MDM2 SNP309 T>G alone or in combination with the TP53 R72P polymorphism does not appear to influence disease expression and age of diagnosis of colorectal cancer in HNPCC patients

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.

Genetic polymorphisms of TP53 (rs1042522) and MDM2 (rs2279744) and colorectal cancer risk: An updated meta-analysis based on 59 case-control studies

OBJECTIVE

Several earlier reports implicated TP53 (rs1042522) and MDM2 (rs2279744) variants in outcome of colorectal cancer (CRC), but with inconclusive findings. This current meta-analysis designed to uncover the role of these variants in CRC risk.

METHODOLOGY

Two independent investigators extracted 59 eligible case-control studies from different electronic databases involving Scopus, Web of Science and PubMed prior to June 2019. Pooled odds ratios (ORs) and "95% confidence intervals (CIs)" were computed for different hereditary models. Stratification and heterogeneity analyses, and "Begg's funnel plots" were conducted. In silico data analyses of the functional and structural properties of the study variants were applied.

RESULTS

In general, 47 and 16 case-control reports for TP53 (11,589 patients and 13,622 controls) and MDM2 (6841 CRC patients and 8792 healthy controls), respectively were enrolled in this meta-analysis. A significant association of TP53 (rs1042522) variant with increased CRC risk in overall pooled subjects under recessive model [(CC vs. GC + GG, OR = 1.134, 95% CI = 1.006-1.278, P = 0.039)] was observed. Moreover, an evidence of MDM2 (rs2279744) association with increased CRC risk in overall pooled subjects under dominant and heterozygote models [(TG + GG vs. TT, OR = 1.120, 95% CI = 1.003-1.250, P = 0.044) and (TG vs. TT, OR = 1.189, 95% CI = 1.076-1.313, P = 0.001), respectively] was reported. Additionally, TP53 (rs1042522) and MDM2 (rs2279744) showed an association with CRC risk among Asians and Africans under a recessive model, and among Asians under different genetic models, respectively, by stratification analysis.

CONCLUSION

TP53 (rs1042522) and MDM2 (rs2279744) variants might represent candidate risk factors for CRC susceptibility.

Long telomeres cooperate with p53, MDM2, and p21 polymorphisms to raise pediatric solid tumor risk

BACKGROUND

While leukocyte telomere length has been linked with altered risk in adult cancer, limited information is available on its association with risk in pediatric solid tumors. We investigated the association of telomeric alterations with risk of pediatric solid tumors. We also investigated whether altered telomeres cooperated with the TP53 rs1042522, MDM2 rs2279744 and CDKN1A (p21^cip1 ) rs1059234 single-nucleotide polymorphisms to modify cancer risk.

METHODS

A total of 101 tumor patients and 202 controls were recruited for this age- and gender-matched case-control study. Relative telomere length (RTL) was determined in peripheral blood leukocytes using quantitative real-time polymerase chain reaction (PCR), and the polymorphisms were genotyped using PCR-restriction fragment length polymorphism.

RESULTS

Using median RTL in the healthy controls as a cut-off, children with longer telomeres were at an increased risk of developing a solid tumor (OR, 2.70; P < 0.01). When participants were categorized according to control RTL quartiles, a significant dose-response relationship was observed (χ²  = 10.95; P < 0.001). The risk for tumors increased nearly threefold (P = 0.001) for the triple interaction RTL × TP53 rs1042522 × p21^cip1 rs1059234 compared with the maximum effect of any single factor, although the interaction effect was less than additive. The MDM2 rs2279744 GG genotype reduced pediatric solid tumor risk significantly (OR, 0.51).

CONCLUSION

Combined analysis of telomeres and genetic polymorphisms in the TP53 pathway can provide important clues to understanding pediatric solid tumor etiology.

Contribution of Murine Double Minute 2 Genotypes to Colorectal Cancer Risk in Taiwan

BACKGROUND/AIM

The genomic role of human mouse double minute 2 (MDM2) in colorectal cancer (CRC) is unclear, therefore, our study aimed to evaluate the contribution of MDM2 genotype to the risk of CRC in Taiwan.

MATERIALS AND METHODS

In this case-control study, MDM2 SNP309 T to G (rs2279744) genotypes were determined and their association with CRC risk were investigated among 362 patients with CRC and 362 age- and gender-matched healthy controls in central Taiwan. In addition, the interaction of MDM2 SNP309 genotypes with personal behaviors and clinicopathological features were also examined.

