Therapeutic efficacy of G207, a conditionally replicating herpes simplex virus type 1 mutant, for gallbladder carcinoma in immunocompetent hamsters

Gallbladder cancer is an extremely difficult disease to cure once metastases occur. In this paper, we explored the potential of G207, an oncolytic, replication-competent herpes simplex virus type 1 mutant, as a new therapeutic means for gallbladder cancer. Gallbladder carcinoma cell lines (four human and one hamster) showed nearly total cell killing within 72 h of G207 infection at a m.o.i. of 0.25 to 2.5 in vitro. The susceptibility to G207 cytopathic activity correlated with the infection efficiency demonstrated by lacZ expression. Intraneoplastic inoculation of G207 (1 × 10⁷ pfu) in immunocompetent hamsters bearing established subcutaneous KIGB-5 tumors caused a significant inhibition of tumor growth and prolongation of survival. Repeated inoculations (three times with 4-day intervals) were significantly more efficacious than a single inoculation. In hamsters with bilateral subcutaneous KIGB-5 tumors, inoculation of one tumor alone with G207 caused regression or growth reduction of uninoculated tumors as well as inoculated tumors. In athymic mice, however, the anti-tumor effect was largely reduced in inoculated tumors and completely abolished in remote tumors, suggesting large contribution of T-cell-mediated immune responses to both local and systemic anti-tumor effect of G207. These results indicate that G207 may be useful as a new strategy for gallbladder cancer treatment.