Section for Studies on Metastasis

15. Section for Studies on Metastasis

In 1997, the Section has focused research on the develop ment of gene therapy for disseminated pancreatic cancer; part of a long-term collabora tive effort with a group in the Genetics Division.
Targeting of the K-ras Mutation in Pancreatic Cancer

A previous report from the Section showed that in vivo lipofection of an antisense K-ras RNA expression vector effectively suppressed peritoneal dissemination of pancreatic cancer cells in the nude mouse model. To clarify the effect of antisense K-ras RNA on various pancreatic cancer cell lines, the antisense K-ras vector was transduced into 7 human pancreatic cancer cell lines (AsPC-1, MIAPaCa-2, Panc-1, PSN-1, BxPC-3, 700T and 766T). Western blot analysis showed a reduction of K-ras-specific p21 protein in all the transfected cells except for BxPC-3 cells, and cell growth was suppressed in cell lines with K-ras point mutations (AsPC-1, MIAPaCa-2, Panc-1 and PSN-1). In contrast, the growth-suppressive effect of the antisense construct was markedly lower in cell lines with a wild type K-ras gene (BxPC-3, 700T and 766T) .⁽¹⁷⁸⁾ These results suggest that the K-ras mediated growth signaling pathway may function differently in pancreatic cancer cells depending on the K-ras mutation status of the cells. The data also suggest a biological basis for the apparent tolerance of normal tissues to the antisense K-ras RNA strategy for pancreatic cancer.
Suicide Gene Therapy for Peritoneal Dissemination of Pancreatic Cancer

Peritoneal dissemination is one of the most common complications of pancreatic cancers, and no effective therapy has been established to date for this devas tating condition. A mouse experiment at the Section has suggested a novel approach of in vivo lipofection-based suicide gene therapy for pancreatic cancer cells disseminated in the peritoneal cavity.⁽¹⁷⁷⁾ Briefly, a human pancreatic cancer cell line, PSN-1, was inoculated into the peritoneal cavity of nude mice. After an interval which allowed formation of multiple small peritoneal tumor nodules, the herpes simplex virus thymidine kinase (HST-tk) gene expression plasmid was injected intraperitoneally as a DNA-lipopolyamine complex. After ganciclovir (GCV) treatment, the mice were examined for tumor development. While all 24 control mice showed macroscopic peritoneal dissemination, eight of the 14 mice treated with the HSV-tk and GCV were free of tumors. The transduction of the lacZ gene in a similar protocol revealed blue-stained cells only in the tumor nodules and not in normal organs, which may partly explain why toxicity was not observed with this suicide gene therapy approach.




	15. Section for Studies on Metastasis



		In 1997, the Section has focused research on the develop ment of gene therapy for disseminated pancreatic cancer; part of a long-term collabora tive effort with a group in the Genetics Division. Targeting of the K-ras Mutation in Pancreatic Cancer A previous report from the Section showed that in vivo lipofection of an antisense K-ras RNA expression vector effectively suppressed peritoneal dissemination of pancreatic cancer cells in the nude mouse model. To clarify the effect of antisense K-ras RNA on various pancreatic cancer cell lines, the antisense K-ras vector was transduced into 7 human pancreatic cancer cell lines (AsPC-1, MIAPaCa-2, Panc-1, PSN-1, BxPC-3, 700T and 766T). Western blot analysis showed a reduction of K-ras-specific p21 protein in all the transfected cells except for BxPC-3 cells, and cell growth was suppressed in cell lines with K-ras point mutations (AsPC-1, MIAPaCa-2, Panc-1 and PSN-1). In contrast, the growth-suppressive effect of the antisense construct was markedly lower in cell lines with a wild type K-ras gene (BxPC-3, 700T and 766T) .⁽¹⁷⁸⁾ These results suggest that the K-ras mediated growth signaling pathway may function differently in pancreatic cancer cells depending on the K-ras mutation status of the cells. The data also suggest a biological basis for the apparent tolerance of normal tissues to the antisense K-ras RNA strategy for pancreatic cancer. Suicide Gene Therapy for Peritoneal Dissemination of Pancreatic Cancer Peritoneal dissemination is one of the most common complications of pancreatic cancers, and no effective therapy has been established to date for this devas tating condition. A mouse experiment at the Section has suggested a novel approach of in vivo lipofection-based suicide gene therapy for pancreatic cancer cells disseminated in the peritoneal cavity.⁽¹⁷⁷⁾ Briefly, a human pancreatic cancer cell line, PSN-1, was inoculated into the peritoneal cavity of nude mice. After an interval which allowed formation of multiple small peritoneal tumor nodules, the herpes simplex virus thymidine kinase (HST-tk) gene expression plasmid was injected intraperitoneally as a DNA-lipopolyamine complex. After ganciclovir (GCV) treatment, the mice were examined for tumor development. While all 24 control mice showed macroscopic peritoneal dissemination, eight of the 14 mice treated with the HSV-tk and GCV were free of tumors. The transduction of the lacZ gene in a similar protocol revealed blue-stained cells only in the tumor nodules and not in normal organs, which may partly explain why toxicity was not observed with this suicide gene therapy approach.

15. Section for Studies on Metastasis

Targeting of the K-ras Mutation in Pancreatic Cancer

Suicide Gene Therapy for Peritoneal Dissemination of Pancreatic Cancer