Research paperKnockdown of linc-OIP5 inhibits proliferation and migration of glioma cells through down-regulation of YAP-NOTCH signaling pathway
Introduction
Gliomas are regarded as the most prevalent malignant carcinoma in central nervous system (CNS), with an annual incidence of approximately 6 per 100,000 in the USA (Ostrom et al., 2015). Under the current WHO classification, gliomas are divided into four histological grades, from WHO grade I to WHO grade IV (Weller et al., 2014). Grade I gliomas are very slow-growing tumors that are potentially curable if completely resected. Grade II gliomas and the more aggressive grade III gliomas have an intermediate clinical course, whereas grade IV gliomas, known as glioblastoma (GBM), is not only the most malignant, but also the most frequent brain tumor. The median survival time of GBM is only 12 to 15 months after diagnosis, despite the use of aggressive treatment with surgery, chemotherapy and postoperative radiotherapy, and adjuvant temozolomide (TMZ)-based chemotherapy (Gilbert et al., 2013, Stupp et al., 2009). Therefore, identifying the pathogenic mechanisms, finding out more accurate prognostic markers, would not only help gliomas prognosis estimations, but also would provide novel potential targets for therapy.
Numerous studies over the past decade have suggested that epigenetic alterations participate in carcinogenesis and progression of malignancies (Easwaran et al., 2014, You and Jones, 2012). The epigenetic patterns of gene expression includes methylation of cytosine, posttranslational modification of histone proteins and chromatin remodeling proteins and RNA-based mechanisms, were regulated by the non-codifying material of the genome. These transcription products are referred to non-coding RNAs (ncRNA) and are divided into several large groups (Lee, 2012). One of them is a class of transcripts at least 200 nucleotides transcribed from the whole genome, called long noncoding RNAs (lncRNAs), which regulate gene expression at epigenetic transcriptional and post-transcriptional levels (Vance and Ponting, 2014). As a subtype of lncRNAs, the long intergenic noncoding RNAs (lincRNAs) have demonstrated to be transcript units located within genomic intervals between two protein coding genes (Luo et al., 2016). Increasing evidences have indicated that abnormal expression of lincRNA play a critical role in tumor biology, including tumor initiation, progression, and metastasis (Meseure et al., 2015, Pandey and Kanduri, 2015). Our previously research had demonstrated that lincRNA-POU3F3 was overexpressed in glioma and play an important role in prompting glioma cells proliferation and colony formation (Guo et al., 2015). However, there are thousands of functional lincRNAs yet to be identified.
Opa interacting protein 5 (OIP5) is a 23.3 kb transcript with 4 exons and is located in the chromosome 15q15.1, increasing evidence shows that OIP5 was consistently upregulated in glioma, renal cell carcinoma, and gastric cancer (Freitas et al., 2013, Gong et al., 2013, Nakamura et al., 2007). (Ulitsky et al., 2011) has demonstrated that linc-OIP5 is overexpressed in the nervous system and is important for controlling neurogenesis during development. The biological function of OIP5 as an oncogene in various human cancers and the highly expression of linc-OIP5 in nervous system suggested that linc-OIP5 may have important role in the development of glioma. However, the expression and detailed function of linc-OIP5 in glioma is still unknown and needs to be investigated.
In the present study, we identified the expression pattern of linc-OIP5 in glioma patients and its correlation with clinicopathological factors of glioma. Furthermore, we investigated the biological function of linc-OIP5 regulate glioma cell proliferation, migration in vitro and tumorigenicity in vivo. At last, we researched the potential signal pathways involved in linc-OIP5′ biological function.
Section snippets
Ethics statement
The protocols employed in this study and the use of human tissues was approved by the Ethics Committee of the Second Affiliated Hospital of Nanchang University and conducted in full accordance with ethical principles, including the World Medical Association Declaration of Helsinki, and the local legislation. All patients were informed and consent to use excess pathological specimens for research purposes. In addition, all experiments protocols were carried out in accordance with the relevant
Increased expression of linc-OIP5 in human glioma samples
The expression level of linc-OIP5 was assessed in 167 paired glioma samples and corresponding adjacent normal tissues using qRT-PCR, with normalization to β-actin. Firstly, we studied the correlation between linc-OIP5 expression and clinical pathological features, as shown in Table 1, linc-OIP5 expression increased correlated with the WHO grade, while did not correlate with patients' sex, age, and tumor size. Compared with their corresponding adjacent normal tissues, linc-OIP5 expression in
Discussion
In the present study, we examined the expression level of linc-OIP5 in a large cohort of human glioma tissue samples, we found that linc-OIP5 was overexpressed in glioma tissues compared with the adjacent normal tissues and positively correlated with the tumor WHO grade. In addition, linc-OIP5 function was investigated in siRNA mediated knockdown studies and we demonstrated that knockdown of linc-OIP5 significantly inhibited glioma cell proliferation, migration in vitro, and tumorigenesis in
Conclusion
Taken together, the findings from our study demonstrated that the down-regulation of the linc-OIP5 expression inhibits glioma cell proliferation, migration, and tumorgenesis potential by influencing the YAP-Notch signaling pathway. Thus, linc-OIP5 could be a promising therapeutic target and novel molecular biomarker for glioma.
Disclosure statement
The authors declare that they have no competing interests.
Author's contributions
LW, XGZ, and HG conceived the study, designed the experiments, and provided their funds to the study; GWH and HLL participated in cell culture, siRNAs infection; YC and WK were responsible for animal experiment and performed statistical analysis of all experimental data. All authors read and approved the final manuscript.
Acknowledgments
This work was supported by the National Science Foundation of China grants (No. 81560411) and Jiangxi Province's Science and Technology Agency Support Program (No. 20151BBG70160). The authors have no financial relationship with the organization that sponsored the research any other conflict of interest regarding this research.
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These authors contributed equally to this work.