CDKN2A and acute lymphoblastic leukemia: ATRA-treated Ink4-Arf deletion (Arf−/−) BCR-ABL ALL cells showed increased apoptosis, fewer S-phase cells, and more G0/G1-phase cells, and ATRA reduced BCR-ABL ALL cell viability by signaling through the retinoid X receptor (Annu et al., 2020).