bypass tumor resistance. Prior studies demonstrated the dependence of early tumor growth on anaerobic metabolism through glycolysis. In fact, the greater preference of tumor cells than normal cells to utilize glycolysis is the basis for the successful development of FDG-PET imaging. More recent studies have also demonstrated that abnormal growth factor and apoptotic pathways, required by tumor cells to resist multiple insults, can drive tumor cells to even further dependence on glycolysis. For example, studies have recently demonstrated that activation of Akt kinase, which occurs commonly in tumors such as prostate cancer, increases dependence on glycolysis. We set up a laboratory co-culture model that could detect the growth effect of autocrine stimulation by tumor cells independent of the changes in anti-apoptotic proteins such as overexpression of bcl-2. Using two dimensional (2D) gel analysis in this co-culture model, we found that seven proteins increased most significantly with autocrine stimulated growth in LNCaP cells and identified all these proteins as specific glycolytic enzymes, suggesting that this was a critical early event (Dvorzhinski, DiPaola et al. Proteomics. 4:3268-3275, 2004). We then began to test 2-deoxyglucose, an inhibitor of glycolysis, and found decreased expression of these enzymes in this co-culture model and inhibition of cell growth at concentrations below what can be obtained safely in humans. In collaboration with Eileen White, we found that Akt activation increased sensitivity to this agent (DiPaola, White et al. Proceedings of the American Society of Clinical Oncology, 2005). These laboratory data supported a recent proposal to conduct additional laboratory studies and a clinical trial in patients with prostate cancer that received funding by the Department of Defense.

In summary, these efforts to translate laboratory discoveries into clinical trials have led to new insights in immune therapies and modulation of resistance mechanisms present in prostate cancer. This work has been supported by
governmental agencies including the NCI and the Department of Defense. Our efforts in early clinical trials have led to the movement of results into high
priority national clinical studies.

Robert DiPaola, MD, is a professor of medicine at UMDNJ-Robert Wood Johnson Medical School. He is currently co-director of the prostate cancer program at The Cancer Institute of New Jersey, the state’s only National Cancer Institute-designated Comprehensive Cancer Center, and executive director of the Dean and Betty Gallo Prostate Cancer Center. His research efforts are based on the translation of laboratory discoveries to clinical trials. Dr. DiPaola’s success is evidenced by being recently elected as chair of the Genito-urinary Committee of the Eastern Cooperative Oncology Group, one of only a few national clinical trials groups funded by the NCI. He has served on both NCI and Department of Defense grant study sections and The American Society of Clinical Oncology Program Committee. His work has been published in the most prominent journals, including The Journal of Clinical Oncology, Clinical Cancer Research, Proteomics, and The New England Journal of Medicine. Examples of his ongoing funded research include the development of vaccine therapies for prostate cancer and bypassing cancer resistance through targeted approaches of the apoptotic pathway and cell metabolism. §