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Title page MiRMAs gene polymorphisms and the risk of colorectal cancer Abstract Objective: To investigate the association between the risk of CRC and the polymorphism of all miRNAs that can be retrieved. Methods: Multiple meta-analyses of reported data were conducted during January 2013 and January 2015 in the Second Affiliated Hospital of Soochow University, OR values and 95% confidence interval (95% CI) were used to assess this association. All data analyzes were performed using the software Stata 11.0. Results: we obtained 38 research literatures about the association between miRNAs polymorphism and colorectal cancer risk and 15 met the requirements in accordance with the opt-in and exclusion criteria were selected. Conclusion: We found that let-7, miR-34b/c, miR-146a and miR-149 are positively correlated to the risk of CRC except miR-192a and miR-27a. However, some miRNAs of them lacked of more relevant literature, which made the results less universal. So, analysis of a larger sample size needs to be made. Keywords:miRNA, Polymorphism, Colorectal cancer, Risk, Meta-analysis Introduction Colorectal cancer (CRC) is one of common malignant tumors in the world. According to statistics, in United States, both incidence and mortality of CRC are in the third place even though its death rates have declined .The vast majority of cases (90%) occur in people over 501. Apart from hereditary CRC syndromes, the development of this cancer type is still poorlyunderstood 1, 2. Both germline and somatic genetic variations have been proposed as contributing factors in CRC development 2-4. microRNAs (miRNAs) are a group of small non‑coding RNAs that are ~22 (18 to 25) nucleotides (nt) and which regulate RNA expression in the translation level5-7 MiRNAs have been associated with a variety of diseases, including cancers. More and more evidences have confirmed the importance of miRNAs on regulating the biological characteristics of the tumor, and have common in different tumors such as: Self-growth signals, insensitive to anti-growth signals, involved in abnormal apoptosis, unlimited replication potential, sustained induction of angiogenesis and participating organizations invasion and metastasis 8. Many researchers have identified tumor-specific miRNA signatures which accurately distinguish malignant tumors from several different parts of the benign tissues, and they show that some miRNA carcinogenic depending on the other genes mutation in tumors9 9. MiRNA regulating tumor cell lines directly affects cell proliferation and apoptosis, similar to this, many studies have confirmed the link between the miRNA abnormal expression and intracellular signal transduction pathway abnormalities as well as tumorigenesis 10-14. For example: miR-9 is activated by YC/MYCN which induces cancer metastasis by regulating metastasis suppressor protein E-cadherin 15; miR-449a can cause RB-dependent cell cycle arrest and cellular senescence of prostate cancer 16. MiRNAs constitute a new class of molecules through the interaction with oncogenes and/or tumor suppressor genes; promote the formation of cancer 17. But different miRNA have different signaling pathways, different target proteins/genes to affect the biological changes of cancer. Studies show that human miRNAs single nucleotide polymorphisms (SNPs) can be one of the main forms of genetic variation in human genomic DNA sequences and it may be core message to the susceptibility of human disease. MiRNAs SNP has inter-individual differences in disease diagnosis, treatment and prognosis in the present the research fields. Recent large scale studies reported significant risk of different germline variations for CRC development 3. Novel reports suggest a potential influence of single nucleotide polymorphisms (SNPs) of microRNA-related genes (miRNAs) for the risk of cancer development. Therefore, we