RARA and acute promyelocytic leukemia: Research findings indicate that vitamins can cause G1 phase arrest and prevent cell progression into the S phase through the upregulation of cyclin-dependent kinase (CDK) inhibitors (CDKIs), which are essential for cell cycle progression, thereby halting cancer cell growth.98, 99, 100 In acute promyelocytic leukemia cells, RAR and CDK-activating kinase interact, and CDK-activating kinase inhibition by all-trans RA (ATRA) results in hypophosphorylation of PML-RARα and myeloid differentiation.