MDM2 SNP309 does not confer an increased risk to oral squamous cell carcinoma but may modulate the age of disease onset

Genotypic distribution of single nucleotide polymorphisms in oral cancer: global scene

Globocan 2012 reports the global oral cancer incidence of 300,373 new oral cancer cases annually, contributing to 2.1 % of the world cancer burden. The major well-established risk factors for oral cancer include tobacco, betel/areca nut, alcohol and high-risk oncogenic human papilloma virus (HPV) 16/18. However, only 5-10 % of individuals with high-risk lifestyle develop oral cancer. Thus, genomic variants in individuals represented as single nucleotide polymorphisms (SNPs) influence susceptibility to oral cancer. With a view to understanding the role of genomic variants in oral cancer, we reviewed SNPs in case-control studies with a minimum of 100 cases and 100 controls. PubMed and HuGE navigator search engines were used to obtain data published from 1990 to 2015, which identified 67 articles investigating the role of SNPs in oral cancer. Single publications reported 93 SNPs in 55 genes, with 34 SNPs associated with a risk of oral cancer. Meta-analysis of data in multiple studies defined nine SNPs associated with a risk of oral cancer. The genes were associated with critical functions deregulated in cancers, including cell proliferation, immune function, inflammation, transcription, DNA repair and xenobiotic metabolism.

Influence of MDM2 polymorphisms on squamous cell carcinoma susceptibility: a meta-analysis

PURPOSE

Controversial associations between single-nucleotide polymorphisms (rs2279744, rs937283, rs3730485) of the MDM2 gene and the etiology of squamous cell carcinomas (SCCs) have been reported. This merits further comprehensive assessment.

MATERIALS AND METHODS

We systematically reviewed the available data and conducted an updated meta-analysis to evaluate the genetic effect of MDM2 polymorphisms in SCC susceptibility, using Stata/SE 12.0 software.

RESULTS

After screening, 7,987 SCC cases and 12,954 controls from 26 eligible case-control studies were enrolled. Overall, compared with the control group, a significantly increased SCC risk was observed for the MDM2 rs2279744 polymorphism in the Asian population (test of association: odds ratio [OR] 1.12, P=0.027 for G vs T; OR 1.26, P=0.016 for GG vs TT; OR 1.25, P<0.001 for GG vs TT + TG; and OR 1.08, P=0.023 for carrier G vs T). In subgroup analysis by SCC type, a similarly increased esophageal SCC risk was detected (OR 1.19, P<0.001 for G vs T; OR 1.46, P<0.001 for GG vs TT; and OR 1.48, P=0.005 for GG vs TT + TG). Furthermore, MDM2-TP53 double mutation was statistically associated with increased SCC susceptibility overall (OR 1.52, P=0.001), especially in the Asian population (OR 1.49, P=0.022). However, no significant difference between the control and case groups was obtained for MDM2 rs937283 or rs3730485 under any genetic model (all P>0.05).

CONCLUSION

Our results highlight a positive association between the GG genotype of MDM2 rs2279744 polymorphism and an increased risk of esophageal SCC in the Asian population, which needs to be clarified by more large-scale studies.

Association of MDM2 promoter T309G polymorphism with oral cancer risk: A meta-analysis of 3,536 subjects

The mouse double minute 2 (MDM2) gene is an important regulator of the p53 suppressor gene. To date, evidence concerning the association of the MDM2 single nucleotide polymorphism (SNP) 309T>G (rs2279744) with the risk of developing oral squamous cell carcinoma (OSCC) remains controversial. Therefore, a meta-analysis of all the eligible studies was performed, in order to derive a more precise estimation of this association. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the degree of association in 5 previous studies, including a total of 1,369 OSCC cases and 2,167 controls. The overall analysis revealed a significant association between MDM2 SNP309 and OSCC risk in the heterozygote (TG vs. TT: OR=0.81; 95% CI: 0.68-0.96; P=0.02) and dominant models (TG+GG vs. TT: OR=0.82; 95% CI: 0.69-0.97; P=0.02). The subgroup analysis based on the source of the controls revealed a significant association between population-based controls and the heterozygote model (TG vs. TT: OR=0.75; 95% CI: 0.62-0.91; P=0.004), dominant model (TG+GG vs. TT: OR=0.76; 95% CI: 0.63-0.91; P=0.003) and allele comparison (G vs. T: OR=0.89; 95% CI: 0.79-0.99; P=0.04). Importantly, no evidence of publication bias or obvious heterogeneity were observed in the meta-analysis. The results of the present study demonstrated a decreased risk of developing OSCC for the MDM2 SNP309 group, suggesting MDM2 SNP309 may be a protection-associated genetic variation for OSCC. Additional well-designed studies, with larger sample sizes, are required to further elucidate this association.

