We further validated the expression of SNHG12 and its correlation with prognosis using samples from the TCGA database. In the tumor samples of the TCGA database, the SNHG12 expression level was low in glioma, BRCA, LAML, LUAD, LUSC and KICH and high in DLBG, HNSC, KIRC and THYM (Figure 1A). Survival curves of the tumor samples indicate that SNHG12 is a carcinogenic factor; the higher the expression in the tumor, the worse the prognosis is (Figure 1B, P=0.0012, HR=1.1). High expression of SNHG12 in these tumors (glioma, ACC, LAML, LIHC, MESO) was associated with poor prognosis (Figure 1c-g).
Analysis Of The Published Studies
Characteristics of the included studies
In accordance with the previously established standards, we used an electronic browser to select 10 articles by using a combination of free words and subject words from the databases. From 2015 to 2019, there were 679 tissue specimens from 124 records in the 10 articles by reading the full text (Fig. 2). All of the patients in the 10 studies were from Asia and had 9 types of tumors, including nasopharyngeal carcinoma (NPC), colorectal cancer (CRC),cervical cancer (CVC), breast cancer (BC), gastric cancer (GC), hepatocellular cancer (HCC), non-small cell lung carcinoma (NSCLC), osteosarcoma, and glioma (Supplementary Table S1). The main items of the 10 studies are listed in Table 1. To evaluate the relationship between the SNHG12 level and clinicopathological characteristics, we examined 9 valid clinicopathological studies, which included 577 clinical tumor tissues (Supplementary Table S2). According to the REMARK quality evaluation guidelines, we scored the articles in compliance with the evaluation form and divided the articles into grades of 55–85% (Supplementary Table S3). We used Engauge Digitizer 4.1 software to extract effect values from the Kaplan-Meier survival curves and calculate the poor HRs and 95% CIs by a previously published method[20].
Table 1
The main characteristics of studies with OS included in the prognosis based meta-analysis. NPC, nasopharyngeal carcinoma; GC, gastric cancer; HCC, hepatocellular cancer, CRC, colorectal cancer; BC, breast cancer; CVC, Cervical Cancer. qRT-PCR, quantitative real-time PCR; OS, overall survival; NG, not given
Study | Year | Region | Tumor type | Sample size | Specimen | Method | Cutoff value | Follow-up | Outcome | Quality score (%) |
Zhou, S | 2018 | china | osteosarcoma | 31 | Tissue | qRT-PCR | mean | 60mons | OS | 70 |
Liu, Z | 2018 | china | NPC | 129 | Tissue | qRT-PCR | median | 60mons | OS | 85 |
Yang, BF | 2018 | china | GC | 54 | Tissue | qRT-PCR | NG | 40mons | OS | 80 |
Zhang,HY | 2017 | china | GC | 60 | Tissue | qRT-PCR | median | 60mons | OS | 75 |
Lan, T | 2017 | china | HCC | 48 | Tissue | qRT-PCR | median | 48mons | OS | 80 |
Lei, W | 2018 | china | glioma | 79 | Tissue | qRT-PCR | median | 60mons | OS | 85 |
Wang, JZ | 2017 | china | CRC | 60 | Tissue | qRT-PCR | median | 60mons | OS | 80 |
Wang,OC | 2017 | china | BC | 102 | Tissue | qRT-PCR | median | 60mons | OS | 65 |
Dong, J | 2018 | china | CVC | 76 | Tissue | qRT-PCR | mean | 60mons | OS | 80 |
Relationship of SNHG12 expression with overall survival in human tumors