RESULTS

The percentage of variant GG for the MDM2 SNP309 genotype was 30.9% in the CRC group and 24.0% in the control group, respectively (odds ratio (OR)=1.78, 95% confidence interval (CI)=1.25-2.86, p=0.0057). The allelic frequency distribution analysis showed that the variant G allele of MDM2 SNP309 conferred a significantly increased susceptibility to CRC compared with the wild-type T allele (OR=1.32, 95% CI=1.14-1.69, p=0.0062). As for the gene-lifestyle interaction, there was an obvious joint effect of MDM2 SNP309 GG genotype on the risk of CRC among ever-smokers and non-alcohol drinkers, but not non-smoker or alcohol drinker subgroups. No statistically significant correlation was observed between MDM2 SNP309 genotypic distributions and age, gender, tumor size, location or metastasis status.

CONCLUSION

The genotypes of MDM2 SNP309 may allow forr early detection of and predictor for CRC risk, especially among smokers and non-alcohol drinkers, but not for prognosis. The combined effects of MDM2 SNP309 and other genes (such as matrix metalloproteinases) on CRC susceptibility and prognosis, should also be taken into consideration in the era of precision medicine.

The association between the TP53 Arg72Pro polymorphism and colorectal cancer: An updated meta-analysis based on 32 studies

Several previous studies evaluated the association between the Arg72Pro (rs1042522) polymorphism in the TP53 tumor suppressor gene and colorectal cancer (CRC). However, the results are conflicting. This meta-analysis aimed to shed new light on the precise association between TP53 variants and CRC. We analyzed 32 published case-control studies involving 8,586 cases and 10,275 controls using crude odd ratios (ORs) with 95% confidence intervals (CIs). The meta-analysis was performed using a fixed-effect or random-effects model, as appropriate. We found that the TP53 Arg72Pro polymorphism was not significantly associated with CRC risk in the overall population. However, subgroup analysis based on ethnicity revealed an increased risk of CRC among Asians (CC vs. GC+GG: OR=1.22, 95% CI: 1.02-1.45), and similar results were found for rectal cancer (CC vs. GC+GG: OR=1.34, 95% CI: 1.120-1.62). These results suggest that the TP53 Arg72Pro polymorphism CC genotype may contribute to an increased risk of CRC, especially for rectal cancer and among Asians.

The association of low penetrance genetic risk modifiers with colorectal cancer in lynch syndrome patients: a systematic review and meta-analysis

Lynch syndrome (LS) is a highly penetrant inherited cancer predisposition syndrome accounting for approximately 1000 cases of colorectal cancer (CRC) in the UK annually. LS is characterised by autosomal dominant inheritance and germline mutations in DNA mismatch repair genes. The penetrance is highly variable and the reasons for this have not been fully elucidated. This study investigates whether low penetrance genetic risk factors may result in phenotype modification in LS patients. To conduct a systematic literature review and meta-analysis to assess the association between low penetrance genetic risk modifiers and CRC in LS patients. A systematic review was conducted of the PubMed and HuGENet databases. Eligibility of studies was determined by pre-defined criteria. Included studies were analysed via the per-allele model and assessed by pooled odds ratios and establishing 95% confidence intervals. Study heterogeneity was assessed via Cochrane's Q statistic and I2 values. Publication bias was evaluated with funnel plots. Subgroup analysis was conducted on gender. Statistical software used was the Metafor package for the R programme version 3.1.3. Sixty-four polymorphisms were identified and sufficient data was available for analysis of ten polymorphisms, with between 279 and 1768 CRC cases per polymorphism. None demonstrated association with CRC risk in LS patients. However in sub-group analysis the polymorphism rs16892766 (8q23.3) was significant in males (OR 1.53, 95% CI 1.12-2.10). The variable phenotype presentation of the disease still remains largely unexplained, and further investigation is warranted. Other factors may also be influencing the high variability of the disease, such as environmental factors, copy number variants and epigenetic alterations. Investigation into these areas is needed as well as larger and more definitive studies of the polymorphisms analysed in this study.

