Prognostic value of lncRNA SNHG20 as a biomarker in human cancers: a systematic review and meta-analysis

Background: Long noncoding RNA small nucleolar RNA host gene 20 (SNHG20) is a novel oncogene and dysregulated in a variety of human cancers. It has been revealed to be associated with the clinicopathological features and prognosis. However, the prognostic value of SNHG20 in various cancers remains unclear. Therefore, we performed this meta-analysis to evaluate the relationship between SNHG20 expression and clinical outcomes in human cancers. Methods: Comprehensive literature search was performed in PubMed, Web of Science, CNKI and Wangfang databases, and eligible studies were obtained according to the inclusion and exclusion criteria. The pooled hazard ratios (HRs) and odds ratios (ORs) were applied to assess the clinical value of SNHG20 expression for overall survival (OS) and clinicopathological features. Results: A total of 16 articles including 1190 cancer patients were included in the study. The pooled results demonstrated that evaluated SNHG20 expression was positively related to a poorer OS of cancers (HR=2.36, 95%CI: 1.85-2.87, P<0.001). Subgroup analysis revealed that SNHG20 overexpression was closely related to the low OS of patients with the digestive system cancer (HR=2.92, 95%CI: 1.96-3.88, P<0.001), sample size >80 (HR=2.42, 95%CI: 1.69-3.14, P<0.001), direct HR estimation method (HR=2.65, 95%CI: 1.78-3.52, P<0.001), and median ratio as cut-off value (HR=2.21, 95%CI: 1.60-2.83, P<0.001). In addition, the pooled data also showed that SNHG20 was positively linked to lymph node metastasis (LNM) (OR=1.65, 95%CI: 1.21-2.26, P=0.002), distant metastasis (DM) (OR=1.76, 95%CI: 1.10-2.83, P=0.02), and advanced TNM stage (OR=1.79, 95%CI: 1.34-2.39, P<0.001). Moreover, the results of the trim and ll analysis conrmed the reliability of our nding. Conclusions: Upregulation of SNHG20 was associated with advanced TNM stage, worse LNM and DM, and shorter OS, suggesting that SNHG20 may serve as a biomarker for prognosis and clinicopathological characteristics in human cancers. cancer; LSCC:laryngeal squamous cell carcinoma; HCC:hepatocellular carcinoma; carcinoma; EOC:epithelial ovarian cancer; ESCC:esophageal squamous cell carcinoma; OS:overall survival; DFS:disease-free

Prognostic value of lncRNA SNHG20 as a biomarker in human cancers: a systematic review and meta-analysis Yongfeng Li Institute of cancer research and basic medical sciences of Chinese Academy of sciences (zhejiang cancer hospital) Xinmiao Rui Institute of cancer research and basic meidical sciences of Chinese Academy of sciences (zhejiang cancer hospital)

Daobao Chen
Institute of cancer research and basic medical sciences of Chinese academy of sciences (zhejiang cancer hospital) Haojun Xuan institute of cancer research and basic medical sciences of Chinese Academy of sciences (zhejiang cancer hospital)

Introduction
Cancer has already become a major threat for human health in the world, and it has been the leading cause of death in China since 2010 [1]. Cancer is a complex disease caused by a variety of molecular change, including chromosomal translocations, deletions and ampli cation, epigenetic alterations and genetic mutations [2][3][4]. Although numerous progress has been achieved in the diagnosis and treatment of human cancers over the past decade, the clinical prognosis remains relatively worse in most cancer patients, mainly owing to the lack of effective biomarker to early diagnose cancer and predict clinical prognosis of cancer patients.
LncRNAs are a typical kinds of ncRNAs with more than 200 nucleotides, which have been proved to play a crucial role in tumorigenesis and tumor progression. Except for a few lncRNAs translate into proteins to involve in cellular and physiological processes, most lncRNAs transcripts directly or indirectly modulate transcriptional and posttranscriptional processes [5]. Moreover, many lncRNAs could serve as enhancers [6], splicing regulators [7], chromatin remodelers [8], and so on. Notably, growing evidence suggested that dysregulated lncRNAs occurred in a broad spectrum of human cancers [9,10], and participated in cancer initiation and progression, indicating the potential value as clinical biomarkers and therapeutic targets. Recently, a new discovered lncRNA NSHG20 has drawn increasing attention.
LncRNA small nucleolar RNA host gene 20 (SNHG20), localized at 17q25.2, is dysregulated in broad ranges of cancers. Increasing evidence from fundamental and clinical studies demonstrated that SNHG20 involved in tumorigenesis and exhibits poor prognostic value in many cancers, such as hepatocellular carcinoma [9,10], non-small cell lung cancer [12], and epithelial ovarian cancer [13]. However, most studies reported the prognostic value of SNHG20 in cancer patients was limited by small sample size and discrete clinical outcome. Therefore, we conducted this systematic review and quantitative meta-analysis to investigate the prognostic value of SNHG20 in human cancers.

