A Gene Therapy for Pancreatic Cancer

Summary

Pancreatic cancer is often resistant to conventional treatment, and the development of a new therapeutic strategy has been eagerly awaited. Characteristically, K-ras point mutation is observed at a high incidence in human pancreatic cancer. To determine if it is feasible to suppress the growth of pancreatic cancer by counteracting mutated K-ras, we constructed a plasmid vector expressing antisense K-ras RNA and transfected into human pancreatic cancer cells by lipofection. The in vitro growth was significantly suppressed for the antisense K-ras-transfected pancreatic cancer cells, but not for the sense K-ras-transfected cells. Immunoblot analysis showed a reduction of up to 20% of K-ras specific p21 protein the antisense K-ras-transfected cells. There was no evidence of the induction of a massive apoptosis or the presence of a bystander effect. In an in vivo treatment model for peritoneal dissemination, the AsPC-1 pancreatic cancer cells were transplanted to the peritoneal cavity of nude mice at day 1. At day 4, the antisense K-ras-vector /lipopolyamine (DOGS) complex was injected intra-peritoneally 3 times every 12hrs. At day 28, 9 of the 10 sense K-ras-injected mice developed peritoneal dissemination and/or solid tumor formation on the pancreas,or liver; in contrast, only 2 of the 12 mice treated with the antisense K-ras vector showed any evidence of intraperitoneal tumors. Although PCR screening indicated that the injected DNA was distributed to various organs except the brain, treatment-related toxicity was observed neither macroscopically nor microscopically. This study showed that the liposome-mediated in vivo gene transfer of antisense K-ras construct may be a useful therapeutic strategy for a subset of pancreatic cancer.