Polymorphisms of cell cycle regulator genes CCND1 G870A and TP53 C215G: Association with colorectal cancer susceptibility risk in a Malaysian population

Colorectal cancer (CRC) occurs as a more common sporadic form and a less common familial form. Our earlier analysis of germline mutations of mismatch repair genes confirmed only 32% of familial CRC cases as Lynch syndrome cases. It was hypothesized that the remaining familial aggregation may be 'polygenic' due to single nucleotide polymorphisms (SNPs) of low penetrance genes involved in cancer predisposition pathways, such as cell cycle regulation and apoptosis pathways. The current case-control study involving 104 CRC patients (52 sporadic and 52 familial) and 104 normal healthy controls investigated the contribution of the SNPs cyclin D1 (CCND1) G870A and tumor protein p53 (TP53) C215G in modulating familial and sporadic CRC susceptibility risk. DNA was extracted from peripheral blood and the polymorphisms were genotyped by employing a polymerase chain reaction-restriction fragment length polymorphism method. The association between these polymorphisms and CRC susceptibility risk was calculated using a binary logistic regression analysis and deriving odds ratios (ORs). The A/A variant genotype of CCND1 and G/G variant genotype of TP53 exhibited a significantly greater association with the risk of sporadic CRC [CCND1: OR, 3.471; 95% confidence interval (CI), 1.443-8.350; P=0.005. TP53: OR, 2.829; CI, 1.119-7.152; P=0.026] as well as familial CRC susceptibility (CCND1: OR, 3.086; CI, 1.270-7.497; P=0.019. TP53: OR, 3.048; CI, 1.147-8.097; P=0.030). The results suggest a potential role of the SNPs CCND1 G870A and TP53 C215G in the modulation of sporadic and familial CRC susceptibility risk.

MDM2 SNP309 polymorphism is associated with colorectal cancer risk

The human murine double minute 2 (MDM2) is known as an oncoprotein through inhibiting P53 transcriptional activity and mediating P53 ubiquitination. Therefore, the amplification of MDM2 may attenuate the P53 pathway and promote tumorigenesis. The SNP309 T>G polymorphism (rs2279744), which is located in the intronic promoter of MDM2 gene, was reported to contribute to the increased level of MDM2 protein. In this hospital-based case-control study, which consisted of 573 cases and 588 controls, we evaluated the association between MDM2 SNP309 and the risk of colorectal cancer (CRC) in a Chinese population by using the TaqMan method to genotype the polymorphism. We found that the MDM2 SNP309 polymorphism was significantly associated with CRC risk. In addition, in our meta-analysis, we found a significant association between MDM2 SNP309 and CRC risk among Asians, which was consistent with our results. In conclusion, we demonstrated that the MDM2 SNP309 polymorphism increased the susceptibility of CRC in Asian populations.

Genetic modifiers of cancer risk in Lynch syndrome: a review

The report by Aldred Scott Warthin in 1913 of a cancer family history and expanded on by Henry T. Lynch demonstrated one of the most enduring traits observed in patients with Lynch syndrome. The recognition of a variety of malignancies occurring at differing ages within a single family suggested the role of genetic variance on disease expression in an autosomal dominantly inherited genetic condition. With the identification of the genetic basis of Lynch syndrome and the subsequent collection of families and their medical records it has become possible to identify subtle genetic effects that influence the age at which disease onset occurs in this cancer predisposition. Knowledge about genetic modifiers influencing disease expression has the potential to be used to personalise prophylactic screening measures to maximise the benefits for family members and their carers.

TP53 and MDM2 gene polymorphisms, gene-gene interaction, and hepatocellular carcinoma risk: evidence from an updated meta-analysis

Background

The association between TP53 R72P and/or MDM2 SNP309 polymorphisms and hepatocellular carcinoma (HCC) risk has been widely reported, but results were inconsistent. To clarify the effects of these polymorphisms on HCC risk, an updated meta-analysis of all available studies was conducted.

Methods

Eligible articles were identified by search of databases including PubMed, Cochrane Library, EMBASE and Chinese Biomedical Literature database (CBM) for the period up to July 2013. Data were extracted by two independent authors and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated. Metaregression and subgroup analyses were performed to identify the source of heterogeneity.

