RA is produced by tumors, presumably at various levels depending on tissues and cancer types.[12, 16] RA rapidly induces RARα modifications (phosphorylation, SUMOylation, and/or ubiquitination) in many cell types including T cells.[17] Particularly, RARα is tagged for degradation by murine double minute‐2 as an E3 ubiquitin ligase for degradation by the ubiquitin‐proteasome pathway.[18] Thus, tissue‐produced RA would affect the protein level of RARα in cells. Here, RARA is linked to cancer.