Lack of association between the MDM2 promoter polymorphism SNP309 and clinical outcome in chronic lymphocytic leukemia

p53 p.Pro72Arg (rs1042522) and Mouse Double Minute 2 (MDM2) Single-Nucleotide Polymorphism (SNP) 309 Variants and Their Interaction in Chronic Lymphocytic Leukemia(CLL): A Survey in CLL Patients from Western Iran

Background: Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. The MDM2 and p53 are interacting proteins that play crucial roles in cell biology. Genetic variations of p53 and MDM2 have been identified in many cancers including CLL; among which are SNP309 in the promoter of MDM2 and SNP codon72 in p53. Materials and Methods: In this study, we sought to find the impact of two SNPs of p53 and MDM2 in the pathogenesis of CLL. A total of 100 CLL patients and 102 healthy controls were recruited. Genomic DNA was extracted, and genotyping was performed using the PCR-RFLP method. The allele and genotype associations were analyzed using the χ2 test. The gene-gene interaction analysis was studied using GMDR v0.9. Results: Our study found the absence of a significant difference between CLL patients and controls related to the allelic frequencies or genotypic distributions for both MDM2 SNP309 and p53 codon72. A significantly higher frequency of p53 C allele was found in patients with disease duration of more than 36 compared to those less than 36 months. However, GMDR analysis suggests genetic interaction between the genes under study. Conclusion: Our findings indicated each polymorphism of p53 codon72 and MDM2 (SNP309) was not a risk factor for CLL but the p53 C allele could be associated with the disease duration. Besides, the interaction between p53/MDM2 genotypes may confer susceptibility to CLL. Our study could be useful in genetic association studies of CLL and the role of gene-gene interactions in the susceptibility to the disease.

Association of the MDM2 SNP285 and SNP309 Genetic Variants with the Risk, Age at Onset and Prognosis of Breast Cancer in Central European Women: A Hospital-Based Case-Control Study

SNP309T>G (rs2279744) and SNP285G>C (rs117039649) in the MDM2 promoter are thought to have opposite effects on the binding of transcription factor SP1 (specificity protein 1), and consequently on MDM2 expression, p53 levels, cancer risk, age at onset, and prognosis. Here, we genotyped SNP309 and SNP285 in 406 Austrian breast cancer patients and 254 female controls. The SNP309GG genotype was associated with an increased breast cancer risk in p53 negative (OR, 1.82; 95% CI, 1.09–3.03; p = 0.02), but not p53 positive or unselected patients. In contrast, the SNP309TT genotype was associated with an earlier age at onset (TT, 57.0 ± 12.9; TG, 58.6 ± 13.9; GG, 59.7 ± 15.0 years; p = 0.048). 31% of SNP309TT, 26% of TG, and 13% of GG tumors were p53 positive (p = 0.034), indicating a lower selective pressure to mutate TP53 in the presence of the G-allele. Moreover, SNP309TT patients exhibited a shortened metastasis-free survival in multivariable analysis. Censoring carriers of the SNP285C-allele hardly altered the strength of these associations of SNP309, thus challenging the proposed antagonistic function of SNP285C towards SNP309G. The minor SNP285C-allele tended to be non-significantly associated with an increased breast cancer risk and a poor disease-free and metastasis-free survival, which may be bystander effects of its complete linkage disequilibrium with SNP309G. We conclude that the SNP309G-allele attenuates the p53-response and leads to a higher breast cancer risk, but also to a later onset of breast cancer and a trend towards a good prognosis.

MDM2 promotor polymorphism and disease characteristics in chronic lymphocytic leukemia: results of an individual patient data-based meta-analysis

A number of single nucleotide polymorphisms have been associated with disease predisposition in chronic lymphocytic leukemia. A single nucleotide polymorphism in the MDM2 promotor region, MDM2SNP309, was shown to soothe the p53 pathway. In the current study, we aimed to clarify the effect of the MDM2SNP309 on chronic lymphocytic leukemia characteristics and outcome. We performed a meta-analysis of data from 2598 individual patients from 10 different cohorts. Patients' data and genetic analysis for MDM2SNP309 genotype, immunoglobulin heavy chain variable region mutation status and fluorescence in situ hybridization results were collected. There were no differences in overall survival based on the polymorphism (log rank test, stratified by study cohort; P=0.76; GG genotype: cohort-adjusted median overall survival of 151 months; TG: 153 months; TT: 149 months). In a multivariable Cox proportional hazards regression analysis, advanced age, male sex and unmutated immunoglobulin heavy chain variable region genes were associated with inferior survival, but not the MDM2 genotype. The MDM2SNP309 is unlikely to influence disease characteristics and prognosis in chronic lymphocytic leukemia. Studies investigating the impact of individual single nucleotide polymorphisms on prognosis are often controversial. This may be due to selection bias and small sample size. A meta-analysis based on individual patient data provides a reasonable strategy for prognostic factor analyses in the case of small individual studies. Individual patient data-based meta-analysis can, therefore, be a powerful tool to assess genetic risk factors in the absence of large studies.

Lack of association between MDM2 promoter SNP309 and clinical outcome in patients with neuroblastoma

While a polymorphism located within the promoter region of the MDM2 proto-oncogene, SNP309 (T > G), has previously been associated with increased risk and aggressiveness of neuroblastoma and other tumor entities, a protective effect has also been reported in certain other cancers. In this study, we evaluated the association of MDM2 SNP309 with outcome in 496 patients with neuroblastoma and its effect on MDM2 expression. No significant difference in overall or event-free survival was observed among patients with neuroblastoma with or without MDM2 SNP309. The presence of SNP309 does not affect MDM2 expression in neuroblastoma.

