Upregulation of dual-specificity phosphatase-26 is required for transforming growth factor β1(TGFβ1)-induced Epithelial-mesenchymal transition in A549 and PANC1 cells

Abstract

Background Transforming Growth Factor beta (TGF beta) proteins are potent inducers of the epithelial-mesenchymal transition (EMT) in tumor cells. Although mitogen-activated protein kinase (MAPK) family has been shown to be involved in TGF beta-induced EMT, role of Dual Specificity Phosphatases (DUSP), key regulators of MAPK activity, in TGF beta-induced EMT is largely unkonwn.Methods and results Real-time qPCR analyses were performed to determine the effect of TGF beta 1 on expression of EMT genes and DUSP proteins in the non-small cell lung cancer model A549 and pancreatic adenocarcinoma model PANC1 cells. Western blot analyses were conducted to study the changes in protein levels of EMT proteins and select DUSP proteins, as well as phosphorylations of MAPK proteins upon TGF beta 1 stimulation. Small interfering RNA (siRNA) was utilized to reduce expressions of DUSP genes. We observed that the EMT phenotype coincided with increases in phosphorylations of the MAPK proteins ERK1/2, p38MAPK, and JNK upon TGF beta 1 stimulation. Real-time qPCR analysis showed increases in DUSP15 and DUSP26 mRNA levels and Western blot analysis confirmed the increase in DUSP26 protein levels in both A549 and PANC1 cells treated with TGF beta 1 relative to control. Silencing of DUSP26 expression by siRNA markedly suppressed the effect of TGF beta 1 on E-cadherin and mesenchymal genes in the cells.Conclusions Data provided suggest that TGF beta 1 modulates the expression of DUSP genes and that upregulation of DUSP26 may be required for TGF beta 1-promoted EMT in A549 and PANC1 cells. Further studies should be carried out to elucidate the requirement of individual DUSPs in TGF beta 1-associated EMT in tumor cells.