The role of 13 cis-retinoic acid in the remission induction of a patient with acute promyelocytic leukemia.

The addition of retinoic acid to human promyelocytic leukemia cells in culture results in their differentiation to mature myeloid forms with acquisition of the differentiated phenotype, i.e., the ability to reduce nitroblue tetrazolium. A heavily pretreated patient with acute promyelocytic leukemia and residual malignant cells in his marrow after multiple courses of chemotherapy was given 13-cis-retinoic acid upon demonstration of both morphologic and functional differentiation of his leukemic cells by transretinoic acid in vitro. The patient achieved a complete remission and was maintained on 13-cis-retinoic acid for 1 year, when the patient relapsed with a population of cells that were resistant to retinoic acid-induced differentiation.