MDM2 SNP309 modifies the prognostic significance of the p53 mutational status in patients with ovarian cancer

A single nucleotide polymorphism (SNP309) of MDM2 causes elevated MDM2 levels and an attenuation of p53 function. The aim of the present study was to examine the clinical relevance of the MDM2 SNP309 in ovarian cancer.MDM2 SNP309 genotype was analyzed in 198 patients with primary ovarian cancer. MDM2 expression was investigated using immunohistochemistry. A functional yeast-based assay and subsequent sequencing were performed to determine p53 mutational status. Of the patients, 44.4% (88 of 198) exhibited the common variant (T/T), 40.9% (81 of 198) the heterozygous variant (T/G) and 14.7% (29 of 198) the homozygous variant (G/G) MDM2 SNP309 genotype. MDM2 SNP309 was not associated with p53 mutational status, MDM2 expression, clinicopathological parameters or prognosis. In patients with the T allele (T/T and T/G genotype), p53 wild type carcinomas were associated with significantly improved recurrence-free (p<0.001) and overall survival (p<0.001) as compared to p53 mutant carcinomas. In contrast, p53 mutational status did not possess prognostic relevance in G/G carriers. A possible functional impairment of the p53 pathway caused by the G/G genotype of the MDM2 SNP309 may modify the association between p53 mutational status and prognosis in ovarian cancer.     

MDM2 and p53 polymorphisms are associated with the development of hepatocellular carcinoma in patients with chronic hepatitis B virus infection

A single-nucleotide polymorphism (SNP) in the promoter region of MDM2, SNP 309, is associated with hepatocellular carcinoma (HCC) in patients with chronic hepatitis C virus infection. The effect of p53 codon 72 polymorphism Arg72Pro on HCC risk remains inconsistent. This study evaluated the association of MDM2 and p53 polymorphisms with the presence and early onset of HCC in Korean patients with chronic hepatitis B virus (HBV) infection. In total, 583 consecutive patients with chronic HBV infection were classified according to the presence (n = 287) or absence (n = 296) of HCC. The MDM2 SNP 309 and p53 Arg72Pro were genotyped using restriction fragment length polymorphism method. The MDM2 G/G and p53 Pro/Pro genotypes were more frequent in HCC group than in non-HCC group (P < 0.001 and P = 0.004, respectively). Multivariate analysis for the presence of HCC revealed that the odds ratio (OR) for MDM2 G/G over T/T was 4.89 (P < 0.001) and that of p53 Pro/Pro over Arg/Arg was 3.03 (P = 0.006). Combined MDM2 G/G and p53 Pro/Pro had a synergistic effect on HCC risk, with an OR of 20.78 (P < 0.001). The mean age of tumor onset in patients with MDM2 G/G genotype was 50.9 years compared with 55.1 with T/T genotype (P = 0.018) and that with p53 Pro/Pro was 49.7 years compared with 52.9 with Arg/Arg (P = 0.040). Thus, MDM2 SNP 309 and p53 Arg72Pro are associated with the early development of HCC in Korean patients with chronic HBV infection.     

Association between MDM2-SNP309 and age at colorectal cancer diagnosis according to p53 mutation status

A single-nucleotide polymorphism (SNP) in the promoter of the MDM2 gene, SNP309 (a T-->G change), was recently implicated in the early onset of cancer in individuals with Li-Fraumeni syndrome and of sporadic soft-tissue sarcoma. SNP309 induces an increase in the level of Mdm2 protein, which causes attenuation of the p53 pathway. To investigate the effect of this polymorphism in colorectal cancer pathogenesis, we genotyped 153 colorectal cancer patients who were randomly selected from among 330 consecutive patients stratified according to p53 mutation status and age at diagnosis, for alleles of MDM2-SNP309. Among the 77 patients with p53 wild-type tumors, the median age at colorectal cancer diagnosis was 71.5 years for patients with the T/T genotype and 61.0 years for patients with SNP309 (T/G or G/G genotype) (estimated difference between medians [Hodges-Lehmann method] = 8.0 years, 95% confidence interval = 1.0 to 16.0 years; P = .03 [two-sided Wilcoxon rank sum test]). Our data indicate that MDM2-SNP309 is a modifier of the age at colorectal cancer onset for patients whose tumors have a wild-type p53 gene.     

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.     

Combined effects of single nucleotide polymorphisms TP53 R72P and MDM2 SNP309, and p53 expression on survival of breast cancer patients

Introduction

Somatic inactivation of the TP53 gene in breast tumors is a marker for poor outcome, and breast cancer outcome might also be affected by germ-line variation in the TP53 gene or its regulators. We investigated the effects of the germ-line single nucleotide polymorphisms TP53 R72P (215G>C) and MDM2 SNP309 (-410T>G), and p53 protein expression in breast tumors on survival.