Nine papers, which included 639 patients, described the relationship between the expression of SNHG12 and OS; the pooled HR was determined to be 2.14 (95% CI: 1.63–2.80, P < 0.00001) by Review Manager 5.3 software. We recalculated the data in another way through Stata software (HR:2.72, 95% CI: 1.95–3.8, P < 0.00001). These results indicate that high expression of SNHG12 can significantly reduce the overall survival of patients, suggesting that the prognosis of the patients is poor. The fixed model was adopted because there was no significant heterogeneity (I2 = 0, P = 1) (Fig. 3A). As shown in Table 2, based on tumor type, cutoff values, and sample size, the original articles were grouped differently. According to the analysis of different tumor types, SNHG12 high expression has a significant correlation with poor OS in the patients with digestive system cancer (HR = 2.12, 95%=1.43–3.15, P = 0.0002), nervous system (2.41, 1.17–4.97, P = 0.02), respiratory system carcinomas (1.94, 1.15–3.28, P = 0.01), cancers of the reproductive system (2.40, 1.12–5.15, P = 0.03) and locomotor system (2.41, 1.17–4.97, P = 0.02). Next, according to the different cutoff scores from the articles, we conducted analysis between different groups, including the median (2.10, 1.53–2.89, P < 0.00001), and other studies (2.23, 1.34–3.71, P = 0.002). Then, based on the sample size (≥ 60 or < 60), we divided the studies into two categories. In this analysis, regardless of whether the study had a large sample size (2.11, 1.51–2.95, P < 0.0001) or a small sample size (2.19, 1.39–3.45, P = 0.0007), high expression of SNHG12 was an obvious prognostic marker for poor OS. However, we divided the studies into categories based on the sample quality score based on a score of 80. Highly expressed SNHG12 predicts short overall survival for patients from studies with a high quality score (2.23, 1.66-3.00, P < 0.00001), but the low quality score subgroup did not show significant results due to the combined effects (1.71, 0.88–3.32, P = 0.11).
Table 2
Subgroup and meta-regression analysis of HRs in different cancer type, cut-off, sample size, and quality score subgroup
subgroup analysis | No. of studies | No. of patients | Pool HR (95% CI) | weight | Heterogeneity random |
Fixed | random | I2(%) | p value |
Overall survival | 9 | 577 | 2.17 [1.69, 2.80] | 2.17 [1.69, 2.80] | 100% | 0 | 0.99 |
cancer type | | | | | | | |
Digestive system | 4 | 222 | 2.12 [1.43, 3.15] | 2.12 [1.43, 3.15] | 41.20% | 0 | 0.81 |
Respiratory system | 2 | 169 | 1.94 [1.15, 3.28] | 1.94 [1.15, 3.28] | 23.30% | 0 | 0.88 |
Reproductive system | 1 | 76 | 2.40 [1.12, 5.15] | 2.40 [1.12, 5.15] | 11.00% | - | - |
nervous system | 1 | 79 | 2.41 [1.17, 4.97] | 2.41 [1.17, 4.97] | 12.30% | - | - |
locomotor system | 1 | 31 | 2.41 [1.17, 4.97] | 2.41 [1.17, 4.97] | 12.30% | - | - |
cut-off | | | | | | | |
others | 3 | 161 | 2.30 [1.51, 3.51] | 2.30 [1.51, 3.51] | 36.20% | 0 | 0.97 |
median | 6 | 416 | 2.10 [1.53, 2.89] | 2.10 [1.53, 2.89] | 63.80% | 0 | 0.95 |
Quality score | | | | | | | |
Score < 80 | 3 | 131 | 1.71 [0.88, 3.32] | 1.71 [0.88, 3.32] | 16.50% | 0 | 0.9 |
Score ≥ 80 | 6 | 446 | 2.23 [1.66, 3.00] | 2.23 [1.66, 3.00] | 83.50% | 0 | 0.99 |
sample size | | | | | | | |
Size < 60 | 3 | 133 | 2.23 [1.23, 4.03] | 2.23 [1.23, 4.03] | 20.6% | 0 | 1 |
Size ≥ 60 | 6 | 444 | 2.12 [1.56, 2.86] | 2.12 [1.56, 2.86] | 79.4% | 0 | 0.94 |
The funnel plot and the Egger method were used to test whether the abovementioned combined effects resulted in a publication bias. The meta-results showed that the results are stable without significant asymmetry (Egger’s P = 0.236, Fig. 3B, and 3C). In the same way, we also performed corresponding tests between the different subgroups. The large tumor sample size (Egger's P = 0.326), high quality score (Egger's P = 0.387) and median subgroups (Egger's P = 0.194, Supplementary table 4) were not found to have a publication bias. In addition, by deleting each study and combining the remaining studies in turn, the sensitivity analysis confirmed that the remaining combined HR of the OS was not significantly affected in Fig. 3D.
