EGF and cancer: Horita and colleagues reported that EGF induces the mono- and multiubiquitination of PD-L1 and precedes EGF-induced increases in the PD-L1 mRNA level.60 This finding partially explains the low expression of the PD-L1 protein in EGFR mutant cancer cells, although the activation of EGFR signaling leads to the transcription of PD-L1 mRNA.