Although the pro-invasive role of epidermal growth factor (EGF) has been reported in human trophoblast cells, the underlying mechanism remains largely unexplored. This work reveals that EGF-induced downregulation of connective tissue growth factor (CTGF) mediates the EGF-stimulated human trophoblast cell invasion.
During the development of the placenta, trophoblast cell invasion must be carefully regulated. Although EGF has been shown to promote trophoblast cell invasion, the underlying mechanism remains largely undetermined. Our previous study using RNA-sequencing (RNA-seq) has identified that kisspeptin-1 is a downstream target of EGF in a human trophoblast cell line, HTR-8/SVneo, and mediates EGF-stimulated cell invasion. In the present study, after re-analysis of our previous RNA-seq data, we found that the CTGF was also downregulated in response to the EGF treatment. The inhibitory effects of EGF on CTGF mRNA and protein levels were confirmed in HTR-8/SVneo cells by reverse transcription quantitative real-time PCR and western blot, respectively. Treatment with EGF activated both PI3K/AKT and ERK1/2 signaling pathways. Using pharmacological inhibitors, our results showed that EGFR-mediated activation of PI3K/AKT signaling was required for the EGF-downregulated CTGF mRNA and protein levels. Matrigel-coated transwell invasion assays demonstrated that EGF treatment stimulated cell invasion. In addition, the invasiveness of HTR-8/SVneo cells was suppressed by treatment with recombinant human CTGF. By contrast, siRNA-mediated knockdown of CTGF increased cell invasion. Notably, the EGF-promoted HTR-8/SVneo cell invasion was attenuated by co-treatment with CTGF. This study provides important insights into the molecular mechanisms mediating EGF-stimulated human trophoblast cell invasion and increases the understanding of the biological functions of CTGF in the human placenta.