Transforming Growth Factor β1 Alters Calcium Mobilizing Properties and Endogenous ATP Release in A549 Cells: Possible Implications for Cell Migration

Abstract

We examined the effects of transforming growth factor β1 (TGFβ1) on cellular functions in human lung cancer cell line A549. Treatment of A549 cells with 1 ng/ml TGFβ1 for more than 3 days altered their morphology from an epithelial cobblestone-like appearance to a fibroblast-like one, reduced the expression of E-cadherin mRNA and protein, and induced the formation of F-actin fibers. These hallmarks indicate that TGF β1 induced the epithelial–mesenchymal transition in A549 cells. Migration of TGF1β1-treated A549 cells, which was quantified by the wound-healing assay, was markedly accelerated by 3 μM ATPγS, a non-hydrolyzable ATP analogue. ATPγS-induced migration of TGFβ1-treated A549 cells was reversed by the P2 antagonist suramin. In contrast, migration of control A549 cells was not altered by ATPγS. TGFβ1-treated A549 cells showed an augmentation of ATP-induced Ca2+ transients, thapsigargin-induced Ca2+ transients, and store-operated Ca2+ entry compared with those in control cells. Basal level of the extracellular ATP concentration was significantly lower in TGFβ1-treated A549 cells than in control cells. We conclude from these results that TGFβ1 augments ATP-induced Ca2+ mobilization, which leads to the acceleration of migration, in A549 cells but, it markedly reduces endogenous ATP release. This implies that the actions of ATP would become a novel therapeutic target for inhibiting cancer cell migration.