Association of breast cancer outcome with status of p53 and MDM2 SNP309

Meta-analysis of associations between the MDM2-T309G polymorphism and prostate cancer risk

The mouse double minute 2 (MDM2) gene plays a key role in the p53 pathway, and the SNP 309T/G single- nucleotide polymorphism in the promoter region of MDM2 has been shown to be associated with increased risk of cancer. However, no consistent results were found concerning the relationships between the polymorphism and prostate cancer risk. This meta-analysis, covering 4 independent case-control studies, was conducted to better understand the association between MDM2-SNP T309G and prostate cancer risk focusing on overall and subgroup aspects. The analysis revealed, no matter what kind of genetic model was used, no significant association between MDM2-SNP T309G and prostate cancer risk in overall analysis (GT/TT: OR = 0.84, 95%CI = 0.60-1.19; GG/TT: OR = 0.69, 95%CI = 0.43-1.11; dominant model: OR = 0.81, 95%CI= 0.58-1.13; recessive model: OR = 1.23, 95%CI = 0.95-1.59). In subgroup analysis, the polymorphism seemed more likely to be a protective factor in Europeans (GG/TT: OR = 0.52, 95%CI = 0.31-0.87; recessive model: OR = 0.58, 95%CI = 0.36-0.95) than in Asian populations, and a protective effect of the polymorphism was also seen in hospital-based studies in all models (GT/TT: OR = 0.74, 95%CI = 0.57-0.97; GG/TT: OR = 0.55, 95%CI = 0.38-0.79; dominant model: OR = 0.69, 95%CI = 0.54-0.89; recessive model: OR = 0.70, 95%CI = 0.51-0.97). However, more primary studies with a larger number of samples are required to confirm our findings.

Assessing SNP-SNP interactions among DNA repair, modification and metabolism related pathway genes in breast cancer susceptibility

Genome-wide association studies (GWASs) have identified low-penetrance common variants (i.e., single nucleotide polymorphisms, SNPs) associated with breast cancer susceptibility. Although GWASs are primarily focused on single-locus effects, gene-gene interactions (i.e., epistasis) are also assumed to contribute to the genetic risks for complex diseases including breast cancer. While it has been hypothesized that moderately ranked (P value based) weak single-locus effects in GWASs could potentially harbor valuable information for evaluating epistasis, we lack systematic efforts to investigate SNPs showing consistent associations with weak statistical significance across independent discovery and replication stages. The objectives of this study were i) to select SNPs showing single-locus effects with weak statistical significance for breast cancer in a GWAS and/or candidate-gene studies; ii) to replicate these SNPs in an independent set of breast cancer cases and controls; and iii) to explore their potential SNP-SNP interactions contributing to breast cancer susceptibility. A total of 17 SNPs related to DNA repair, modification and metabolism pathway genes were selected since these pathways offer a priori knowledge for potential epistatic interactions and an overall role in breast carcinogenesis. The study design included predominantly Caucasian women (2,795 cases and 4,505 controls) from Alberta, Canada. We observed two two-way SNP-SNP interactions (APEX1-rs1130409 and RPAP1-rs2297381; MLH1-rs1799977 and MDM2-rs769412) in logistic regression that conferred elevated risks for breast cancer (P_interaction<7.3×10⁻³). Logic regression identified an interaction involving four SNPs (MBD2-rs4041245, MLH1-rs1799977, MDM2-rs769412, BRCA2-rs1799943) (P_permutation = 2.4×10⁻³). SNPs involved in SNP-SNP interactions also showed single-locus effects with weak statistical significance, while BRCA2-rs1799943 showed stronger statistical significance (P_{correlation/trend} = 3.2×10⁻⁴) than the others. These single-locus effects were independent of body mass index. Our results provide a framework for evaluating SNPs showing statistically weak but reproducible single-locus effects for epistatic effects contributing to disease susceptibility.

