““The basis for the potential of all virolytic therapeutics resides in the exquisite selectivity they exhibit for infecting and killing cancer cells. The very nature of cancer cells makes them extremely susceptible to virus infection: they divide in an uncontrolled fashion and are metabolically hyperactive, thus they exhibit greatly diminished capacity for apoptosis and innate immune defense against virus infection. While normal cells reduce metabolic activity, activate apoptotic signaling pathways, and block cell cycle progression in response to virus infection, cancer cells remain oblivious. These are perfect conditions for the growth of viruses, particularly those that are attenuated for growth in normal cells. Consequently, oncolytic viruses are specific reagents that target cancer cells and spread from cell to cell within tumors. It has become apparent that the direct lytic effects of viruses on cancer cells is just one element of their therapeutic effects, the cytolisis of infected cells releases viral and cellular antigens that can provoke anti-tumor immune responses, and some cancer therapeutic viruses are engineered to deliver additional genes such as immune activators to augment these effects.””
