Genetic polymorphisms of MDM2, cumulative cigarette smoking and nonsmall cell lung cancer risk

Genetic Variations in MDM2 Gene Contribute to Renal Cell Carcinoma Susceptibility: A Genotype-Phenotype Correlation Study

BACKGROUND

This study aimed to investigate the polymorphic genotypes of MDM2 rs937282, rs937283, rs2279744, and rs769412, as well as the combined effects of MDM2 genotypes and environmental factors on RCC susceptibility.

METHODS

A total of 135 RCC patients and 590 controls were recruited for MDM2 genotyping using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Quantitative PCR was performed to assess MDM2 mRNA levels among 30 healthy individuals and 22 RCC patients.

RESULTS

MDM2 rs2279744, but not other polymorphisms, was significantly associated with an increased RCC risk (p = 0.0133). The MDM2 rs2279744 G allele was identified as a risk factor for RCC (odds ratio [OR] = 1.49, 95% confidence interval [CI] = 1.14-1.96, p = 0.0047). Among smokers (p = 0.0070), alcohol drinkers (p = 0.0233), individuals with hypertension (p = 0.0041), diabetes (p = 0.0225), and those with a family history of cancer (p = 0.0020), the MDM2 rs2279744 GT and GG genotypes exhibited increased RCC risks. However, this risk effect was not observed in non-smokers, non-drinkers, or individuals without hypertension, diabetes, or a family cancer history (all p > 0.05). Moreover, MDM2 mRNA levels were significantly higher in RCC patients compared to controls and varied among the rs2279744 genotypes, with GG genotype exhibiting the highest expression levels among both RCC patients and controls.

CONCLUSIONS

This study highlights the association between MDM2 rs2279744 genotypes and RCC risk, suggesting that genotype-associated MDM2 mRNA levels could contribute to early RCC detection. Further studies are warranted to elucidate the detailed mechanisms underlying the role of MDM2 in RCC development.

Association of Murine Double Minute 2 Genotypes and Lung Cancer Risk

AIM

The aim of this study was to evaluate the contribution of human mouse double minute 2 (MDM2) gene polymorphisms to the risk of Taiwan lung cancer.

MATERIALS AND METHODS

In this case-control study, the association of MDM2 rs2279744 genotypes with lung cancer risk was investigated among 358 lung cancer patients and 716 age-, gender- and smoking status-matched controls in Taiwan.

RESULTS

The percentages of MDM2 rs2279744 GT and GG genotypes were 50.0% and 27.4% in lung cancer group and 50.0% and 26.5% in control group, respectively [odds ratio (OR)=1.03 and 1.07, 95% confidence interval (CI)=0.75-1.43 and 0.75-1.53, respectively]. The analysis about allelic frequency showed that G allele at MDM2 rs2279744 conferred a non-significant increased cancer risk (OR=1.03, 95%CI=0.86-1.24).

CONCLUSION

Polymorphisms of MDM2 rs2279744 may play a role in lung carcinogenesis. However, the studied genotypes were not shown as predictors of lung cancer susceptibility.

The cell cycle regulatory gene polymorphisms TP53 (rs1042522) and MDM2 (rs2279744) in lung cancer: a meta-analysis

Lung cancer is one of the most common types of cancer in the world. Although the mechanism of lung cancer is still unknown, a large number of studies have found a link between gene polymorphisms and the risk of lung cancer. The tumor suppressor p53 plays a crucial role in maintaining genomic stability and tumor prevention. MDM2 is a critical regulator of the p53 protein. Despite the importance of p53 pathway in cancer, data on the contribution of SNPs of TP53 (rs1042522) and MDM2 (rs2279744) to the development of lung cancer are very contradictory. A metaanalysis that collects quantitative data from individual studies and combines their results has the advantage of improving accuracy, providing reliable estimates, and resolving those issues in which studies on individual associations are not effective enough. The aim of this study was to determine whether the TP53 (rs1042522) and MDM2 (rs2279744) polymorphisms confer susceptibility to lung cancer. A meta-analysis was conducted on the associations between the TP53 (rs1042522) and MDM2 (rs2279744) polymorphisms and lung cancer. A total of 51 comparison studies including 25,366 patients and 25,239 controls were considered in this meta-analysis. The meta-analysis showed no association between lung cancer and MDM2 (rs2279744) under any model. A noteworthy association of TP53 (rs1042522) with susceptibility to lung cancer in overall pooled subjects was observed under three different models (allele contrast, homozygote contrast (additive) and dominant). Stratification by ethnicity indicated an association between the TP53 (rs1042522) and lung cancer in Asians and Caucasians. This meta-analysis demonstrates that the TP53 (rs1042522), but not MDM2 (rs2279744) polymorphism may confer susceptibility to lung cancer.

