The majority of patients with pancreatic cancer are resistant to gemcitabine. One of the mechanisms involved is the anti-apoptotic ability of these cells. The median lethal dose (LD 50 ) of gemcitabine for PANC-1 cells was higher than that for Mia PaCa-2 cells and the former had higher nuclear factor-κB (NF-κB) and X-linked inhibitor of apoptosis protein (XIAP) levels. NF-κB contributes to the inhibition of apoptosis by the downregulation of downstream genes, such as XIAP and Bcl-2 and it

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... s chemoresistance. The two cell lines were infected with NF-κB p65 small interfering RNA (siRNA). p65 protein was effectively downregulated accompanied by the downregulation of XIAP protein. The combination treatment with gemcitabine and p65 siRNA increased the apoptotic rates in both cell lines; however, this was not sufficient. XIAP is involved in apoptosis to a greater extent compated to Bcl-2. XIAP may serve as another factor affecting the sufficiency of chemotherapy. XIAP siRNA was designed to knockdown XIAP. Mia PaCa-2 and PANC-1 cells were co-infected with XIAP siRNA and p65 siRNA. XIAP and p65 proteins were effectively downregulated and the gemcitabine-induced apoptotic rates were significantly increased. These results suggest that XIAP and NF-κB are two important factors conferring the chemoresistance of pancreatic cancer cells, and that their downregulation via RNAi effectively enhances the chemosensitivity of pancreatic cancer cells to gemcitabine.