The Activation of STAT3 Contributes to the Effect of Autocrined G-CSF On the Proliferation of HL60 Cells Induced by ATRA.

In previous works, we detected several significant cytokines in the serum of patients with APL after treatment with ATRA, and the results revealed a close association of serum G-CSF and the number of promyelocytes or more mature granulocytes. Some of the results also indicate that ATRA in vitro has a conspicuous effect on the expression of some cytokines, such as IL-1β, IL-8, TNF, G-CSF, and so on. At least, it is showed that cytokines in serum or supernatant secreted by APL cells perhaps played an important role in the genesis of leukocytosis. However, the role of G-CSF in proliferation of APL cells has not yet been explained clearly. In the present study, we analyse the secretion and expression of cytokines in APL patients who has hyperleukocytosis, study the relationship between cytokines and leukocytosis, and detect the signal transduction pathway of cytokines.

To detect the signal pathway of IL-1β and G-CSF secreted by primary acute promyelocytic leukemia (APL) cells induced by all-trans retinoic acid (ATRA).

Primary APL cells from ATRA-treated patients were cultured in RPMI 1640, then the level of supernatant IL-1β and G-CSF were detected by ELISA assay. The expression of IL-1β or G-CSF mRNA was measured by RT-PCR, and the level of STAT1α and STAT3 evaluated by Western blot.

Treated with ATRA, the peripheral blood leucocytes of patients with APL was obviously up-regulated, and peaked at 12 days averagely, of which mainly were myelocytes and metamyelocytes. The secretion of IL-1β or G-CSF in supernatant was up-regulated (P<0.05). RT-PCR assay confirmed that in the primary APL cells, with higher secretion of IL-1β and/or G-CSF, the expression of IL-1β and/or G-CSF was up-regulated, correspondingly. Cytokines and signal transduction factors analysis indicated that the expression of STAT1α protein increased in all the patients, irrelevant to the expression of IL-1β or G-CSF, but the increase of STAT3 expression was consistent with the expression and secretion of G-CSF.

The higher expression of G-CSF in primary APL cells induced by ATRA contributes to the activation of STAT3.

No relevant conflicts of interest to declare.