Interaction between common variants of MDM2 and PPP1R13L and CD3EAP and TP53 SNPs in relation to lung cancer risk among Chinese

Background

Lung cancer is a complex disease that diagnosed the most common cancer and led cause of cancer death. MDM2 (MDM2 proto-oncogene) encodes a nuclear-localized E3 ubiquitin ligase. The encoded protein can promote tumor formation by targeting tumor suppressor proteins, such as TP53, for proteasomal degradation. Epidemiology studies have investigated the association of MDM2 single nucleotide polymorphisms (SNP) and interaction between genetic and environmental factors with lung cancer.

Methods

This Chinese case-control study comprised 627 cases and 633 controls explored the role of MDM2 five htSNPs (rs1690924, rs1846402, rs2291857, rs3730581 and rs3730635, haplotype-tagging SNP) tagging 95% of the common haplotypes across the gene and the interactions of MDM2, PPP1R13L, CD3EAP and TP53 in the same pathological pathway on lung cancer risk, together with smoking-duration.

Results

None of the htSNPs in MDM2 were associated with lung cancer risk in co-dominant, dominant, recessive, and log-additive models (adjusted for smoking-duration). Haplotype analysis showed that global haplotype association was statistically significant (P=0.0036, adjusted for smoking-duration) and haplotype5 (rs1690924^A-rs1846402^G-rs2291857^C-rs3730581^G-rs3730635^A) was associated with reduced risk of lung cancer [OR (95%) =0.52 (0.33–0.82), P=0.0053, adjusted for smoking-duration]. MDR interaction analysis showed that two the best significant models and strong synergy between MDM2 and TP53.

Conclusions

MDM2 five-htSNPs haplotype exhibited association with lung cancer susceptibility, interaction of MDM2 and TP53 htSNPs and smoking-duration contributed to lung cancer risk and strong synergy between MDM2 and TP53 htSNPs influenced lung cancer predisposition. Our results suggest that MDM2, TP53 and smoking-duration interact in relation to lung carcinogenesis.

A cohort study on the association of MDM2 SNP309 with lung cancer risk in Bangladeshi population

BACKGROUND/AIMS

Bangladesh is a densely populated country with an increased incidence of lung cancer, mostly due to smoking. Therefore, elucidating the association of mouse double minute 2 homolog (MDM2) single nucleotide polymorphism (SNP) 309 (rs2279744) with lung cancer risk from smoking in Bangladeshi population has become necessary.

METHODS

DNA was extracted from blood samples of 126 lung cancer patient and 133 healthy controls. The MDM2 SNP309 was genotyped by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP), using the restriction enzymes MspA1I. Logistic regression was then carried out to calculate odds ratios (ORs) and 95% confidence intervals (CIs) to estimate the risk of lung cancer. A meta-analysis of SNP309 was also carried out on 12,758 control subjects and 11,638 patient subjects.

RESULTS

In multivariate logistic regression, significantly increased risk of lung cancer was observed for MDM2 SNP309 in the dominant model (TG + GG vs. TT: OR, 2.13; 95% CI, 1.29 to 3.53). Stratification analysis revealed that age, sex, obesity, and smoking also increases the risk of lung cancer when carrying the MDM2 SNP309. Our meta-analysis revealed that MDM2 SNP309 was considerably associated with lung cancer in Asian populations (TG + GG vs. TT: OR, 1.32; 95% CI , 1.12 to 1.56; p = 0.019 for heterogeneity).

CONCLUSION

The MDM2 SNP309 was associated with high risk of lung cancer in Bangladeshi and Asian population, particularly with increased age, smoking, and body mass index.

DNA replication in progenitor cells and epithelial regeneration after lung injury requires the oncoprotein MDM2

Depletion of epithelial cells after lung injury prompts proliferation and epithelial mesenchymal transition (EMT) of progenitor cells, and this repopulates the lost epithelial layer. To investigate the cell proliferative function of human oncoprotein MDM2, we generated mouse models targeting human MDM2 expression in either lung Club or alveolar cells after doxycycline treatment. We report that MDM2 expression in lung Club or alveolar cells activates DNA replication specifically in lung progenitor cells only after chemical- or radiation-induced lung injury, irrespective of their p53 status. Activation of DNA replication by MDM2 triggered by injury leads to proliferation of lung progenitor cells and restoration of the lost epithelial layers. Mouse lung with no Mdm2 allele loses its ability to replicate DNA, whereas loss of 1 Mdm2 allele compromises this function, demonstrating the requirement of endogenous MDM2. We show that the p53-independent ability of MDM2 to activate Akt signaling is essential for initiating DNA replication in lung progenitor cells. Furthermore, MDM2 activates the Notch signaling pathway and expression of EMT markers, indicative of epithelial regeneration. This is the first report to our knowledge demonstrating a direct p53-independent participation of MDM2 in progenitor cell proliferation and epithelial repair after lung injury, distinct from a p53-degrading antiapoptotic effect preventing injury.