Germline variation in TP53 regulatory network genes associates with breast cancer survival and treatment outcome

Germline variation in the TP53 network genes PRKAG2, PPP2R2B, CCNG1, PIAS1 and YWHAQ was previously suggested to have an impact on drug response in vitro. Here, we investigated the effect on breast cancer survival of germline variation in these genes in 925 Finnish breast cancer patients and further analyzed five single nucleotide polymorphisms (SNPs) in PRKAG2 (rs1029946, rs4726050, rs6464153, rs7789699) and PPP2R2B (rs10477313) for 10-year survival in breast cancer patients, interaction with TP53 R72P and MDM2-SNP309, outcome after specific adjuvant therapy and correlation to tumor characteristics in 4,701 invasive cases from four data sets. We found evidence for carriers of PRKAG2-rs1029946 and PRKAG2-rs4726050 having improved survival in the pooled data (HR 0.53, 95% CI 0.3-0.9; p = 0.023 for homozygous carriers of the rare G-allele and HR 0.85, 95% CI 0.7-0.9; p = 0.049 for carriers of the rare G allele, respectively). PRKAG2-rs4726050 showed a significant interaction with MDM2-SNP309, with PRKAG2-rs4726050 rare G-allele having a dose-dependent effect for better breast cancer survival confined only to MDM2 SNP309 rare G-allele carriers (HR 0.45, 95% CI 0.2-0.7; p = 0.001). This interaction also emerged as an independent predictor of better survival (p = 0.047). PPP2R2B-rs10477313 rare A-allele was found to predict better survival (HR 0.82, 95% CI 0.6-0.9; p = 0.018), especially after hormonal therapy (HR 0.66, 95% CI 0.5-0.9; p = 0.048). These findings warrant further studies and suggest that genetic markers in TP53 network genes such as PRKAG2 and PPP2R2B might affect prognosis and treatment outcome in breast cancer patients.

Fine mapping of breast cancer genome-wide association studies loci in women of African ancestry identifies novel susceptibility markers

Numerous single nucleotide polymorphisms (SNPs) associated with breast cancer susceptibility have been identified by genome-wide association studies (GWAS). However, these SNPs were primarily discovered and validated in women of European and Asian ancestry. Because linkage disequilibrium is ancestry-dependent and heterogeneous among racial/ethnic populations, we evaluated common genetic variants at 22 GWAS-identified breast cancer susceptibility loci in a pooled sample of 1502 breast cancer cases and 1378 controls of African ancestry. None of the 22 GWAS index SNPs could be validated, challenging the direct generalizability of breast cancer risk variants identified in Caucasians or Asians to other populations. Novel breast cancer risk variants for women of African ancestry were identified in regions including 5p12 (odds ratio [OR] = 1.40, 95% confidence interval [CI] = 1.11-1.76; P = 0.004), 5q11.2 (OR = 1.22, 95% CI = 1.09-1.36; P = 0.00053) and 10p15.1 (OR = 1.22, 95% CI = 1.08-1.38; P = 0.0015). We also found positive association signals in three regions (6q25.1, 10q26.13 and 16q12.1-q12.2) previously confirmed by fine mapping in women of African ancestry. In addition, polygenic model indicated that eight best markers in this study, compared with 22 GWAS-identified SNPs, could better predict breast cancer risk in women of African ancestry (per-allele OR = 1.21, 95% CI = 1.16-1.27; P = 9.7 × 10(-16)). Our results demonstrate that fine mapping is a powerful approach to better characterize the breast cancer risk alleles in diverse populations. Future studies and new GWAS in women of African ancestry hold promise to discover additional variants for breast cancer susceptibility with clinical implications throughout the African diaspora.

Household income is associated with the p53 mutation frequency in human breast tumors

BACKGROUND

A study from Scotland reported that the p53 mutation frequency in breast tumors is associated with socio-economic deprivation.

METHODS

We analyzed the association of the tumor p53 mutational status with tumor characteristics, education, and self-reported annual household income (HI) among 173 breast cancer patients from the greater Baltimore area, United States.

