High BANCR may manifest worse prognosis in human malignant carcinomas: An updated systematic review and meta-analysis

Background BRAF-activated non-coding RNA (BANCR) was reported to be aberrantly expressed in various tumor tissues and has been confirmed to function as tumor suppressor or oncogene in many types of cancers. Considering the conflicting results and insufficient sampling, a meta-analysis was performed to explore the prognostic value of BANCR in various carcinomas. Methods A comprehensive literature search of PubMed, Web of Science, EMBASE, Cochrane Library and the China National Knowledge Infrastructure (CNKI) was conducted to collected relevant articles. Results Pooling results showed strong relevance of high BANCR expression and poor overall survival (OS) (HR=1.60, 95% confidence interval (CI): 1.19-2.15, P =0.002) and recurrence-free survival (RFS) (HR=1.53, 95%CI: 1.27-1.85, P <0.00001). In addition, high BANCR expression predicts advanced tumor stage (OR=2.39, 95%CI: 1.26-4.53, P =0.008), present lymph node metastasis (OR=2.03, 95%CI: 1.08-3.83, P =0.03), positive distant metastasis (OR=3.08, 95%CI: 1.92-4.96, P <0.00001) and bigger tumor size (OR: 1.63, 95%CI: 1.09-2.46, P =0.02). The results showed that elevated BANCR expression was associated with unfavorable prognosis for most of cancer patients, and BANCR could be served as a promising therapeutic target and independent prognostic predictor for cancers.


Introduction
Currently, cancer remains one of the major public health concerns worldwide [1]. It's reported that 1,762,450 new cancer cases and 606,880 cancer deaths are predicted to occur in the United States in 2019 [2]. Notably, due to the rapid advancement of cancer research, treatment and diagnostic methods, the cancer mortality continuously dropped by a total of 27% in the last two decades [3]. In spite of this, the 5-year relative survival rate of patients is still disappointing [4]. When the cancer is diagnosed, many patients are already in the middle and late stages of the disease, and there is still no ideal effective treatment. Therefore, it's critical to explore specific and sensitive therapeutic target and promising prognostic biomarkers for effective treatment of cancer.
Increasing studies have suggested that long non-coding RNA (lncRNA),with longer than 200 nucleotides and without the ability to code proteins, plays a vital role in multifarious biological processes including cell differentiation, growth, apoptosis, cell cycle and metabolism [5]. Moreover, abnormal lncRNA expression has been observed in various tumor tissues and involved in the proliferation, invasion and metastasis of tumor cells [6,7]. Growing number of publications uncovered the great application value of long non-coding RNA in target treatment and cancer prognosis [8]. For example, MALAT1 [9], CRNDE [10], ZEB1-AS1 [11] etc. By using RNA-sequencing, Flockhart et al. originally found that BRAF-activated non-coding RNA (BANCR), a 693-bp lncRNA located in chromosome 9, was overexpressed in melanoma cell.
However, due to small sample size and discrepant conclusions among those studies, the association of BANCR expression with prognosis of patients is still undefined. Thus, a meta-analysis was performed to investigate the prognostic value of BANCR in various cancers.

Materials And Methods 2.1. Literature search strategies
The literature search was conducted on electronic databases of PubMed, Cochrane Library, EMBASE, Web of science and Chinese National Knowledge Infrastructure (CNKI) by using ("BANCR" OR "Lnc RNA BANCR" OR "lncBANCR" OR "BRAF-activated non-coding RNA") AND ("neoplasm" OR "carcinoma" OR "tumor" OR "cancer"). The latest literature search was up to July 25, 2019.

Inclusion and exclusion criteria
The selection of studies was completed by two independent researchers. The inclusion standards are as followed: (a) studies investigated the correlation of BANCR expression with survival outcome and clinical prognosis of cancer patients; (b) patients were classified into high expression group and low expression group in accordance with primary literature; (c) the expression level of BANCR was detected by validate techniques; (d) publications provide sufficient and usable data to calculate OR and HR; (e) studies in English or Chinese. The exclusion standards are: (a) publication explore the molecular biological mechanisms of BANCR but not investigate the relationship between the expression level of BANCR and the prognosis of cancer patients but; (b) reviews and meta-analysis, letters, animal studies, conference literature; (c) studies without enough data to perform prognostic analysis; (d) repetitive publication.

