Circ-PGAM1 promotes malignant progression of epithelial ovarian cancer through regulation of the miR-542-3p/CDC5L/PEAK1 pathway.

Epithelial ovarian cancer (EOC) is the most common ovarian malignant cancer. Circular RNA is a type of endogenous noncoding RNA and is considered as a novel regulatory molecule in the development and progression of tumors. This study investigated the expression and functions of a circular RNA, circular-phosphoglycerate mutase 1 (circ-PGAM1), in EOC tissues and cells. The expression of circ-PGAM1 and miR-542-3p in EOC was analyzed using quantitative RT-PCR. Immunohistochemistry and western blot were performed to confirm the localization and expression of cell division cycle 5-like (CDC5L) and pseudopodium enriched atypical kinase 1 (PEAK1) in EOC tissues. Cell lines (CAOV3 and OVCAR3) overexpressing or silencingcirc-PGAM1 and miR-542-3p were established to explore the functions of circ-PGAM1 and miR-542-3p in ovarian cancer cells. Furthermore, dual-luciferase reporter assay was performed to study the interactions between circ-PGAM1 and miR-542-3p and between miR-542-3p and CDC5L. CCK-8, transwell, and flow cytometry were used to study the effect of circ-PGAM1 and miR-542-3p on cell biological behaviors including proliferation, migration, invasion, and apoptosis. The interaction between CDC5L and the PEAK1 gene promoter was confirmed using chromatin immunoprecipitation (ChIP). Circ-PGAM1 was upregulated in EOC tissues, whereas linear PGAM1 was not deregulated in EOC tissues. Silencing of circ-PAGM1 inhibited proliferation, migration, and invasion of ovarian cancer cells and promoted cell apoptosis. MiR-542-3p was downregulated in EOC tissues, and miR-542-3p overexpression inhibited malignant progression of ovarian cancer cells. Circ-PGAM1 directly interacted with miR-542-3p, with mutual negative feedback between them. CDC5L was a direct target of miR-542-3p and played an oncogenic role in ovarian cancer cells. Furthermore, the CDC5L protein binds directly to the PEAK1 promoter to promote its transcription. PEAK1 overexpression activated ERK1/2 and JAK2 signaling pathways and promoted malignant biological behaviors of ovarian cancer cells. Circ-PAGM1 silencing combined with miR-542-3p overexpression played the greatest anticancer role in vivo. The circ-PGAM1/miR-542-3p/CDC5L/PEAK1 pathway played an important role in the progression of ovarian cancer and might be a novel therapeutic target for ovarian cancer.

Zhang C ，Li Y ，Zhao W ，Liu G ，Yang Q ... -  《Cancer Medicine》

RNA-binding protein IGF2BP2 enhances circ_0000745 abundancy and promotes aggressiveness and stemness of ovarian cancer cells via the microRNA-3187-3p/ERBB4/PI3K/AKT axis.

Circular RNAs (circRNAs) are increasingly recognized as important regulators in cancer including ovarian cancer (OC). This work focuses on the effects of circ_0000745 on the OC development of and molecules involved. Expression of circ_0000745 in collected OC tissues and the acquired OC cell lines was examined by RT-qPCR. The stability of circ_0000745 in cells was examined by RNase R treatment. The target transcripts interacted with circ_0000745 were predicted using bioinformatic systems. Gain- and loss-of-function studies of circ_0000745, microRNA (miR)-3187-3p and erb-b2 receptor tyrosine kinase 4 (ERBB4) were conducted to determine their functions on proliferation, migration, invasion and stem cell property of OC cells. Circ_0000745 and ERBB4 were abundantly expressed while miR-3187-3p was poorly expressed in OC tissues and cells. Circ_0000745 sequestered miR-3187-3p and blocked its repressive effect on ERBB4. Downregulation of circ_0000745 reduced proliferation, aggressiveness, epithelial-mesenchymal transition, and stemness of SK-OV-3 cells, but this reduction was blocked upon miR-3187-3p inhibition or ERBB4 upregulation. By contrast, artificial induction of circ_0000745 upregulation, miR-3187-3p upregulation and ERBB4 downregulation led to inverse trends in ES-2 cells. ERBB4 promoted the phosphorylation of the PI3K/AKT signaling pathway. An RNA binding protein IGF2BP2 was found to circ_0000745 bind to and promote its expression and stability. This study demonstrated that circ_0000745 upregulated by IGF2BP2 promotes aggressiveness and stemness of OC cells through a miR-3187-3p/ERBB4/PI3K/AKT axis. Circ_0000745 may serve as a promising target for OC treatment.

