| Pancreatic adenocarcinoma is a common malignancy with no effective therapy and a poor prognosis. The Cancer-associated Sm-like (CaSm) oncogene has been recently identified and is overexpressed in 87% of human pancreatic cancers. This dissertation project examines the efficacy of CaSm as a novel target for gene therapy of pancreatic cancer.; An adenoviral vector that expresses antisense to CaSm (Ad-antiCaSm) decreases the in vitro proliferation and reduces the anchorage independent growth of pancreatic cancer cells. Furthermore, in vivo experiments demonstrate a clear decrease in tumor volume and a significant increase in median survival after infection. DNA fragmentation assays, TUNEL assays, and activated Caspase-3 assays all fail to detect a significant induction of apoptosis following decreased CaSm expression. However, propidium iodide and DAPI staining reveal a marked impact on the cell cycle with a substantial increase in nuclear DNA content and a striking decrease in metaphase cells. Northern blot analysis, real-time RT-PCR, western blot, flow cytometry, and immunoprecipitation indicate a significant decrease in cyclin B expression and activity following CaSm downregulation. In addition, the combination of gemcitabine and Ad-antiCaSm had an additive effect on in vitro proliferation and prolonged survival in the in vivo model of subcutaneous tumor growth.; In conclusion, CaSm in a novel oncogene that plays a significant role in the pathogenesis of pancreatic adenocarcinoma. CaSm is overexpressed in the vast majority of human pancreatic cancer samples and cell lines and reduced CaSm expression decreases both in vitro and in vivo tumor growth. This anti-tumor effect appears to occur through a cytostatic inhibition of the cell cycle that is mediated at least in part by decreased expression and activity of cyclin B/CDK1, and sensitizes pancreatic cancer cells to gemcitabine chemotherapy. Thus CaSm is an exciting new oncogene and warrants further study as a member of the normal cell cycle control machinery, as a contributing factor in the pathogenesis of pancreatic adenocarcinoma, and as a target for early clinical trials. |