Is MDM2 SNP309 Variation a Risk Factor for Head and Neck Carcinoma?: An Updated Meta-Analysis Based on 11,552 Individuals

Murine double minute-2 (MDM2) is a negative regulator of P53, and its T309G polymorphism has been suggested as a risk factor for a variety of cancers. Increasing evidence has shown the association of MDM2 T309G polymorphism with head and neck carcinoma (HNC) risk. However, the results are inconsistent. Thus, we performed a meta-analysis to elucidate the association. The meta-analysis retrieved studies published up to August 2015, and essential information was extracted for analysis. Separate analyses on ethnicity, source of controls, sample size, detection method, and cancer types were also conducted. Odds ratios (ORs) and their 95% confidence intervals (CIs) were used to estimate the association. Pooled data from 16 case-control studies including 4625 cases and 6927 controls failed to indicate a significant association. However, in the subgroup analysis of sample sizes, an increased risk was observed in the largest sample size group (>1000) under a recessive model (OR = 1.52; 95% CI = 1.08-2.13). Increased risks were also found in the nasopharyngeal cancer in the subgroup analysis of cancer types (GG vs TT: OR = 2.07; 95% CI = 1.38-3.12; dominant model: OR = 1.48; 95% CI = 1.13-1.93; recessive model: OR = 1.76; 95% CI = 1.17-2.65). The results suggest that homozygote GG alleles of MDM2 SNP309 may be a low-penetrant risk factor for HNC, and G allele may confer nasopharyngeal cancer susceptibility.

Impact of MDM2 single nucleotide polymorphism on oral squamous cell carcinoma risk

Mouse Double Minute 2 (MDM2) has emerged as a pivotal cellular antagonist of p53 by destructing the suppressive function of p53 against tumorigenesis. The MDM2 309 T > G polymorphism has been studied for its association with oral squamous cell carcinoma (OSCC) susceptibility, but the evidence was confusing and inconclusive. Here, we performed a meta-analysis to estimate the effects of the 309 T > G polymorphism on the development of OSCC. The relevant studies were searched on both PubMed and Embase. We estimated the risk of OSCC using odds ratio (OR) and 95 % confidence interval (CI). In addition, between-study heterogeneity was measured by the χ (2)-based statistic test; sensitivity analysis, and the funnel plots and Egger's test were also performed in this meta-analysis. Based on five case-control studies with a total of 1,369 OSCC cases and 2,167 control subjects, the meta-analysis result showed neither increased nor decreased risk of OSCC associated with any genetic model of the 309 T > G polymorphism. Similar results were observed in the subgroup of Asians. No significant heterogeneity and publication bias were detected in the meta-analysis. The evidence provided in our study indicated that the 309 T > G polymorphism might have no significant contribution to susceptibility toward OSCC.

The Role of p53 and MDM2 in Head and Neck Cancer

Head and neck cancer is a complex disorder that includes mostly squamous cell carcinomas that can develop in the throat, larynx, nose, sinuses, and mouth. Etiopathogenesis is due to tobacco and alcohol consumption and to infection by human papillomavirus (HPV) type 16/18. Tumors often develop within preneoplastic fields of genetically altered cells. Most head and neck cancers result from multistep accumulation of genetic alterationsm resulting in clonal outgrowth of transformed cells. These DNA changes are caused by a variety of mechanisms like endogenous mutations and exogenous mutations. Dysregulated molecular pathway includes alterations of critical inhibitor of cyclin CDK complexes, inactivating mutations of p53 gene, and activation of oncogenes and growth factors. This paper attempts to review the role of p53 and MDM2 genetic aberrations and pathways in head and neck cancer.

MDM2 SNP309 contributes to tumor susceptibility: a meta-analysis

The potentially functional polymorphism, SNP309, in the promoter region of MDM2 gene has been implicated in cancer risk, but individual published studies showed inconclusive results. To obtain a more precise estimate of the association between MDM2 SNP309 and risk of cancer, we performed a meta-analysis of 70 individual studies in 59 publications that included 26,160 cases with different types of tumors and 33,046 controls. Summary odds ratios (OR) and corresponding 95% confidence intervals (CIs) were estimated using fixed- and random-effects models when appropriate. Overall, the variant genotypes were associated with a significantly increased cancer risk for all cancer types in different genetic models (GG vs. TT: OR, 1.123; 95% CI, 1.056-1.193; GG/GT vs. TT: OR, 1.028; 95% CI, 1.006-1.050). In the stratified analyses, the increased risk remained for the studies of most types of cancers, Asian populations, and hospital- /population-based studies in different genetic models, whereas significantly decreased risk was found in prostate cancer (GG vs. TT: OR, 0.606; 95% CI, 0.407-0.903; GG/GT vs. TT: OR, 0.748; 95% CI, 0.579-0.968). In conclusion, the data of meta-analysis suggests that MDM2 SNP309 is a potential biomarker for cancer risk.

