Role of the MDM2 Promoter Polymorphism (-309T>G) in Acute Myeloid Leukemia Development

Background: The human homologue of the mouse double minute 2 (MDM2) gene is a negative regulator ofTp53. MDM2-309T>G a functional promoter polymorphism was found to be associated with overexpressionthereby attenuation of Tp53 stress response and increased cancer susceptibility. We have planned to evaluate thepossible role of MDM2-309T>G polymorphism with risk and response to chemotherapy in AML. Materials andMethods: A total of 223 de novo AML cases and 304 age and sex matched healthy controls were genotyped for theMDM2-309T>G polymorphism through the tetra-primer amplification refractory mutation system (ARMS)-PCRmethod. In order to assess the functional relationship of -309T>G SNP with MDM2 expression level, we quantifiedMDM2 mRNA in 30 primary AML blood samples through quantitative RT-PCR. Both the (-309T>G) genotypesand the MDM2 expression were correlated with disease free survival (DFS) rates among patients who haveachieved complete remission (CR) after first induction chemotherapy. Results: MDM2-309T>G polymorphismwas significantly associated with AML development (p<0.0001). The presence of either GG genotype or G alleleat MDM2-309 confered 1.79 (95% CI: 1.12-2.86; p<0.001) and 1.46 fold (95%CI: 1.14-1.86; p= 0.003) increasedAML risk. Survival analysis revealed that CR+ve cases with GG genotype had significantly increased DFS rates(16months, p=0.05) compared to CR+ve TT (11 months) and TG (9 months) genotype groups. Further, MDM2expression was also found to be significantly elevated in GG genotype patients (p=0.0039) and among CR+vecases (p=0.0036). Conclusions: The MDM2-309T>G polymorphism might be involved in AML development andalso serve as a good prognostic indicator.     

MDM2 SNP309T>G polymorphism and risk of hepatocellular carcinoma: A case–control analysis in a Moroccan population

Background: The Murine double minute 2 (MDM2) gene encodes a negative regulator of the p53 tumor suppressor protein. A single nucleotide polymorphism (SNP) in the MDM2 promoter (a T to G exchange at nucleotide 309) has been reported to produce accelerated tumor formation. The aim of this study was to investigate whether this functional SNP is associated with an enhanced risk of liver tumorigenesis in Moroccan patients. Methods: The study consisted in the comparison of 96 hepatocellular carcinomas (HCC) cases and 222 controls without HCC matched for age, gender and ethnicity. PCR–RFLP and sequencing methods were used to determine the genotype at the MDM2 SNP309T>G locus. Results: Overall, our results indicate that the GG genotype of SNP309 is significantly associated with an increased risk of HCC (odds ratio, OR = 2.60, 95% CI, 1.08–6.28). Interestingly, despite a wide range of confidence interval, there is a trend associating the GG genotype with a high risk of HCC in males (OR = 3.31; 95% CI, 0.93–11.82) and in HCV-infected patients (OR = 3.7; 95% CI, 0.82–16.45). By contrast, no association between age at diagnosis and MDM2 SNP309 genotypes was observed in HCC patients (P = 0.610). Conclusion: Our findings suggest that the MDM2 309T>G polymorphism is an important modulator of hepatocellular carcinoma development in Moroccan patients.     

MDM2 SNP309 accelerates breast and ovarian carcinogenesis in BRCA1 and BRCA2 carriers of Jewish–Ashkenazi descent

A functional single nucleotide polymorphism in the promoter of the MDM2 gene, SNP309 (T>G), was recently found to accelerate tumorigenesis in early onset cancer cases. The SNP309 G-allele, introduces an SP1 site in the MDM2 promoter, resulting in enhanced MDM2 expression and activity. Thus, the G-allele of MDM2 SNP309 may represent a cancer predisposing allele. In this report, we assessed the role of SNP309 as a modifier of mutant BRCA1/BRCA2 alleles in inherited breast and ovarian cancer cases among Ashkenazi–Jewish (AJ) women. We genotyped several subsets of AJ women: 138 healthy women, 140 affected BRCA1/2 mutation carriers, 120 asymptomatic BRCA1/2 mutation carriers and 187 sporadic breast cancer patients. The frequency of GG genotype of SNP309 was similar among the different groups. Interestingly, we found almost three times higher frequency of the GG genotype among BRCA1/2 carriers diagnosed with breast and/or ovarian cancer at or under the age of 51 years compared with carriers diagnosed with cancer above the age of 51 years (allele frequency, P = 0.019). The GG genotype was significantly associated with breast and ovarian cancer risk among BRCA1/2 carriers diagnosed before 51 years of age (OR, 3.93; 95% CI, 1.41–10.90, P = 0.009). No significant difference in frequency of the GG genotype was observed between early and late onset non-carrier cancer patients and no association with risk, OR, 1.30; 95% CI 0.69–2.47, P = 0.419). These data suggest that MDM2 SNP309 acts as a modifier of mutant BRCA1/2 mutant alleles in AJ and may accelerate breast and ovarian carcinogenesis in genetically predisposed individuals.     

