RETRACTED: Long noncoding RNA TUG1 facilitates cell ovarian cancer progression through targeting MiR-29b-3p/MDM2 axis
Abstract
Ovarian cancer (OC) is one of the most aggressive female cancers in the world. OC trends to be diagnosed at an advanced stage with abdominal metastasis. Our study explored the biological function and underlying mechanism of lncRNA on OC cell proliferation and migration. The expression of turine up-regulated gene 1 (TUG1) in human OC tissues and cell lines was measured by qRT-PCR. OC cell proliferation, viability, migration, and invasion were measured by MTT assays, colony formation assays, and transwell assays in vitro. Furthermore, the nude mice xenograft model was established to determine the effects of TUG1 in vivo. The relationship between TUG1 and miR-29b-3p, as well as miR-29b-3p and MDM2 were identified using the luciferase reporter assays. We showed that the expression of TUG1 and MDM2 were significantly increased, but the expression of miR-29b-3p was remarkably decreased in OC tissues and cell lines. Knockdown of TUG1 strongly inhibited the ability of cell proliferation, colony formation, migration, and invasion in vitro. The relationship between TUG1 and miR-29b-3p, or miR-29b-3p and MDM2 were predicted by StarBase and miRanda online software. Besides, miR-29b-3p reversed the positive effect of TUG1 on the OC cell proliferation, migration, and invasion through inhibiting MDM2 expression and increasing p53 phosphorylation level. Moreover, knockdown of TUG1 suppressed tumor growth in vivo. Taken all together, this study shows that TUG1 plays a crucial oncogenic role and facilitates cell proliferation, migration, and invasion in OC through regulating miR-29b-3p/MDM2 axis.
1 INTRODUCTION
OC is one of the malignant tumors among women (Torre et al., 2018). There are expected 521,000 new OC cases (each year?) in China (Chen et al., 2016). OC exhibits low survival rates because of late diagnoses (Torre et al., 2018), limited therapeutic strategies (Hoskins & Gotlieb, 2017), and cancer metastasis and recurrence (Jayson, Kohn, Kitchener, & Ledermann, 2014). Hence, it is urgent to explore the underlying molecular mechanism of OC and to identify a novel biomarker for early detection and tailored therapeutics of OC.
Long noncoding RNAs (lncRNAs) are a class of noncoding RNAs and are characterized by endogenous transcripts longer than 200 nucleotides. Various studies indicated that lncRNAs regulate cell proliferation, survival, differentiation, apoptosis, migration, invasion, tumorigenesis and metastasis, and interact with microRNAs (miRNAs), DNA, RNA, and proteins. lncRNA turine up-regulated gene 1 (TUG1) contributes to the photoreceptor formation and retina development and locates at chromosome band 22q12 (Young, Matsuda, & Cepko, 2005). A variety of studies demonstrated that TUG1 is highly expressed in multiple cancers, and it has been found to contribute to carcinogenesis in laryngocarcinoma (Zhuang, Liu, & Wu, 2019), osteosarcoma (Yu, Hu, et al., 2019), multiple myeloma (Liu, Wang, & Liu, 2019), pancreatic cancer (Hui et al., 2019), melanoma (Wang, Liu, Ren, Wang, & Liu, 2019), and OC (Fan, Li, et al., 2019). Previous studies have illustrated that TUG1 promotes cancer progression by regulating LRG1 secretion through modulating tumor growth factor-β pathway (Fan, Li, et al., 2019), and by promoting cell proliferation and invasion through regulating WNT/β-catenin pathway (Liu et al., 2018). Additionally, TUG1 promotes cancer progression through accelerating cell proliferation and inhibiting cell apoptosis (Kuang, Zhang, Hua, Dong, & Li, 2016; Li, Chen, Zhang, & Liu, 2018; Li, Zhang, Liu, & Chen, 2018). It has also been reported that TUG1 promotes multiple myeloma cell proliferation and inhibits apoptosis by suppressing miR-29b-3p (Liu, Wang, & Liu, 2019), and TUG1 induces cardiac hypertrophy through sponging miR-29b-3p (Zou, Wang, Tang, & Wen, 2019). Moreover, TUG1 promotes OC cell proliferation and invasion by regulating WNT/β-catenin pathway (Liu, Liu et al., 2018), or regulates angiogenesis by regulating expression of LRG1 (Fan, Li, et al., 2019). Besides, TUG1 promotes OC cell proliferation, metastasis, and inhibits apoptosis through regulating multiple signaling pathways (Kuang et al., 2016; Li, Chen, et al., 2018; Plantin, Sassolas, Guillet, Tater, & Guillet, 1988). However, the function and the underlying molecular mechanism of TUG1 in OC were largely unknown.
