AIM: To study the effect of red oil A5 on pancreatic cancer cells and its possible mechanisms.METHODS: Effect of different concentrations of red oil A5on proliferation of three pancreatic cancer cell lines, AsPC-1,MiaPaCa-2 and S2013, was measured by 3H-methyl thymidine incorporation. Time-dependent effects of 1:32 000 red oil A5 on proliferation of three pancreatic cancer cell lines, were also measured by 3H-methyl thymidine incorporation, and Time-course effects of 1:32 000 red oil A5 on cell number.The cells were counted by Z1-Coulter Counter. Fiowcytometric analysis of cellular DNA content in the control and red oil A5 treated AsPC-1, MiaPaCa-2 and S2013 cells,were stained with propidium iodide. TUNEL assay of red oil A5-induced pancreatic cancer cell apoptosis was performed.West blotting of the cytochrome c protein in AsPC-1,MiaPaCa-2 and S2013 cells treated 24 hours with 1:32 000red oil A5 was performed. Proteins in cytosolic fraction and in mitochondria fraction were extracted. Proteins extracted from each sample were electrophoresed on SDS-PAGE gels and then were transferred to nitrocellulose membranes.Cytochrome c was identified using a monoclonal cytochrome c antibody. West blotting of the caspase-3 protein in AsPC-1, MliaPaCa-2 and S2013 cells treated with 1:32 000 red oil A5 for 24 hours was carried out. Proteins in whole cellular lysates were electrophoresed on SDS-PAGE gels and then transferred to nitrocellulose membranes. Caspase-3 was identified using a specific antibody. West blotting of polyADP ribose polymerase (PARP) protein in AsPC-1, MiaPaCa2 and S2013 cells treated with 1:32 000 red oil A5 for 24 hours was performed. Proteins in whole cellular lysates were separated by electrophoresis on SDS-PAGE gels and then transferred to nitrocellulose membranes. PARP was identified by using a monoclonal antibody.RESULTS: Red oil A5 caused dose- and time-dependent inhibition of pancreatic cancer cell proliferation. Propidium iodide DNA staining showed an increase of the sub-G0/G1 cell population. The DNA fragmentation induced by red oil A5 in these three cell lines was confirmed by the TUNEL assay.Furthermore, Westem blotting analysis indicated that cytochrome c was released from mitochondria to cytosol during apoptosis,and caspase-3 was activated following red oil A5 treaent which was measured by procaspase-3 cleavage and PARP cleavage.CONCLUSION: These findings show that red oil A5 has potent anti-proliferative effects on human pancreatic cancer cells with induction of apoptosis in vitro.