Effects of retinoids on in vitro differentiation of bone marrow cells in the myelodysplastic syndrome.

The effect of retinoids on cell differentiation in the myelodysplastic syndrome was studied in short-term liquid cultures of bone marrow from 13 patients. After incubation with 13-cis-retinoic acid there was a significant decrease in the percentages of promyelocytes and in Leu-M3-binding cells. Lue-M3 is mainly a monocyte marker, and retinoids thus seem to induce a shift from monocytoid to myeloid differentiation. Patients with refractory anemia with an excess of blasts responded the most, and did also show a significant decrease in OKIa1-binding cells. Etretinate, on the other hand, did not show any differentiation-inducing activity. The results support earlier reports that retinoic acid might be useful in the treatment of the myelodysplastic syndrome. Whether this in vitro technique offers a possibility to predict the clinical outcome remains to be shown.