A549DKO human lung carcinoma cells in which the PKR and RNase L genes were knocked out via CRISPR/Cas9 are very useful in studying VACV decapping enzyme functions since it excludes the PKR and RNase L activation-related RNA degradation and translation repression during decapping enzyme-inactivated VACV infection (34). This evidence concerns the gene EIF2AK2 and lung carcinoma.