Oncolytic Viruses: Newest Frontier for Cancer Immunotherapy

SIMPLE SUMMARY: Oncolytic viruses (OVs) are viruses that selectively target and kill cancer cells while sparing normal ones. OVs are from diverse families of viruses, but naturally occurring OVs have been genetically engineered due to their limitations in therapeutic application. These engineered OVs with enhanced tumor targeting ability, oncolytic activity, or generating potent anti-tumor immune responses are tested in preclinical animal models and cancer patients in clinical trials. Due to their multi-mechanistic anti-tumor effects, OVs have emerged one of the key cancer immunotherapy agents. However, due to the limited success with novel anti-cancer therapies such as immunotherapies and cell-based therapies, combination therapies should be tested with OVs. We discuss such combination therapies that are explored to further improve oncolytic virotherapy. ABSTRACT: Cancer remains a leading cause of death worldwide. Despite many signs of progress, currently available cancer treatments often do not provide desired outcomes for too many cancers. Therefore, newer and more effective therapeutic approaches are needed. Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively targets and kills cancer cells while sparing normal ones. In the past several decades, many different OV candidates have been developed and tested in both laboratory settings as well as in cancer patient clinical trials. Many approaches have been taken to overcome the limitations of OVs, including engineering OVs to selectively activate anti-tumor immune responses. However, newer approaches like the combination of OVs with current immunotherapies to convert “immune-cold” tumors to “immune-hot” will almost certainly improve the potency of OVs. Here, we discuss strategies that are explored to further improve oncolytic virotherapy.