Circ_0070203 Promotes Epithelial-mesenchymal Transition in Ovarian Serous Cystadenocarcinoma through miR-370-3p/TGFR2 Axis

Introduction: Circular RNAs (circRNAs) are important biological molecules associated with the pathogenesis of multiple cancers. Objective: This work aimed to investigate the function and molecular mechanism of circ_0070203 in high-grade serous ovarian cystadenocarcinoma (HGSOC). Methods: circRNA microarray was conducted to detect the circ_0070203 expression in HGSOC tissues. Bioinformatics analysis was used to find the binding sites between circ_0070203, miR-370-3p and TGF beta R2. Real-time quantitative reverse transcription PCR (RT-qPCR) was executed to detect the expressions of circ_0070203, miR-370-3p and TGF beta R2 in HGSOC tissues and SKOV3 cells. Dual-luciferase reporter gene assay was used to validate the relationships between miR-370-3p and circ_0070203 or TGF beta R2. Besides, transwell assays were conducted to assess the migrative, invasive abilities of ovarian cancer (OC) cells. Western blotting was adopted to detect the expression of epithelial-mesenchymal transition (EMT)-related proteins. The related patents were also studied during the research. Results: Circ_0070203 and TGF beta R2 were upregulated, while miR-370-3p was downregulated in FIGO stage III-IV HGSOC tissues and SKOV-3 cell lines. circ_0070203 overexpression changed the expression of other EMT-related proteins and enhanced the migrative, invasive abilities of OC cells, while silencing circ_0070203 worked oppositely. Mechanistically, circ_0070203 could upregulate TGF beta R2 expression in OC cells via sponging miR-370-3p. Conclusion: Circ_0070203 could promote the epithelial-mesenchymal transition, invasion, and metastasis of HGSOC via regulating the miR-370-3p/TGF beta R2 axis. Our findings provided a potential biomarker for HGSOC therapy.