MDM2 is a well-known oncogene that is significantly overexpressed in a variety of cancers (Liu, Wang, Wang, et al., 2019; Xu et al., 2019). MDM2 gene is cloned from double minute, which is an abnormal chromosome and located in human chromosome 12q14.3-q15 and is a target gene of p53. The full length MDM2 contains 491 amino acids (Liu, Wang, Wang, et al., 2019). MDM2 is segmented into different functional regions of p53 from N-terminal to C-terminal. MDM2 negatively regulates p53 through binding to the transcriptional activation domain at the N-terminal of p53, and influences the stability and activity of p53 protein through suppressing cell growth, regulating cell cycle, and inducing apoptosis (Zhao, Yu, & Hu, 2014). MDM2 acts as a crucial oncogene by promoting ovarian cancer progression and chemical-resistant (Cui, Zhou, Chen, & Wang, 2019; Gansmo et al., 2017; Wu et al., 2019). It is reported that MDM2 promotes OC cell epithelial–mesenchymal transition (EMT) and metastasis (Gansmo et al., 2017), and miR-194-5p inhibits OC cell paclitaxel resistance by suppressing MDM2 expression (Nakamura et al., 2019). It is also reported that the combination treatment with MDM2 inhibitors and rucaparib increases cell cycle arrest and apoptosis in OC (Zanjirband, Curtin, Edmondson, & Lunec, 2017). All the above studies indicate that MDM2 plays a crucial role in OC tumorigenesis and development.
In this study, we aimed to explore the effects and molecular mechanisms of TUG1 in OC. We found that TUG1 acts as an oncogene and promotes OC cell proliferation and migration by suppressing miR-29b-3p via upregulating MDM2 expression.
2 MATERIALS AND METHODS
2.1 Tissue samples
Sixty-five OC tissues and paired-adjacent tissues were provided by the Affiliated Hospital of Qingdao University. All patients had no radiotherapy and chemotherapy received prior to the sampling, and they understood the purpose of this study and provided written informed consent. The experiment was approved by the Ethics committee of the Affiliated Hospital of Qingdao University (No. 20190623). All of the samples were frozen in liquid nitrogen and stored at −80°C in ultra-low temperature freezer.
2.2 Cell culture
Human ovarian epithelial cell line IOSE-80 and four OC cell lines A2780, SKOV3, ES-2, and C30 were purchased from Shanghai Cell Bank of Chinese Academy of Sciences. Cells were maintained in RPMI-1640 medium (Invitrogen, CA) supplemented with 10% fetal bovine serum (FBS) (Invitrogen, CA), and then cells were incubated in a humidified incubator at 37°C, 5% CO2 (Li, Zhang, et al., 2019).
2.3 Plasmid construction and transfection
TUG1 small interfering RNAs (siRNA) and its negative control, miR-29b-3p mimics, miR-29b-3p inhibitor, and their negative controls, pcDNA-MDM2 vector and negative control pcDNA3.1 (+) vector were constructed and obtained from GenePharma (Shanghai, China). Oligonucleotide and vector transfection in this study were carried out using Lipofectamine 2000 (Invitrogen, CA). The transfection efficiency was assessed by qRT-PCR.
Before transfection, cells were seeded into 24-well plates for 24 hr. Lipofectamine 2000 was diluted with FBS-free medium, and then mixed with miR-29b-3p mimics, or miR-29b-3p inhibitor and their negative controls, or si-TUG1 and negative control, or pcDNA-MDM2 vector and negative control pcDNA3.1 (+) vector diluents for 20 min at room temperature. The 100 μl mixture was added into each well and then incubated at 37°C for 24 hr. The transfection efficiency was measured by qRT-PCR.