Association Between The Snhg12 Level And Clinicopathological Characteristics
The clinical and pathological characteristics of the included research articles were statistically analyzed, and the results, including the ORs and 95% CIs, are shown in Tables 3–6. The summary results show that the expression of SNHG12 is elevated with high stages (OR = 3.94, 95%CI = 2.80–5.53, P < 0.00001), lymphatic metastasis (2.66, 1.65–4.29, P < 0.0001), high grade (2.04, 1.18–3.51, P = 0.01), tumor size (2.79, 1.89–4.14, P < 0.00001) and distant metastasis (2.20, 1.40–3.46, P = 0.0006). However, there was no significant difference in patient age (1.27, 0.93–1.74) or gender (1.14, 0.78–1.65).
Table 3
The subgroup of the relationship and heterogeneity between high SNHG12 expression and tumor stage
Subgroup analysis | No. of studies | No. of patients | Pool OR (95% CI) | weight | Heterogeneity random |
Fixed | random | I2(%) | p value |
ORs of tumor stage subgroup | 9 | 639 | 3.94 [2.80, 5.53] | 3.91 [2.77, 5.51] | 100% | 0 | 0.46 |
Cancer type | | | | | | | |
Digestive system | 4 | 222 | 4.54 [2.58, 8.00] | 4.54 [2.58, 8.00] | 36.60% | 0 | 0.76 |
Respiratory system | 1 | 129 | 3.79 [1.75, 8.19] | 3.79 [1.75, 8.19] | 20.00% | - | - |
Reproductive system | 2 | 178 | 2.24 [1.19, 4.21] | 2.24 [1.19, 4.21] | 29.70% | 0 | 0.87 |
nervous system | 1 | 79 | 8.79 [3.17, 24.32] | 8.79 [3.17, 24.32] | 11.40% | - | - |
locomotor system | 1 | 31 | 10.89 [1.14, 103.98] | 10.89 [1.14, 103.98] | 2.30% | - | - |
cut-off | | | | | | | |
others | 3 | | 3.59 [1.83, 7.02] | 3.79[1.58, 9.07] | 25.00% | 28.5 | 0.247 |
median | 6 | | 4.07 [2.74, 6.03] | 4.06[2.73,6.05] | 75.00% | 0 | 0.445 |
Sample size | | | | | | | |
Size < 60 | 4 | 235 | 3.76 [2.11, 6.69] | 3.69 [2.05, 6.62] | 34.70% | 0 | 0.48 |
Size ≥ 60 | 5 | 404 | 4.04 [2.65, 6.14] | 4.07 [2.50, 6.65] | 65.30% | 23 | 0.46 |
Quality scores | | | | | | | |
Score < 80 | 4 | 269 | 2.70 [1.60, 4.54] | 2.62 [1.55, 4.44] | 42.70% | 0 | 0.6 |
Score ≥ 80 | 5 | 370 | 5.25 [3.34, 8.26] | 5.25 [3.33, 8.28] | 57.30% | 0 | 0.73 |
Table 4
The subgroup of the relationship and heterogeneity between high SNHG12 expression and Lymphatic metastasis
Subgroup analysis | No. of studies | No. of patients | Pool HR (95% CI) | weight | Heterogeneity random |
Fixed | random | I2(%) | p value |
ORs of Lymphatic metastasis subgroup | 5 | 421 | 2.60 [1.72, 3.91] | 2.66 [1.65, 4.29] | 100% | 22 | 0.28 |
Cancer type | | | | | | | |
Digestive system | 2 | 114 | 5.60 [2.44, 12.89] | 5.57 [2.41, 12.86] | 27.70% | 0 | 0.62 |
