It has been reported that ATRA can enhance the efficacy of the anti‐PD‐1 antibody pembrolizumab in stage IV melanoma patients,[19] and PD‐L1 has been reported as a substrate of β‐TrCP.[20] In addition, in Otud6b WT mice, we found that ATRA treatment significantly reduced the expression levels of PD‐L1, but not in Otud6b cKO mice (Figure 7G). Here, OTUD6B is linked to melanoma.