Association of p53 codon 72 polymorphism and MDM2 SNP309 with clinical outcome of advanced nonsmall cell lung cancer

BACKGROUND: The purpose of the study was to investigate whether polymorphisms of p53 codon 72 (Arg72Pro) and MDM2 SNP309 (309T>G) affect p53 expression and the clinical outcome of patients with advanced nonsmall cell lung cancer (NSCLC). METHODS: A total of 148 NSCLC patients, previously enrolled in 2 different prospective clinical trials, were genotyped for the p53 Arg72Pro and MDM2 309T>G polymorphisms. Immunohistochemical staining of p53 protein was performed on 61 tumor samples. Genotypes were correlated with p53 expression, clinicopathologic factors, tumor response, and survival. Multivariate logistic or Cox regression analyses were used to adjust for possible confounding variables. RESULTS: The distribution of sex, age, performance status, stage, tumor histology, and smoking habit was not significantly different among polymorphism variants. However, a significant association was observed between p53 Arg72Pro polymorphism and primary resistance to chemotherapy. Patients with the Pro/Pro variant were more likely to be resistant to first-line chemotherapy, especially the irinotecan plus cisplatin regimen, than those with Arg/Arg or Arg/Pro variants (60% vs 27%, P = .014). In multivariate analysis, the Pro/Pro genotype was strongly predictive for shorter progression-free survival (PFS) (hazard ratio [HR] = 1.952, P = .01). The p53 overexpression was associated with MDM2 SNP309. The TT genotype showed more p53 overexpression than TG or GG genotypes (P = .036). In multivariate analysis, the MDM2 TT genotype was independently predictive for longer survival (HR = 1.742, P = .032). CONCLUSIONS: The p53 72Pro/Pro variant was predictive for primary resistance to chemotherapy and shorter progression-free survival. The MDM2 SNP309 was associated with less p53 overexpression and prognostic for worse survival. Genotyping these polymorphisms may be useful for predicting the clinical outcome of advanced NSCLC.     

No association of the MDM2 SNP309 polymorphism with risk of breast or ovarian cancer

A functional T to G germline polymorphism in the promoter region of MDM2 (SNP309) has been reported to profoundly accelerate tumor formation suggesting that it may also represent a powerful cancer predisposing allele. To investigate the role of SNP309 in cancer predisposition we undertook a case-control study of this polymorphism among 351 women diagnosed with breast cancer, 302 women diagnosed with ovarian and 258 female controls from a British population. The GG genotype was not associated with either breast cancer (OR 1.04, 95% CI 0.67–1.60) or ovarian cancer (OR 0.86, 95% CI 0.53–1.37). This study has found no evidence that the GG genotype of the MDM2 SNP309 polymorphism is associated with early onset or familial breast cancer or with ovarian cancer.     

MDM2 promoter SNP309 is associated with risk of occurrence and advanced lymph node metastasis of nasopharyngeal carcinoma in Chinese population.

PURPOSE: Mouse double minute 2 (MDM2) is a key negative regulator of the p53 activity. Recently, a polymorphism in the MDM2 intronic promoter, SNP309, was shown to influence MDM2 expression and p53 activity. We examined whether the SNP309 was related to the risk of developing nasopharyngeal carcinoma (NPC) among Chinese populations. EXPERIMENTAL DESIGN: We genotyped the SNP309 in two independent case-control populations in southern China, one is from Guangxi province (including 593 NPC patients and 480 controls) and the other is from Guangdong province (including 239 patients and 286 controls), by PCR direct sequencing. Multivariate logistic regression analysis was used to calculate adjusted odds ratio (OR) and 95% confidence interval (95% CI). RESULTS: We observed that compared with the TT genotype, the genotypes containing G allele (GT + GG genotype) were associated with significant increased susceptibility to NPC in both Guangxi (OR, 1.43; 95% CI, 1.04-1.91) and Guangdong population (OR, 1.53; 95% CI, 1.00-2.36). When these two sample sets were combined, the OR of the GT + GG genotype developing NPC was 1.45 (95% CI, 1.12-1.85) compared with the TT genotype. Furthermore, compared with the TT genotype, the GT + GG genotype was also significantly associated with the advanced lymph node metastasis (OR, 1.84; 95% CI, 1.09-3.05). CONCLUSIONS: Our findings suggest that the MDM2 SNP309 may be a risk factor for the occurrence and advanced neck lymph node metastasis of NPC in Chinese population.     