RESULTS

p53 mutational frequency was significantly associated with HI. Patients with < $15,000 HI had the highest p53 mutation frequency (21%), followed by the income group between $15,000 and $60,000 (18%), while those above $60,000 HI had the fewest mutations (5%). When dichotomized at $60,000, 26 out of 135 patients in the low income category had acquired a p53 mutation, while only 2 out of 38 with a high income carried a mutation (P < 0.05). In the adjusted logistic regression analysis with 3 income categories (trend test), the association between HI and p53 mutational status was independent of tumor characteristics, age, race/ethnicity, tobacco smoking and body mass. Further analyses revealed that HI may impact the p53 mutational frequency preferentially in patients who develop an estrogen receptor (ER)-negative disease. Within this group, 42% of the low income patients (< $15,000 HI) carried a mutation, followed by the middle income group (21%), while those above $60,000 HI did not carry mutations (Ptrend < 0.05).

CONCLUSIONS

HI is associated with the p53 mutational frequency in patients who develop an ER-negative disease. Furthermore, high income patients may acquire fewer p53 mutations than other patients, suggesting that lifetime exposures associated with socio-economic status may impact breast cancer biology.

MDM2 SNP309 promoter polymorphism and p53 mutations in urinary bladder carcinoma stage T1

Background

Urinary bladder carcinoma stage T1 is an unpredictable disease that in some cases has a good prognosis with only local or no recurrence, but in others can appear as a more aggressive tumor with progression to more advanced stages. The aim here was to investigate stage T1 tumors regarding MDM2 promoter SNP309 polymorphism, mutations in the p53 gene, and expression of p53 and p16 measured by immunohistochemistry, and subsequently relate these changes to tumor recurrence and progression. We examined a cohort of patients with primary stage T1 urothelial carcinoma of the bladder and their tumors.

Methods

After re-evaluation of the original slides and exclusions, the study population comprised 141 patients, all with primary stage T1 urothelial carcinoma of the bladder. The hospital records were screened for clinical parameters and information concerning presence of histologically proven recurrence and progression. The paraffin-embedded tumor material was evaluated by immunohistochemistry. Any mutations found in the p53 gene were studied by single-strand conformation analysis and Sanger sequencing. The MDM2 SNP309 polymorphism was investigated by pyrosequencing. Multivariate analyses concerning association with prognosis were performed, and Kaplan-Meier analysis was conducted for a combination of changes and time to progression.

Results

Of the 141 patients, 82 had at least one MDM2 SNP309 G allele, and 53 had a mutation in the p53 gene, but neither of those anomalies was associated with a worse prognosis. A mutation in the p53 gene was associated with immunohistochemically visualized p53 protein expression at a cut-off value of 50%. In the group with p53 mutation Kaplan-Meier analysis showed higher rate of progression and shorter time to progression in patients with immunohistochemically abnormal p16 expression compared to them with normal p16 expression (p = 0.038).

Conclusions

MDM2 SNP309 promoter polymorphism and mutations in p53 were not associated with worse prognosis in this cohort of patients with primary stage T1 urinary bladder carcinoma. However, patients with abnormal p16 expression and a mutated p53 gene had a higher rate of and a shorter time to progression, and p53 gene mutation was associated with an abnormal immunohistochemistry for p53 at a cut-off of 50%.

Analysis of indoleamine 2-3 dioxygenase (IDO1) expression in breast cancer tissue by immunohistochemistry

INTRODUCTION

The immunosuppressive enzyme, indoleamine 2,3 dioxygenase (IDO), is overexpressed in many different tumor types including breast cancer. IDO inhibitors synergize with chemotherapy in breast cancer murine models. Characterizing IDO expression in breast cancer could define which patients receive IDO inhibitors. This study analyzed IDO protein expression in 203 breast cancer cases. The relationship between IDO, overall survival (OS), disease-specific survival (DSS), clinicopathologic, molecular, and immune tumor infiltrate factors was evaluated.

