Abstract
4-[5H-2, 3-(2, 5-Dimethyl-2, 5-hexano)-5-methyldibenzo[b, e]diazepin-11-yl]benzoic acid (4) enhanced the differentiation-inducing activity of retinoic acid (1) and of a synthetic retinoid Am80 (2) toward human promyelocytic leukemia cells HL-60, although 4 alone did not induce differentiation. The synergistic effect of 4 on the activities of retinoids was also seen in suppression of proliferation of HL-60 cells.