Search strategy
We comprehensively searched in PubMed, Web of Science, CNKI and Wangfang database for eligible studies which reported the relationship between lncRNA SNHG20 and OS before August 26, 2019. A combination of the following subjects were applied for the online search: ("carcinoma" OR "cancer" OR "tumor" OR "neoplasm") AND ("prognosis" OR "outcome" OR "diagnosis" OR "survival") AND ("SNHG20" OR "small nucleolar RNA host gene 20"). The reference lists of primary publications were also manually searched to obtain potential eligible studies.

Inclusion And Exclusion Criteria
We used the following inclusion criteria for eligible studies: 1) Studies reported the relationship between SNHG20 and prognosis in human cancers; 2) Available data for HRs and corresponding 95%CI extraction; 3) patients were divided into high and low expression groups based on the expression of SNHG20. The following articles were excluded from the study: 1) reviews, letters, or case reports; 2) non-human studies; 3) duplicated publication.

Data Extraction And Quality Assessment
The essential information were screened and extracted from each eligible study by two researchers (Li and Rui) independently, including the name of rst author, year of publication, origin country, cancer type, sample size, detection method of SNHG20, HR and corresponding 95%CI for OS, as well as clinicopathological features. The HRs with 95%CIs were obtained directly from eligible studies carried out the multivariate analysis. For those studies without multivariate analysis, HRs and 95%CIs were calculated based on the survival curve according to the method described in the previous publication [14]. The Newcastle-Ottawa Scale (NOS) was applied to evaluate the quality of the included study.

Statistical analysis
The present meta-analysis was performed with Stata SE15.0 (Stata Corporation). HR and corresponding 95%CI for OS were applied to determine the pooled effect, and the odds ratio (OR) were used as the outcome estimation for data pooling. The xed-effect model was selected while heterogeneity exists (I2 > 50% and p < 0.05), otherwise, the random-effect model was applied. Begg's funnel plot and egger's regression test were used to assess the publication bias. P-value < 0.05 was considered as statistical signi cance.

Summary of eligible studies
The detailed literature selection is shown in Fig. 1. A total of 55 potentially relevant articles were identi ed in this meta-analysis. 15 duplicate articles and 15 irrelevant articles were excluded after screening the titles and abstracts. Finally, 16 eligible studies were included owing to the lack of su cient data in the other 9 articles. The characteristics of the included 16 studies were summarized in Table 1. A total of 1190 patients from 16 studies between 2016 and 2019 were included [14]. All of the included studies were conducted in China and published in English. The study sample size ranged from 32 to 144 patients, and 5 studies enrolled more than 80 patients. The types of carcinoma included NSCLC (n = 2), GC (n = 1), OSCC (n = 1), Glioblastoma (n = 1), CRC (n = 1), glioma (n = 1), LSCC (n = 1), HCC (n = 2), NC (n = 1), EOC (n = 1), Osteosarcoma (n = 2), Bladder cancer (n = 1), ESCC (n = 1). The level of SNHG20 expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR) in all included studies. Multivariate analyze was performed in 6 studies. Clinical outcomes were recorded including 16 studies for OS, 2 for DFS, 1 for PFS, and 1 for RFS. HRs with corresponding 95% CIs were extracted from the original data in 6 studies, and calculated from survival curves in the other 10 studies.