METHODS

Expression of IDO, estrogen receptor (ER), progesterone receptor (PR), human epithelial receptor 2, cytokeratin 5/6, epithelial growth factor receptor, phosphorylated AKT, neoangiogenesis, nitrogen oxide synthetase 2 (NOS2), cyclooxygenase 2 (COX2), FoxP3, CD8, and CD11b on archival breast cancer tissue sections was evaluated by immunohistochemistry. Associations between IDO and these markers were explored by a univariate and multivariate analysis. Survival was analyzed using Kaplan-Meier (OS) and Wilcoxon two-sample (DSS) tests.

RESULTS

IDO expression was higher in ER+ tumors compared to ER- tumors. IDO was lower in those with higher neoangiogenesis. OS was better in ER+ patients with high IDO expression. DSS was better in node-positive patients with high IDO expression. IDO activity positively correlates with NOS2. COX2 as positively correlated with IDO on univariate but not multivariate analysis. There was a trend toward greater numbers of CD11b+ cells in IDO-low tumors.

CONCLUSIONS

IDO protein expression is lower in ER- breast tumors with greater neoangiogenesis. Future clinical trials evaluating the synergy between IDO inhibitors and chemotherapy should take this finding into account and stratify for ER status in the trial design.

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.

MDM2 SNP285 does not antagonize the effect of SNP309 in lung cancer

Conflicting reports exist regarding the contribution of SNP309 in MDM2 to cancer risk. Recently, SNP285 was shown to act as an antagonist to SNP309 by overriding the effect of SNP309 on SP1-mediated transcription. Moreover, SNP285 modified the relationship between SNP309 and risk of breast, ovarian and endometrial cancer. We assessed whether SNP285 confounded the effect of SNP309 in lung cancer in a cohort of 720 controls and 556 cases. Our cohort included both Caucasians and African Americans. Neither SNP309 nor SNP285 was associated with lung cancer risk or survival. In addition, removal of individuals who carried the variant C allele of SNP285 did not modify the association between SNP309 with either lung cancer risk or survival. Although an effect of SNP285 has been demonstrated in breast, ovarian and endometrial cancer, our findings do not support a role for this SNP in lung cancer and raise the possibility that the effect of SNP285 is restricted to cancers in women.

Effect of the MDM2 promoter polymorphisms SNP309T>G and SNP285G>C on the risk of ovarian cancer in BRCA1 mutation carriers

Background

While BRCA mutation carriers possess a 20-40% lifetime risk of developing ovarian cancer, knowledge about genetic modifying factors influencing the phenotypic expression remains obscure. We explored the distribution of the MDM2 polymorphisms SNP309T>G and the recently discovered SNP285G>C in Norwegian patients with BRCA related ovarian cancer.

Methods

221 BRCA related ovarian cancer cases (BRCA1; n = 161 and BRCA2; n = 60) were tested for the MDM2 polymorphisms. Results were compared to healthy controls (n = 2,465).

Results

The SNP309G allele was associated with elevated OR for ovarian cancer in BRCA1 mutation carriers (SNP309TG: OR 1.53; CI 1.07-2.19; p = 0.020; SNP309GG: OR 1.92; CI 1.19-3.10; p = 0.009; SNP309TG+GG combined: OR 1.61; CI 1.15-2.27; p = 0.005). In contrast, the SNP285C allele reduced risk of BRCA1 related ovarian cancer in carriers of the SNP309G allele (OR 0.50; CI 0.24-1.04; p = 0.057). Censoring individuals carrying the SNP285C/309G haplotype from the analysis elevated the OR related to the SNP309G allele (OR 1.73; CI 1.23-2.45; p = 0.002). The mean age at disease onset was 3.1 years earlier in carriers of SNP309TG+GG as compared to carriers of SNP309TT (p = 0.068). No such associations were found in BRCA2 related ovarian cancer.

