Xu et al. Journal of Ovarian Research (2020) 13:81 https://doi.org/10.1186/s13048-020-00685-w RESEARCH Open Access circRNA-UBAP2 promotes the proliferation and inhibits apoptosis of ovarian cancer though miR-382-5p/PRPF8 axis Qin Xu1†, Bo Deng1†, Manlin Li2, Yang Chen2 and Li Zhuan1* Abstract Objective: circular RNAs (circRNAs) have been reported to be essential regulators of multiple malignant cancers. However, the functions of circRNAs in ovarian cancer need to be further explored. The aim of our study is to explore the role of circRNA-UBAP2 in ovarian cancer and its mechanism. Results: circRNA-UBAP2 was upregulated in ovarian cancer tissues and cell lines. Knockdown of circRNA-UBAP2 inhibited cell proliferation and promoted cell apoptosis, but circRNA-UBAP2 overexpressed got opposite results. In addition, circRNA-UBAP2 targeted miR-382-5p and downregulated its expression, PRPF8 was a target gene of miR- 382-5p. Furthemore, circRNA-UBAP2/miR-382-5p/PRPF8 axis affected the proliferation, apoptosis and cell cycle of ovarian cancer through the mechanism of competing endogenous RNAs (ceRNA). Conclusion: circRNA-UBAP2 acted as a ceRNA to sponged miR-382-5p, increased the expression level of PRPF8, and prompted proliferation and inhibited apoptosis in ovarian cancer cells. Keywords: circRNA-UBAP2, miR-382-5p, PRPF8, Proliferation, Apoptosis, Ovarian cancer Background particularly urgent to find the gene target which Ovarian cancer is one of the most common gynecologic regulates the proliferation and apoptosis of ovarian malignancy in the world [1]. However, it generally cancer cells. presents at an advanced stage which is one of the main Recently many studies conformed that circRNAs play factors contributing to the high death to incidence rate an important role in the malignant biological behavior of [2]. Although operation, combined chemotherapy and cancer cells. For example, circRNA-UBAP2 effects the radiotherapy play an important role in the treatment of proliferation and invasion of lung cancer cells [4], ovarian cancer, 75% patients have experienced a cancer circRNA-UBAP2 also serves as a promising therapeutic recurrence, and malignant proliferation is one of the target for triple-negative breast cancer patients [5]. But major poor prognostic factors for ovarian cancer [3]. the role of circRNA-UBAP2 in ovarian cancer remains Inhibiting ovarian cancer cell malignant proliferation is to be further explored. Besides, even a great deal of re- very important for the treatment, thus it becomes searches on the genesis and development of ovarian can- cer have been done, but the pathophysiology of ovarian cancer development is complex and involves numerous * Correspondence: [email protected] biological pathways [6], the etiology of ovarian cancer is †Qin Xu and Bo Deng contributed equally to this work. poorly understood. This study explored how circRNA- 1Department of Reproductive Medicine, Reproductive Medical Centre, The UBAP2 affects the ovarian cancer and its mechanisms, First People’s Hospital of Yunnan Province, No. 157 Jin Bi Road, Kunming, People’s Republic of China we hoped that our study will support the use of Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Xu et al. Journal of Ovarian Research (2020) 13:81 Page 2 of 10 circRNA-UBAP2 as prognostic and predictive markers circRNA-UBAP2 regulated the malignant biological in ovarian cancer. behavior of ovarian cancer cells circRNAs may use their circularization to competi- Based on the high expression of circRNA-UBAP2 in tively inhibit the linear splicing and sponge function of ovarian cancer tissues and cell lines, in order to further microRNAs (miRNAs), and modulate the expression of explored the effect of circRNA-UBAP2 on biological metastasis-evoking genes, thus contributing to the devel- behavior of OVCAR-3 and ES-2 cells, we either knock- opment of cancer. It was reported that miR-382-5p may down or overexpression circRNA-UBAP2 in OVCAR-3 engaged in various cancers. For instance, there was an and ES-2 cells, and verified the expression level of upregulation of miR-382-5p in primary myelofibrosis circRNA-UBAP2 by RT-qPCR in both OVCAR-3 and cells [7], but the expression of miR-382-5p was down- ES-2 cells (Figs. 2a, 3a). CCK-8 showed that knockdown regulated in glioma-exposed endothelial cells [8]. But of circRNA-UBAP2 inhibited the proliferation of there have been no