Effect of TGF-β on Gli2 expression in HL60 and U937 cell lines

Abstract

Abstract. The Hedgehog (Hh) signaling pathway is involved in a variety of tumor-related diseases, including leukemia. The aim of this study was to determine whether there is an interaction between the Hh signaling pathway and transforming growth factor-β (TGF-β) in the HL60 and U937 cell lines. HL60 and U937 cells were treated with TGF-β, tumor necrosis factor-α (TNF-α) and specific inhibitor of Smad3 (SIS3). The expression of Gli2 was detected by real-time PCR and western blotting. The results showed that TGF-β alone did not affect the Gli2 expression in HL60 cells, while it significantly reduced the level of Gli2 expression in U937 cells. TGF-β+TNF-α reduced the expression of Gli2 in HL60 cells and U937 cells. The reduction in the level of Gli2 expression in U937 cells by TGF-β+TNF-α was greater than that caused by TGF-β alone. SIS3 inhibited the effect of TGF-β. Our results suggest that the effect on Gli2 expression in HL60 and U937 cells induced by TGF-β is Smad3-dependent and independent of Hh receptor signaling. IntroductionThe Hedgehog (Hh) signaling pathway is associated with cell growth and differentiation, with a normal role in embryonic pattern formation and adult tissue homeostasis and pathological roles in tumor initiation and growth (1). Gli transcription factors are the final effectors of the Hh signaling pathway. In a number of tumors, including those of the pancreas, prostate, skin and lung, the ectopic activation of Gli proteins has been linked to tumorigenesis (2). Evidence suggests additional, non-canonical mechanisms of Gli activation (2). Certain studies have suggested that in normal fibroblasts and keratinocytes, as well as in various cancer cell lines, the Gli transcription factors are not solely regulated by Hh/Smo signaling, but also by other pathways, including the transforming growth factor-β (TGF-β) signaling pathway. TGF-β induces Gli2 expression in a Smad3-dependent manner and this effect is independent from the Patched/Smoothened (Ptch/Smo) axis (3).In hematopoiesis, Hh family members are also significant in the regulation of stem/progenitor cell expansion in vitro and in vivo (4). The components of Hh signaling have been detected in several leukemia cell lines; Ptch and Smo were expressed in Jurkat cells (5), Shh and Gli1 in HL60 and KG-1 cells (6) and Gli2 in U937 and HL60 cells (7). Similar to Hh members, TGF-β is involved in regulating the balance between proliferation and differentiation in hematopoietic cells (8,9).To find a new target for leukemia treatment, we hypothe sized that there is also crosstalk between the Hh signaling pathway and TGF-β in leukemia cells. In this study, we examined the ability of TGF-β to modulate the expression of the Hh signaling molecule Gli2 in the HL60 and U937 cell lines. Targeting the interaction between Hh and TGF-β signaling may provide new therapeutic opportunities for leukemia treatment. Materials and methodsCell cultures and reagents. The human myeloid leukemia cell lines HL60 and U937 were gifts from the Institute of Hematology (Chine...

Carcinosarcoma of the Parotid

“…The expression of Gli2 in this context most likely indicates the induction of the TGF-β signaling pathway that depends on SMAD3, as well as independent activation of Hh receptor signaling. 26 Both TGF-β and Hh signaling pathways have been implicated in activating EMT. 14,19,27 Thus, the expression of Gli2 most likely represents induction of EMT triggered, at least in part, by TGF-β and Hh signaling pathways.…”