MDM2 SNP309 contributes to non-small cell lung cancer survival in Chinese

Murine double minute 2 (MDM2) is a negative regulator of the tumor suppressor gene p53. Single nucleotide polymorphisms in MDM2 and p53 can affect patient's response to chemotherapy as well as overall survival of many cancers. This study aimed to assess the associations between polymorphisms in MDM2 and p53 and survival of non‐small cell lung cancer (NSCLC) patients in Chinese. We selected and genotyped both potentially functional SNPs and tagging SNPs in MDM2 and p53 using Illumina Golden Gate platform in a cohort of 568 NSCLC patients. Associations between genotypes and NSCLC median survival time (MST) were assessed using the Kaplan–Meier method. Cox proportional hazard models were performed with the adjustment for age, stage, smoking, histology, surgical operation, and chemo‐ or radiotherapy status. We found that the MDM2 SNP309 (rs2279744) GT/TT genotypes were associated with a significantly worse survival (MST: 23.0 mo for GT/TT vs. 33.0 mo for GG; log‐rank P = 0.028). In the multivariate Cox regression analyses, the MDM2 SNP309GT/TT genotypes were associated with a 1.42‐fold [HR = 1.42, 95% confidence interval (CI), 1.09–1.84] increased risk of death of NSCLC, compared with SNP309GG genotype. MDM2 SNP309 may be used as one of the candidate biomarkers to predict NSCLC survival. © 2011 Wiley‐Liss, Inc.     

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

The MDM2 SNP309 has been associated with increased expression of the protein which could suppress p53 function, and has been shown to modulate risk to cancer. We have previously shown that overexpression of MDM2 is a common event in oral cancers. In the present study, we determined the association between the MDM2 SNP309 polymorphism and oral cancer in 207 oral cancer patients and 116 normal subjects. We genotyped the MDM2 SNP309 by PCR-RFLP. Logistic regression was adapted to calculate odds ratios for MDM2 SNP309 polymorphism from univariate and multivariable adjusted models. Our results suggest that MDM2 SNP309 does not confer increased risk to oral cancer (OR=1.55, 95% CI=0.77-3.11). However, the GG/TG genotype was associated with later disease onset in women above 55 years of age. Collectively, our data suggests that MDM2 SNP309 may modulate the risk to oral cancer and is a modifier of the age at oral cancer onset in women above the age of 55 years.     

P53 Arg72Pro and MDM2 SNP309 Polymorphisms Cooperate to Increase Lung Adenocarcinoma Risk in Chinese Female Non-smokers: A Case Control Study

Background: Cell cycle deregulation is a major component of carcinogenesis. The p53 tumor suppressorgene plays an important role in regulating cell cycle arrest, and mouse double minute 2 (MDM2) is a keyregulator of p53 activity and degradation. Abnormal expression of p53 and MDM2 occurs in various cancersincluding lung cancer. Methods: We investigated the distribution of the p53 Arg72Pro (rs1042522) and MDM2SNP309 (rs2279744) genotypes in patients and healthy control subjects to assess whether these single nucleotidepolymorphisms (SNPs) are associated with an increased risk of lung adenocarcinomas in Chinese female nonsmokers.Genotypes of 764 patients and 983 healthy controls were determined using the TaqMan SNP genotypingassay. Results: The p53 Pro/Pro genotype (adjusted OR = 1.55, 95% CI = 1.17–2.06) significantly correlated withan increased risk of lung adenocarcinoma, compared with the Arg/Arg genotype. An increased risk was also notedfor MDM2 GG genotype (adjusted OR = 1.68, 95% CI = 1.27–2.21) compared with the TT genotype. Combinedp53 Pro/Pro and MDM2 GG genotypes (adjusted OR = 2.66, 95% CI = 1.54–4.60) had a supermultiplicativeinteraction with respect to lung adenocarcinoma risk. We also found that cooking oil fumes, fuel smoke, andpassive smoking may increase the risk of lung adenocarcinomas in Chinese female non-smokers who carry p53or MDM2 mutant alleles. Conclusions: P53 Arg72Pro and MDM2 SNP309 polymorphisms, either alone or incombination, are associated with an increased lung adenocarcinoma risk in Chinese female non-smokers.     

