Final answer:
All-trans-retinoic acid induces the differentiation of blasts in APL, causing them to mature into normal blood cells.
Step-by-step explanation:
All-trans-retinoic acid, a form of vitamin A, induces the differentiation of blasts (immature blood cells) in acute promyelocytic leukemia (APL). It binds to the altered retinoic acid receptor in APL, causing the blasts to mature into normal blood cells.