Data extraction and quality assessment
The data was extracted by two independent investigators (FSX and LZ), including first author's name, publication date, cancer type, sample size, overall survival (OS), recurrence-free survival (RFS), disease free survival (DFS), (TNM) stage, tumor size, distant metastasis (DM), histological grade, lymph node metastasis (LNM), depth of invasion, detection methods of BANCR and HR. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of included articles, and the highquality studies are with NOS score more than 6 [20].

Statistical analysis
The meta-analysis was conducted to calculate the pooled ORs, HRs with corresponding 95% CI by using the Review Manager 5.3 software (Cochrane Collaboration, London, UK) and STATA 12.0 software (Stata, College Station, TX). Random-effect model was adopted when I 2 > 50%, which demonstrating meaningful heterogeneity among enrolled studies, instead, fixed-effect model was applied. The latent publication bias was assessed by using Funnel plots and Begg's test. When significant heterogeneity exists, the subgroup analysis was conducted to explore the source of heterogeneity. The sensitivity analysis was carried out for stability test of results. Specially, when survival data cannot be directly extracted and only Kaplan-Meier curves was provided by primary articles, the Enguage Digitizer tool (Version 4.1) was used to extract time-dependent survival rate from Kaplan-Meier curves, the HRs and 95%CI were calculated according to the method [21].
Statistically significance was deemed when P < 0.05.

Study characteristics
386 studies were searched from the databases, among them, 174 duplicate studies were excluded and 158 studies were abandoned after reading abstract and full text. Furthermore, 16 publications did not investigate the association between BANCR expression and the prognosis of patients, 6 publications did not divided patients into high and low BANCR expression group, 12 publications lack usable data. Lastly, 20 eligible studies were included for qualitative and quantitative synthesis ( Figure 1).

The association of BANCR with OS
A total of 10 studies comprising 1151 patients were enrolled to inquiry the relationship between BANCR with OS. The random-effect model was applied for marked heterogeneity (I 2 =60%, p=0.008).
Pooling result supported the conclusion that patients with high BANCR expression tended to undergo shorter overall survival (HR=1.60, 95%CI: 1.19-2.15, p=0.002, Figure 2A). Moreover, subgroup analysis was conducted to explore the sources of heterogeneity based on cancer types, the sources of HR (direct/indirect extraction), simple size (less/more than 100 patients) and NOS score (9 score/ less than 9 score). A strong correlation was revealed between high BANCR expression and poor OS in  Table 3. Bad prognosis of BANCR could also be identified by revealing the positive association between high BANCR

The association of BANCR with other clinic pathological parameters
Other prognostic parameters were also assessed, and obvious correlation between increasing BANCR expression and advanced lymph node metastasis (OR=2.03, 95%CI=1.08-3.83, p<0.05) (Figure 4

Publication bias and sensibility analysis
Sensibility analysis was performed to assess the outcome stability of OS among including studies, we found that removing each researches successively did not influence the total results significantly, means the results of each publications were almost consistent with combing result (Figure 7).

