circCELSR1 facilitates ovarian cancer proliferation and metastasis by sponging miR-598 to activate BRD4 signals.

BACKGROUND: Ovarian cancer is one of the most common gynecologic cancers and has high mortality rate due to the lack of early diagnosis method and efficient therapeutic agents. circCELSR1 is up-regulated in ovarian cancer, but its role and mechanisms in ovarian cancer are unclear. METHODS: Gene expression of circCELSR1, miR-598 and BRD4 in ovarian cells was examined by qRT-PCR. Protein level was determined by Western blotting. Bioinformatic analysis and luciferase assay determined the molecular binding among circCELSR1, miR-598 and BRD4 3' UTR. Cell proliferation, migration, invasion and apoptosis were determined by colony formation, wound healing assay, transwell assay and flow cytometry analysis, respectively. An abdominal cavity metastasis nude mice model was used to determine the in vivo function of circCELSR1. RESULTS: circCELSR1 and BRD4 were promoted, but miR-598 was suppressed in various ovarian cancer cells. circCELSR1 bound to miR-598 and promoted expression of its downstream target BRD4. Knockdown of circCELSR1 suppressed proliferation, migration, invasion and epithelial-mesenchymal transition (EMT), but promoted apoptosis in ovarian cancer cells, and these effects were reversed by miR-598 inhibition or BRD4 overexpression. circCELSR1 inhibition decreased the expression of BRD4 and its downstream proliferation/migration related genes by targeting miR-598. Furthermore, knockdown of circCELSR1 suppressed ovarian cancer growth and metastasis in nude mice. CONCLUSION: Knockdown of circCELSR1 inhibited BRD4-mediated proliferation/migration related signaling via sponging miR-598, thereby repressing ovarian cancer progression. This study provides a new regulatory mechanism of ovarian cancer may facilitate the development of therapeutic agents for ovarian cancer.

lncRNA ABHD11-AS1, regulated by the EGFR pathway, contributes to the ovarian cancer tumorigenesis by epigenetically suppressing TIMP2.

OBJECTIVE: Epithelial ovarian cancer (EOC) is a common gynecologic malignancy characterized by extensive peritoneal metastasis and high mortality rate. ABHD11 Antisense RNA1 (ABHD11-AS1) has recently been identified as a regulator of growth and metastasis in multiple tumors, including EOC. However, the biological function and potential mechanism of ABHD11-AS1 in EOC remains poorly understood. METHODS: Immunohistochemistry, western blot, and qRT-PCR analysis were used to determine the expression pattern of ABHD11-AS1 and epidermal growth factor receptor (EGFR) in both EOC tissues and cell lines, respectively. Colony formation, transwell and wound healing assays were performed to evaluate the roles of EGFR and ABHD11-AS1 on the capacity of cell proliferation, migration, and invasion. Western blot analysis was performed to measure the regulation of EGFR pathway on STAT3. Moreover, chromatin immunoprecipitation was employed to demonstrate the interaction between ABHD11-AS1 and STAT3. RNA immunoprecipitation was subjected to prove the direct binding between ABHD11-AS1 and EZH2. Immunofluorescence staining was performed to measure the expression and localization of TIMP2. EOC mouse model was conducted for validating the role of ABHD11-AS1 in vivo. RESULTS: EGFR and ABHD11-AS1 were highly expressed in EOC tissues and cell lines. Knockdown of EGFR or ABHD11-AS1 inhibited cell growth, migration, and invasion of EOC cells. Expression of ABHD11-AS1 was regulated by the activation of EGFR signaling pathway, mediated by STAT3. Besides, ABHD11-AS1 was shown to silence TIMP2 by binding to chromatin-modifying enzyme EZH2. Furthermore, inhibition of EGFR pathway or ABHD11-AS1 repressed the tumor growth of EOC. CONCLUSION: We defined the regulatory relationship between the EGFR signaling pathway, ABHD11-AS1, EZH2, and TIMP2 suggesting that ABHD11-AS1 may act as an oncogene and a potential target for antitumor therapies in ovarian cancer.

M2-like tumor-associated macrophages-secreted EGF promotes epithelial ovarian cancer metastasis via activating EGFR-ERK signaling and suppressing lncRNA LIMT expression.

Background: Ovarian cancer (OC) is the gynecologic malignant tumor with high mortality. Accumulating evidence indicates that M2-like tumor-associated macrophages (TAMs) can secret EGF to participate in ovarian cancer growth, migration, and metastasis. An EGF-downregulated lncRNA, LIMT (lncRNA inhibiting metastasis), was identified as a critical regulator of mammary cell migration and invasion. Nevertheless, whether EGF secreted from M2-like TAMs regulates LIMT expression in ovarian cancer progression remains largely unknown. Methods: The human OC cell lines OV90 and OVCA429 were recruited in this study. The differentiation of the human monocyte cell line THP-1 into M2-like TAMs was confirmed using flow cytometry within the application of phorbol 12-myristate 13-acetate (PMA). ELISA was performed to detect EGF concentration in co-culture system of M2-like TAMs and OC cell lines. Moreover, CCK-8, flow cytometry and immunofluorescence staining of Ki67 were performed to assess the capacity of cell proliferation. Besides, cell migration and invasion were determined by wound healing and transwell assays. Furthermore, the expression levels of epithelial-mesenchymal transition (EMT) markers and EGFR/ERK signals were analyzed by qRT-PCR and western blot. Female athymic nude mice (8-12 weeks of age; n = 8 for each group) were recruited for in vivo study. Results: In the present study, THP-1 cells exhibited the phenotype markers of M2-like TAMs with low proportion of CD14+ marker and high proportion of CD68+, CD204+, CD206+ markers within the application of PMA. After co-culturing with M2-like TAMs, EGF concentration in the supernatants was significantly increased in a time-dependent manner. Besides, OC cells presented better cell viability, higher cell proliferation, and stronger migration and invasion. The expression of EMT-related markers N-cadherin, Vimentin and EGFR/ERK signals were markedly up-regulated, while E-cadherin was significantly decreased. However, these effects induced by co-culture system were reversed by the application of AG1478 (an EGFR inhibitor) or LIMT overexpression. Furthermore, the endogenous expression of LIMT was decreased in OC cell lines compared with the control group. Also, the in vivo experiments verified that the inhibition of EGFR signaling by AG1478 or overexpression of LIMT effectively repressed the tumor growth. Conclusion: Taken together, we demonstrated that EGF secreted by M2-like TAMs might suppress LIMT expression via activating EGFR-ERK signaling pathway to promote the progression of OC.