studies about circRNA-UBAP2 OVCAR-3 and ES-2 cells (Fig. 2b). Moreover, flow regulated miR-382-5p. cytometry results showed that knockdown of circRNA- miRNAs as a small non-coding RNAs can participate UBAP2 promoted cell apoptosis of OVCAR-3 and ES-2 in the cancer process through modulate post- (Fig. 2c), as well as arrested cell cycle at G0/G1 phase transcriptional gene expression. Whether miRNA is an (Fig. 2d). Besides, western blotting showed that knock- oncogene or anti-oncogene was determined by its target down of circRNA-UBAP2 decreased the expression level mRNA. Disruption of RNA splicing causes genome in- of anti-apoptotic protein Bcl-2, while increased the pro- stability, which could contribute to cancer etiology [9]. apoptotic proteins Bax and caspase-3 in OVCAR-3 and As RNA splicing becomes an emerging anti-cancer tar- ES-2 (Fig. 2e). Importantly overexpression of circRNA- get, pre-mRNA processing factor 8 (PRPF8) which is the UBAP2 had the opposite effect (Fig. 3b-e). Therefore, core protein of splicing has been extensively studied in knockdown of circRNA-UBAP2 significantly inhibited recent years. Knockdown of pan-cancer drivers PRPF8 cell proliferation and promoted cell apoptosis in these caused cell apoptosis in breast cancer, which dedicated two ovarian cancer cells. that PRPF8 is a proto-oncogene regulating cell viability [10]. However, there is no report about the miR-382-5p circRNA-UBAP2 targeted miR-382-5p targeted PRPF8 and effect on ovarian cancer. Prediction results of bioinformatics database showed In this study, we found that circRNA-UBAP2 was that miR-382-5p was one of the target genes of highly expressed in ovarian cancer tissues and cell circRNA-UBAP2 (Fig. 4a). Dual-luciferase reporter gene lines. Then we assessed that circRNA-UBAP2 system results showed that overexpression of miR-382- promoted the malignant biological behavior of ovarian 5p decreased the luciferase activity of circRNA-UBAP2 cancer cells in vitro. The mechanism that circRNA- WT reporter, but no effect on the circRNA-UBAP2 UBAP2 promoted cell proliferation and inhibited cell MUT reporter (Fig. 4b). Besides, RT-qPCR showed that apoptosis in ovarian cancer cells was regulated miR- downregulated of circRNA-UBAP2 remarkably increased 382-5p/PRPF8 axis. This article was written to the expression levels of miR-382-5p in both OVCAR-3 provide a molecular target for early diagnosis and and ES-2 cells, and overexpression of circRNA-UBAP2 treatment of ovarian cancer. significantly decreased the expression of miR-382-5p (Fig. 4c). Moreover, compared with the adjacent tissues, Results the expression level of miR-382-5p was significant lower circRNA-UBAP2 was upregulated in ovarian cancer tissues in ovarian cancer tissues (Fig. 4d). Thus, we confirmed and cell lines that circRNA-UBAP2 sponged miR-382-5p and reduced circRNAs act as an oncogene in a variety of tumors, we the expression of miR-382-5p in both ovarian cancer tis- measured the expression level of circRNA-UBAP2 in sues and cell lines. ovarian cancer tissues and cell lines by RT-qPCR assay, the results showed that expression level of circRNA- miR-382-5p targeted PRPF8 UBAP2 was significant higher in ovarian cancer tissues Further we confirmed that miR-382-5p targeted PRPF8 than that in adjacent tissues (Fig. 1a). Moreover, the (Fig. 5a). And overexpressed miR-382-5p decreased the expression levels of circRNA-UBAP2 was markedly luciferase activity of PRPF8 WT reporter, but not the upregulated in ovarian cancer cells compared with PRPF8 MUT reporter (Fig. 5b). Besides, western blotting normal ovarian epithelial cells, especially in OVCAR-3 showed that overexpression of miR-382-5p reduced the and ES-2 (Fig. 1b). Thus, the above results showed that expression levels of PRPF8 in OVCAR-3 and ES-2 cells circRNA-UBAP2 was highly expressed in ovarian cancer (Fig. 5c). Additionally, RT-qPCR result showed that the tissues and cell lines, and we chose OVCAR-3 and ES-2 expression of PRPF8 was higher in ovarian cancer tissues to do further experiments. than that in adjacent tissues (Fig. 4d). Moreover, there Xu et al. Journal of Ovarian Research (2020) 13:81 Page 3 of 10 Fig. 1 circRNA-UBAP2 was upregulated in ovarian cancer tissues and cell lines. a, Differentially expressed circRNA-UBAP2 in ovarian cancer tissues and adjacent tissues were measured by RT-qPCR assay. **P < 0.01 vs adjacent tissues.