Dr. Cho is a board certified oncologist currently on staff at the Beth Israel Deaconess Medical Center. Dr. Cho is committed to a career in academic medicine and his long-term objective in this application is to become expert in clinically oriented laboratory research. Under the mentorship of Dr. James Mier and Dr. Lewis Cantley, Dr. Cho has chosen to focus his research career on developing novel therapies for the treatment of renal cell carcinoma (RCC). Responses to currently available VEGF-targeted therapies in RCC are neither complete nor durable, highlighting the limitations of agents that primarily target the tumor endothelium. More robust tumor responses will require the identification of critical oncogenic signaling pathways within RCC tumor cells and development of agents which inhibit them. One such critical target is the PI3-K/Akt pathway. The clinical activity of inhibitors of the Akt-regulated kinase mTOR confirms the importance of this pathway in RCC. As PI3-K/Akt regulates numerous other signaling pathways critical to survival and viability in addition to mTOR, there is strong rationale to expect even greater results by targeting upstream of mTOR. In support of this hypothesis, Dr. Cho has shown that treatment of RCC cell lines and xenografts with BEZ235, a novel dual inhibitor of PI3-K/mTOR, results in greater arrest of tumor proliferation compared with rapamycin. However, not all consequences of PI3-K are pro-apoptotic or anti- proliferative. Preliminary studies have shown that inhibition of PI3-K does not consistently suppress production of VEGF, a potent mediator of tumor-driven angiogenesis. Inhibition of PI3-K also results in the activation of GSK32, which may have numerous anti-apoptotic effects which undermine the anti-tumor effects of these drugs. In fact, concurrent inhibition of GSK32 appears to significantly enhance the anti- tumor effect of BEZ235. In this application, the mechanism and consequences of the failure of PI3-K inhibitors to suppress VEGF levels will be determined in both in vitro and in vivo systems. Also, the mechanism through which GSK32 inhibition enhances the pro-apoptotic effects of PI3-K/Akt inhibition will be determined and the efficacy of this therapeutic strategy (concurrent inhibition of GSK32 and PI3-K) will be assessed in a xenograft model. The PI3-K/Akt pathway is the second most frequently mutated pathway in human malignancy. Therefore, this project has relevance to public health in the potential benefit not only to the thousands of patients with metastatic RCC but also in nearly all other malignancies. The studies proposed in the application may also identify critical mechanisms of resistance to agents inhibiting the PI3- K/Akt pathway and thereby direct rationale combinational therapy.
Therapies for renal cell carcinoma (RCC), the seventh most common malignancy in the United States, have improved substantially over the last several years with the development of agents targeting vascular endothelial growth factor signaling. However, responses to these primarily anti-angiogenic agents are neither complete nor durable off of therapy, suggesting that greater anti-tumor effects will require targeting critical oncogenic signaling pathways in tumor cells themselves. The PI3-K/Akt pathway, the second most frequency mutated pathway in human cancer, is one such potential therapeutic target in RCC. With several novel inhibitors of PI3-K/Akt in active clinical development, this application will explore potential shortcomings of these agents in an effort to identify strategies to maximally therapeutically exploit drugs targeting this critical signaling pathway in RCC.