Results

Finally, a total of 10 studies including 2,243 cases and 3,615 controls were available for MDM2 SNP309 polymorphism and 14 studies containing 4,855 cases and 6,630 controls were included for TP53 R72P polymorphism. With respect to MDM2 SNP309 polymorphism, significantly increased HCC risk was found in the overall population. In subgroup analysis by ethnicity and hepatitis virus infection status, significantly increased HCC risk was found in Asians, Caucasians, Africans, and HCV positive patients. With respect to TP53 R72P polymorphism, no significant association with HCC risk was observed in the overall and subgroup analyses. In the MDM2 SNP309–TP53 R72P interaction analysis, we found that subjects with MDM2 309TT and TP53 Pro/Pro genotype, MDM2 309 TG and TP53 Arg/Pro genotype, and MDM2 309 GG and TP53 Pro/Pro genotype were associated with significantly increased risk of developing HCC as compared with the reference MDM2 309TT and TP53 Arg/Arg genotype.

Conclusions

We concluded that MDM2 SNP309 polymorphism may play an important role in the carcinogenesis of HCC. In addition, our findings further suggest that the combination of MDM2 SNP 309 and TP53 Arg72Pro genotypes confers higher risk to develop HCC. Further large and well-designed studies are needed to confirm this association.

An updated meta-analysis on the association of MDM2 SNP309 polymorphism with colorectal cancer risk

BACKGROUND

The mouse double minute 2 (MDM2) gene encodes a phosphoprotein that interacts with P53 and negatively regulates its activity. The SNP309 polymorphism (T-G) in the promoter of MDM2 gene has been reported to be associated with enhanced MDM2 expression and tumor development. Studies investigating the association between MDM2 SNP309 polymorphism and colorectal cancer (CRC) risk reported conflicting results. We performed a meta-analysis of all available studies to explore the association of this polymorphism with CRC risk.

METHODS

All studies published up to July 2013 on the association between MDM2 SNP309 polymorphism and CRC risk were identified by searching electronic databases PubMed, EMBASE, and Chinese Biomedical Literature database (CBM) databases. The association between the MDM2 SNP309 polymorphism and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

RESULTS

A total of 14 case-control studies including 4460 CRC cases and 4828 controls were identified. We did not find a significant association between the MDM2 SNP309 polymorphism and CRC risk in all genetic models in overall population. However, in subgroup analysis by ethnicity, significant associations were found in Asians (TG vs. TT: OR = 1.197, 95% CI = 1.055-1.358, P=0.005; GG+TG vs. TT: OR = 1.246, 95% CI = 1.106-1.404, P=0.000) and Africans. When stratified by HWE in controls, significantly increased risk was also found among the studies consistent with HWE (TG vs. TT: OR = 1.166, 95% CI = 1.037-1.311, P= 0.010). In subgroup analysis according to p53 mutation status, and gender, no any significant association was detected.

CONCLUSIONS

The present meta-analysis suggests that the MDM2 is a candidate gene for CRC susceptibility. The MDM2 SNP309 polymorphism may be a risk factor for CRC in Asians.

Current evidence on the relationship between SNP309 polymorphism in the MDM2 gene and colorectal cancer risk

It has been demonstrated that MDM2 is a well-established negative regulator of the p53 protein and might be associated with a significantly earlier age of onset of several tumors, including colorectal cancer (CRC). In recent years, a T to G substitution (SNP309) in the promoter of MDM2 has been extensively studied as a potential CRC risk factor; however, the results are inconsistent. To derive a more precise estimation of association between MDM2 SNP309 polymorphism and CRC risk, we conducted a meta-analysis of 11 studies with 4,050 CRC cases and 3,688 controls. For MDM2 SNP309 polymorphism, no obvious associations were found for all genetic models when all studies were pooled into the meta-analysis. In the subgroup analyses by ethnicity, source of controls, and Hardy-Weinberg equilibrium (HWE) in controls, a significantly increased risk was observed among Asians (heterozygous model: odds ratio (OR) = 1.21, 95% confidence interval (CI) = 1.06-1.39, P = 0.005), population-based studies (heterozygous model: OR = 1.17, 95% CI = 1.02-1.34, P = 0.027), and among studies without the HWE (recessive model: OR = 1.42, 95% CI = 1.03-1.94, P = 0.030). When excluding three studies deviated from HWE, the significant results were also observed for heterozygous model in overall population (OR = 1.16, 95% CI = 1.02-1.31, P = 0.020). No publication bias was found in the present study. In conclusion, this meta-analysis suggests that MDM2 SNP309 polymorphism was associated with CRC susceptibility, especially among Asians. Further research is needed to assess possible gene-gene or gene-environment-lifestyle interactions on CRC.

