Background and methods: Vitamin D3 metabolites have been shown to be able to induce monocytic differentiation both in vitro and in vivo. In this paper we report the preliminary results of an uncontrolled clinical trial where low doses of ARA-C and 1(OH)D3 were administered to patients affected by acute non lymphoid leukemia. The achievement of complete or partial remission was recorded. Morphological and cytochemical studies were performed in order to control the blastic populations under therapy. Immunocytochemical studies were also performed in some patients in order to detect the presence of 1,25(OH)2D3 receptors in the blast population. Seventeen percent reached complete remission and 45% reached only a partial remission.
Results and conclusions: The results are in line with those showing that low doses of ARA-C are an effective treatment in this type of leukemia. In some cases (7/11), a monocytic/monoblastic shift was detected. The demonstration of 1,25(OH)2D3 receptors in some blasts is also reported. Thus it is possible to suggest that the vitamin D metabolite displays "in vivo" the differentiating activity already shown "in vitro".