CCR1 and acute promyelocytic leukemia: In acute promyelocytic leukemia (APL) cells, RH potentiated all-trans retinoic acid (ATRA)-induced macrophage differentiation in NB4 cells by inducing changes in morphology, expression of the differentiation markers CD11b and CD14, reactive oxygen species (ROS) production, phagocytic activity, and expression of CCR1 and CCR2.