Experimental study on pancreatic cancer gene therapy using the HSV-TK gene mediated by a retroviral vector

OBJECTIVE: To study the value of the herpes simplex virus type I thymidine kinase (HSV-TK) gene mediated by a retroviral vector in the treatment of human pancreatic cancer cell line 8988. METHODS: The HSV-TK gene was directionally cloned into a site following the SV40 promoter that was adjacent to the 5′ LTR (long terminal repeats) and the neomycin phosphotransferase gene in the retroviral vector pMNSM. This enabled the TK gene to integrate into the chromatin of the host cell. The recombinant plasmid pMNS-TK-M was then transfected into the retrovirus-packaging cell Pa317. Finally, the HSV-TK gene was transfected into pancreatic cancer cell line 8988 by the recombinant retrovirus after selection with G418. RESULTS: The HSV-TK gene was stably integrated into the host cell and its expression confirmed by Southern blotting and drug-sensitivity tests. In vitro studies showed that the acyclovir (ACV) sensitivity level in the 8988/TK+ cells was higher than that of the parent cells. The cells that were transfected with the TK gene were significantly susceptible to ACV. In vivo studies in nude mice showed that intraperitoneal injection of ACV might postpone the formation of implanted tumors and produce a treatment effect on the tumors. CONCLUSIONS: This study demonstrated that the HSV-TK/ACV retroviral system could be used in vivo to treat pancreatic cancer.