Molecular pathways: multimodal cancer-killing mechanisms employed by oncolytic vesiculoviruses

Cancer is a heterogeneous disease that, for the most part, is not effectively managed with existing therapies. Oncolytic viruses are an attractive class of experimental cancer medicine because, unlike conventional chemotherapeutic and molecularly targeted drugs, they orchestrate tumor cell death in multiple ways simultaneously. In this review, we discuss the numerous cancer-killing "pathways" marshalled by oncolytic vesiculoviruses. From directly infecting and lysing malignant cells, to engaging the host's innate and adaptive anticancer immune responses, to inducing vascular collapse within a tumor, oncolytic vesiculovirus therapy commandeers a coordinated, multipronged assault on cancer that is curative in numerous preclinical models. And as our appreciation of these mechanisms has progressed, so has our capacity to engineer improved outcomes. Notably, efforts to polarize the host's immune system toward the tumor and away from the virus have been particularly effective in immunocompetent murine models, and hold tremendous therapeutic promise for human patients. With a first-in-man phase I trial recently initiated in the United States, the clinical significance of oncolytic vesiculorivus therapy, after nearly 15 years of development, may soon come into focus.