Association of MDM2 gene SNP 309 polymorphism and human non-small cell lung cancer susceptibility: A meta-analysis

This updated meta-analysis was performed to evaluate the relationship of a common polymorphism (T309 G, rs2279744 T > G) in the murine double minute 2 (MDM2) gene with susceptibility and prognosis of non-small cell lung cancer (NSCLC). The Cochrane Library, PubMed, Embase, CNKI, WanFang and CNKI databases were searched comprehensively for related study. Odds ratios (ORs) with their 95% confidence intervals (95% CI) were calculated. 11 articles with a total 6470 NSCLC patients and 8027 controls met the inclusion criteria were included. MDM2 T309 G polymorphism might be strongly correlated with an increased risk of NSCLC. The overall pooled analysis indicated that MDM2 309 T/G polymorphism was significantly associated with NSCLC susceptibility in the whole population under allelic (OR: 1.22, 95% CI: 1.08-1.38), recessive (OR: 1.37, 95% CI: 1.15-1.63), dominant (OR: 1.23, 95% CI: 1.04-1.45), and homozygous genetic models (OR: 1.49, 95% CI: 1.20-1.86). The subgroup analysis showed a significant association of MDM2 309 T/G polymorphism with NSCLC susceptibility in Asian population, but not in Caucasian population. Besides, a significant association was found again in the female population. The meta-analysis provides convincing evidence that the MDM2 T309 G polymorphism may contribute to NSCLC susceptibility, especially for Asians and women.

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.

Cross-Cancer Genome-Wide Analysis of Lung, Ovary, Breast, Prostate, and Colorectal Cancer Reveals Novel Pleiotropic Associations

Identifying genetic variants with pleiotropic associations can uncover common pathways influencing multiple cancers. We took a two-stage approach to conduct genome-wide association studies for lung, ovary, breast, prostate, and colorectal cancer from the GAME-ON/GECCO Network (61,851 cases, 61,820 controls) to identify pleiotropic loci. Findings were replicated in independent association studies (55,789 cases, 330,490 controls). We identified a novel pleiotropic association at 1q22 involving breast and lung squamous cell carcinoma, with eQTL analysis showing an association with ADAM15/THBS3 gene expression in lung. We also identified a known breast cancer locus CASP8/ALS2CR12 associated with prostate cancer, a known cancer locus at CDKN2B-AS1 with different variants associated with lung adenocarcinoma and prostate cancer, and confirmed the associations of a breast BRCA2 locus with lung and serous ovarian cancer. This is the largest study to date examining pleiotropy across multiple cancer-associated loci, identifying common mechanisms of cancer development and progression. Cancer Res; 76(17); 5103-14. ©2016 AACR.

Homozygous G/G variant of SNP309 in the human MDM2 gene is associated with earlier tumor onset in Caucasian female renal cell carcinoma patients

Human mouse double minute 2 (Mdm2) plays an essential role in the regulation of the tumor suppressor p53. The G/G variant of SNP309 was shown to increase Mdm2 mRNA/protein expression and to be associated with an increased risk and earlier onset of different cancers in Asian populations. However, the frequency and impact of these G/G variants have not been studied in Caucasian renal cell carcinoma (RCC) patients. Therefore, we analyzed an unselected German cohort of 197 consecutive RCC patients and detected the G/G variant in 18 (9.1%) patients, the G/T variant in 116 (58.9%) patients and the T/T variant in 63 (32.0%) patients. Studying the association between age at tumor onset and SNP309 genotypes, no correlation was detected in the entire RCC cohort or among the male RCC patients. However, the female G/G patients (median age 59.5 years) were diagnosed 13.5 years earlier than the T/T females (median age 73 years). When separating all females into two groups at their median age (68 years), 7 and 1 patients with the G/G variant and 9 and 13 patients with the T/T variant were noted in these age groups (P=0.024). To study the age dependency of tumor onset further, a second, age-selected cohort of 205 RCC patients was investigated, which comprised especially young and old patients. Interestingly, the G/G type occurred more often at lower tumor stages and tumor grades compared with higher stages (P=0.039 and 0.004, respectively). In females, the percentage of the G/G variant was only slightly higher in the younger age group, whereas in males, the percentage of the G/G variant was remarkably higher in the younger age group (19.4% vs 8.0%). In summary, female Caucasian RCC patients with the MDM2 SNP309 G/G genotype showed significantly earlier tumor onset than patients with the wild-type T/T genotype.

