We obtained 59 articles in the initial search. After removing 16 papers due to duplication and 32 papers that did not meet the eligibility criteria though the full-text reading, we included 11 papers [11,12,13, 22,23,24,25,26,27,28,29] published between 2015 and 2020 in the final analysis (Fig. 1).
Characteristics of included studies and quality evaluation
A total of 11 studies with 1633 cancer patients were included in this meta-analysis. All the included studies were retrospective and most of them were conducted in China. Tissues were used for detection in these articles. The relevant malignant tumors included: glioma, colorectal cancer, gastric cancer, endometrial carcinoma, osteosarcoma, renal cell carcinoma and hepatocellular carcinoma. The sample size of these studies ranged from 30 to 543. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of lncFTX in these included studies. These studies also provided the clinicopathological data of cancer patients, which included gender, age, tumor size, tumor differentiation, tumor node metastasis (TNM) stage, vessel invasion, lymph nodes metastasis, distant metastasis, and overall survival. For the evaluation of study quality, the NOS score of included publications ranged from 7 to 8 with an average score of 7.6 (Table 1 and Table S1).
Association between the expression of lncFTX and cancer clinicopathological features
As shown in Fig. 2, we found that an elevated expression of lncFTX was significantly associated with more advanced TNM stage (III-IV VS I-II) (OR = 2.30, 95% CI: 1.74–3.03, P < 0.05) (Fig. 2B), greater lymph nodes metastasis (OR = 3.01, 95% CI: 2.00–4.52, P < 0.05) (Fig. 2D) and distant metastasis (OR = 3.68, 95% CI: 2.13–6.34, P < 0.05) (Fig. 2E), and shorter overall survival (HR = 1.83, 95% CI: 1.20–2.81, P < 0.05) (Fig. 2F). However, lncFTX expression was not associated with tumor differentiation (poor differentiation [PD] versus well or moderate differentiation [WD/MD]) (OR = 1.54, 95% CI: 0.56–4.21, P > 0.05) (Fig. 2A) or vessel invasion (OR = 1.28, 95% CI: 0.80–2.05, P > 0.05) (Fig. 2C) of cancer. OR/HR, 95% CI and the heterogeneity of this meta-analysis were presented in Table 2.
In sensitivity analysis by removing one study iteratively in the meta-analysis for each study outcome, the ORs with their corresponding CIs varied in the range from 1.03 (95% CI: 0.70–1.50) to 1.91 (95% CI: 1.30–2.82) for tumor differentiation (Fig. 3A), from 2.10 (95% CI: 1.56–2.84) to 2.62 (95% CI: 1.91–3.60) for TNM stage (III-IV VS I-II) (Fig. 3B), from 1.18 (95% CI: 0.57–2.42) to 1.32 (95% CI: 0.78–2.23) for vessel invasion (Fig. 3C), from 2.54 (95% CI: 1.54–4.20) to 3.52 (95% CI: 2.21–5.60) for lymph nodes metastasis (Fig. 3D), from 3.42 (95% CI: 1.85–6.33) to 3.98 (95% CI: 2.05–7.70) for distant metastasis (Fig. 3E), and the HRs varied in the range from 1.58 (95% CI: 1.27–1.97) to 2.02 (95% CI: 1.61–2.52) for overall survival (Fig. 3F). These results did not vary much as compared with the main study results, suggesting that the main study results were not driven by a single study (Fig. 3). In terms of potential publication bias, no asymmetry was observed in the funnel plot (Fig. 4) and no publication bias was found according to Egger’s test result (P > 0.05).
Association between elevated expression of lncFTX and survival for cancers
Results from eight included studies (Table 3) were pooled to analyze the association between high expression of lncFTX and survival rates for multiple cancers. Subgroup analyses were conducted by dividing the studies according to the sample size (≥100 and < 100) and cancer type (glioma, osteosarcoma, colorectal cancer, and others). We found that higher expression of lncFTX was associated with a greater cancer mortality in studies with sample size less than 100 (HR = 2.50, 95% CI: 1.57–3.99, P < 0.05) (Fig. 5A). Additionally, the results of subgroup analysis showed that elevated expression of lncFTX was associated with shortened OS of glioma (HR = 3.99, 95% CI: 1.98–8.06, P < 0.05), osteosarcoma (HR = 2.48, 95% CI: 1.46–4.20, P < 0.05) and colorectal cancer (HR = 1.76, 95% CI: 1.25–2.46, P < 0.05) (Fig. 5B). The detailed information was shown in Table 4. Considering the high heterogeneity, the data were pooled with a random effects model. Sensitivity analysis showed that the consistent result and the HR was in the range from 1.58 (95% CI: 1.27–1.97) to 2.02 (95% CI: 1.61–2.52) for overall survival (Fig. 5C). These results did not vary much as compared with the main study results, and no publication bias was found (Fig. 5D).
TCGA dataset analysis of prognostic value of FTX
We compared the FTX expression between multiple cancers and normal tissues with using TCGA dataset. Data from 1318 cancer patients and 342 normal controls were used. We found a significant difference in the FTX expression between normal tissues and multiple cancer types including cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), acute myeloid leukemia (LAML), ovarian serous cystadenocarcinoma (OV), pheochromocytoma and paraganglioma (PCPG), uterine corpus endometrial carcinoma (UCEC) and uterine carcinosarcoma (UCS) (Fig. 6A).
Moreover, we found that the expression of FTX was significantly related to the advanced stage of cancers (p < 0.05) (Fig. 6B). Furthermore, we used data from 4668 patients with high FTX expression and 4691 patients with low FTX expression to analyze the prognostic role of FTX in cancer. We found that FTX was significantly associated with OS (p < 0.05) (Fig. 6C) and DFS (p < 0.05) (Fig. 6D).
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