Respiratory system | 1 | 129 | 1.62 [0.76, 3.45] | 1.62 [0.76, 3.45] | 27.80% | - | - |
Reproductive system | 2 | 178 | 2.29 [1.23, 4.26] | 2.29 [1.23, 4.26] | 44.50% | 0 | 0.92 |
cut-off | | | | | | | |
others | 2 | 130 | 3.38 [1.60, 7.15] | 3.65 [1.16, 11.44] | 31.70% | 51 | 0.15 |
median | 3 | 291 | 2.31 [1.41, 3.78] | 2.35 [1.35, 4.10] | 68.30% | 22 | 0.28 |
Sample size | | | | | | | |
Size < 60 | 2 | 156 | 3.29 [1.66, 6.52] | 3.65 [1.25, 10.65] | 36.30% | 50 | 0.16 |
Size ≥ 60 | 3 | 265 | 2.27 [1.36, 3.79] | 2.31 [1.29, 4.14] | 63.70% | 19 | 0.29 |
Quality scores | | | | | | | |
Score < 80 | 3 | 238 | 2.73 [1.59, 4.67] | 2.73 [1.59, 4.68] | 60.50% | 0 | 0.54 |
Score ≥ 80 | 2 | 183 | 2.42 [1.28, 4.57] | 3.09 [0.72, 13.17] | 39.50% | 73 | 0.05 |
Table 5
The subgroup of the relationship and heterogeneity between high SNHG12 expression and distant metastasis
Subgroup analysis | No. of studies | No. of patients | Pool HR (95% CI) | weight | Heterogeneity random |
Fixed | random | I2(%) | p value |
ORs of distant metastasis subgroup | 6 | 458 | 2.20 [1.40, 3.46] | 2.23 [1.20, 4.11] | 100% | 38 | 0.15 |
Cancer type | | | | | | | |
Digestive system | 2 | 120 | 3.63 [1.68, 7.87] | 3.64 [1.57, 8.44] | 36.70% | 14 | 0.28 |
Respiratory system | 1 | 129 | 1.70 [0.75, 3.85] | 1.70 [0.75, 3.85] | 25.00% | - | - |
Reproductive system | 2 | 178 | 1.00 [0.39, 2.54] | 1.00 [0.39, 2.56] | 29.00% | 0 | 0.63 |
locomotor system | 1 | 31 | 8.00 [1.33, 48.18] | 8.00 [1.33, 48.18] | 9.30% | - | - |
cut-off | | | | | | | |
others | 2 | 107 | 2.43 [0.90, 6.55] | 2.82 [0.46, 17.38] | 24.50% | 64 | 0.1 |
median | 4 | 351 | 2.14 [1.29, 3.57] | 2.14 [1.05, 4.37] | 75.50% | 43 | 0.15 |
Sample size | | | | | | | |
Size < 60 | 2 | 133 | 1.97 [0.72, 5.33] | 2.32 [0.24, 22.63] | 23.10% | 75 | 0.04 |
Size ≥ 60 | 4 | 325 | 2.27 [1.36, 3.77] | 2.28 [1.25, 4.15] | 76.90% | 38 | 0.15 |
Quality scores | | | | | | | |
Score < 80 | 4 | 269 | 2.47 [0.83, 7.30] | 2.49 [1.32, 4.69] | 48.30% | 60 | 0.06 |
Score ≥ 80 | 2 | 189 | 1.93 [1.00, 3.70] | 1.93 [1.01, 3.70] | 51.70% | 0 | 0.61 |
Table 6
The subgroup of the relationship and heterogeneity between high SNHG12 expression and tumor size
Subgroup analysis | No. of studies | No. of patients | Pool OR (95% CI) | weight | Heterogeneity random |
Fixed | random | I2(%) | p value |
ORs of tumor size subgroup | 8 | 510 | 2.79 [1.89, 4.14] | 3.29 [1.66, 6.51] | 100% | 60 | 0.01 |
Cancer type | | | | | | | |
Digestive system | 4 | 222 | 5.43 [3.02, 9.76] | 5.43 [3.01, 9.79] | 52.70% | 0 | 0.8 |
