Studies characteristics and quality assessment
A total of 208 studies were found. After removing duplication, we further screened 113 studies based on their title, abstract. 51 studies need to read the full text, and eventually 21[19, 26-45] were included in this meta-analysis (Figure 1). This study included 1,080 patients, all from China. Each included study had a minimum sample size of 24 and a maximum sample size of 99. The included studies consisted of 11 types of cancer, including colorectal cancer, hepatocellular carcinoma, bladder cancer, non-small cell lung cancer, endometrial carcinoma, acute myeloid leukemia, retinoblastoma, prostate cancer, cervical cancer, pancreatic cancer, and ovarian cancer. The expression of SNHG14 was detected by qPCR in 21 studies. Among the included studies, 16 [19, 27, 28, 31-33, 35-39, 41-45]reported on OS and 17[19, 26-40, 43] on clinical outcomes. The NOS scores for all included studies were ≥7, which indicates that the methodological quality of included studies was high. The details are listed in Table 1.
Association between the expression level of SNHG14 and OS
Among the 21 studies included in this study, 16 involved 1578 patients. In these studies, OS was linked to expression levels in cancer patients. Our meta-analysis revealed a statistically significant difference (HR = 1.39; 95% CI: 1.06-1.83; P = 0.017) (Figure 2a). In the high SNHG14 expression group, the number of patients with low survival rates increased significantly, indicating that SNHG14 is an independent factor in the survival of patients with malignant tumors. A subgroup analysis was also performed to look into the relationship between SNHG14 expression and the operating system based on the following factors: analysis method (multivariate and univariate analysis) (Figure 2b), cancer type (digestive system, female reproductive system, or others) (Figure 2c), follow-up time (60 or 60 months) (Figure 2d), and sample size (60 or 60 tissues) (Figure 2e). The follow-up duration was >=60 months, the sample size was 60 tissues, and the multivariate analysis approach and the female reproductive system were statistically significant, according to subgroup analysis. These analysis results are shown in Table 2.
Association between SNHG14 and clinicopathological features
Among the 21 studies, 17 reported a link between clinicopathological characteristics and SNHG14. These analysis results are shown in Figure 3 and Table 3. High SNHG14 expression was found to be significantly correlated with TNM Staging (OR = 0.54; 95% CI: 0.40-0.71; P <0.001) (Figure 3c), tumor size (OR = 1.60; 95% CI :1.20-2.14; P = 0.001) (Figure 3d), lymph node metastasis (OR = 1.86; 95% CI: 1.35-2.55; P <0.001) (Figure 3e), differentiation grade (OR = 1.95; 95% CI: 1.36-2.80; P <0.001) (Figure 3f), and distant metastasis (OR = 2.44; 95% CI: 1.30-4.58; P = 0.005) (Figure 3g). However, meta-analysis revealed that SNHG14 expression was unrelated to age (OR = 0.98; 95% CI: 0.72-1.35; P = 0.915) (Figure 3a) and gender (OR = 0.98; 95% CI: 0.72-1.35; P = 0.915) (Figure 3b).
Publication bias and sensitivity analysis
The publication bias of the papers in our meta-analysis was investigated using Begg and Egger regression tests, and a funnel plot was created to measure publication bias. [Begg funnel plot (Pr> |z|= 0.528) (Figure 4a) and Egger funnel plot (P>|t|= 0.480) (Figure 4b)] revealed no publication bias, indicating that our pooled results were reliable. A sensitivity analysis was also utilized to investigate their possible source and analyze the validity of these results. The results of OS remained steady following testing after disregarding each included study in turn for each outcome. Therefore, the operating system's anticipated aggregated results based on SNHG14 expression were accurate (Figure 5).