Wang S ，Li Z ，Zhu G ，Hong L ，Hu C ，Wang K ，Cui K ，Hao C ... -  《Journal of Ovarian Research》

CircFAM188A Regulates Autophagy via miR-670-3p and ULK1 in Epithelial Ovarian Carcinoma.

CircRNAs and autophagy are closely involved in the physiological and pathological processes of ovarian cancer; however, their exact mechanisms are still undetermined. This investigation aimed to elucidate the function and associated pathways of circFAM188A, which modulates proliferation, autophagy, and invasion in ovarian cancer (EOC). The expression of circFAM188A in the tissues of EOC patients was assessed via RT-PCR. To elucidate proliferation, invasion, and autophagy in the tumor cells, Transwell, 5-ethynyl-2'-deoxyuridine (EdU), and mRFP-GFP-LC3 reporter assays were conducted. The binding sites between circ-FAM188A and the miR-670-3p, miR-670-3p and YY1 were predicted using bioinformatics and verified by dual-luciferase reporter assays. Pulldown assays demonstrated binding between ULK1 and circ-FAM188A. ULK1 was found to be crucial in the initial stage of autophagy. Moreover, an in vivo xenograft model was established by subcutaneous injection of nude mice with EOC cells. Expression of circ-FAM188A was increased in EOC tissues relative to normal ovarian tissues and circ-FAM188A overexpression promoted proliferation, invasion, and autophagy; these effects were reversed by circ-FAM188A silencing. miR-670-3p and circ-FAM188A co-localized in the cytoplasm. circ-FAM188A enhanced YY1 expression by sponging miR-670-3p and was also shown to interact with ULK1. It is thus suggested that circ-FAM188A modulates autophagy by sponging miR-670-3p as well as interacting with ULK1.

Yong M ，Zeng Y ，Yao Y ，Yang M ，Tang F ，Zhu H ，Hu J ... -  《Cancer Reports》

MiR-539-3p promotes the progression of epithelial ovarian cancer by targeting SPARCL1.

Gong YB ，Fan XH 《-》

Circular RNA PVT1 enhances cell proliferation but inhibits apoptosis through sponging microRNA-149 in epithelial ovarian cancer.

This study aimed to investigate the influence of circular RNA PVT1 (circ-PVT1) on epithelial ovarian cancer (EOC) cell proliferation and apoptosis, more importantly, to identify the target microRNAs (miRNA) of circ-PVT1 in EOC. Circ-PVT1 expression in EOC cell lines and nonmalignant control cells was detected. Cell proliferation, apoptosis and candidate target miRNA (miR-149, miR-183 and miR-194) expressions were detected in circ-PVT1 overexpression treated CAOV3 cells and circ-PVT1 knock-down treated SKOV3 cells. Furthermore, miR-149 overexpression and miR-149 knock-down plasmids were transfected into circ-PVT1 dysregulated CAOV3 cells and SKOV3 cells, respectively, and cell proliferation as well as apoptosis were detected. Circ-PVT1 expression was increased in human EOC cell lines (CAOV3, SKOV3, SNU119 and OVCAR3) compared to human normal ovary surface epithelial cell line (HOSEpiC). In SKOV3 cells, cell proliferation was reduced at 48 and 72 h but cell apoptosis rate was increased at 48 h by circ-PVT1 knock-down. In CAOV3 cells, cell proliferation was increased at 48 and 72 h but cell apoptosis rate was decreased at 48 h by circ-PVT1 overexpression. Besides, circ-PVT1 negatively regulated miR-149 but not miR-183 or miR-194 in SKOV3 and CAOV3 cells. Rescue experiments showed that miR-149 knock-down increased cell proliferation but decreased apoptosis in circ-PVT1 knock-down treated SKOV3 cells, while miR-149 overexpression reduced cell proliferation but enhanced apoptosis in circ-PVT1 overexpression treated CAOV3 cells. Circ-PVT1 enhances cell proliferation but inhibits cell apoptosis through sponging miR-149 in EOC cells, which suggests that circ-PVT1 may serve as a treatment target in EOC.

Sun X ，Luo L ，Gao Y 《-》