Syncytium-forming HSV-1 in cancer gene therapy: From molecular mechanisms to clinical translation

Gene therapy has emerged as a promising strategy for cancer treatment, yet challenges in efficient gene delivery remain a major barrier. Herpes simplex virus type 1 (HSV-1), as an oncolytic virus, has garnered attention for its potential in cancer therapy due to its replicative capacity, large genomic payload, and relatively low toxicity. Notably, syncytium-forming HSV-1 (SF-HSV-1) not only exhibits enhanced and sustained antitumor efficacy but also triggers profound immune responses. However, the exact molecular mechanisms orchestrating HSV-1-induced syncytium formation, its resulting cytotoxicity, and its precise role in immune modulation remain incompletely understood. This review aims to provide an in-depth exploration of the mechanisms underlying HSV-1 syncytium formation and its therapeutic implications in cancer gene therapy.