Combined effects of p53 and MDM2 polymorphisms on susceptibility and surgical prognosis in hepatitis B virus-related hepatocellular carcinoma

The p53 signaling pathway works as a potent barrier to tumor progression. Two single nucleotide polymorphisms (SNPs) in the gene loci of p53 pathway, p53 codon 72 Arg72Pro and MDM2 SNP309 (T > G), have been shown to cause perturbation of p53 function, but the effect of the two SNPs on the risk of hepatocellular carcinoma (HCC) remains inconsistent. This study investigated the influence of combined p53 Arg72Pro and MDM2 SNP309 on the risk of developing HCC in patients with chronic hepatitis B virus infection, and evaluated the significance of the two combined SNPs on patient prognosis. In total, 350 HCC patients, 230 non-HCC patients, and 96 healthy controls were genotyped for the p53 Arg72Pro and MDM2 SNP309. The combined p53 Pro/Pro and MDM2 G/G genotype was significantly associated with HCC risk (P = 0.047). Multivariate analysis indicated that combined p53 Pro/Pro and MDM2 G/G genotype was an independent factor affecting recurrence and survival (P < 0.05). Patients with combined p53 Pro/Pro and MDM2 G/G genotypes had a poorer prognosis than other genotypes, P < 0.01 for both disease-free survival (DFS) and overall survival (OS). DFS and OS rates also differed significantly between Barcelona Clinic Liver Cancer (BCLC) stage A patients with combined p53 Pro/Pro and MDM2 G/G and other genotypes (P < 0.05). Thus, the combined p53 Pro/Pro and MDM2 G/G genotype is associated with increased risk of developing HCC and is an independent adverse prognostic indicator in early stage HCC.

TP53 R72P and MDM2 SNP309 polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

OBJECTIVE

Tumor protein p53 gene and its negative regulator, murine double minute 2 homolog are important components for cell-cycle arrest and apoptosis. An arginine-to-proline substitution at codon 72 in the p53 gene is reported to decrease apoptotic potential, while a thymine-to-guanine polymorphism at nucleotide 309, named SNP309, of murine double minute 2 gene increases transcription of the gene. These two polymorphisms therefore may be of importance in colorectal carcinogenesis. The relation of these polymorphisms to colorectal cancer risk was addressed in the Fukuoka Colorectal Cancer Study.

METHODS

We genotyped the two polymorphisms in 685 incident cases of colorectal cancer and 778 community controls by the polymerase chain reaction-restriction fragment length polymorphism method. Statistical adjustment was made for sex and age.

RESULTS

The proline allele of p53 gene and the guanine allele of SNP309 were each associated with a small, statistically non-significant increase in the odds ratio of colorectal cancer; the adjusted odds ratio (95% confidence interval) for arginine/proline and proline/proline genotypes combined versus arginine/arginine genotype of p53 gene was 1.23 (0.99-1.52) and that for thymine/guanine and guanine/guanine genotypes combined versus thymine/thymine genotype of SNP309 was 1.27 (0.98-1.63). Individuals harboring the proline allele of p53 gene and the guanine allele of SNP309 showed an odds ratio of 1.67 (95% confidence interval, 1.11-2.51).

CONCLUSIONS

Codon 72 polymorphism of p53 and SNP309 in combination may confer an increased risk of colorectal cancer.

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.

MDM2 SNP309 and p53 Arg72Pro in cutaneous melanoma: association between SNP309 GG genotype and tumor Breslow thickness

A functional single nucleotide polymorphism (SNP) 309 T/G within mouse double minute 2 (MDM2) gene has been linked to onset and outcome of disease in tumors. Two published studies have shown discordant results regarding the effect of this SNP on age at diagnosis of cutaneous melanoma (CM) in Caucasian female populations. Here, we examined the age at diagnosis and clinical associations of CM with SNP309 and the related polymorphism, p53 Arg72Pro, in an Italian population (249 CM patients and 291 cancer-free controls) composed of women and men. MDM2 intronic region of 294 bp was directly sequenced, whereas Arg72Pro SNP was analyzed by polymerase chain reaction-restriction fragment length polymorphism. No associations were found among the SNP309, Arg72Pro, risk of CM, age at diagnosis and presence of metastasis in total subjects and when stratified according to the gender. The SNP309 was significantly associated with tumor Breslow thickness. The P-value in the minor allele recessive mode was 0.02, and the odds ratio (OR) adjusted for gender and age was 3.11 (95% confidential interval (CI)=1.21-8.00). The SNP309 is not associated with the risk and age of onset of CM, and the presence of metastasis in an Italian population but the SNP309 GG may be a risk genotype for increasing in tumor Breslow thickness.