Methods

We pooled data from four breast cancer cohorts within the Breast Cancer Association Consortium for which both TP53 R72P and MDM2 SNP309 were genotyped and follow-up was available (n = 3,749). Overall and breast cancer-specific survival analyses were performed using Kaplan-Meier analysis and multivariate Cox's proportional hazards regression models.

Results

Survival of patients did not differ by carriership of either germ-line variant, R72P (215G>C) or SNP309 (-410G>T) alone. Immunohistochemical p53 staining of the tumor was available for two cohorts (n = 1,109 patients). Survival was worse in patients with p53-positive tumors (n = 301) compared to patients with p53-negative tumors (n = 808); breast cancer-specific survival: HR 1.6 (95% CI 1.2 to 2.1), P = 0.001. Within the patient group with p53-negative tumors, TP53 rare homozygous (CC) carriers had a worse survival than G-allele (GG/GC) carriers; actuarial breast cancer-specific survival 71% versus 80%, P = 0.07; HR 1.8 (1.1 to 3.1), P = 0.03. We also found a differential effect of combinations of the two germ-line variants on overall survival; homozygous carriers of the G-allele in MDM2 had worse survival only within the group of TP53 C-allele carriers; actuarial overall survival (GG versus TT/TG) 64% versus 75%, P = 0.001; HR (GG versus TT) 1.5 (1.1 to 2.0), P = 0.01. We found no evidence for a differential effect of MDM2 SNP309 by p53 protein expression on survival.

Conclusions

The TP53 R72P variant may be an independent predictor for survival of patients with p53-negative tumors. The combined effect of TP53 R72P and MDM2 SNP309 on survival is in line with our a priori biologically-supported hypothesis, that is, the role of enhanced DNA repair function of the TP53 Pro-variant, combined with increased expression of the Mdm2 protein, and thus overall attenuation of the p53 pathway in the tumor cells.     

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.     

Clinical implications of the MDM2 SNP309 and p53 Arg72Pro polymorphisms in transitional cell carcinoma of the bladder

Recent studies have shown that functional polymorphisms at the MDM2 SNP309 T/G and p53 Arg72Pro may be associated with cancer susceptibility. However, the role of these polymorphisms on the risk of transitional cell carcinoma of the bladder (TCCB) and clinical outcome remains unknown. SNP309 and p53 Arg72Pro polymorphisms were genotyped in 227 patients and 266 control subjects. The association between each polymorphism, TCCB risk and clinical outcome was evaluated by using a logistic regression model, a Kaplan-Meier curve with the log-rank test, or a Cox proportional hazard model. No significant associations between the polymorphisms and TCCB risk were found. On the MDM2 SNP309, the TT patients with superficial TCCB tended to have a longer recurrence-free survival than the TG or GG patients after transurethral resection (P=0.074). On the p53 Arg72Pro, the Pro/Pro patients with superficial TCCB had a significantly lower risk for recurrence than the Arg/Pro or Arg/Arg patients [Hazard ratio (HR), 0.364; 95% confidence interval (CI), 0.14-0.93]. In contrast, the Pro/Pro patients following radical cystectomy showed a significantly poorer survival and a higher risk of disease-specific death than the Arg/Pro + Arg/Arg patients (HR, 2.76; 95% CI, 1.11-6.84). MDM2 SNP309 and p53 Arg72Pro polymorphisms might influence the clinical outcome of TCCB in a distinctive way between superficial TCCB and invasive TCCB. The results may reflect marked differences in the genetic background between superficial and an invasive type of TCCB.     

Risk of MDM2 SNP309 alone or in combination with the p53 codon 72 polymorphism in acute myeloid leukemia

A single nucleotide polymorphism (SNP) in the promoter of MDM2 gene, SNP309 T > G (a T–G exchange at nucleotide 309 in the first intron), can increase the expression level of MDM2, thereby causing an impairment of p53 tumor suppressor activity. A G–C exchange at p53 codon 72 polymorphism results in a substitution of proline (Pro) for arginine (Arg) in the transactivation domain, which was shown to alter the primary structure of the p53 protein. Both polymorphisms have been implicated in cancer. To investigate whether that MDM2 SNP309 and p53 codon 72 polymorphism should be at least partially responsible for genetic susceptibility to acute myeloid leukemia (AML), both polymorphisms were determined in a case–control study consisting of 231 AML patients and 128 normal individuals. The MDM2 SNP309G allele was associated with increased risk of AML. Furthermore, the p53 codon 72 and MDM2 SNP309 polymorphisms did not associate with age of onset and any other clinical parameters studied. When the p53 and MDM2 polymorphisms were combined, no multiplicative joint effect between the MDM2 GG and p53 Pro/Pro genotypes exists in the risk of developing AML. These results suggest that the MDM2 SNP309 homozygous GG genotype may be a genetic susceptibility factor in the pathogenesis of AML.     

