Apart from promoting cell differentiation and suppressing stemness, retinoids and VD3 promote cell cycle arrest/senescence by modulating various cyclin-dependent protein kinase inhibitors, such as p16(INK4A), p21(CDKN1A), p27 (CDKN1B), and p57, which was apparent in a PTEN-deficient cell-based model of GBM with ATRA [23]. Here, CDKN1A is linked to glioblastoma.