MDM2 309 T/G polymorphism is associated with colorectal cancer risk especially in Asians: a meta-analysis

The murine double minute 2 (MDM2) gene encodes an important regulator which mainly functions as an E3 ligase. The role of the MDM2 protein in the P53 pathway has been especially well-studied. In this study, our aim was to explore the relationship between MDM2 gene 309 T/G polymorphism and colorectal cancer risk. Performing both the overall meta-analysis and the subgroup meta-analysis based on ethnicity and source of controls with a total of 7 eligible studies (2,543 cases and 2,115 controls in all), we detected a significant colorectal cancer risk variation for TG versus GG (OR=0.73, 95% CI=0.62-0.86) in the overall analysis and another significant colorectal cancer risk variation for TG versus GG (OR=0.70, 95% CI=0.59-0.83) in the population-based controls' subgroup as well. Moreover, in the subgroup analysis based on ethnicity, significant associations were observed for all genetic models in Asians (OR=0.51, 95% CI=0.41-0.64 for TT versus GG; OR=0.64, 95% CI=0.53-0.78 for TG versus GG; OR=0.59, 95% CI=0.49-0.71 for dominant model; OR=0.69, 95% CI=0.57-0.82 for recessive model), while in Caucasians there was no obvious association. In summary, according to the results of our meta-analysis, the MDM2 309 G allele probably acts as a colorectal cancer risk factor, especially in Asians.

Association between MDM2-SNP309 and hepatocellular carcinoma in Taiwanese population

AIM: To investigate the risk association and compare the onset age of hepatocellular carcinoma (HCC) patients in Taiwan with different genotypes of MDM2-SNP309.

METHODS: We analyzed MDM2-SNP309 genotypes from 58 patients with HCC and 138 cancer-free healthy controls consecutively. Genotyping of MDM2-SNP309 was conducted by restriction fragment length polymorphism assay.

RESULTS: The proportion of homozygous MDM2-SNP309 genotype (G/G) in cases and cancer-free healthy controls was similar (17.2% vs 16.7%). Multivariate analysis showed that the risk of G/G genotype of MDM2-SNP309 vs wild-type T/T genotype in patients with HCC was not significant (OR = 1.265, 95% CI = 0.074-21.77) after adjustment for sex, hepatitis B or C virus infection, age, and cardiovascular disease/diabetes. Nevertheless, there was a trend that GG genotype of MDM2-SNP309 might increase the risk in HCC patients infected with hepatitis virus (OR = 2.568, 95% CI = 0.054-121.69). Besides, the homozygous MDM2-SNP309 genotype did not exhibit a significantly earlier age of onset for HCC.

CONCLUSION: Current data suggest that the association between MDM2-SNP309 GG genotype and HCC is not significant, while the risk may be enhanced in patients infected by hepatitis virus in Taiwan.

Association of MDM2 SNP309, age of onset, and gender in cutaneous melanoma

PURPOSE

In certain cancers, MDM2 SNP309 has been associated with early tumor onset in women. In melanoma, incidence rates are higher in women than in men among individuals less than 40 years of age, but among those older than 50 years of age, melanoma is more frequent in men than in women. To investigate this difference, we examined the association among MDM2 SNP309, age at diagnosis, and gender among melanoma patients.

EXPERIMENTAL DESIGN

Prospectively enrolled melanoma patients (N = 227) were evaluated for MDM2 SNP309 and the related polymorphism, p53 Arg72Pro. DNA was isolated from patient blood samples, and genotypes were analyzed by PCR-restriction fragment length polymorphism. Associations among MDM2 SNP309, p53 Arg72Pro, age at diagnosis, and clinicopathologic features of melanoma were analyzed.

RESULTS

The median age at diagnosis was 13 years earlier among women with a SNP309 GG genotype (46 years) compared with women with TG+TT genotypes (59 years; P = 0.19). Analyses using age dichotomized at each decade indicated that women with a GG genotype had significantly higher risks of being diagnosed with melanoma at ages <50 years compared with women >or=50 years, but not when the comparison was made between women <60 and >or=60 years. At ages <50 years, women with a GG genotype had a 3.89 times greater chance of being diagnosed compared with women with TG+TT genotypes (P = 0.01). Similar observations were not seen among men.

