PKCα-induced drug resistance in pancreatic cancer cells is associated with transforming growth factor-β1

Background: Drug resistance remains a great challenge in the treatment of pancreatic cancer. The goal of this study was to determine whether TGF-beta 1 is associated with drug resistance in pancreatic cancer. Methods: Pancreatic cancer BxPC3 cells were stably transfected with TGF-beta 1 cDNA. Cellular morphology and cell cycle were determined and the suppressive subtracted hybridization (SSH) assay was performed to identify differentially expressed genes induced by TGF-beta 1. Western blotting and immunohistochemistry were used to detect expression of TGF-beta 1-related genes in the cells and tissue samples. After that, the cells were further treated with an anti-cancer drug (e. g., cisplatin) after pre-incubated with the recombinant TGF-beta 1 plus PKC alpha inhibitor Go6976. TGF-beta 1 type II receptor, T beta RII was also knocked down using TbRII siRNA to assess the effects of these drugs in the cells. Cell viability was assessed by MTT assay. Results: Overexpression of TGF-beta 1 leads to a markedly increased invasion potential but a reduced growth rate in BxPC3 cells. Recombinant TGF-beta 1 protein increases expression of PKC alpha in BxPC3 cells, a result that we confirmed by SSH. Moreover, TGF-beta 1 reduced the sensitivity of BxPC3 cells to cisplatin treatment, and this was mediated by upregulation of PKC alpha. However, blockage of PKC alpha with G6976 and TbRII with siRNA reversed the resistance of BxPC3 cells to gemcitabine, even in the presence of TGF-beta 1. Immunohistochemical data show that pancreatic cancers overexpress TGF-beta 1 and P-gp relative to normal tissues. In addition, TGF-beta 1 expression is associated with P-gp and membranous PKC alpha expression in pancreatic cancer. Conclusions: TGF-beta 1-induced drug resistance in pancreatic cancer cells was associated with PKC alpha expression. The PKC alpha inhibitor Go6976 could be a promising agent to sensitize pancreatic cancer cells to chemotherapy.