Single-nucleotide polymorphism (c.309T>G) in the MDM2 gene and lung cancer risk

Murine double minute 2 (MDM2) is a negative regulator of p53. A single-nucleotide polymorphism (SNP) (rs2279744: c.309T>G) in the promoter region of the MDM2 gene has been shown to result in higher levels of MDM2 RNA and protein. Regarding the contribution of c.309T>G in the MDM2 gene to the lung cancer risk, previous studies are conflicting. In order to evaluate the association between c.309T>G and the lung cancer risk, a case-control study was performed. The MDM2 genotypes were determined in 762 lung cancer patients and in 700 cancer-free control subjects using the Smart Amplification Process. Statistical adjustment was performed for gender, age and pack-years of smoking. The distributions of c.309T>G (T/T, T/G, G/G) were 20.1, 49.7, 30.2% in the case group and 21.7, 47.9, 30.4% in the healthy-control group. There were no overall associations between the MDM2 genotypes and the risk of lung cancer [T/G genotype: Adjusted odds ratio (AOR), 1.30; 95% confidence interval (CI), 0.88-1.93; and G/G genotype: AOR, 1.18; 95% CI, 0.78-1.80]. The subgroup analysis of gender, histology, smoking status and epidermal growth factor receptor mutation status also indicated that there was no association with lung cancer. Additionally, the genotypes did not have an effect on the age at the time of diagnosis of lung cancer (P=0.25). In conclusion, the G allele frequency in the lung cancer cases was 0.551, which was similar to other studies. The results of the present study suggest that the c.309T>G is not significantly associated with lung cancer.

The Mdm network and its regulation of p53 activities: a rheostat of cancer risk

The potent transcriptional activity of p53 (Trp53, TP53) must be kept in check for normal cell growth and survival. Tumors, which drastically deviate from these parameters, have evolved multiple mechanisms to inactivate TP53, the most prevalent of which is the emergence of TP53 missense mutations, some of which have gain-of-function activities. Another important mechanism by which tumors bypass TP53 functions is via increased levels of two TP53 inhibitors, MDM2, and MDM4. Studies in humans and in mice reveal the complexity of TP53 regulation and the exquisite sensitivity of this pathway to small changes in regulation. Here, we summarize the factors that impinge on TP53 activity and thus cell death/arrest or tumor development.

Apoptosis-Related Single Nucleotide Polymorphisms and the Risk of Non-Small Cell Lung Cancer in Women

BACKGROUND

Germline apoptosis-related single nucleotide polymorphisms (SNPs) have been shown to contribute to the risk of developing non-small cell lung cancer (NSCLC). However, very few studies have looked specifically at apoptosis-related SNPs in a racially-stratified analysis of white and African-American women.

METHODS

We examined the risk of developing NSCLC associated with 98 germline SNPs in 32 apoptosis-related genes among women in a population-based case-control study from the Detroit metropolitan area. We examined 453 cases of NSCLC and 478 control subjects. We used an unconditional logistic regression with a dominant model, stratified by race, and adjusted for age, pack-years smoked, ever/never smoking status, family history of lung cancer, history of COPD, BMI and education.

RESULTS

Our logistic regression identified 3 significant apoptosis-related SNPs in whites (APAF-1, rs1007573; CD40 rs3765459, and CD40 rs1535045), and 7 significant SNPs (ATM, rs1801516; BAK1, rs513349; TNF, rs1800629; TP63, rs6790167; TP63, rs7613791, TP63, rs35592567 and TP63, rs3856775) in African-Americans. In a downstream analysis, these SNPs were further prioritized utilizing the False Positive Report Percentage (FPRP) methodology and backwards elimination. In whites, APAF-1 (rs1007573), CD40 (rs3765459) and CD40 (rs1535045) were all found to be significant by FPRP. In African-Americans, TP63 SNPs rs6790167 and rs7613791 were found to have a significant FPRP. In parallel, a backward elimination procedure was used on the 3 significant SNPs in whites and 7 significant SNPs in African-Americans. This procedure identified APAF-1 rs1007573 (OR=1.86, 95% CI: 1.17-2.95) and CD40 rs1535045 (OR=0.58, 95% CI: 0.40-0.84) as significant independent predictors of risk among whites, and ATM rs1801516 (OR=24.15, 95% CI: 3.50-166.55), TNF rs1800629 (OR= 0.42, 95% CI: 0.18-0.99) and TP63 rs6790167 (OR: 2.85, 95% CI: 1.33-6.09) as significant, independent predictors in African-Americans.

