NFKB1 and neoplasm: Indeed, we found that the noncanonical NF‐κB signaling specifically mediated the expression of Bclx1, as demonstrated by dramatically decreased Bcl‐XL protein levels without affecting other apoptosis‐related proteins in the NIK‐knockdown tumor cells after IR treatment (Fig. 6F), suggesting NIK‐mediated noncanonical NF‐κB is dispensable for irradiation‐induced Mcl‐1 and Bcl‐2 protein expression.