CONCLUSIONS

Our data suggest that MDM2 may play an important role in the development of melanoma in women. The MDM2 SNP309 genotype may help identify women at risk of developing melanoma at a young age.

Genetic epidemiology studies in hereditary non-polyposis colorectal cancer

Genetic epidemiology studies in hereditary non-polyposis colorectal cancer (HNPCC) have the potential to radically improve assessment of disease risk such that more individualised information can be provided to patients susceptible to developing disease. Studies of HNPCC initially focused on disease associations and the definition of the disease and its association with different cancers within the context of an inherited predisposition. With the identification of the genetic basis of HNPCC, new insights into the disease have been forthcoming and many advances in our understanding have been made. There have been many reports examining potential modifier genes in HNPCC, yet the results remain controversial as many findings have not been replicated and therefore no clear consensus as to the role of specific modifier genes has been reached. This review focuses on some of the factors associated with disease risk in HNPCC and where some of the difficulties lie in assessing the value of genetic epidemiology studies in this disorder.

Genotyping of single nucleotide polymorphism in MDM2 genes by universal fluorescence primer PCR and capillary electrophoresis

Single nucleotide polymorphism (SNP) 309 in the promoter region of the murine double minute 2 (MDM2) gene plays an important role in human tumorigenesis. We established a simple and effective CE method for SNP detection in the MDM2 gene. We designed one universal fluorescence-based nonhuman-sequence primer and one fragment-oriented primer, which were combined in one tube, and proceeded with the polymerase chain reaction (PCR). The amplicons were analyzed by capillary electrophoresis using single-strand conformation polymorphism method. PCR fragments generated from this two-in-one PCR displayed either T/T or G/G homozygosity or T/G heterozygosity. A total of 304 samples were blindly genotyped using this developed method, which included the DNA from 138 healthy volunteers, 43 chronic myeloid leukemia (CML) patients, and 123 colorectal cancer (CRC) patients. The results were confirmed by DNA sequencing and showed good agreement. The SSCP-CE method was feasible for SNP screening of MDM2 in large populations.

p53-independent mechanisms regulate the P2-MDM2 promoter in adult astrocytic tumours

The MDM2 gene is amplified and/or overexpressed in about 10% of glioblastomas and constitutes one of a number of ways the p53 pathway is disrupted in these tumours. MDM2 encodes a nuclear phosphoprotein that regulates several cell proteins by binding and/or ubiquitinating them, with p53 being a well-established partner. MDM2 has two promoters, P1 and P2 that give rise to transcripts with distinct 5′ untranslated regions. Transcription from P2 is believed to be controlled by p53 and a single-nucleotide polymorphism (SNP309, T>G) in P2 is reported to be associated with increased risk for, and early development of, malignancies. The use of P1 and P2 has not been investigated in gliomas. We used RT–PCR to study P1- and P2-MDM2 transcript expression in astrocytic tumours, xenografts and cell lines with known MDM2, TP53 and p14^ARF gene status. Both promoters were used in all genetic backgrounds including the use of the P2 promoter in TP53 null cells, indicating a p53-independent induction of transcription. Transcripts from the P1 promoter formed a greater proportion of the total MDM2 transcripts in tumours with MDM2 amplification, despite these tumours having two wild-type TP53 alleles. Examination of SNP309 in glioblastoma patients showed a borderline association with survival but no apparent correlation with age at diagnosis nor with TP53 and p14^ARF status of their tumours. Our findings also indicate that elevated MDM2 mRNA levels in tumours with MDM2 amplification are preferentially driven by the P1 promoter and that the P2 promoter is not only regulated by p53 but also by other transcription factor(s).

Risk stratification in cancer predisposition syndromes: lessons learned from novel molecular developments in Li-Fraumeni syndrome

Germ-line mutations in specific genes predispose family members to cancer. Prediction of the exact tumor type and timing of cancer initiation is fundamental to the development of management strategies for these individuals. Recent advances in our understanding of the general processes that control cancer initiation may enable us to tailor more precise risk stratification. This, in turn, will lead to more effective early detection strategies, which would result in more favorable clinical outcomes. In this review, we highlight the steps and methods used to reach this futuristic model.