2.4 qRT-PCR
Total RNA was extracted from tissue specimens or cells using Trizol reagent (Invitrogen) according to the manufacturer's protocol. cDNA was synthesized using Reverse Transcription Kit (TaKaRa, Dalian, China) according to the manufacturer's protocol. qRT-PCR was performed using One Step PrimeScript™ RT-PCR Kit (TaKaRa, Dalian, China) according to the manufacturer's protocol. The conditions used for qRT-PCR were as the followings: 95°C for 30 s, and then at 95°C for 5 s and 58°C for 30 s by 40 cycles. U6 and GAPDH were used as the internal control. The relative expression levels were calculated by 2-∆∆Ct methods. All primers were obtained from Sangon (Shanghai, China). Primer sequences are as the followings, TUG1, 5′-CTGAAGAAAGGCAACATC-3′ and 5′-GTAGGCTACTACAGGATTTG-3′; miR-29b-3p, 5′-TCAGGAAGCTGGTTTCATATGGT-3′ and 5′-CCCCCAAGAACACTGATTTCAA-3′; MDM2, 5′-TACAGGGACGCCATCGAATC-3′ and 5′-TGAAGTGCATTCCAATGTC AGC-3′; U6, 5′-CTCGCTTCGGCAGCACATATACT-3′ and 5′-CGCTTCACGAATTTGCGTGT-3′; GAPDH, 5′-TGTGTCCGTCGTGGATCTGA-3′ and 5′-CCTGCTTCACCACCTTCTTGA-3′.
2.5 MTT assay
After cell transfection, SKOV3 and ES-2 cells (1 × 105 cells/ml) were seeded into 24-well plates (Corning, NY) for 24 hr. then 5 mg/ml MTT (Invitrogen, CA) was added into wells (20 μl per well). After that, 150 μl DMSO was added into each well and incubated at room temperature for 15 min to sufficiently dissolve the crystals. The absorbance at 490 nm was detected using an enzyme-linked immunometric meter.
2.6 Colony formation assay
After cell transfection, SKOV3 and ES-2 cells were harvested and seeded into six-well plates (Corning, NY) at a density of 500 cells. Cells were maintained in RPMI-1640 medium (Invitrogen, CA) supplemented with 10% FBS (Invitrogen, CA), and then cultured at 37°C with 5% CO2 for 2 weeks. The cells were fixed with methanol and stained with 0.5% crystal violet (Beyotime, Shanghai, China), then cell colony formation was visualized and counted using an inverted microscope (Leica, Wetzlar, Germany).
2.7 Transwell assay
Cell migration and invasion assays were performed according to specific procedures (Han et al., 2018). For invasion assay, the transwell chamber was covered with Matrigel (8-mm pore size; BD, CA) before the starting of the invasion experiment. In brief, after cell transfection, SKOV3 and ES-2 cells were harvested and resuspended with 200 μl serum-free RPMI-1640 medium, and seeded into the bottom chamber of 24-well (2 × 105 cells/well) plates. After that, 600 μl RPMI-1640 medium (Invitrogen, CA) containing 10% FBS (Invitrogen, CA) was added into the lower chamber, and cells were incubated at 37°C for 48 hr. The cotton swab was utilized to clean the nonmigrated and non-invaded cells that located in the front of the filter. The migrated and invaded cells were fixed with methanol and stained with crystal violet. The migration and invasion of cells per field was observed and counted under a microscope (Leica, Wetzlar, Germany).
2.8 Xenograft model
All animals were kept in a pathogen-free environment and fed ad lib. The procedures for care and use of animals were approved by the Ethics Committee of The Affiliated Hospital of Qingdao University. Four to six-week-old BALB/c female nude mice were obtained from Kunming Institute of Zoology, Chinese Academy of Sciences. Briefly, SKOV3 cells (1 × 106) were stably transfected with si-TUG1 and si-NC vector before subcutaneously injected into the back flank of each mouse. The tumors size was calculated every 4 days for 28 days. Nude mice were executed via anesthesia at 28 days, and the final tumor volume was determined using a Vernier caliper.
2.9 Luciferase activity assay
SKOV3 and ES-2 cells were seeded into 96-well plates (Corning, NY), and then transfected with Firefly luciferase reporter plasmid (PGL3-TUG1 WT, PGL3-TUG1 MUT, PGL3-MDM2 WT, PGL3-MDM2 MUT) and Renilla luciferase vector (PRL-SV40, Promega) and small RNAs (miR-29b-3p mimic or negative control RNAs). After 48 hr, a dual-luciferase reporter assay (Promega, CA) was utilized to detect the luciferase activities according to the manufacturer's protocol.