Association Between Snhg20 And Clinicopathological Features
The correlation between SNHG20 expression and clinicopathological characteristics were examined with OR analysis in 15 studies with 1148 cancer patients. 9 studies with 615 patients were included to analysis the link between SNHG20 and TNM stage, and the pooled data found an obvious association between SNHG20 overexpression and advanced TNM stage (OR = 1.79, 95%CI: 1.34-2.39, P < 0.001) (Fig. 4A). As shown in Fig. 4B, 495 cancer patients from 8 studies were included to evaluate the correlation between SNHG20 and LNM, and the results indicated that the patients with elevated SNHG20 expression were more susceptibility to develop LNM (OR = 1.65, 95%CI: 1.21-2.26, P = 0.002). In addition, 3 studies with 218 patients were included to analyze the link between SNHG20 and DM, the results revealed an obvious association between SNHG20 expression and DM (OR = 1.76, 95%CI: 1.10-2.83, P = 0.02) (Fig. 4C).

Publication Bias And Sensitivity Analysis
To evaluate the publication bias, the Begg's funnel plot and Egger's linear regression tests were applied in this meta-analysis. In the analysis of evaluating the association between SNHG20 expression on OS, visual inspection of the Begg's funnel plot revealed asymmetry (Fig. 5A), and Egger's test suggested the probable evidence of publication bias (t = 27.76, p < 0.001). Furthermore, to assess the impact of potential publication bias, the trim and ll analysis were performed with the xed-effect model. Seven which conservatively imputes hypothetical negative unpublished studies to mirror the positive studies that cause funnel plot asymmetry. The imputed studies produce a symmetrical funnel plot (Fig. 5A). The pooled analysis incorporation the hypothetical studies continued to show a statistically signi cant association between SNGH20 expression and OS in human cancers (corrected HR = 2.39, 95%CI: 2.01-2.84, P < 0.001). We also detected the heterogeneity through sensitivity analysis, and the pooled HR was not signi cantly changed after removing each study, suggesting that the results were stable (Fig. 5B).

Discussion
Collective evidence has indicated that lncRNA SNHG20 is closely related to cancer. Initially, lncRNA SNHG20 was identi ed as an overexpressed oncogene in hepatocellular carcinoma [11]. Its overexpression is associated with tumor size, clinical stage, and poor prognosis in patients with hepatocellular carcinoma. Currently, lncRNA SNHG20 has been con rmed as a dysregulated oncogene in other several malignancies, such as gastric cancer [11], glioblastoma [17], NSCLC [18]. Moreover, the silence of SNHG20 signi cantly suppressed cell proliferation, migration, and invasion in a variety of human cancers. It has drawn great attention as carcinogenic lncRNA in many kinds of cancers. Many researchers focused on the clinical potential value in predicting cancer prognosis. However, inconsistency regarding the predictive value of lncRNA SNHG20 in some prognostic parameters, e.g., TNM stage, LNM, and DM, arise from a wide range of studies due to heterogeneity.
In the present meta-analysis, we found that patients with elevated SNHG20 expression tended to have poorer OS in cancer patients. Namely, high lncRNA SNHG20 expression may serve as an independent predictive factor for the prognosis of cancer patients. Meanwhile, this study also revealed that SNHG20 overexpression signi cantly associated with more advanced TNM stage, higher risk of LNM and DM. To sum up, our nding suggested that lncRNA could serve as a potential independent prognostic factor for predicting clinical outcomes for cancer patients. However, the underlying molecular mechanism of aberrant SNHG20 expression correlated with poor clinical prognosis remains elusive.
Several limitations existed in this meta-analysis owing to the discrete data across these clinical studies. First, all included studies were performed in China, which might limit the applicability of our results for other ethnic population. Second, the cut-off values are different among the included articles. Third, some of the HRs were calculated by reconstructing survival curves, which might result in a calculation bias. Finally, only studies published in English or Chinese were obtained in this meta-analysis, and the data collection may be incomplete.

Conclusion
In conclusion, this meta-analysis demonstrated that SNHG20 overexpression was signi cantly correlated with poorer overall survival in patients with human cancers, and related to lymph node metastasis, distant metastasis, and advanced TNM stage. Thus, lncRNA SNHG20 might serve as a novel effective prognostic biomarker in cancer patients. Further high-quality studies are required to explore the role of SNHG20 in cancers and support this study.

Competing interests
The authors declare that they have no competing interests.

Funding
The study was supported by the Natural Science  Forest plot of studies evaluating the association between SNHG20 expression and overall survival (OS).   Begg's funnel plot and sensitivity analysis