Influence of MDM2 SNP309 alone or in combination with the TP53 R72P polymorphism in oligodendroglial tumors

The transcription factor p53 and its negative regulator MDM2 are pivotal in normal and cancer cells biology. Recently, a functional single-nucleotide polymorphism in the promoter region of MDM2 (MDM2 SNP309), alone or in combination with TP53 R72P, was shown to be associated with the risk, prognosis, age at onset, molecular markers, and response to chemotherapy of various cancers. This SNP has never been specifically investigated in a large series of oligodendroglial tumors. In a comparison with 232 healthy controls, we retrospectively analyzed blood samples of 293 oligodendroglial tumor patients for MDM2 SNP309. In addition, the TP53 R72P polymorphism and chromosome 1p/19q status, a major biomarker in oligodendroglial tumors, were investigated. The frequencies of T/T, T/G, and G/G genotypes in patients and controls did not suggest an increased risk of oligodendroglial tumor formation correlating with MDM2 SNP309. A borderline association was found between MDM2 SNP309 and overall survival (p=0.05), but in multivariate analysis, MDM2 SNP309 did not provide prognostic information complementary to age, tumor phenotype, grade, and 1p/19q status in oligodendroglial tumors. Finally, MDM2 SNP309, alone or in combination with TP53 R72P, was not associated with oligodendroglial tumors.

MDM2 SNP309 and cancer risk: a combined analysis

A paper by Bond et al. reported that a single-nucleotide polymorphism (SNP) in the intronic promoter region of the mouse double minute 2 (MDM2) gene (called SNP309) can significantly change the expression of MDM2 and thereby suppress the p53 pathway. Furthermore, it was shown that SNP309 accelerates tumor formation in Li-Fraumeni patients. This initial report aroused the attention of many researchers, which investigated the role of SNP309 for the risk and the onset of cancer in different tissues. To provide a more robust estimate of the effect of this polymorphism on cancer risk, we combined the available genotype data for breast, colorectal and lung cancers. For breast cancer, we combined the data from 11 studies including 5737 cases and 6703 controls. For colorectal cancer, we combined the data from five studies with 1620 cases and 886 controls. For lung cancer, we performed a fixed-effect meta-analysis from seven studies including 4276 cases and 5318 controls. Our results suggest that the SNP309 variant does not have an impact on the risk of breast [odds ratio (OR) = 0.97, 95% confidence interval (CI) = 0.87-1.08] or colorectal cancers (OR = 0.97, 95% CI = 0.76-1.25). However, the combined estimate of the ORs for lung cancer revealed an increased risk for GG versus TT (OR = 1.27, 95% CI = 1.12-1.44). The data show that SNP309 alone has little or no effect on the risk of common cancers, but it might modify the time of tumor onset and prognosis.

A Polymorphism in HDM2 (SNP309) Associates with Early Onset in Superficial Tumors, TP53 Mutations, and Poor Outcome in Invasive Bladder Cancer

PURPOSE

The HDM2 gene represents one of the central nodes in the p53 pathway. A recent study reported the association of a single nucleotide polymorphism (SNP309) in the HDM2 promoter region with accelerated tumor formation in both hereditary and sporadic cancers. In this study, we aim to evaluate the SNP309 in bladder cancer and to link it to TP53 status.

EXPERIMENTAL DESIGN

SNP309 genotyping and TP53 mutation status were done on 141 bladder tumors and 8 bladder cancer cell lines using a RFLP strategy and TP53 genotyping arrays, respectively. Transcript profiling of a subset of cases (n = 41) was done using oligonucleotide arrays to identify genes differentially expressed regarding their SNP309 status.

RESULTS

Of 141 bladder tumors analyzed, 36.9% displayed the SNP309 wild-type (WT; T/T) genotype, whereas 11.3% were homozygous (G/G) and 51.8% were heterozygous (T/G) cases. Patients with superficial disease and the G/G genotype had an earlier age on onset than those with the T/G or T/T genotypes (P = 0.029). Tumors with SNP309 WT genotype significantly displayed TP53 mutations when compared with tumors harboring G/G or T/G genotypes (P < 0.05). SNP309 WT cases had a poorer overall survival than cases with G/G and T/G genotypes (P < 0.05). TP53 mutation status provided enhanced prognostic value (P < 0.001). Transcript profiling identified TP53 targets among those differentially expressed between tumors displaying G/G or T/G SNP309 versus WT cases.

CONCLUSIONS

SNP309 is a frequent event in bladder cancer, related to earlier onset of superficial disease and TP53 mutation status. SNP309 genotypes were found to be associated with clinical outcome.