Telomerase Activated Thymidine Analogue Pro-drug Is A New Molecule Targeting Hepatocellular Carcinoma

Background and aim: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. However, there is no effective treatment for HCC. It has been shown that sustained activation of telomerase is essential for the growth and progression of HCC, suggesting that telomerase is a rational target for HCC therapy. We develop a thymidine analogue prodrug, acycloguanosyl 5’-thymidyltriphosphate (ACV-TP-T) that is specifically metabolized by telomerase and releases the active form of acyclovir. We investigate the anti-tumor efficacy of ACV-TP-T in vitro and in vivo models. Material and methods: We evaluated proliferation and apoptosis of different hepatic cancer cell lines (HepG2, Hep3B, HuH7 and Hepa1-6) incubated with ACV-TP-T. We tested the in vivo efficacy of the treatment in HBV transgenic mice (TgAlb43Bri), that spontaneously develop hepatic tumors, and in a syngeneic orthotopic murine HCC model, where HCC cells were implanted directly in the liver. Results: The pro-drug was actively metabolized inside the hepatic cancer cells into the activate form of acyclovir; proliferation assessed by thymidine incorporation, was reduced, and apoptosis, assessed by caspase activity, was increased. Alteration in the cell cycle profile was induced by pre-incubating the hepatic cancer cells with ACT-TP-T. Treatment with ACT-TP-T reduced growth, increased apoptosis, and reduced proliferation of the tumors in the transgenic and in the orthotopic murine model. Conclusions: ACT-TP-T, thymidine analogue pro-drug, is activated by telomerase in HCC cells and releases active acyclovir that reduces proliferation and induce apoptosis in human and murine cancer cell lines as well as in animal models.