Background: Receptor-associated protein 80 (RAP80) increases substantially in pancreatic cancer. The involvement of RAP80 in the chemoresistance of pancreatic cancer should be elucidated.
Aims: We investigated the effects of inhibiting RAP80 expression on the sensitivity of pancreatic cancer cells to gemcitabine chemotherapy by using small interfering RNA (siRNA).
Methods: Chemically synthesized siRNA RAP80 was transfected into human pancreatic cancer cell lines SW1990 and Capan-2. The IC(50) of gemcitabine was determined by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell apoptosis was detected by using flow cytometry. Expression of apoptosis-related genes, Bax, Bcl-2, TRAIL, survivin, and caspase-8 was detected by using reverse transcription-polymerase chain reaction (RT-PCR) and western blot.
Results: Gemcitabine inhibits proliferation of SW1990 and Capan-2 cells in a concentration-dependent manner. Inhibition of RAP80 expression significantly reduced the IC(50) of gemcitabine (P < 0.01). RAP80 siRNA combined with gemcitabine significantly increased (P < 0.01) apoptosis of pancreatic cancer cell lines SW1990 and Capan-2, increased expression of Bax mRNA, reduced Bcl-2 mRNA expression (P < 0.01), and slightly increased TRAIL mRNA expression (P < 0.01). Correspondingly, in the RAP80 siRNA combined with gemcitabine group, both Bax and cleaved caspase-8 protein levels were increased (P < 0.01), whereas Bcl-2 protein decreased significantly (P < 0.01). No change in survivin mRNA expression was observed (P < 0.01).
Conclusion: Inhibition of RAP80 expression can induce apoptosis in pancreatic cancer cells and improve chemosensitivity to gemcitabine.