EIF2AK2 and cancer: The K3L gene product of vaccinia virus acts as a competitive inhibitor of the double-stranded RNA-dependent protein kinase (PKR) in infected host cells to prevent apoptotic cell death.16 However, in cancer cells, the PKR pathway is dysfunctional, and the vaccinia virus is able to continue replicating without a shortage of host cell resources even in the absence of the K3L gene.