Thymosin β4 and AcSDKP inhibit the proliferation of HL‐60 cells and induce their differentiation and apoptosis

Abstract

Our previous works have shown that bone marrow stromal cells secrete thymosin beta4 (Tbeta4) and AcSDKP. Tbeta4 and AcSDKP are existed in the conditioned medium of bone marrow endothelial cells. They exerted inhibitory effects on hematopoietic cells and then had protective effect on the early hematopoietic cells, which were cultured in the presence of hematopoietic stimulators. Thymosin beta4 consists of 43 peptides with a molecular weight of 4963. It contains at its N-terminal end the sequence of the acetylated tetrapeptide Ac-N-Ser-Asp-Lys-Pro (AcSDKP). This study was performed to evaluate the effect of Tbeta4 and AcSDKP on the growth of HL-60 cells. It was showed that Tbeta4 (10(-11)-10(-7)mol/L) and AcSDKP (10(-11)-10(-7)mol/L) had the dose-dependent inhibitory effect on the proliferation of HL-60 cells. Based on cell morphology and NBT reduction, Tbeta4 and AcSDKP induced differentiation of HL-60 cells. Morphologic and DNA fragment analysis proved that Tbeta4 and AcSDKP induced apoptosis of HL-60 cells. In order to analyze the mechanism of the effects of Tbeta4 and AcSDKP, intracellular free Ca(2+) concentration ([Ca(2+)](i)) of HL-60 leukemic cells was tested and Atlas cDNA Expression Array was performed. The results showed that Tbeta4 and AcSDKP could increased [Ca(2+)](i) by stimulating the release of Ca(2+) from intracellular Ca(2+) pool. Moreover, AcSDKP could also elicit a potent extracelluar calcium influx in HL-60 cells. Tbeta4 could also change apoptotic-related gene expression in leukemic cells, and resulted in the inhibition of proliferation and induction of differentiation and apoptosis of leukemic cells.

Thymosin 4 has tumor suppressive effects and its decreased expression results in poor prognosis and decreased survival in multiple myeloma

“…Addition of this protein fraction to different leukemic cell lines resulted in a decrease in growth responses. 21 Similar inhibitory effects were recently described for Tβ4 on hematopoietic stem cells, 22 bone marrow derived mast cells 23 and human promyelocytic leukemia cells, 24 in agreement with the results presented here. Whereas a mechanistic explanation of this discrepancy is beyond the scope of this paper, further investigations are clearly merited.…”

Expression of thymosin β4 in odontoblasts during mouse tooth development

“…Treatment with Tβ4 increases the release and influx of Ca 2+ in human myeloid leukemic cells along with extocytosis of β-Hex, histamine, and tryptase from mast cells in a dose-dependent manner (32,33). Further, Tβ4 increases the exocytosis of cytolytic granules from natural killer cells (34).…”

Expression pattern of thymosin beta 4 in the adult human liver

“…10 Tβ4 is thought to be also involved in many critical biological processes including angiogenesis, 11 wound healing, 12 inflammatory response 13 and cell migration. 14 Similarly, Tβ4 activity was implicated in differentiation of hematopoietic cells, 15 in carcinogenesis, 16 in apoptosis, 17 and in blood coagulation. 18 …”