Inhibition of Cytotrophoblastic (JEG-3) Cell Invasion by Interleukin 12 Involves an Interferon γ-mediated Pathway

Abstract

Trophoblast invasion, like tumor invasion, shares common biochemical mechanisms. However, in contrast to tumor invasion of a host tissue, trophoblastic invasion during implantation is strictly regulated, temporospatially. Factors responsible for these important regulatory processes are presently unknown; however, studies indicate that cytokines and growth factors present in the peri-implantation uterine milieu as the possible candidates. In this study we investigated the role of interleukin (IL) 12 in regulating trophoblast invasion and the expression of trophoblast proteases (matrix metalloprotease (MMP)-2, MMP-9, and urokinase-type plasminogen activators) and their inhibitors (tissue inhibitors of metalloprotease (TIMP) 1, TIMP-2, and plasminogen activator inhibitor (PAI)-1) using an in vitro tissue culture system of human choriocarcinoma cell line JEG-3. Our major findings show an anti-invasive role of IL-12, associated with an inhibitory effect on the proteases but with an opposite up-regulating influence on the protease inhibitor, TIMP-1, whereas TIMP-2 and plasminogen activator inhibitor 1 remained unaltered. Stimulation of JEG-3 cells with IL-12 also induced interferon (IFN)-␥ production, which when neutralized using a monoclonal anti-IFN-␥ antibody, F12, abrogates its ability to down-regulate the MMPs. IL-12 also mediates an IFN-␥-dependent up-regulation of E-cadherin, thereby implying that alteration in cell-cell adhesion besides regulating the proteases and the inhibitors possibly contributes to the observed anti-invasive role of this cytokine. TIMP-1, although stimulated by IL-12, was found to be unaltered by antibody F12, thereby implying a possibility of an IL-12-dependent-IFN-␥ independent regulation. These findings thereby suggest an important role of IL-12 in modulation of trophoblast proteases and their inhibitors besides regulating cell-cell interactions and invasion during implantation, with far reaching possibilities for understanding the mechanism(s) and regulations of invasion and metastasis.Implantation is an excellent example of successive interactions between two dissimilar tissues, the receptive uterus and the developing blastocyst, each genetically distinct from the other. This two-way interaction is largely mediated by the intimate contact between the uterine luminal epithelium and the outermost polarized epithelial cells of the blastocyst, the trophoblast. Trophoblast cells are instrumental during implantation and placentation both in terms of molecular recognition and cross-talk at the feto-maternal interface as well as a repository of variety of cytokines and growth factors that influence both the conceptus and the maternal physiology in an autocrine, paracrine, or juxtacrine manner (1, 2). This represents a highly complex but coordinated process involving the participation of different trophoblast cell populations with specific functions (3, 4). The interaction begins as the blastocyst enters the uterine lumen and becomes apposed to the uterine epithelium with its trophoblast cell...

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