Prognostic value of SNHG14 in cancer
The predictive significance of SNHG14 in cancer was investigated using a variety of online database resources. SNHG14 expression is associated to the prognosis of various malignancies from the TCGA database, according to the Kaplan-Meier cumulative curve. Patients with greater SNHG14 expression showed a better survival rate than those with lower SNHG14 expression, such as those with brain lower grade glioma (LGG) (OS: N = 529, P = 0.017) (Figure 6a) and pancreatic adenocarcinoma (PAAD) (OS: N = 182, P = 0.022). (Figure 6b). SNHG14, on the other hand, showed a negative effect on mesothelioma (MESO) (OS: N=86, P=0.026) (Figure 6c), with patients with increased SNHG14 expression having a poorer survival rate.
COX analysis was used to look at the survival rate linked with SNHG14, and PrognoScan was used as the primary database retrieved from the GEO. The researchers discovered that SNHG14 expression was related to LGG (HR = 0.644; 95 % CI: 0.442-0.939; P = 0.022), PAAD (HR = 0.502; 95 % CI: 0.298-0.854; P= 0.009), and skin cutaneous melanoma (SKCM) (HR = 0.777; 95 % CI: 0.622-0.971; P = 0.027), while liver hepatocellular carcinoma (LIHC) (Figure 6d).
The relationship between SNHG14 expression in cancer and TMB and MSI
TMB and MSI are essential determinants in tumor incidence and progression, thus we used a bubble diagram to show the relationship between SNHG14 expression and TMB or MSI to assess its immunogenicity[46]. Our findings revealed that SNHG14 expression is associated with TMB in a representative number of malignancies (n = 14; P<0.05), with TMB positively associating with colon adenocarcinoma (COAD), thymoma (THYM), and acute myeloid leukemia (AML) (LAML). In eleven other cancer types, however, SNHG14 expression is negatively correlated with TMB: esophageal carcinoma (ESCA), lung adenocarcinoma (LUAD), PAAD, stomach adenocarcinoma (STAD), thyroid carcinoma (THCA), bladder urothelial carcinoma (BLCA), head and neck squamous cell carcinoma (HNSC), LGG, LIHC, rectum adenocarcinoma (READ) (Figure 7a).
The next step was to see if SNHG14 expression is linked to MSI in certain cancers. Our findings revealed that SNHG14 expression is strongly connected with MSI in nine cancer types, with four cancer types (LUAD, cholangiocarcinoma (CHOL), LGG, lung squamous cell carcinoma (LUSC)) positively correlating with MSI. In ESCA, STAD, COAD, lymphoid neoplasm diffuse large B-cell lymphoma (DLBC), and PAAD, however, SNHG14 expression is negatively linked with MSI (Figure 7b).
Correlation of SNHG14 expression in cancer with (TME) and immune cell infiltration
The concentration of immunosuppressive cell subsets inside the TME appears to impact cancer prognosis and therapeutic benefit, according to growing research. [47]. SNHG14 expression is related with the OS of various malignancies, according to Kaplan-Meier and Cox survival analyses (LGG, PAAD, MESO, SKCM, LIHC). For these cancer types, the ESTIMATE method was used to determine stromal and immune cell scores. The immunological scores of PAAD (Figure 8c) are favorably connected, but the immune scores of LGG (Figure 8a) and SKCM (Figure 8d), as well as the stromal scores of the LGG, are negatively correlated (Figure 8b).
SNHG14 expression is also favorably connected with infiltrated active mast cells and monocytes in LGG, but negatively correlated with infiltrating M0 macrophages, M1 macrophages, and CD8 T cells, according to our findings. SNHG14 expression is favorably connected with naïve B cells and CD8 T cells infiltrated in PAAD, and negatively correlated with memory B cells, M0 macrophages, and activated NK cells infiltrated in PAAD. The expression of SNHG14 in infiltrating M0 macrophages is favorably connected with infiltrating M0 macrophages and negatively correlated with infiltrating CD8 T cells in LIHC. SNHG14 expression is favorably connected with invading resting memory CD4 T cells and regulatory T cells (Tregs) in SKCM, but negatively correlated with CD8 T cells (Figure 9).