CONCLUSION

In whites, only SNPs APAF-1 rs1007573 and CD40 rs1535045 were significant by both FPRP and backwards elimination, while in African-Americans, only TP63 rs6790167 was significant by both methodologies. Thus, we have identified three promising variants associated with increased risk of NSCLC that warrant additional investigation in future studies.

Mdm2 SNP309 G-variant is associated with invasive growth of human urinary bladder cancer

OBJECTIVE

Human mouse double minute 2 (Mdm2) is essential in degrading p53 by acting as an ubiquitin ligase and therefore plays a vital role in cell cycle and survival. The G-variant of the Mdm2 SNP309, which is located within the promoter of the Mdm2 gene, increases expression of Mdm2 and thereby inhibits the p53 pathway. Several studies have investigated the influence of this SNP on disease risk and onset of various malignancies. The impact of Mdm2 SNP309 on bladder cancer is still to be established due to inconsistent data.

METHODS

In a case-control study we determined the distribution of Mdm2 SNP309 genotypes in 111 patients with an early-onset bladder cancer (diagnosis <45 years of age), in 113 consecutive bladder cancer patients and in a control group consisting of 140 patients without any malignancy.

RESULTS

There was no significant association between the allelic distribution of the Mdm2 SNP309 and tumor risk, early onset, gender or grade of the tumor. According to tumor stage we found a significant difference in the distribution of the Mdm2 SNP309 between patients with noninvasive and invasive (≥pT1) tumor growth (p = 0.016). In patients with invasive tumors a significant increase of the G allele was found (T/T vs. T/G + G/G; p = 0.023; OR 2.203, 95% CI 1.111-4.369).

CONCLUSION

These data indicate that the G-variant of the Mdm2 SNP309 might influence the development of a more aggressive tumor phenotype in patients with bladder cancer without affecting the overall tumor risk.

Rapid detection of SNP (c.309T>G) in the MDM2 gene by the Duplex SmartAmp method

Background

Genetic polymorphisms in the human MDM2 gene are suggested to be a tumor susceptibility marker and a prognostic factor for cancer. It has been reported that a single nucleotide polymorphism (SNP) c.309T>G in the MDM2 gene attenuates the tumor suppressor activity of p53 and accelerates tumor formation in humans.

Methodology

In this study, to detect the SNP c.309T>G in the MDM2 gene, we have developed a new SNP detection method, named “Duplex SmartAmp,” which enabled us to simultaneously detect both 309T and 309G alleles in one tube. To develop this new method, we introduced new primers i.e., nBP and oBPs, as well as two different fluorescent dyes that separately detect those genetic polymorphisms.

Results and Conclusions

By the Duplex SmartAmp method, the genetic polymorphisms of the MDM2 gene were detected directly from a small amount of genomic DNA or blood samples. We used 96 genomic DNA and 24 blood samples to validate the Duplex SmartAmp by comparison with results of the conventional PCR-RFLP method; consequently, the Duplex SmartAmp results agreed totally with those of the PCR-RFLP method. Thus, the new SNP detection method is considered useful for detecting the SNP c.309T>G in the MDM2 gene so as to judge cancer susceptibility against some cellular stress in the clinical setting, and also to handle a large number of samples and enable rapid clinical diagnosis.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

MDM2 SNP309 polymorphism is associated with lung cancer risk in women: A meta-analysis using METAGEN

Lung cancer is the most common diagnosed malignancy and the leading cause of cancer-related mortality worldwide. Murine double minute 2 (MDM2) SNP309 polymorphisms have been reported to influence the risk of lung cancer. However, the published studies together with four subsequent meta-analyses have yielded contradictory results. To examine this inconsistency, we conducted a meta-analysis of 6,696 lung cancer cases and 7,972 controls from eight published case-control studies using METAGEN. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated with STATA software and used to assess the strength of the association. In the overall analysis, a significant association between MDM2 SNP309 polymorphism and lung cancer risk was observed (OR, 1.143; 95% CI, 1.047-1.247). Moreover, stratified by ethnicity, a significant association was found in Asians (OR, 1.260; 95% CI, 1.111-1.429), but not in Europeans. Subgroup analysis of gender, histology and smoking status suggested that the MDM2 SNP309 genotype was associated with increased lung cancer risk in women (OR, 1.282; 95% CI, 1.062-1.548) and never smokers (OR, 1.328; 95% CI, 1.119-1.575). No statistically significant association was observed in males and ever smoking population, and no association was found in subgroup analysis based on histology. In conclusion, the association between MDM2 SNP309 and lung cancer was statistically significant, particularly in Asians, women and never smoking population.

