Differentiating agents in the treatment of leukemia.

The aim of differentiation therapy is to induce a maturation of the leukemic clone. Various approaches have been used: suppression of proliferation by low dose Ara-C in acute myeloid leukemia (AML); enhancement of differentiation by retinoic acid derivatives in acute promyelocytic leukemia (APL) or by differentiation-inducing factors; modulation of cell metabolism by breaking an autocrine loop in hairy cell leukemia (HCL). In all cases the treatment is given continuously at small doses over a long period of time. The very significant clinical results which have been obtained mainly in APL with all-trans retinoic acid and in HCL with alpha-interferon are briefly discussed.