VITAMIN-D(3) ADMINISTRATION AND MULTIDRUG-RESISTANCE IN ACUTE NONLYMPHOBLASTIC LEUKEMIA

This article reports preliminary results from a pilot study started in 1986 on patients with acute myeloblastic leukemia treated for several months with low-dose arabinosylcytosine and 1(OH)D3. During treatment or at the time of relapse, a monoblastic component was frequently fou nd. A high percentage of patients were P-170-positive. In 2 patients i t was possible to show that blasts, previously P-170-negative, became positive after treatment. In these 2 patients, failure of clinical res ponse to antileukemic therapy was associated with this phenotype. The addition of the revertant drug nicardipine to the previously inactive treatment induced a partial response. Thus, previously reported in vit ro observations on the differentiating activity of vitamin D3 metaboli tes, possible induction of multidrug chemoresistance by differentiatin g agents and the revertant activity of the Ca++ antagonist nicardipine appear to be confirmed in vivo in the reported patients.