Combined effects of MDM2 SNP 309 and p53 mutation on oral squamous cell carcinomas associated with areca quid chewing

The recently identified single nucleotide polymorphism in the MDM2 promoter (SNP 309) may contribute to the early onset of both sporadic and hereditary malignancies in patients with defective p53. We tested this hypothesis by examining the effects of combined MDM2 polymorphisms and somatic p53 mutations on 351 oral squamous cell carcinomas (OSCCs) associated with areca quid chewing. We found that the G allele of MDM2 SNP 309 was associated with early age of onset (p=0.02) and poor differentiation of OSCC tumors (p=0.01). The frequency of lymph node extracapsular spread (LNECS) was increased in individuals having both the MDM2 SNP 309 GG genotype and p53 mutation (chi(2) for trend p=0.04). MDM2 GG genotype and p53 mutations were associated with poor disease-free survival in both early and lymph node positive advanced stage OSCC patients (Hazard ratio=2.77 and 1.93, respectively). Taken together, an interaction between MDM2 SNP 309 and p53 with respect to tumor behaviors (including disease onset, tumor differentiation, LNECS and disease-free survival) was observed in sporadic Taiwanese OSCCs.     

Genetic Polymorphism of MDM2 SNP309 in Patients with Helicobacter Pylori-Associated Gastritis

Background: Helicobacter pylori plays an important role in gastric cancer, which has a relatively low inciduencein Thailand. MDM2 is a major negative regulator of p53, the key tumor suppressor involved in tumorigenesis ofthe majority of human cancers. Whether its expression might explain the relative lack of gastric cancer in Thailandwas assessed here. Materials and Methods: This single-center study was conducted in the northeast region ofThailand. Gastric mucosa from 100 patients with Helicobacter pylori associated gastritis was analyzed for MDM2SNP309 using real-time PCR hybridization (light-cycler) probes. Results: In the total 100 Helicobacter pyloriassociated gastritis cases the incidence of SNP 309 T/T homozygous was 78 % with SNP309 G/T heterozygousfound in 19% and SNP309 G/G homozygous in 3%. The result show SNP 309 T/T and SNP 309 G/T to be rathercommon in the Thai population. Conclusions: Our study indicates that the MDM2 SNP309 G/G homozygousgenotype might be a risk factor for gastric cancer in Thailand and the fact that it is infrequent could explain tosome extent the low incidence of gastric cancer in the Thai population.     

E2F3a在U251胶质瘤细胞中的功能研究

背景与目的：E2F3a是一种重要的转录激活因子，在多种肿瘤组织中均呈现表达上调。E2F3a在恶性化程度较高的神经胶质瘤中表达较高，目前它在胶质瘤细胞中的功能尚不清楚。本文的目的是研究E2F3。对U251胶质瘤细胞周期和凋亡的影响。方法：通过脂质体介导质粒转染在U251细胞中过表达E2F3a：用Western blotting检测细胞内E2F3a蛋白质的表达水平：用PT-核DNA染色结合流式细胞术分析细胞周期分布：用Annexin V—PE和7-AAD染色结合流式细胞术分析细胞凋亡比例；用实时荧光定量PCR方法测定细胞内A2、B1、D1和E细胞周期素mRNA的相对表达水平。结果：与空载体转染对照组相比．E2F3a过表达可将位于S期的细胞比例提高28％（P〈0．01），将位于G0/G1期和G2/M的细胞比例分别降低15％和13％（P〈0．01）。E2F3a过表达对细胞凋亡无明显影响。进一步研究发现，E2F3a可显著上调细胞周期素D1和E的mRNA表达．而不影响周期素A2和B1的mRNA表达。结论：E2F3a是胶质瘤细胞增殖的促进因子，它可通过上调细胞周期素D1和E的表达加速细胞由G，期进入S期。     

Impact of MDM2 SNP309 genotype on progression and survival of stage 4 neuroblastoma

Circumvention of the p53 checkpoint in neuroblastoma (NB) might arise from increased expression of its main negative regulator MDM2. The SNP309, a T-to-G substitution in the MDM2 promoter, was associated with higher levels of MDM2 mRNA and protein, with consequent attenuation of the p53 pathway. The association between MDM2 SNP309 and disease progression and survival was evaluated in a cohort of 142 children with stage 4 NB. The SNP309 GG patients had a worse overall survival and a worse survival after relapse than the TT ones, whereas the heterozygotes showed an intermediate behaviour (p=0.043 and p=0.049, respectively, log-rank test for trend). No evident association between SNP309 and event free survival was found. The lack of association between SNP309 and MYCN status indicates that MDM2 SNP309 may be a new independent prognostic factor for stage 4 NB.     