want to investigate the correlation between miRNAs gene polymorphism and CRC by reviewing the literatures. Materials and methods Screening and identification of relevant studies Identification and eligibility of relevant studies search terms “miRNA/microRNA”, “colorectal cancer”, “genotype”, “polymorphism” and “variant” were employed to explore publications in PubMed, Ovid, Embase databases and the Cochrane Library for relevant reports during January 2013 and January 2015 in the Second Affiliated Hospital of Soochow University. The search was limited to English language papers and only published studies with full text articles were included. We evaluated potentially relevant publications by examining their titles and abstract by hand. All of the selected studies in our meta-analysis should also match the following inclusion criteria: (1) assessment of miRNA polymorphism and the risk of suffering from CRC, (2) a separate case-control study about human , (3) statistics sufficient genotype data by OR values and 95% confidence intervals. (4) Full-Text Search. Exclusion criteria: (1) lack of controlled studies, (2) repeat the previous literature (3) summary, comments, reviews and editorials (4) focus on benign tumor of CRC. Data extraction and study characteristics Two researchers extracted all data that meet the above inclusion criteria independently and the existing differences were resolved by our team discussion. For each study, the following information were extracted: first name of first author, year of publication, ethnicity, miRNA type, SNP ID, source of research, Genotyping method, the number of cases and controls, the number of various genotypes of cases and controls, Hardy-Weinberg equilibrium (HWE) of control subjects. If one literature has not provided a complete data, we sent request messages to the corresponding author for the data. A total of 15 eligible studies met the inclusion criteria (Table 1). Quality assessment Two researchers evaluated uniform quality of literature which met the inclusion criteria, and cross-checked in case disagreement is resolved by discussion. The quality of the included studies using a modified Jadad score18, 1-3 points considered low quality studies, 4-7 points considered high-quality research. Evaluation include: whether to generate a random sequence of proper randomized allocation is hidden; whether blinded; observe whether lost, quit the case (Table 1) Statistical analysis According to the cases and controls genotype frequencies, the correlation between miRNA polymorphism and CRC risk was assessed via OR values with 95% confidence intervals.Statistical analysis of OR values and 95% confidence interval for five different genetic makeup: the allele, the dominant genetic model, the recessive genetic model, the homozygote comparison and the heterozygous comparison. The Chi-square based Q statistic was used to assess heterogeneity between studies, P <0.05 were considered significant heterogeneity between studies. I2 index is expressed as a percentage for the total variability throughout the study. I2 value as 25%, 50% and 75% respectively meant low, medium and high heterogeneity. Funnel plots was used to assess publication bias. When the effects were assumed to be homogenous, the fixed-effects model was used (Mantel–Haenszel method). If heterogeneity was present, the random-effects model was applied (DerSimonian-Laird method) to account for inter-study heterogeneity instead of the fixed-effect model. All data analyzes were performed using the software Stata 11.0, all the P values are two-sided test19, 20. Results Study characteristics A total of 681 papers relevant to the search words were identified and only 38 studies were about the association between CRC and miRNA polymorphism. According to the above inclusion and exclusion criteria, 15 publications (4 using population-based controls and 11 using hospital-based controls) were