[The role of cytokines on hyperleukocytosis associated with acute promyelocytic leukemia induced by all-trans retinoic acid therapy].

The mechanism of the cause of hyperleukocytosis induced by differntiation induction therapy of acute promyelocytic leukemia (APL) by all-trans retinoic acid (ATRA) was studies. Of 11 patients treated by ATRA in our hospital, 3 developed hyperleukocytosis. Moreover, 2 out of 4 patients with retinoic acid syndrome (ATRA syndrome) had hyperleukocytosis. Using the patients' leukemia cells as test material, we obteined the following results. In the presence of ATRA at a concentration that induced differentiation in vitro, promotion or supression of differentiation and lineage determination during the differentiation of APL cells involved factors other than ATRA, such as cytokines. Moreover, APL cells that differentiated into monocytoid cells possessed the capability of producing endogenous cytokines such as TNF alpha, which might be involved in the development of ATRA syndrome. Compared to cells from patients without hyperleukocytosis they had a stronger TNF alpha producing capability and lower sensitivity to TGF beta, showing hyperdifferentiation in response to ATRA. Depending on the case, those with the same sensitivity to ATRA might show different sensitivities to cytokines.