TNF(alpha)-Induced Apoptosis and Integrin Switching in Human Extravillous Trophoblast Cell Line

Differentiation of extravillous trophoblast cells (EVT) to an invasive phenotype plays an essential role in establishing and maintaining feto-placental organization during human pregnancy. A switch in integrin expression occurs during this differentiation and is accompanied by changes in the extracellular matrix (ECM). Alteration of EVT behavior is also modulated by cytokines. To investigate the molecular interactions involved in the EVT differentiation, we examined the effects of cytokines and ECM on the human EVT cell line, TCL1 cells. We found that tumor necrosis factor alpha (TNF(alpha)) induced apoptosis in TCL1 cells but not in JEG3 cells derived from choriocarcinoma while the addition of interleukin-1(beta), leukemia inhibitory factor, or transforming growth factor had no effect on TCL1 cells. This apoptosis was suppressed when TCL1 cells were seeded on fibronectin (Fn), collagen type I (C1), collagen type IV (C4), or laminin (Ln). Wortmannin, a specific PI3 kinase inhibitor, inhibited this suppression. Spreading assays and adhesion blocking assays indicated that TCL1 cells express integrin-(alpha)5 and -(alpha)6 and (beta)1 and (beta)4 subunits. Adhesion on Fn is mediated by (alpha)5(beta)1, and adhesion on C1, C4, or Ln is mediated by (alpha)6(beta)1 integrins. TNF(alpha) suppressed (alpha)6 integrin expression and enhanced (alpha) 1 integrin expression in a dose-dependent manner. In addition, aggregation of (beta)1 subunits on C4 was detected after addition of TNF(alpha). Taken together, these results suggest that TNF(alpha) and ECM, through activation of PI3 kinase mediated by (beta)1 integrin signaling, might collaboratively regulate differentiation of trophoblast cells through integrin signaling in establishing and maintaining successful pregnancy.