Loss of connective tissue growth factor permits mesenchymal transition in ovarian cancer (260)

Abstract

<b>Objectives:</b> Epithelial-mesenchymal transition (EMT) is a characteristic feature of ovarian cancer (OC) metastasis. Our study aimed to determine the role of Connective Tissue Growth Factor (CTGF) in EMT. <b>Methods:</b> R182 and R2615 are epithelial OC cell lines that are CK18+, b-catenin+, TWIST -, and vimentin+. Time-course experiments +/- Transforming Growth Factor-b (TGF-b) and a TGF-b inhibitor were performed to evaluate the timing of CTGF expression in EMT. R182 and R2615 CTGF knockouts (KO) were derived utilizing a Cas9/CRISPR-Cas9 lentivirus plasmid vector. Phenotypic characterization of wild types (WT) and CTGF KO cell lines were performed with the assays, including scratch wound, proliferation, and anoikis resistance assays. Scratch wound assays were treated with 50 ng/mL and 100 ng/mL concentrations of recombinant CTGF for 48 hours (hr). Cells were plated in triplicate, and confluence was measured. Proliferation was determined by cell count using Biotek Cytation over 72 hr. For anoikis resistance, cells were plated in triplicate in an ultra-low adhesive cell plate with cell growth media. Using Promega CellTiter assay, cell viability was quantified by absorbance at 490 nm at the following time points: 1hr, 24hr, 48hr, and 120hr. Western blots were performed to evaluate the expression of epithelial and mesenchymal markers. RNA sequence analysis was performed, and pathway analysis was evaluated using the iPathway guide. <b>Results:</b> TGF-b induced CTGF expression in both OC cell lines tested. CTGF was induced as early as 30 minutes post-treatment, continued to increase until 6hr, and expression was maintained until 24 hr. No CTGF expression was seen in the mesenchymal mR182 and mR2615 OC cell lines. CTGF KO was confirmed by western blot analysis and indel sequencing. CTGF KO had no effect on the expression of epithelial markers, b-catenin, CK18, and vimentin, but SNAIL, a mesenchymal marker, was induced. Loss of CTGF also had no effect on cell proliferation but promoted anoikis resistance. R182 CTGF KO cells displayed 80% viability when grown in detached conditions for 48hr compared to only 20% viability in WT cells. At 120hr, 30% of KO cells remain viable compared to <10% for WT cells. R2615 WT and KO cells demonstrated similar results. Finally, the scratch assay showed that CTGF KO cells decrease the time to confluence compared to WT. Administration of recombinant CTGF does not rescue the phenotype to WT levels.Fig. 1 <b>Conclusions:</b> CTGF is expressed early in epithelial OC cells during EMT and is regulated by TGF-b. Our data suggest that CTGF permits maintenance of an epithelial phenotype through inhibition of SNAIL expression, and loss of CTGF should be evaluated as a poor prognosis indicator in OC.