Abstract
Oncolytic herpes simplex virus (oHSV)-1-based vectors selectively replicate in tumor cells causing direct killing, that is, oncolysis, while sparing normal cells. The oHSVs are promising anticancer agents, but their efficacy, when used as single agents, leaves room for improvement. We hypothesized that combining the direct oncolytic and antiangiogenic activities of the interleukin (IL)-12-secreting NV1042 oHSV with microtubule disrupting agents (MDAs) would be an effective means to enhance antitumor efficacy. Vinblastine (VB) was identified among several MDAs screened, which displayed consistent and potent cytotoxic killing of both prostate cancer and endothelial cell lines. In matrigel tube-forming assays, VB was found to be highly effective at inhibiting tube formation of human umbilical vein endothelial cells. The combination of VB with NV1023 (the parental virus lacking IL-12) or NV1042 showed additive or synergistic activity against prostate cancer cell lines, and was not due to increased oHSV replication by VB. In athymic mice bearing CWR22 prostate tumors, VB in combination with NV1042 was superior to the combination of VB plus NV1023 in reducing tumor burden, appeared to be nontoxic and resulted in a statistically significant diminution in the number of CD31(+) cells as compared with other treatment groups. In human organotypic cultures using surgical samples from radical prostatectomies, both NV1023 and NV1042 were localized specifically to the epithelial cells of prostatic glands but not to the surrounding stroma. These data highlight the therapeutic advantage of combining the dual-acting antitumor and antiangiogenic activities of oHSVs and MDAs.