We excluded that the RA growth-promoting action is limited to either the specific RARA403 mutation or the T74D breast cancer cell context, because we observed RA induction of cell growth also when we took into consideration another dominant negative RARA allele (RARAG303E) (Figure S2A) and another breast cancer cell context (MCF7) (Supplementary Figure S3). Here, RARA is linked to breast cancer.