2.10 Western blotting
Total protein of OC tissues and cells were separated using RIPA lysis buffer (Beyotime, Shanghai, China). The concentration of proteins was determined using BCA protein assay kit (Beyotime, Shanghai, China). Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and then transferred to polyvinylidene fluoride membrane (PVDF). The membranes were blocked by 5% (wt/vol) skim milk at room temperature for 1 hr, and then incubated with primary antibodies overnight at 4°C. The next day, primary antibodies were removed and membranes were incubated with HRP-conjugated anti-IgG at room temperature for 1 hr. ECL (Beyotime, Haimen, China) and the Image Lab Software (Bio-Rad, Shanghai, China) were utilized to visualize and analyze the protein bands. The primary antibodies utilized in this experiment were listed below: anti-Ki67, anti-PCNA, anti-E-cadherin, anti-N-cadherin, anti-Vimentin, anti-MDM2, anti-p53, anti-p53 (phospho S46), anti-GAPDH.
2.11 Statistical analysis
All data in this study were presented as mean ± SD, SPSS 20.0 and GraphPad primer 7.0 were used for statistical analyses in this study. Statistical significance was analyzed by Student's t test or one-way ANOVA. p < .05 was regarded as statistically significant.
3 RESULTS
3.1 Upregulation of TUG1 in OC tissues and cell lines
The results of qRT-PCR exhibited that the expression of TUG1 was increased in OC tissues compared to corresponding adjacent normal tissues (Figure 1a). Besides, the expression of TUG1 was significantly upregulated in OC cell lines (A2780, SKOV3, ES-2, and C30) compared to human ovarian epithelial cell line IOSE-80 (Figure 1b). The results indicated that TUG1 might act as an oncogene in OC.
3.2 Knockdown of TUG1 inhibits OC cells proliferation, migration, and invasion in vitro
We investigated the biological effects of TUG1 on OC cells by knocking down TUG1 in SKOV3 and ES-2 cells. In order to prevent off-target effects, si-TUG1 #3 was used for the subsequent experiment (Figure 2a,b). MTT assay results showed that the proliferation of SKOV3 and ES-2 cells was significantly inhibited by si-TUG1 at 48 and 72 hr (Figure 2c,d), and colony formation assay results showed that cell viability of SKOV3 and ES-2 cells was inhibited by si-TUG1 (Figure 2e). Besides, SKOV3 and ES-2 cell migration and invasion were inhibited by si-TUG1 (Figure 2f,g). Furthermore, to confirm the effects of TUG1 on the proliferation, migration, and invasion, the protein levels of special markers were analyzed by western blotting. The results demonstrated that Ki67, PCNA, and E-cadherin levels were significantly downregulated by si-TUG1. Reversely, N-cadherin and Vimentin levels were markedly upregulated by si-TUG1 (Figure 2h). All results illustrated that the knockdown of TUG1 inhibits cell proliferation, viability, migration, and invasion in OC.
3.3 Knockdown of TUG1 inhibits OC growth in vivo
To further verify the inhibition effects of TUG1 in OC, SKOV3 cells were stalely expressed with si-TUG1 or negative control, then the SKOV3 cells were subcutaneously injected into nude mice. The results showed that the knockdown of TUG1 significantly suppressed tumor growth (Figure 3a), and the tumor volume was decreased by the knockdown of TUG1 compared with the control group (Figure 3b). The results confirmed that TUG1 acts as a tumor accelerator in OC growth.
3.4 TUG1 directly binds with miR-29b-3p
To explore the underlying mechanism of TUG1 regulating OC progression, the target genes of TUG1 were identified by bioinformatics prediction (Figure 4a). miR-29b-3p is the most important target gene of TUG1 because it acts as a tumor suppressor gene in many tumors (Inoue et al., 2018; Sun et al., 2019), thus we focused on the relationship between miR-29b-3p and TUG1. The binding sites of miR-29b-3p in TUG1 are shown in Figure 1b. The luciferase activity was decreased by miR-29b-3p mimics co-transfected with the luciferase reporter gene containing wild-type TUG1 (Figure 4c,d). However, miR-29b-3p mimics had no obvious effects on luciferase activity when co-transfected with the luciferase reporter plasmids which containing mutant TUG1 (Figure 4c,d). The results demonstrated that TUG1 directly interacted with miR-29b-3p. Moreover, the expression of miR-29b-3p was upregulated by the knockdown of TUG1 in SKOV3 and ES-2 cells (Figure 4e). Moreover, miR-29b-3p was markedly decreased in OC tissues and cell lines (Figure 4f,g). We also found that the expression of TUG1 had a negative correlation with the expression of miR-29b-3p in OC tissues (Figure 4h). Our data indicated that TUG1 directly binds with miR-29b-3p, and negatively regulated the expression of miR-29b-3p.
