Modulation of IL-8, IL-1 beta, and G-CSF secretion by all-trans retinoic acid in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a homogeneous subgroup of acute myeloid leukemias (AML) characterized by the presence of the t(15;17) translocation and the resulting PML/RAR alpha fusion proteins. To date APL is the only AML which is sufficiently sensitive to all-trans retinoic acid (ATRA) differentiating effect. We have recently reported that APL express and secrete hematopoietic growth factors (HGF) such as IL-1 beta, TNF alpha, and IL-6. In vivo ATRA alone allows achievement of complete remission in APL patients. One of ATRA therapy's drawbacks is the increase of peripheral blast cells often associated with the ATRA leukocyte activation syndrome. To determine if this specific side-effect was linked to an increase of HGF release by APL cells, we studied the modulation of cytokine production by APL cells, we studied the modulation of cytokine production by APL samples (n = 12) before and after incubation with ATRA. ATRA failed to modulate TNF alpha, IL-6 or GM-CSF secretion levels; however, IL-8 levels decreased in 11 cases, and in four cases up-regulation of IL-1 beta and G-CSF protein expression was observed. These modulations were found to be linked to ATRA sensitivity as ATRA failed to modulate cytokine production in non-APL cells (n = 8). Interestingly, the increase of IL-1 beta and G-CSF production in the presence of ATRA was highly correlated to an increase in APL cell count in vitro and in vivo hyperleukocytosis, resulting in fatal outcome. IL-1 beta, TNF alpha, IL-6, and IL-8 are known to be implicated in leukocyte activation. The results of this study suggest that ATRA-induced hyperleukocytosis and ATRA leukocyte activation syndrome in APL may be inherent to the secretion of specific hematopoietic growth factors by the APL cells.