Figure 1.

Viral oncolysis dependent on RNA-activated protein kinase (PKR) inactivation. In normal cells (A), the presence of oncolytic viruses activates interferon type I pathway, leading to PKR expression and activation. Activated PKR phosphorylates elF2α, impairing GTP recycling and blocking cell translation. The presence of PKR may induce apoptosis of the infected cell. In tumor cells (B) where interferon type I response is disrupted, oncolytic viruses does not induces PKR expression, allowing GTP recycling in elF2α and viral protein translation.