Discussion
BRAF activated non-coding RNA (BANCR), was firstly found in melanoma cell by Flockhart RJ et al., was reported to involving in the occurrence and development of disease, such as coronary artery disease [37], diabetic retinopathy [38] and cancer [12]. After years of investigation, increasing researches reported that BANCR could serve as both oncogene and tumor suppressor gene in various cancers. In addition, growing literature reported that aberrant BANCR expression could be detected in breast cancer, gastric cancer, esophagus cancer, hepatocellular carcinoma, endometrial cancer, retinoblastoma and osteosarcoma, high BANCR expression predicts poor survival outcome, advanced TNM stage, positive lymph node metastasis, bad histological grade and earlier distant metastasis of tumor cells. However, there are several publications manifested that BANCR could act as favorable prognostic factor in non-small cell lung cancer and renal carcinoma.
Based on the controversial conclusions. some researchers tried to explore the potential molecular biological mechanisms of BANCR in the occurrence and development of cancer ( Table 5 and  [34]; Also, it's reported that the expression of BANCR increased in colorectal cancer (CRC), BANCR could strengthen the ability of migration and proliferation of CRC by inducing epithelial-mesenchymal transition (EMT) via activating the MEK/ERK signaling pathway [43,44]. Inversely, Liao et al discovered that among papillary thyroid cancer (PTC) patients, the expression of BANCR was downregulated, which partially suppress the proliferation, migration and invasion of PTC cells via ERK/MAPK signaling pathway [24]. Likewise, Sun et al implied that the decreased expression of BANCR could be observed in NSCLC cells, low BANCR expression may drive NSCLC cell invasion and metastasis by affecting EMT. In short, the expression level and role of BANCR varies from cancer to cancer, possibly due to inconsistency between tumors. A comprehensive analysis is therefore needed to accurately assess the prognostic value of BANCR in cancer.
In accordance with controversial conclusions mentioned above, 20 studies with 1997 patients and 11 types of cancers were finally enrolled to explore the relationship between BANCR expression level and the prognosis of cancer patients. Combining HR showed the marked association between high BANCR expression and worse OS. In view of underlying heterogeneity, an subgroup analysis according to cancer type, HR estimation method, NOS scores and sample size were conducted to investigate the sources of heterogeneity, and obvious association were uncovered in digestive system (HR=1.87,  (Figure S4). In a word, in spite of serving as both oncogene and suppressor gene in different cancers, the pooling results still supported the conclusions most of primary researches provided that high BANCR expression indicating worse cancer prognosis. The results of sensitivity analysis in OS showed that the total results would not be significantly affected by the arbitrary deletion of a certain study, which proved the stability of the results. In addition, small publication bias was observed in the included studies. Therefore, the expression level of BANCR could be used to evaluate the prognosis of tumor patients in most of cancers.

Although the relationship between BANCR expression and clinical prognosis has been performed by
Hu et al. and Fan et al. [45,46], there are several differences between previous investigations and our research, first, pooling results uncovered the significant association between high BANCR expression and worse OS, RFS, advanced TNM stage and high risk of lymph node metastasis, which failed to be concluded by previous meta-analysis; second, larger sample size and more cancer type were included in this meta-analysis; thirdly, comprehensive subgroup analysis was performed and the connection between BANCR and tumor size, histologic grade, invasion depth, smoking, number of local tumor, age and gender were firstly explored in this study, which was not investigated in previous meta-analysis; finally, detail molecular biological mechanisms of BANCR in various cancers were discussed and summarized. Meanwhile, there exist some limitations in this meta-analysis: (a) most of the patients included in this study were came from China, which may limit the applicability of the results; (b) the sample size included is not large enough, which may affect the reliability of the results; (c) merely 11 types of cancers were enrolled to investigate the connection between BANCR and cancer prognosis, thus, the conclusions of this study could not represent all cancers; (d) HR value is partly extracted from the survival curve, may partly exist extraction bias.

Conclusion
In general, high expression of BANCR is significantly associated with shorter OS and poor clinical prognosis, BANCR may be treated as a biological indicator and therapeutic target for cancer. High quality, larger sample size and multi-center study was necessary to be conducted to further confirm the reliability of this conclusion.

Availability of data and materials
All data analyzed during this study are available from the corresponding author on reasonable request.

Conflicts of interest
The authors proclaimed no underlying conflict of interest.       Forest plot about the relationship between BANCR expression and TNM stage Figure 4 Forest plot about the relationship between BANCR expression and Lymph node metastasis (LNM). Forest plot about the relationship between BANCR expression and tumor size.