The E3 ubiquitin ligase STUB1 (STIP1 homology and U-box containing protein 1) also polyubiquitinates PD-L1 in the cytoplasmic domain at lysine residues and downregulates PD-L1 expression, whereas CMTM6 maintains PD-L1 stability by blocking ubiquitination in tumor cells [293]. This evidence concerns the gene CD274 and neoplasm.