Induction of Differentiation of Acute Promyelocytic Leukemia Cells by a Cytidine Deaminase-resistant Analogue of 1-b-D-Arabinofuranosylcytosine, 1-(2-Deoxy-2- methylene-b-D-erythro-pentofuranosyl)cytidine

Since the establishment of all-trans retinoic acid (ATRA) differentiation therapy, the prognosis of acute promyelocytic leukemia (APL) has improved, and APL has become a curable subtype of acute myelocytic leukemia. Complete remission can be achieved with ATRA alone, but disease-free survival is still too short because of relapse. To overcome this drawback, ATRA has been used in combination with chemotherapeutic agents such as 1-b-D-arabinofuranosylcytosine (araC) and daunorubicin. However, growth of the APL cell lines NB4 and HT93 is less sensitive to araC than to that of other myeloid leukemia cell lines such as HL-60 and U937. ATRA effectively induced granulocytic differentiation of NB4 and HT93 cells, whereas araC did not, even in a high concentration. A cytidine deaminase-resistant analogue of araC, 1-(2-deoxy-2-methylene-b-D-erythro-pentofuranosyl)cytidine (DMDC), inhibited the growth of NB4 and HT-93 cells and was also effective on HL-60 and U937 cells. The promyelocytic cell lines were induced to differentiate by DMDC and other cytidine deaminase-resistant analogues. Among them, DMDC was the most potent in inducing differentiation and inhibiting the growth of NB4 cells. The ATRA-induced differentiation of NB4 cells was not augmented by araC, whereas combined treatment with ATRA and DMDC had more than additive effects in inducing the differentiation of NB4 cells. Similar results were observed in a primary culture of leukemia cells that had been freshly isolated from APL patients. These results suggest that DMDC may play a role in the treatment of APL.