Abstract 4702: Caveolin-1 confers a multi-modality therapy resistance phenotype in pancreatic cancer cells

Abstract

Abstract Caveolin-1 (Cav-1) is a 21kDa protein found in 50-100nm omega-shaped invaginations of the plasma membrane known as caveolae. It has been implicated in the processes of oncogenic cell transformation, tumorigenesis and metastasis. Cav-1 is upregulated in pancreatic cancer and has been shown to be correlated with poor prognosis. We hypothesized that Cav-1 promotes resistance to chemotherapy and radiation, and that downregulation may lead to sensitization to radiation and/or chemotherapy. We found that radiation and chemotherapy up-regulate Cav-1 expression, and that downregulating Cav-1 in multiple pancreatic cancer cell lines by small interfering RNA induces sensitization to chemotherapeutics such as gemcitabine and 5-fluorouracil. Furthermore, genetic knockdown causes reduction in tumor cell proliferation and colony formation. Knockdown of caveolin-1 also led to radiosensitization of tumor cells and resulted in delayed DNA repair as demonstrated by delayed pH2.AX foci resolution, increased mitotic catastrophe, as well as decreased formation of BRCA1 and DNAPK-cs foci in the nuclei of these cells. Furthermore, Cav-1 loss promoted cleavage of Caspase-9 and PARP after treatment with gemcitabine. These results indicate that knocking down Cav-1 in pancreatic cancer cells sensitizes them to radiation with delayed DNA damage repair and also to chemotherapeutics with the onset of apoptosis. In vivo, stable knockdown of Cav-1 attenuated the rate of tumor growth significantly compared to control tumors in subcutaneous xenograft pancreatic tumors. In summary we conclude that Cav-1 is responsible in promoting resistance to radiation and chemotherapy in pancreatic cancer cells and that downregulation of this protein leads to improved therapeutic response. Thus, it is possible that caveolin-1 may serve as a prognostic predictive biomarker in pancreatic cancer patients for response to radiation and chemotherapy. Citation Format: Moumita Chatterjee, Terence M. Williams. Caveolin-1 confers a multi-modality therapy resistance phenotype in pancreatic cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4702. doi:10.1158/1538-7445.AM2014-4702