included in the final meta-analysis 4-7, 19-35 (Fig.1). In the 15 articles miR-146a has seven; miRNA-149 has three; miRNA-196a2 has eight; miRNA-27a and miRNA-34b/c has two each; miRNA-let-7, miRNA-603 and miRNA-608 have one each. The main characteristics of the studies included in the meta-analysis are summarized in Table 1. Overall analyses Table 2 showed that the overall analysis of all studies revealed a statistically significant positive association between let-7, miR-34b/c, miR-146a, miR-603 and miR-149 polymorphism and risk of CRC. However, miR-192a, miR-608 and miR-27a have no correlation with it. Results are as follows: let-7:Allele T vs. G: OR=1.49, 95% CI:(1.15-1.94); Dominant genetic model TT + TG vs. GG:OR=1.48, 95% CI:(1.08-2.03); Recessive genetic model TT vs. TG + GG:OR=2.52, 95% CI:(1.19-5.31); Homozygous TT vs.GG: OR=2.81, 95% CI:(1.32-5.98); miR-34b/c: Allele T vs. C: OR=1.15, 95% CI:(1.00-1.33), P heterogeneity= 0.154; Dominant genetic model TT + TC vs. CC:OR=1.49, 95% CI:(1.08-2.06), P heterogeneity=0.519; Homozygous TT vs.CC: OR=1.52, 95% CI:(1.08-2.13), P heterogeneity=0.342; Heterozygous TC vs. CC: OR=1.46, 95% CI:(1.03-2.05), P heterogeneity=0.812; miR-146a: Allele G vs. C: OR=1.09, 95% CI :( 1.01-1.18), P heterogeneity=0.227; Recessive genetic model GG vs. GC + CC:OR=1.13, 95% CI:(1.00-1.27), P heterogeneity=0.207; Homozygous GG vs.CC: OR=1.19, 95% CI:(1.01-1.40), P heterogeneity=0.237; MiR-603: Allele C vs. T: OR=3.65, 95% CI :( 1.84-7.24); MiR-149: Recessive genetic model CC vs. CG + GG: OR=1.24, 95% CI :( 1.03-1.5), P heterogeneity=0.582 These results indicate that: let-7, miR-34b/c, miR-146a, miR-603 and miR-149 polymorphism were positively correlated to colorectal carcinoma. Statistical sensitivity Statistical sensitivity in which one study was removed and the rest were analyzed, the pooled RRs were similar with the overall pooled RRs (data not shown), supporting the robustness of our results 1 Publication bias Egger’s test was used to assess the publication bias of literatures (Table 2). However, the results show some evidence of publication bias in some comparisons. Discussion At present, many articles reported miRNAs gene polymorphisms affect tumor susceptibility to, such as: De et al found that a let-7 microRNA polymorphism in the KRAS 3'-UTR is prognostic in oropharyngeal cancer 4, 7. Study has shown that miR-146aG>C and miR-196a2C>T polymorphism are associated with risk of HCC patients in China, especially in patients with HBV infection37. Palmieri et al found that miR-146a polymorphism is not associated with tumor development. However, a slight increase in the frequency of the variant allele was observed in Stage II tumors4. There is also a lot of meta-analysis which is a statistical correlation analysis of miRNA and cancer risk. Some meta-analysis analyzed the correlation between one miRNA and certain cancer susceptibility,such as WA NG et al confirmed the association of the polymorphism miR-196a2 rs11614913 with the risk of CRC, but not with tumor stage and grade5. Some meta-analysis analyzed the correlation between one miRNA and a variety of cancers susceptibility such as Tao et al suggested that hsa-miR-34b/c rs4938723 polymorphism may play an opposite role in different types of cancer based on current studies, subgroup analysis revealed that the variant CT and genotypes were associated with an increased risk of hepatocellular carcinoma (HCC) compared with wild-type TT genotype. However, a decreased risk of colorectal cancer (CRC) was found in the genetic model of CC/TT and CC/CT+TT 6. Li et al insisted that miR-146a rs2910164 polymorphism may decrease the susceptibility of digestive system cancers, especially in Asian population 7, 36. Some meta-analysis analyzed the correlation between a variety of miRNAs and a variety of cancers susceptibility such as one meta-analysis provided evidence that miR-196a2 rs11614913 