Reproductive system | 2 | 178 | 0.91 [0.40, 2.09] | 1.01 [0.30, 3.43] | 21.90% | 26 | 0.24 |
locomotor system | 1 | 31 | 8.80 [1.69, 45.76] | 8.80 [1.69, 45.76] | 9.60% | - | - |
nervous system | 1 | 79 | 1.58 [0.65, 3.84] | 1.58 [0.65, 3.84] | 15.90% | - | - |
cut-off | | | | | | | |
others | 3 | 161 | 1.96 [1.05, 3.66] | 2.82 [0.58, 13.63] | 37.90% | 79 | 0.008 |
median | 5 | 349 | 3.53 [2.12, 5.88] | 3.73 [1.92, 7.24] | 62.10% | 33 | 0.2 |
Sample size | | | | | | | |
Size < 60 | 4 | 235 | 4.89 [2.36, 10.14] | 4.92 [2.37, 10.19] | 41.30% | 0 | 0.87 |
Size ≥ 60 | 4 | 275 | 2.18 [1.36, 3.50] | 2.52 [0.86, 7.42] | 58.70% | 78 | 0.003 |
Quality scores | | | | | | | |
Score < 80 | 4 | 269 | 2.13 [1.18, 3.82] | 2.83 [0.79, 10.10] | 45.40% | 71 | 0.02 |
Score ≥ 80 | 4 | 241 | 3.51 [2.06, 5.99] | 3.83 [1.75, 8.41] | 54.60% | 49 | 0.12 |
Tumor size (I2 = 60%, P = 0.01) showed obvious statistical heterogeneity in 8 studies (Table 6). The existence of heterogeneity in each subgroup was shown in the random effects model. In the tumor size heterogeneity analysis, we discovered notable heterogeneity in the low quality score subgroup (I2 = 71, P = 0.02), the large sample size subgroup (I2 = 78%, P = 0.003), and other the cutoff subgroups (I2 = 79, P = 0.008). According to the three subgroups, we found that the Jing Dong study (HR = 0.72, 95% CI = 0.29–1.81) was in the above three subgroups and may be the main source of heterogeneity. No proof of statistical heterogeneity was found in lymphatic metastasis subgroup, the tumor stage subgroup and distant metastasis subgroup (I2 = 22%, P = 0.28; I2 = 0%, P = 0.46; and I2 = 38%, P = 0.15). However, Zhi-Biao Liu (OR = 1.62, 95%=0.76–3.45) showed no clinical significance or obvious heterogeneity by stratification analysis of the lymphatic quality subgroup. Further investigation of heterogeneity in distant metastasis revealed obvious heterogeneity in the low quality score (HR = 2.47, 95% CI = 0.83–7.30, P > 0.01, I2 = 60%, P = 0.06) subgroups and tumor size (OR = 2.32, 95% CI = 0.24–22.63 P > 0.01, I2 = 75%, P = 0.04).
We are concerned about publication bias in the statistical analysis of clinicopathological characteristics. We performed the Egger linear regression test. The results showed that there were no published biases in lymph node metastasis, the tumor stage, metastasis and size subgroups (Egger's P = 0.238, Egger's P = 0.192, Egger's P = 0.149 and Egger's P = 0.097) (Supplementary Table 5) (4). Sensitivity analysis of different subgroups showed stable results (Supplementary Fig. 1).