Induction of differentiation of human promyelocytic leukemia cell line HL-60 by retinoyl glucuronide, a biologically active metabolite of vitamin A.

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Abstract
We examined the differentiation activity of retinoyl .beta.-D-glucuronide, a biologically active physiological metabolite of vitamin A, using the human promyelocytic leukemic cell line HL-60, which can be induced to differentiate with retinoic acid. Retinoyl .beta.-D-glucuronide (1 .mu.M) inhibited HL-60 cell proliferation by 55-75%, inhibited tritiated thymidine incorporation into DNA by 63-80%, and induced 38-50% of the cells to differentiate into mature granulocytes. The potency of growth inhibition and induction of differentiation by retinoyl .beta.-D-glucuronide was similar to that of all-trans-retinoic acid. The continuous presence of either retinoyl .beta.-D-glucuronide or all-trans-retinoic acid was not required to obtain maximum growth arrest and differentiation: a 1-hr exposure of HL-60 cells to the retinoids gave the same response (measured after a total incubation time of 48 hr) as a 24-hr or 48-hr continuous treatment. Retinoyl .beta.-D-glucuronide (0.1-0.2 mM) was 50% less cytotoxic to HL-60 cells than all-trans-retinoic acid at an equimolar concentration. Retinoyl .beta.-D-glucuronide was not significantly metabolized to other retinoids; retinoic acid was not formed during incubation. We conclude that retinoyl .beta.-D-glucuronide can arrest HL-60 cell proliferation and induce their differentiation into mature granulocytes; it may act by itself or by being hydrolyzed to retinoic acid, which could be immediately utilized and metabolized. The therapeutic use of this retinoid as an antineoplastic agent is suggested.