polymorphism is associated with an increased cancer risk and rs2910164 in miR-146a might be associated with susceptibility to papillary thyroid carcinoma and cervical cancer33. In addition, some meta-analysis analyzed the correlation between a variety of miRNAs and one certain cancer susceptibility such as Dikeakos et al did an investigation on the association of the miR-146aC>G, miR-149T>C, and miR-196a2T>C polymorphisms with gastric cancer risk and survival in the Greek population. And they found that that the risk for GC was significantly higher for the carriers of miR-149 rs2292832CC and miR-196a2 rs11614913CC genotypes, as well as for the carriers of the rs2910164/rs2292832/rs11614913 CCC and GTC haplotype. The rs2910164/rs2292832/rs11614913 CTT and CCT haplotypes seems to have a protective role against GC. Their data demonstrate that specific miRNA SNPs are associated with GC susceptibility in the Greek population25. In this study, we made an overview statistical analysis of the relationship between miRNA polymorphism and CRC.We investigated the effects of miRNA-196a2, miRNA-146a, miRNA-27a, miRNA-34b / c, miRNA-let-7, miRNA-603, miRNA-608 and miRNA-149 on CRC susceptibility respectively. This is a more comprehensive statistical analysis of various miRNAs affect the risk of CRC. However, although the above miRNA and colorectal cancer risk is not highly relevant or not, but they are combined with other factors such as Helicobacter pylori 33, smoking 4, 7, age, and drugs can lead to increased cancer risk. Therefore, stratified analysis is necessary. In addition, this study is the lack of some samples collected mostly from Asian populations, so the results do not lead to global. Therefore, we need a larger sample size of the statistical analysis, the relationship between the collection of more miRNA gene polymorphism and colorectal cancer among non-Asian populations, have been more reliable conclusions. Conclusion We analyze the relationship between the recently published miRNA gene polymorphism and colorectal cancer prevalence among statistical, informed of let-7, miR-34b / c, miR-146a, miR-603 and miR-149 gene polymorphism can significantly increase the risk of colorectal cancer, while miR-192a and miR-27a polymorphism nothing to do with the risk of colorectal cancer. Analysis of a larger sample size needs to be. Acknowledgements This work was partially supported by National Natural Science Foundation of China (Grant No: 81172348, 81301933 and 81172597), Health Research Projects in Jiangsu province (H201313). Reference 1. Vinci S, Gelmini S, Mancini I, Malentacchi F, Pazzagli M, Beltrami C, et al. Genetic and epigenetic factors in regulation of microRNA in colorectal cancers. Methods. 2013;59:138-146. 2. Hu X, Li L, Shang M, Zhou J, Song X, Lu X, et al. Association between microRNA genetic variants and susceptibility to colorectal cancer in Chinese population. 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[Relationship between genetic polymorphism in microRNAs precursor and genetic predisposition of hepatocellular carcinoma]. Zhonghua Yu Fang Yi Xue Za Zhi. 2011;45:239-243. 28. Xiang Y, Fan S, Cao J, Huang S, Zhang LP. Association of the microRNA-499 variants with susceptibility to hepatocellular carcinoma in a Chinese population. Mol Biol Rep. 2012;39:7019-7023. 29. Kim WH, Min KT, Jeon YJ, Kwon CI, Ko KH, Park PW, et al. Association study of microRNA polymorphisms with hepatocellular carcinoma in Korean population. Gene. 2012;504:92-97. 30. Ahn DH, Rah H, Choi YK, Jeon YJ, Min KT, Kwack K, et al. Association of the miR-146aC>G, miR-149T>C, miR-196a2T>C, and miR-499A>G polymorphisms with gastric cancer risk and survival in the Korean population. Mol Carcinog. 2012. 31. Mihalache F, Hoblinger A, Acalovschi M, Sauerbruch T, Lammert F, Zimmer V. A common variant in the precursor miR-146a sequence does not predispose to cholangiocarcinoma in a large European cohort. 