3.5 TUG1 promotes MDM2 expression via inhibiting miR-29b-3p
We then verified the downstream target genes of miR-29b-3p and predicted that MDM2 was one of the direct targets of miR-29b-3p by bioinformatics analysis (Figure 5a). We first confirmed the connection between miR-29b-3p and 3'-UTR of MDM2 by dual-luciferase reporter assay. We found that miR-29b-3p mimics reduced the luciferase activities of the luciferase reporter plasmids containing wild-type MDM2, but had no obvious effects on the plasmid containing mutant MDM2 (Figure 5b,c). Furthermore, we revealed that the mRNAs and protein expression of MDM2 was significantly decreased by downregulation of TUG1 or upregulation of miR-29b-3p in SKOV3 and ES-2 cells (Figure 5d). In addition, we found that MDM2 was upregulated in OC tissues and cell lines (Figure 5e,f). Meanwhile, we found that miR-29b-3p had a negative correlation with MDM2 in OC tissues (Figure 5g). In contrast, there was a positive relationship between TUG1 and MDM2 in OC tissues (Figure 5h). The phosphorylation of p53 was increased by the knockdown of TUG1 or upregulation of miR-29b-3p (Figure 5i). These results indicated that TUG1 promotes MDM2 expression through inhibiting miR-29b-3p in OC.
3.6 Knockdown of TUG1 inhibits OC cells proliferation, migration, and invasion via regulating miR-29b-3p/MDM2 axis in vitro
Next, we investigated the regulatory effects of MDM2 by TUG1 via miR-29b-3p and verified the effects of TUG1/miR-29b-3p/MDM2 axis on OC cell proliferation, migration, and invasion. We found that knockdown of TUG1 inhibited SKOV3 and ES-2cell proliferation, colony formation, migration and invasion (Figure 6a–e). The inhibitory effects of TUG1 knockdown were suppressed by the knockdown of miR-29b-3p or upregulation of MDM2 (Figure 6a–e). Additionally, the western blot results showed that the expression of Ki-67, PCNA, E-cadherin, and MDM2 were inhibited, and the expression of N-cadherin, Vimentin, and phosphorylation of p53 was upregulated in SKOV3 and ES-2 cells. However, the effects of TUG1 knockdown were reversed by knockdown of miR-29b-3p or upregulation of MDM2 (Figure 6f). The data suggested that TUG1 promotes OC cells proliferation, migration, and invasion by regulating miR-29b-3p/MDM2 axis.
4 DISCUSSION
OC is a high incidence tumor in women; it is one of the main causes of gynecologic cancer-related death in the world (Webb & Jordan, 2017). There were 295,414 estimated new OC cases and 184,799 OC deaths worldwide in 2018 (Webb & Jordan, 2017). In the current study, we found that TUG1 played a crucial role in OC tumorigenesis and development. Our results showed that TUG1 was significant upregulated in OC tissues and cells. Knockdown of TUG1 significantly inhibited OC cells proliferation, migration, and invasion through regulating miR-29b-3p and its target gene MDM2. In addition, knockdown of TUG1 strongly reduced the tumor growth in vivo. TUG1 has been shown to be involved in tumorigenesis of multiple human cancers, including bladder cancer (Yu, Zhou, Yao, Meng, & Lang, 2019), oral squamous cell carcinoma (Liu, Liu, Hu, & Wang, 2019) and multiple myeloma (Liu, Wang, & Liu, 2019). It has been reported that TUG1 promotes tumorigenesis and tumor development by upregulating cell proliferation and invasion in epithelial ovarian cancer through regulating WNT/β-catenin pathway (Webb & Jordan, 2017). Other studies showed that TUG1 promotes epithelial ovarian cancer proliferation and inhibits cell apoptosis by regulating AURKA (Li, Chen, et al., 2018; Li, Zhang, et al., 2018). Previous studies indicated that TUG1 is an important oncogene in OC, it regulates tumorigenesis and tumor development by regulating cell proliferation, cell cycle, migration, invasion, apoptosis, angiogenesis, chemical-resistant, and EMT (Fan, Li, et al., 2019; Kuang et al., 2016; Li, Gan, Qin, Jiao, & Shi, 2017).