Association of MDM2 SNP309 variation with lung cancer risk: evidence from 7196 cases and 8456 controls

Background

Evidence suggests that MDM2 T309G polymorphism may be a risk factor for several cancers. Increasing investigations have been conducted on the association of MDM2 T309G polymorphisms with lung cancer risk and have yielded conflicting results. Previous meta-analyses on this issue have reported inconclusive data. The aim of the present study was to derive a more precise estimation of the relationship.

Methods and Findings

Updated meta-analyses examining the association between MDM2 T309G polymorphism and lung cancer risk were performed. Separate analyses on ethnicity, smoking status, histological types and gender as well as source of controls were also implemented. Eligible studies were identified for the period up to Feb 2012. Lastly, ten publications including eleven case-control studies were selected for analysis. The overall data failed to indicate a significant association between MDM2 T309G polymorphism and lung cancer risk (GG vs TT OR = 1.14; 95%CI = 0.95−1.37; dominant model: OR = 1.05; 95%CI = 0.92−1.19; recessive model: OR = 1.12; 95%CI = 0.99−1.27). In a subgroup analysis by smoking status, increased lung cancer risk was shown among never-smokers (GG vs TT: OR = 1.76; 95%CI = 1.36−2.29; dominant model: OR = 1.48; 95%CI = 1.22−1.81; recessive model: OR = 1.37; 95%CI = 1.11−1.69). In subgroup analysis by gender, elevated risk was presented among women under a recessive model (OR = 1.29; 95%CI = 1.04−1.59). In the subgroup analysis by ethnicity, histological types and source of controls, no marked associations were observed.

Conclusions

Compared to the previous meta-analyses, the results of this study confirmed that MDM2 T309G polymorphism might be a risk factor for lung cancer among never-smokers. However, the data failed to suggest a marked association between the G allele of MDM2 T309G and lung cancer risk among Asians. More interestingly, subgroup analysis by gender indicated that homozygous GG alleles might raise lung cancer risk among females.

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.

MDM2 SNP309, gene-gene interaction, and tumor susceptibility: an updated meta-analysis

Background

The tumor suppressor gene p53 is involved in multiple cellular pathways including apoptosis, transcriptional control, and cell cycle regulation. In the last decade it has been demonstrated that the single nucleotide polymorphism (SNP) at codon 72 of the p53 gene is associated with the risk for development of various neoplasms. MDM2 SNP309 is a single nucleotide T to G polymorphism located in the MDM2 gene promoter. From the time that this well-characterized functional polymorphism was identified, a variety of case-control studies have been published that investigate the possible association between MDM2 SNP309 and cancer risk. However, the results of the published studies, as well as the subsequent meta-analyses, remain contradictory.

Methods

To investigate whether currently published epidemiological studies can clarify the potential interaction between MDM2 SNP309 and the functional genetic variant in p53 codon72 (Arg72Pro) and p53 mutation status, we performed a meta-analysis of the risk estimate on 27,813 cases with various tumor types and 30,295 controls.

Results

The data we reviewed indicated that variant homozygote 309GG and heterozygote 309TG were associated with a significant increased risk of all tumor types (homozygote comparison: odds ratio (OR) = 1.25, 95% confidence interval (CI) = 1.13-1.37; heterozygote comparison: OR = 1.10, 95% CI = 1.03-1.17). We also found that the combination of GG and Pro/Pro, TG and Pro/Pro, GG and Arg/Arg significantly increased the risk of cancer (OR = 3.38, 95% CI = 1.77-6.47; OR = 1.88, 95% CI = 1.26-2.81; OR = 1.96, 95% CI = 1.01-3.78, respectively). In a stratified analysis by tumor location, we also found a significant increased risk in brain, liver, stomach and uterus cancer (OR = 1.47, 95% CI = 1.06-2.03; OR = 2.24, 95%CI = 1.57-3.18; OR = 1.54, 95%CI = 1.04-2.29; OR = 1.34, 95%CI = 1.07-1.29, respectively). However, no association was seen between MDM2 SNP309 and tumor susceptibility in the stratified analysis by p53 mutation status (GG vs TT: OR = 1.17, 95% CI = 0.75-1.82 and TG vs TT: OR = 1.09, 95% CI = 0.89-1.34 for positive p53 mutation status; GG vs TT: OR = 0.95, 95% CI = 0.72-1.25 and TG vs TT: OR = 1.06, 95% CI = 0.85-1.30 for negative p53 mutation status).

Conclusions

The analyses indicate that MDM2 SNP309 serves as a tumor susceptibility marker, and that there is an association between MDM2 SNP309 and p53 Arg72Pro regarding tumor susceptibility. Further studies that take into consideration environmental stresses and functional genetic variants in the p53-MDM2-related genes are warranted.

