LPA receptor 2 mediates LPA-induced endometrial cancer invasion

Abstract

Objective We have previously shown that lysophosphatidic acid (LPA) promotes the ovarian cancer metastatic cascade. In this study, we evaluated the role of LPA on endometrial cancer invasion. Methods Transient mRNA knockdown was accomplished using pre-designed siRNA duplexes against LPA receptor 2 (LPA2) and human matrix metalloproteinase-7 (MMP-7). RT-PCR was used to characterize LPA receptor and MMP-7 expression. Analysis of in vitro invasion was performed with rat-tail collagen type I coated Boyden chambers. Gelatin zymography was used to evaluate the MMP activity in cell culture conditioned media. Cell–cell and cell–matrix attachment was also assessed upon LPA2 knockdown to further illuminate the LPA2 cascade. Results LPA increases HEC1A cellular invasion at physiologic concentrations (0.1–1 μM). Of the four principle LPA receptors, LPA2 is predominantly expressed by HEC1A cells. Transient transfection of LPA2 siRNA reduced LPA2 mRNA expression in HEC1A cells by 93% ( P < 0.01). Silencing LPA2 eliminated the LPA-stimulated increase in invasion ( P < 0.05) and reduced LPA-induced MMP-7 secretion/activation, without significantly affecting cell–cell or cell–matrix adhesion. Silencing MMP-7 reduced overall invasion but did not eliminate LPA's pro-invasive effect on HEC1A cells, as compared to negative control ( P < 0.05). Gelatin zymography confirmed that LPA2 and MMP-7 knockdown reduced MMP-7 activation in HEC1A conditioned media. Conclusion LPA2 mediates LPA-stimulated HEC1A invasion and the subsequent activation of MMP-7.