Abstract: Objective To investigate the expression of PTEN and PIK3CA in pemetrexed-resistant human pancreatic cancer cell line Patu8988,and evaluate their effects on the biological behaviors of pancreatic cancer cell line.Methods The expression of PTEN and PIK3CA in pemetrexed-resistant pancreatic cancer cell line and normal pancreatic cancer cell line were detected by RT-PCR and Western blot analysis,respectively;Transwell test was used to detect the discrepancy between pemetrexed-resistant and non drug-resistant pancreatic cancer cell line.Result Over-expression of PTEN and PIK3CA in pemetrexed-resistant pancreatic cancer cell line Patu8988 were determined both by RT-PCR and Western blot.In pemetrexed-resistant cell line,PTEN and PIK3CA were ascended by 89% and 76% respectively as showed by Western blot,comparing with that of normal pancreatic cancer cell line.Transwell test showed that the capabilities of migration and invasion of pemetrexed-resistant pancreatic cancer cell were significantly weakened than that of normal pancreatic cancer cell line(P＜0.05).Conclusion Both PTEN and PIK3CA enhanced abnormally in pemetrexed-resistant pancreatic cancer cell line Patu8988 and the co-existence of high level of PTEN and PIK3CA induced significant decrease in capabilities of migration and invasion of pemetrexed-resistant pancreatic cancer cell,which suggested mechanism of resisting to pemetrexed may involved function of PTEN and PIK3CA.They may also change the biological behavior of cancer cell.