Liposome-mediated in vivo gene transfer of antisense K-ras construct inhibits pancreatic tumor dissemination in the murine peritoneal cavity.

K-ras point mutation occurs at a characteristically high incidence in human pancreatic cancer. Plasmids expressing antisense (AS), AS-K-ras-LNSX or sense K-ras gene fragment, were first transduced into three human pancreatic cancer cell lines (AsPC-1, MIAPaCa-2, and BxPC-3) by liposome-mediated transfection. A stable expression of antisense or sense K-ras RNA was detected by Northern blot analysis, and Western blot analysis confirmed a reduction of up to 20% of K-ras-specific p21 protein in AsPC-1 cells transduced with AS-K-ras-LNSX. The growth of pancreatic cancer cells with K-ras point mutations (AsPC-1 and MIAPaCa-2) was significantly suppressed after transduction of AS-K-ras-LNSX, although the effect of antisense construct was not found in cells with a wild-type K-ras gene (BxPC-3). Next, to test the efficacy in vivo, AsPC-1 cells were inoculated into the intraperitoneal cavity of nude mice, and 3 days later, the AS-K-ras-LNSX:liposome complex was injected i.p. 3 times. Twenty-eight days after tumor cell inoculation, 9 of 10 control mice developed peritoneal dissemination and/or solid tumors on the pancreas, whereas only 2 of 12 mice treated with AS-K-ras-LNSX showed any evidence of tumors. Although PCR analysis indicated that the injected DNA was delivered to various organs except for the brain, treatment-related toxicity was not observed. This study shows that the liposome-mediated in vivo gene transfer of antisense K-ras construct may be a useful therapeutic strategy for pancreatic cancer.