MDM2 promoter polymorphism and p53 codon 72 polymorphism in chronic myeloid leukemia: the association between MDM2 promoter genotype and disease susceptibility, age of onset, and blast-free survival in chronic phase patients receiving imatinib

The genetic or functional inactivation of the p53 pathway plays an important role with regards to disease progression from the chronic phase (CP) to blast phase (BP) and imatinib treatment response in chronic myeloid leukemia (CML). Two functional single nucleotide polymorphisms (SNPs), p53 R72P and MDM2 SNP309, are associated with alternation of p53 activity, however the association regarding CML susceptibility and BP transformation under imatinib treatment is unclear. The MDM2 SNP309 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism and confirmed by direct sequencing from 116 CML patients, including 104 in the CP at diagnosis, and 162 healthy Taiwanese controls. The p53 R72P polymorphism was examined in all CML patients. The SNP309 G/G genotype was associated with an increased risk of CML susceptibility (OR: 1.82, 95% CI: 1.03-3.22, P = 0.037), and an earlier age of disease onset (log-rank P = 0.005) compared with the T/T + T/G genotypes. Higher MDM2 mRNA expression was found in G/G genotype compared with T/T (P = 0.034) and T/T + T/G (P = 0.056) genotypes. No associations were found between the p53 R72P genotypes and clinical parameters and survival outcomes. Among 62 CP patients receiving imatinib as first-line therapy, the G/G genotype was associated with a shorter blast-free survival (log-rank P = 0.048) and more clonal evolution compared with the T/T + T/G genotypes. In patients with advanced diseases at diagnosis, the G/G genotype was associated with a poor overall survival (log-rank P = 0.006). Closely monitoring CML patients harboring the G/G genotype and further large-scale studies are warranted.

MDM2 SNP309 variation contributes to leukemia risk: meta-analyses based on 7259 subjects

Evidence implicates MDM2 (murine double minute-2) T309G polymorphism as a risk factor for several cancers. Increasing numbers of studies have been carried out on the association of MDM2 T309G polymorphism with susceptibility to leukemia and have generated conflicting results. The aim of the present study was to derive a more precise estimation of the relationship. Meta-analyses assessing the association of MDM2 T309G variation with leukemia were conducted. Separate analyses on ethnicity and clinical types were also performed. Eligible studies were identified for the period up to February 2012. Consequently, seven publications including eight case-control studies with 1777 cases and 5482 controls were selected for analysis. The overall data indicated a significant association of the MDM2 T309G polymorphism with leukemia risk (GG vs. TT: odds ratio [OR] = 1.62; 95% confidence interval [CI] = 1.14-2.29; dominant model: OR = 1.20; 95% CI = 1.06-1.36; recessive model: OR = 1.47; 95% CI = 1.07-2.03). In subgroup analysis by ethnicity, the G allele may increase leukemia susceptibility among Asians (GG vs. TT: OR = 3.06; 95% CI = 2.05-4.56; dominant model: OR = 1.82; 95% CI = 1.31-2.51; recessive model: OR = 2.32; 95% CI = 1.69-3.19) but not Caucasians. In subgroup analysis by clinical types, data suggested increased risk for acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) under additive and recessive models, respectively. Similarly, elevated risk for chronic lymphocytic leukemia (CLL) was shown under the dominant model. Collectively, the results of the present study suggest that MDM2 T309G polymorphism might be a low-penetrant risk factor for leukemia among Asians but not Caucasians. The G allele might increase CLL susceptibility and homozygous GG might elevate AML and CML risk.

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.

Prognostic impact of the MDM2SNP309 allele in leukemia and lymphoma

A T-to-G germline single nucleotide polymorphism in the promoter region of MDM2 (SNP309) has been reported to markedly accelerate tumor formation in humans suggesting that it may represent a powerful cancer predisposing allele. Since its first description in 2004, a large number of retrospective analyses involving a wide variety of human malignancies have been reported, showing conflicting results regarding the impact of Mdm2SNP309 status on cancer risk and response to cancer therapy. Here, we appraise the available information on the effect of Mdm2SNP309 in lymphoma and leukemia and discuss the factors that likely account for the conflicting results observed in the studies reported to date.

MDM2 SNP309 promoter polymorphism, an independent prognostic factor in chronic lymphocytic leukemia

BACKGROUND

The single nucleotide polymorphism SNP309 with a change from T to G in the promoter region of the MDM2 gene is shown to increase the MDM2 protein levels and attenuate the p53 levels and associates with disease progression in several tumors.

OBJECTIVE

In this study, the role of the polymorphism was investigated with regard to the clinical outcome in B-cell chronic lymphocytic leukemia (B-CLL).

PATIENTS

A total of 210 patients with B-CLL were followed for up to 19 yr.

RESULTS

The overall survival (OS) of patients with at least one G-allele was significantly shorter when compared with those with two T-alleles (P = 0.024) with a more pronounced difference in patients below the median age. Age at onset of B-CLL was similar irrespective of MDM2 status. The presence of a G-allele in combination with TP53 mutations or unmutated IgVH gene status resulted in an additive risk of death.

CONCLUSION

In this report, with a high proportion of B-CLL patients with an advanced Binet stage and with an unmutated IgVH gene, MDM2 SNP309 was found to be independently associated with OS. The survival difference was more pronounced in younger patients.