Liposomal insulin promoter–thymidine kinase gene therapy followed by ganciclovir effectively ablates human pancreatic cancer in mice

• Insulin promoter–thymidine kinase (IP-TK) used to treat pancreatic cancer in mice.
• Liposomal IP-TK maintained efficacy with repeat doses.
• Improved survival with repeat low doses of liposomal IP-TK versus single high dose.
• Liposomal IP-TK resulted in less toxicity compared to adenoviral IP-TK.
• No significant impact of IP-TK on pancreatic islets, glucose metabolism.

PDX1 is overexpressed in pancreatic cancer, and activates the insulin promoter (IP). Adenoviral IP–thymidine kinase and ganciclovir (TK/GCV) suppresses human pancreatic ductal carcinoma (PDAC) in mice, but repeated doses carry significant toxicity. We hypothesized that multiple cycles of liposomal IP-TK/GCV ablate human PDAC in SCID mice with minimal toxicity compared to adenoviral IP-TK/GCV. SCID mice with intraperitoneal human pancreatic cancer PANC-1 tumor implants were given a single cycle of 35 µg iv L-IP-TK, or four cycles of 1, 10, 20, 30, or 35 µg iv L-IP-TK (n = 20 per group), followed by intraperitoneal GCV. Insulin and glucose levels were monitored in mice treated with four cycles of 35 µg iv L-IP-TK. We found that four cycles of 10–35 µg L-IP-TK/GCV ablated more PANC-1 tumor volume compared to a single cycle with 35 µg. Mice that received four cycles of 10 µg L-IP-TK demonstrated the longest survival (P < 0.05), with a median survival of 126 days. In comparison, mice that received a single cycle of 35 µg L-IP-TK/GCV or GCV alone survived a median of 92 days and 68.7 days, respectively. There were no significant changes in glucose or insulin levels following treatment. In conclusion, multiple cycles of liposomal IP-TK/GCV ablate human PDAC in SCID mice with minimal toxicity, suggesting non-viral vectors are superior to adenoviral vectors for IP-gene therapy.