MIB2 and melanoma: MIB2 is an E3 ligase, which has recently been shown to mediate ubiquitination of PD-L1 in murine melanoma B16 cells and colorectal carcinoma MC38 cells, and to thereby facilitate the transport of PD-L1 from the trans-Golgi network to the plasma membrane to prevent T-cell-mediated tumor cells death [31].