Chemoradiotherapy is the standard treatment for locally-advanced pancreas cancer, but results are suboptimal with high rates of local failure and metastatic spread. Our group has pioneered novel regimens combining gemcitabine-based chemotherapy with radiation to simultaneously maximize systemic effects and local radiation effects. The long-term goal of this proposal is to improve upon the efficacy of gemcitabine and radiation through the addition of the PKC? inhibitor enzastaurin. Our preliminary data suggest that enzastaurin can enhance radiation as well as gemcitabine effects in pancreas cancer. In this application we will explore the mechanism of this observed enhancement.
In Specific Aim 1 we will determine the effects of PKC?- mediated inhibition of the Wnt signaling pathway on the radiosensitivity of pancreas cancer. We hypothesize that PKC? promotes tumor survival through its effects on GSK3? and activation of the Wnt signaling pathway. Our preliminary data suggests that radiation inhibits GSK3? (thereby increasing levels of ?-catenin) and enzastaurin can abrogate this increase through inhibition of phosphorylation of GSK3?. To the best of our knowledge, the Wnt pathway has never before been implicated in control of the radiation response. We will investigate in-vitro whether this suppression is causally related to the observed radiosensitization by use of pharmacological modulators of GSK3? and stable cell lines expressing dominant negative and constitutively active ?-catenin.
In Specific Aim 2 we will elucidate the mechanisms of interaction between gemcitabine and PKC? inhibition in pancreas cancer. Our preliminary data suggests that enzastaurin enhances gemcitabine cytotoxicity in pancreas cancer cell lines. We hypothesize that through a mechanism similar to that described in SA1, gemcitabine induces activation of the Wnt signaling pathway and that this effect can be abrogated by enzastaurin. We will study these effects in-vitro using an approach similar to that described in SA1.
In Specific Aim 3 we will determine the combined effects of PKC? inhibition, gemcitabine and radiation on Wnt signaling and pancreas cancer growth. Our preliminary data demonstrates that enzastaurin, at non-cytotoxic concentrations achievable in patients, enhances the cytotoxicity of gemcitabine and radiation. Based on knowledge gained in Specific Aims 1 and 2, we will optimize this combination in-vitro and then in nude mice bearing human tumor xenografts. Although this application focuses on understanding the synergy with chemoradiotherapy, modalities used primarily for locally advanced pancreatic cancer, data regarding the effects of PKC? inhibition in pancreas cancer, and in particular regarding the interaction with gemcitabine would be readily applicable to patients with metastatic disease. This data will be used to rationally integrate PKC? inhibition into novel treatment regimens in pancreas cancer. Based on its scientific merit and our institutional track record in translational research in pancreas cancer, we feel it is highly likely that this research will prove beneficial. ? ? ?
| Yao, Hongren; Zeng, Zhao-Zhu; Fay, Kevin S et al. (2011) Role of ?(5)?(1) Integrin Up-regulation in Radiation-Induced Invasion by Human Pancreatic Cancer Cells. Transl Oncol 4:282-92 |
| Watson, Richard L; Spalding, Aaron C; Zielske, Steven P et al. (2010) GSK3beta and beta-catenin modulate radiation cytotoxicity in pancreatic cancer. Neoplasia 12:357-65 |
| Spalding, Aaron C; Watson, Richard; Davis, Mary E et al. (2007) Inhibition of protein kinase Cbeta by enzastaurin enhances radiation cytotoxicity in pancreatic cancer. Clin Cancer Res 13:6827-33 |