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.     

The MDM2 285G–309G haplotype is associated with an earlier age of tumour onset in patients with Li-Fraumeni syndrome

In the Li-Fraumeni syndrome (LFS) resulting from germline TP53 mutations, the MDM2 SNP309G allele has been shown to be associated with an earlier age of tumour onset, however the significance of this association is controversial. The 285C variation, also located in the MDM2 promoter, has been shown to reduce the strength of Sp1 binding to MDM2 promoter, antagonizing the effect of the 309G variation. In this study, we investigated the interaction of the MDM2 SNP285 and 309 in a large series of 195 LFS patients. Although we observed a lower mean age of tumour onset in patients with MDM2 SNP309 T/G or G/G genotype (23.1 years) than in patients with T/T genotype (27.3 years), the difference was not statistically significant. In contrast, patients with the 285–309 G–G haplotype develop tumours 5 years earlier than patients harbouring other haplotypes (p = 0.044). This result shows that the MDM2 285–309 G–G is a higher risk haplotype in patients with germline TP53 mutations. This study confirms that the MDM2 309G variation is deleterious when its effect is not neutralized by the 285C variation and illustrates the interfering effects of SNPs located within a gene acting as modifier factor in a Mendelian disease.     

The loss of mdm2 induces p53-mediated apoptosis

The p53 tumor suppressor gene product is negatively regulated by the product of its downstream target, mdm2. The deletion of mdm2 in the mouse results in embryonic lethality at 5.5 days post coitum (d.p.c.) which can be overcome by simultaneous loss of the p53 tumor suppressor, substantiating the importance of the negative regulatory function of MDM2 on p53 function in vivo. Hence, the loss of MDM2 allowed the unregulated p53 protein to continuously exert its growth-suppressing activity, which either led to a complete G1 arrest or induced the p53-dependent apoptotic pathway, resulting in the death of the mdm2-/- embryos. To determine which of these possibilities is occurring, mouse embryo fibroblasts (MEFs) from p53 null and p53/mdm2 double null embryos were transfected with a retroviral vector carrying a temperature-sensitive p53 (tsp53) cDNA. Shifting of single-cell clonal populations to the permissive temperature caused the p53-/-mdm2-/- fibroblasts expressing tsp53 to undergo apoptosis in a dose-dependent manner. This phenotype was not observed in the tsp53 expressing p53-/- clones nor the parental cell lines. Thus, our data indicate that the simple loss of mdm2 can induce the p53-dependent apoptotic pathway in vivo.     

p53 signaling pathway polymorphisms,cancer risk and tumor phenotype in <Emphasis Type="Italic">TP53</Emphasis> R337H mutation carriers

Li-Fraumeni and Li-Fraumeni-like syndrome (LFS/LFL) are clinically heterogeneous cancer predisposition syndromes characterized by diagnosis of early-onset and often multiple cancers with variable tumor patterns and incomplete penetrance. To date, the genetic modifiers described in LFS/LFL have been shown to map to either TP53 or its main negative regulator, MDM2. Additionally, all studies were focused on families with different TP53 germline mutations. Hence, in this study we explored the effect of the most studied polymorphisms of p53 pathway genes on clinical manifestations of individuals carrying the founder TP53 mutation R337H (n?=?136) and controls (n?=?186). Cancer-affected carriers had been diagnosed either with adrenocortical carcinoma (ACC, n?=?29) or breast cancer (BC, n?=?43). Allelic discrimation using TaqMan assay was used for genotyping MDM2 SNP 309 (rs2279744) as well as MDM4 (rs1563828) and USP7 (rs1529916) polymorphisms. We found significantly higher MDM2 SNP 309 GG genotype and G allele frequencies in the LFS cohort than in controls. Furthermore, median age at first diagnosis was earlier in MDM2 SNP309 GG carriers when compared to other genotypes for both cancers (ACC: age 1 vs. 2 years; BC: age 35 vs. 43 years, respectively), although not statistically different. The allelic and genotypic frequencies for all SNPs did not differ between cancer affected and unaffected carriers, neither between patients with ACC or BC. In conclusion, our results suggest that MDM2 SNP 309 may contribute to the LFL phenotype and also to an earlier age at diagnosis of ACC and BC cancer in carriers of the R337H founder mutation.     

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.