In recent years, lncRNAs' key role in regulating tumor cell proliferation, apoptosis, metastasis, senescence, self-renewal, stem cell potential, and drug-resistant has been recognized (Guo et al., 2019; Qiu, Ma, Li, Sun, & Zeng, 2019; Shi et al., 2019; Wang, Lou, et al., 2019; Yu, Zhou, Yao, Meng, & Lang, 2019). TUG1 has been regarded as a pivotal regulator in tumorigenesis and the development of multiple human cancers (Barbagallo et al., 2018; He et al., 2018; Zhang et al., 2018). Nevertheless, the biological function and underlying mechanisms of TUG1 in OC remain fully unknown. Our study showed that TUG1 was significant upregulated in OC, and the biological function of TUG1 was proven by the lose-function experiments. The results are in accordance with existing studies that indicate TUG1 facilitates proliferation and invasion in epithelial OC cells (Li, Zhang, et al., 2018; Liu et al., 2018).
miRNAs are a class of small noncoding RNA with a length of 18–22 nucleotides that participate in the expression regulation of target gene. Moreover, lncRNAs may endogenously compete with miRNA, and counteract the repression function of miRNA in downstream targets. For example, TUG1 promotes papillary thyroid cancer cell proliferation, migration, and EMT by inhibiting miR-145 (Lei, Gao, & Xu, 2017). TUG1 promotes melanoma cell proliferation and metastasis by recruiting miR-29c-3p (Wang, Liu, et al., 2019), and TUG1 promotes pancreatic cancer cell proliferation, invasion, and migration by targeting miR-29c (Lu et al., 2018). lncRNAs interacting with miRNAs is the most important regulatory mechanism in tumorigenesis and tumor development. miR-29 family including miR-29a, miR-29b, and miR-29c have been reported as tumor suppressors in multiple cancers by restraining tumor progression (Chen, Zhang, et al., 2017; Yamada et al., 2018). It has been reported that high expression of miR-29b-3p correlates to better prognosis in pancreatic cancer, and miR-29b-3p inhibits pancreatic cancer cell proliferation and promotes apoptosis (Yamada et al., 2018). It also has been reported that miR-29b-3p significantly inhibits cell proliferation of the KRAS-mutant colorectal cancer (Inoue et al., 2018). Here, we found that miR-29b-3p was significantly decreased in OC tissues and cell lines, and overexpression of miR-29b-3p strongly inhibited OC cells proliferation, migration, and invasion. Moreover, miR-29b-3p was the target gene of TUG1, and it significantly reversed the effects of TUG1 on OC cells. Therefore, we assumed that TUG1 might inhibit the activation of miR-29b-3p through modulating its downstream target mRNAs in OC.
It has been reported that MDM2 involves in a negative regulatory loop between p53 and MDM2. MDM2 plays as an oncogene through negatively regulating the expression and activation of p53 (Xu et al., 2019; Zhang et al., 2019). MDM2 is a primary regulator of p53, p53 is well known as a crucial tumor suppressor in cancer through initiating cell cycle arrest, cell apoptosis, and promotes cancer cell senescence (Ning et al., 2019). MDM2 inhibits p53-mediated transcriptional regulation and induces p53 polyubiquitination and degradation. Furthermore, p53 enhances MDM2 transcription to form a feedback regulatory loop (Meng, Franklin, Dong, & Zhang, 2014). It has been reported that MDM2 acts as an oncogene to promote ovarian cancer SKOV3 cell EMT and metastasis (Chen, Wang, et al., 2017). The MDM2 inhibitor RG7388 inhibits nasopharyngeal carcinoma by inhibiting MDM2 and activating p53 pathway (Fan, Wang, et al., 2019). In this study, we observed that MDM2 was remarkably upregulated in OC tissues and cell lines. Besides, knockdown of TUG1 or overexpression of miR-29b-3p significantly reduced the expression of MDM2 protein in OC cells. On the contrary, knockdown of TUG1 or overexpression of miR-29b-3p remarkably activated the p53 phosphorylation. Furthermore, overexpression of MDM2 rescued the effect of TUG1 on OC cells. These results indicated that TUG1 might regulate MDM2 expression to affect p53 expression and to modulate OC cells proliferation, migration, and invasion.
The current study illustrates that TUG1 plays an oncogenic role to facilitate OC cell proliferation, migration, and invasion through regulating miR-29b-3p/MDM2 axis. Our finding indicates that the modulation of expression of TUG1 and MDM2 may be the new potential therapeutic approach in OC.
Taken all together, this study demonstrates that TUG1 functions as a crucial oncogene to facilitate cell proliferation, migration, and invasion in OC through regulating miR-29b-3p/MDM2 axis.
ACKNOWLEDGMENTS
Thanks to the participants who provided paired of 65 OC tissues and adjacent tissues for our research.
CONFLICT OF INTEREST
The authors declare that they have no conflict of interest.
