Several studies have shown that a metabolite of vitamin A (all-trans retinoic acid, atRA) induces re-differentiation of transformed cells during the early stages of the neoplastic process and promotes the apoptosis of human breast cancer cells by regulating the Tet Methylcytosine Dioxygenase 2-Protein Kinase C zeta (TET2–PKCζ) pathway [55,56,57]. This evidence concerns the gene TET2 and breast cancer.