Effects of MDM2 promoter polymorphisms and p53 codon 72 polymorphism on risk and age at onset of squamous cell carcinoma of the head and neck

Both p53 tumor suppressor and murine double minute 2 (MDM2) oncoprotein are crucial in carcinogenesis. We hypothesized that MDM2 promoter single nucleotide polymorphisms (SNPs) SNP309 T > G, A2164G, and p53 codon 72 are associated with risk and age at onset of squamous cell carcinoma of head and neck (SCCHN). We genotyped these SNPs in a study of 1,083 Caucasian SCCHN cases and 1,090 cancer-free controls. Although none of these SNPs individually had a significant effect on risk of SCCHN, nor did their combined putative risk genotypes (i.e., MDM2 SNP309 GT + GG, 2164 AA, and p53 codon 72 CC), we found that individuals with two to three risk genotypes had significantly increased risk of non-oropharyngeal cancer (OR = 1.42; 95% CI = 1.07-1.88). This increased risk was more pronounced among young subjects, men, smokers, and drinkers. In addition, female patients carrying the MDM2 SNP309 GT and GG genotypes showed a 3-yr (56.7 yr) and 9-yr (51.2 yr) earlier age at onset of non-oropharyngeal cancer (P(trend) = 0.007), respectively, compared with those carrying the TT genotype (60.1 yr). The youngest age (42.5 yr) at onset of non-oropharyngeal cancer was observed in female patients with the combined MDM2 SNP309 GG and p53 codon 72 CC genotypes. The findings suggest that MDM2 SNP309, A2164G, and p53 codon 72 SNPs may collectively contribute to non-oropharyngeal cancer risk and that MDM2 SNP309 individually or in combination with p53 codon 72 may accelerate the development of non-oropharyngeal cancer in women. Further studies with large sample sizes are warranted to validate these results.

Human papillomavirus seropositivity synergizes with MDM2 variants to increase the risk of oral squamous cell carcinoma

The increasing incidence of oral squamous cell carcinoma (OSCC) in young adults has been associated with sexually transmitted infections of human papillomavirus (HPV), particularly HPV16. Given the roles of p53 in tumor suppression and of HPV E6 and MDM2 oncoproteins in p53 degradation, we evaluated HPV16 L1 seropositivity and MDM2 promoter variants to examine their possible associations with OSCC risk in a case-control study of 325 patients and 335 cancer-free matched controls. Compared with individuals having MDM2-rs2279744 GT or GG genotypes and HPV16 L1 seronegativity, the TT genotype and HPV16 L1 seronegativity were found to be associated with an odds ratio (OR) of 1.25 [95% confidence interval (CI), 1.06-2.19] for OSCC risk, and GT/GG and HPV16 L1 seropositivity were associated with an OR of 2.81 (95% CI, 1.67-4.74). For those with both the TT genotype and HPV16 L1 seropositivity, the associated OR was 5.57 (95% CI, 2.93-10.6). Similar results were observed for the MDM2-rs937283 polymorphism. Moreover, there was a borderline significant or significant interaction between the individual or combined MDM2 genotypes of the two polymorphisms and HPV16 L1 seropositivity (P(int) = 0.060 for MDM2-rs2279744, P(int) = 0.009 for MDM2-rs937283, and P(int) = 0.005 for the combined MDM2 genotypes) on risk of OSCC. Notably, that effect modification was particularly pronounced in never smokers and never drinkers, and for oropharyngeal as opposed to oral cavity cancer. Taken together, our results indicate that the risk of OSCC associated with HPV16 L1 seropositivity is modified by MDM2 promoter polymorphisms.

Germline mutations and polymorphisms in the origins of cancers in women

Several female malignancies including breast, ovarian, and endometrial cancers can be characterized based on known somatic and germline mutations. Initiation and propagation of tumors reflect underlying genomic alterations such as mutations, polymorphisms, and copy number variations found in genes of multiple cellular pathways. The contributions of any single genetic variation or mutation in a population depend on its frequency and penetrance as well as tissue-specific functionality. Genome wide association studies, fluorescence in situ hybridization, comparative genomic hybridization, and candidate gene studies have enumerated genetic contributors to cancers in women. These include p53, BRCA1, BRCA2, STK11, PTEN, CHEK2, ATM, BRIP1, PALB2, FGFR2, TGFB1, MDM2, MDM4 as well as several other chromosomal loci. Based on the heterogeneity within a specific tumor type, a combination of genomic alterations defines the cancer subtype, biologic behavior, and in some cases, response to therapeutics. Consideration of tumor heterogeneity is therefore important in the critical analysis of gene associations in cancer.