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Association of the miR-146aC>G, miR-149T>C, miR-196a2T>C, and miR-499A>G polymorphisms with gastric cancer risk and survival in the Korean population. Mol Carcinog. 2013;52 Suppl 1:E39-51. 37. Xu X, Lao J, Zhao X. How to prevent injury to the palmar cutaneous branch of median nerve and ulnar nerve in a palmar incision in carpal tunnel release, a cadaveric study. Acta Neurochir (Wien). 2013;155:1751-1755. Figure 1. Flowchart of study selection Table 1. Characteristics of the 15 studies included in the meta-analysis First miRNA SNP ID author miRNA-146a rs2910164 Min Year Ethnicity 2012 Asian Hezova 2012 Caucasian rs2292832 Cases Controls design method Allele number number PB PCR-RFLP C/G 446 HB TaqMan C/G HWE(P) Jadad 502 0.44 7 197 212 0.41 7 2013 Asian HB Taqman C/G 1147 1203 0.075 7 Lv 2013 Asian HB PCR–RFLP C/G 353 540 0.08 7 2013 Caucasian PB HRM C/G 160 178 0.11 6 Hu 2013 Asian HB PCR–RFLP C/G 276 373 0.14 7 Parlayan 2014 Asian HB Taqman C/G 116 524 0.75 7 Min 2012 Asian PB PCR-RFLP C/T 446 502 0.17 7 Lv 2013 Asian HB PCR–RFLP C/T 353 540 <0.05 7 2013 Caucasian PB HRM C/T 160 178 0.91 6 Zhu 2011 Asian HB TaqMan T/C 573 588 0.17 7 Zhan 2011 Asian HB PCReRFLP T/C 252 543 0.77 7 Chen 2012 Asian HB PCR–LDR T/C 126 407 0.82 7 HB TaqMan T/C 197 212 0.81 7 Vinci miRNA-196a2 rs11614913 Genotyping Ma Vinci miRNA-149 Study Hezova 2012 Caucasian Min 2012 Asian PB PCR-RFLP T/C 446 502 0.63 7 Lv 2013 Asian PB PCR–RFLP T/C 353 540 <0.05 7 2013 Caucasian PB HRM T/C 160 178 0.09 6 2014 HB TaqMan T/C 116 524 0.78 7 Vinci Parlayan Asian miRNA-27a miRNA-34b/c miRNA-let-7 rs895819 Hezova 2012 Caucasian HB TaqMan G/A 197 212 0.78 7 Wang 2014 Asian HB TaqMan G/A 205 455 <0.05 7 Gao 2013 Asian HB PCR-RFLP T/C 347 488 0.83 7 Oh 2014 Asian PB PCR-RFLP T/C 428 545 0.4 7 Pan 2014 Asian HB PCR-RFLP G/T 339 313 0.41 7 rs4938723 rs712 Sequenom miRNA-603 rs11014002 Wang 2014 Asian miRNA-608 rs4919510 Ryan 2014 Caucasian HB Mass C/T 102 204 0.59 7 PB Taqman C/G 245 446 0.94 7 PB: population-based case–control studies; HB: hospital-based case–control studies; PCR–RFLP: polymerase chain reaction with restriction fragment length polymorphism; SNP: single nucleotide polymorphisms; HWE: Hardy–Weinberg equilibrium; Jadad: Modified Jadad score Table 2. Analysis of the association between eight kinds of miRNAs gene polymorphism and colorectal cancer risk miRNA a 2 b OR (95% CI) I (%) P G/C GC + GG/CC 1.09(1.01,1.18) 1.13(0.99,1.27) 26.4 75.1 0.227 0.001 0.036 0.527 GG/CC + GC GG/CC + GC GC/CC 1.13(1,1.28) 1.19(1.01,1.41) 1.09(0.94,1.24) 28.9 25.2 79.8 0.207 0.237 <0.001 0.155 0.141 0.646 1.13(0.96,1.3) 1.02(0.79,1.31) 0 0 0.533 0.655 0.805 0.06 Contrast miRNA-146a N Pc 7 miRNA-149 3 T/C TT+CT/CC TT/TC+CC TT/CC 1.24(1.03,1.5) 1.19(0.89,1.6) 0 0 0.582 0.591 0.332 0.4 TC/CC 0.88(0.67,1.16) 0 0.89 0.191 T/C TT+TC/CC 1.01(0.94,1.1) 1.03(0.9,1.17) 89.2 87.6 <0.001 TT/TC+CC TT/CC TC/CC 1.01(0.89,1.15) 1.03(0.87,1.21) 1.05(0.91,1.2) 83 90.2 84.7 <0.001 <0.001 <0.001 <0.001 0.595 0.011 G/A (GG+GA)/AA 1.19(0.99,1.43) 1.14(0.9,1.55) 66.4 48.1 0.085 0.165 - GG/(GA+AA) GG/AA GA/AA 1.3(0.97,1.74) 1.38(0.97,1.95) 1.09(0.81,1.47) 3.3 39 0 0.309 0.201 0.408 - 1.15(1,1.33) 1.49(1.08,2.06) 1.11(0.92,1.33) 1.52(1.08,2.13) 1.46(1.03,2.05) 50.9 0 50 0 0 0.154 0.519 0.157 0.342 0.812 - 1.49(1.15,1.94) 1.48(1.08,2.03) 2.52(1.19,5.31) - - - miRNA-196a2 8 miRNA-27a 0.636 0.061 0.023 2 miRNA-34b/c 2 T/C TT+TC/CC TT/(TC+CC) TT/CC TC/CC miRNA-let-7 1 T/G TT+TG/GG TT/TG+GG TT/GG TG/GG 2.81(1.32,5.98) 1.35(0.97,1.88) - - - C/T CC+CT/TT CC/CT+TT 0.97(0.76,1.25) 1.05(0.59,1.87) 0.94(0.69,1.29) - - - CC/TT CT/TT 1.02(0.56,1.85) 1.10(1.60,2.02) - - - C/G 0.97(0.76,1.25) - - - CG+CC/GG CC/CG+GG CC/GG CG/GG 1.05(0.59,1.87) 0.94(0.69,1.29) 1.02(0.56,1.85) 1.10(0.59,2.02) - - - miRNA-603 1 miRNA-608 a Number of comparison b P value of test for overall effect c Egger’s test