Effect of MDM2 SNP309 and p53 codon 72 polymorphisms on lung cancer risk and survival among non-smoking Chinese women in Singapore

Background

Single nucleotide polymorphism (SNP) 309 resulting in a T or G allele in the promoter of MDM2, the negative regulator of p53, has been suggested to affect cancer predisposition and age of onset, primarily in females. However, findings have been inconsistent in various cancers, and ethnicity appears to be a critical factor influencing the effects of the SNP on cancer risk. An increasing trend has been observed in the prevalence of lung cancers in non-smokers, especially females, though the underlying genetic basis is unclear.

Methods

We therefore examined the role of the SNPs in the p53 pathway (p53 codon 72 and MDM2 SNP309) on lung cancer risk and prognosis of a life-time non-smoking female Chinese population, in a hospital-based case-control study of 123 cases and 159 age-matched controls, by PCR analysis.

Results

Our findings reveal that the risk of lung cancer among individuals with the MDM2 SNP309 TT genotype was 2.1 (95% CI 1.01-4.36) relative to the GG genotype, contrary to initial expectations that the GG genotype with elevated MDM2 levels will increase cancer risk. Those who had this genotype in combination with the p53 Pro allele had a risk of 2.5 (95% CI 1.2-5.0). There was however no effect of either polymorphism on age at diagnosis of lung cancer or on overall survival.

Conclusions

The results thus demonstrate that the MDM2 SNP309 TT rather than the GG genotype is associated with increased risk of lung cancer in this population, suggesting that other mechanisms independent of increased MDM2 levels can influence cancer susceptibility.

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.

Cigarette smoking, MDM2 SNP309, gene-environment interactions, and lung cancer risk: a meta-analysis

MDM2 SNP309 polymorphism was found to contribute to genetic susceptibility to lung cancer in humans. However, association studies on these polymorphisms in lung cancer cases have shown conflicting results. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. Odds ratio (OR) with 95% confidence interval (CI) was applied to assess the strength of association between MDM2 SNP309 polymorphism and risk of lung cancer development. The logistic regression indicated that the genetic model was most likely to be recessive. Using a recessive model, the pooled OR estimating the genotype GG against the T-allele carriers (GT + TT) were calculated. Eight studies, including 6063 cases and 6678 controls, were involved in this meta-analysis. Overall meta-analysis indicated that MDM2 SNP309 GG genotypes have an approximate 16% increased risk for lung cancer development with a statistical significance (OR = 1.16; 95% CI: 1.01-1.34). In the subgroup analyses based on ethnicities, no significant elevated risk was associated with MDM2 SNP309 genotypes found in Asian and Europeans. No significant increased risk was associated with MDM2 SNP309 genotypes found in ever smokers. MDM2 SNP309 GG genotype had an approximate 36% enhanced risk of lung cancer development with statistical significance in never smokers (OR = 1.36; 95% CI: 1.10-1.68). Although some bias cannot be excluded, this meta-analysis supports the view that MDM2 SNP309 gene is a low-penetrance susceptible gene in the development of lung cancer, and the relationship of MDM2 SNP309 and lung cancer is stronger for never smokers.

A SNP in a let-7 microRNA complementary site in the KRAS 3' untranslated region increases non-small cell lung cancer risk

Lung cancer is the leading cause of cancer deaths worldwide, yet few genetic markers of lung cancer risk useful for screening exist. The let-7 family-of-microRNAs (miRNA) are global genetic regulators important in controlling lung cancer oncogene expression by binding to the 3' untranslated regions of their target mRNAs. The purpose of this study was to identify single nucleotide polymorphisms (SNP) that could modify let-7 binding and to assess the effect of such SNPs on target gene regulation and risk for non-small cell lung cancer (NSCLC). let-7 complementary sites (LCS) were sequenced in the KRAS 3' untranslated region from 74 NSCLC cases to identify mutations and SNPs that correlated with NSCLC. The allele frequency of a previously unidentified SNP at LCS6 was characterized in 2,433 people (representing 46 human populations). The frequency of the variant allele is 18.1% to 20.3% in NSCLC patients and 5.8% in world populations. The association between the SNP and the risk for NSCLC was defined in two independent case-control studies. A case-control study of lung cancer from New Mexico showed a 2.3-fold increased risk (confidence interval, 1.1-4.6; P = 0.02) for NSCLC cancer in patients who smoked <40 pack-years. This association was validated in a second independent case-control study. Functionally, the variant allele results in KRAS overexpression in vitro. The LCS6 variant allele in a KRAS miRANA complementary site is significantly associated with increased risk for NSCLC among moderate smokers and represents a new paradigm for let-7 miRNAs in lung cancer susceptibility.