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.     

MDM2 promoter SNP309 is associated with an increased susceptibility to chronic lymphocytic leukemia and correlates with MDM2 mRNA expression in Chinese patients with CLL

A single nucleotide polymorphism (SNP) at position 309 in the promoter region of MDM2 leading to increased expression of MDM2 and attenuated function of p53 has recently been suggested as an unfavorable prognostic marker in chronic lymphocytic leukemia (CLL) although this has been questioned. The MDM2 SNP309 genotypes in 173 CLL patients and 260 healthy controls were detected by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, which was confirmed by direct DNA sequencing. Compared with the T/T genotype, the SNP309 G/G genotype instead of T/G heterozygote was associated with a significantly increased risk of CLL (OR = 2.84; 95% CI 1.61-5.03; p < 0.001). Age at onset of CLL was similar irrespective of MDM2 status. MDM2 mRNA expression within CLL of G/G genotype was significantly higher than that in T/G (p = 0.009) and T/T genotypes (p < 0.001). Excluding patients with p53 deletions or mutations enhanced the significance of the findings (G/G vs. T/T, p < 0.001; G/G vs. T/G p = 0.001), which prompted us to study the role of the polymorphism in p53 wild-type individuals. In the p53 wild-type groups, survival analysis showed that the patients with MDM2 SNP309 G/G and T/G genotypes both had significantly shorter treatment-free survival (TFS) than SNP309 T/T genotype. Notably, univariate and multivariate analyses showed that MDM2 SNP309 genotypes were associated with TFS. These data show that MDM2 309G polymorphisms contribute to the risk of developing CLL. The unfavorable MDM2 SNP309 G/G genotype was associated with an increase of MDM2 mRNA expression. MDM2 SNP309 was found to be associated with TFS in p53 wild-type Chinese CLL populations.     

Association Between MDM2 SNP309 T>G and Risk of GastricCancer: A Meta-analysis

Background: As a negative regulator of P53, MDM2 plays an important role in carcinogenesis; a polymorphismin its promoter region. SNP309 T>G, is known to increase the expression of MDM2, thus being considered relatedto higher susceptibility to neoplasia. However, no agreement has been achieved regarding its effects on gastriccancer. Methods: The present systematic meta-analysis was performed based on comprehensive literature searchfrom Pubmed, Web of science and CBM databases. Results: It was suggested from 6 independent studies thatthe GG genotype is associated with a significantly increased risk of gastric cancer (Recessive: OR = 1.43, 95%CI = 1.08-1.91, P = 0.013), and subgroup analysis also confirmed the relationship (English publications-recessivemodel: OR = 1.45, 95% CI = 1.10-1.91, P = 0.009; Studies in China-recessive model: OR = 1.58, 95% CI =1.08-2.30, P = 0.017). No publication bias was detected. Conclusion: The meta-analysis indicated a significantinverse association between GG genotype carriage and elevated risk of gastric cancer. However, more studiesand detailed information are needed to fully address the topic.     

Association of PIK3CA and MDM2 SNP309 with Cervical Squamous Cell Carcinoma in a Philippine Population

Background: PIK3CA and MDM2 SNP309 have been studied to be associated with cervical cancer. PIK3CA mutationis associated with poor treatment response and low survival rate while MDM2 is associated with tumorigenesis andpoor prognosis in cervical cancer. Thus, we determined the prevalence of PIK3CA and MDM2 mutations in Filipinocervical cancer patients. Methods: Twenty-eight formalin-fixed paraffin-embedded cervical squamous cell carcinomaand 16 non-malignant cervix tissue biopsies of Filipino patients were subjected to PIK3CA gene and MDM2 SNP309(rs2279744) analysis. Results: PIK3CA gene was found mutated in three (10.71 %) out of 28 cervical cancer patientsincluded in this study. Among the HPV-negative cervical cancer patients, two (28.57 %) were positive for PIK3CAmutation and only one (4.76 %) tested positive among the HPV-positive cervical cancer patients. MDM2 SNP309analysis revealed that T allele (71.43%) was more common in cervical cancer patients compared to the control group.TG genotype (p = 0.03; OR = 0.18, 95% CI 0.04-0.76) was associated with lower rates of cervical cancer when TTgenotype was used as a reference point. Conclusion: PIK3CA gene mutation was present among Filipino cervicalcancer patients and not in control patients. MDM2 SNP309 analysis revealed that TG genotype has lower associationto cervical cancer when compared with the TT and GG genotypes.