EIF2AK3 and neoplasm: To confirm the hypothesis which viral oncoproteins promote tumor growth by increasing ROS production via inhibiting PERK, we implanted cells stably expressing WT or 4A-mutant LMP1 or E7 into nude mice, and observed a remarkable decrease in tumor growth in the mice implanted with cells stably expressing a 4A-mutant oncogene (Fig. 5c–e and g–i).