Research progress in roles of murine double minute 2 gene in the gastrointestinal tumor

Murine double minute 2 (MDM2), an oncogene discovered in recent years, can enhance cell survival activity, prolong cell survival duration, promote cell proliferation and stimulate tumor growth. In recent years, it was shown that MDM2 participated in the genesis and development of various tumors. In addition, MDM2 is associated with the invasion, metastasis and poor prognosis of malignant tumors, especially gastrointestinal tumors such as esophageal cancer, gastric cancer, colon cancer, liver cancer, etc. So it is significant to study the relationship between MDM2 and gastrointestinal tumors for tumor prevention and treatment. In combination with domestic and overseas literatures, this article provides a brief review of the research progress in the roles of MDM2 in the genesis, development and metastasis of gastrointestinal tumors.

Genetic susceptibility to cancer: the role of polymorphisms in candidate genes

CONTEXT

Continuing advances in genotyping technologies and the inclusion of DNA collection in observational studies have resulted in an increasing number of genetic association studies.

OBJECTIVE

To evaluate the overall progress and contribution of candidate gene association studies to current understanding of the genetic susceptibility to cancer.

DATA SOURCES

We systematically examined the results of meta-analyses and pooled analyses for genetic polymorphisms and cancer risk published through March 2008.

STUDY SELECTION

We identified 161 meta-analyses and pooled analyses, encompassing 18 cancer sites and 99 genes. Analyses had to meet the following criteria: include at least 500 cases, have cancer risk as outcome, not be focused on HLA antigen genetic markers, and be published in English.

DATA EXTRACTION

Information on cancer site, gene name, variant, point estimate and 95% confidence interval (CI), allelic frequency, number of studies and cases, tests of study heterogeneity, and publication bias were extracted by 1 investigator and reviewed by other investigators.

RESULTS

These 161 analyses evaluated 344 gene-variant cancer associations and included on average 7.3 studies and 3551 cases (range, 508-19 729 cases) per investigated association. The summary odds ratio (OR) for 98 (28%) statistically significant associations (P value <.05) were further evaluated by estimating the false-positive report probability (FPRP) at a given prior probability and statistical power. At a prior probability level of 0.001 and statistical power to detect an OR of 1.5, 13 gene-variant cancer associations remained noteworthy (FPRP <0.2). Assuming a very low prior probability of 0.000001, similar to a probability assumed for a randomly selected single-nucleotide polymorphism in a genome-wide association study, and statistical power to detect an OR of 1.5, 4 associations were considered noteworthy as denoted by an FPRP value <0.2: GSTM1 null and bladder cancer (OR, 1.5; 95% CI, 1.3-1.6; P = 1.9 x 10(-14)), NAT2 slow acetylator and bladder cancer (OR, 1.46; 95% CI, 1.26-1.68; P = 2.5 x 10(-7)), MTHFR C677T and gastric cancer (OR, 1.52; 95% CI, 1.31-1.77; P = 4.9 x 10(-8)), and GSTM1 null and acute leukemia (OR, 1.20; 95% CI, 1.14-1.25; P = 8.6 x 10(-15)). When the OR used to determine statistical power was lowered to 1.2, 2 of the 4 noteworthy associations remained so: GSTM1 null with bladder cancer and acute leukemia.

CONCLUSION

In this review of candidate gene association studies, nearly one-third of gene-variant cancer associations were statistically significant, with variants in genes encoding for metabolizing enzymes among the most consistent and highly significant associations.

Early onset lung cancer, cigarette smoking and the SNP309 of the murine double minute-2 (MDM2) gene

The polymorphism SNP309 (rs2279744) in the promoter region of the MDM2 gene has been shown to alter protein expression and may play a role in the susceptibility to lung cancer. The MDM2 protein is a key inhibitor of p53 and several mechanisms of MDM2/p53 interactions are presently known: modulating DNA-repair, cell-cycle control, cell growth and apoptosis.

We used 635 Caucasian patients diagnosed with lung cancer before 51 years of age and 1300 healthy gender and age frequency matched population Caucasian controls to investigate the association between the MDM2 SNP309 and the risk of developing early onset lung cancer. Conditional logistic models were applied to assess the genotype-phenotype association, adjusted for smoking.

Compared to the GG genotype, the adjusted ORs for the TG and TT genotype were 0.9 (95% CI: 0.7–1.5) and 1.0 (95% CI: 0.7–1.5), respectively. Also no association was found for histological subtypes of lung cancer. The strength of this study is that within young cases the genetic component to develop lung cancer may be greater. Our results indicate that the MDM2 SNP309 is not significantly associated with lung carcinogenesis but point towards gender-specific differences.