Conclusions

Our results indicate the SNP309G allele to increase and the SNP285C allele to reduce the risk of BRCA1 related ovarian cancer. If confirmed in independent studies, this finding may have implications to counseling and decision-making regarding risk reducing measures in BRCA1 mutation carriers.

Macrophages, nitric oxide and microRNAs are associated with DNA damage response pathway and senescence in inflammatory bowel disease

BACKGROUND

Cellular senescence can be a functional barrier to carcinogenesis. We hypothesized that inflammation modulates carcinogenesis through senescence and DNA damage response (DDR). We examined the association between senescence and DDR with macrophage levels in inflammatory bowel disease (IBD). In vitro experiments tested the ability of macrophages to induce senescence in primary cells. Inflammation modulating microRNAs were identified in senescence colon tissue for further investigation.

METHODOLOGY/PRINCIPAL FINDINGS

Quantitative immunohistochemistry identified protein expression by colon cell type. Increased cellular senescence (HP1γ; P = 0.01) or DDR (γH2A.X; P = 0.031, phospho-Chk2, P = 0.014) was associated with high macrophage infiltration in UC. Co-culture with macrophages (ANA-1) induced senescence in >80% of primary cells (fibroblasts MRC5, WI38), illustrating that macrophages induce senescence. Interestingly, macrophage-induced senescence was partly dependent on nitric oxide synthase, and clinically relevant NO• levels alone induced senescence. NO• induced DDR in vitro, as detected by immunofluorescence. In contrast to UC, we noted in Crohn's disease (CD) that senescence (HP1γ; P<0.001) and DDR (γH2A.X; P<0.05, phospho-Chk2; P<0.001) were higher, and macrophages were not associated with senescence. We hypothesize that nitric oxide may modulate senescence in CD; epithelial cells of CD had higher levels of NOS2 expression than in UC (P = 0.001). Microarrays and quantitative-PCR identified miR-21 expression associated with macrophage infiltration and NOS2 expression.

CONCLUSIONS

Senescence was observed in IBD with senescence-associated β-galactosidase and HP1γ. Macrophages were associated with senescence and DDR in UC, and in vitro experiments with primary human cells showed that macrophages induce senescence, partly through NO•, and that NO• can induce DDR associated with senescence. Future experiments will investigate the role of NO• and miR-21 in senescence. This is the first study to implicate macrophages and nitrosative stress in a direct effect on senescence and DDR, which is relevant to many diseases of inflammation, cancer, and aging.

Murine double minute clone 2,309T/G and 285G/C promoter single nucleotide polymorphism as a risk factor for breast cancer: a Polish experience

BACKGROUND

Breast cancer is a multifactorial disease caused by complex interactions between genetic and environmental factors. Recently, a functional polymorphism, MDM2 285G>C (rs117039649), has been discovered. This polymorphism antagonizes the effect of the 309T>G (rs2279744) polymorphism on the same gene, resulting in decreased MDM2 transcription.

METHODS

The MDM2 285G>C and 309T>G polymorphisms were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing analysis in women with breast cancer (n=468) and controls (n=550).

RESULTS

The odds ratio (OR) for breast cancer patients with the MDM2 285C/C and 285G/C genotypes was 0.4768 (95% confidence interval [CI] 0.2906-0.7824; p=0.0033, pcorr=0.0066). We also found a significantly lower frequency of the MDM2 285C allele in patients with breast cancer than in controls: the OR for the C allele in patients with breast cancer was 0.4930 (95% CI=0.3059-0.7947, p=0.0031, pcorr=0.0062). The p value of the chi-square test for the trend observed for the MDM2 285G>C polymorphism was statistically significant (ptrend=0.0036). The statistical power of this study amounted to 85% for the G/C or C/C genotypes and 85% for the C allele. However, we did not observe significant differences between the distribution of MDM2 309T>G genotypes and alleles in patients with breast cancer and healthy controls.

CONCLUSION

In a sample of the Polish population, we observed that the MDM2 285C gene variant may be a significant protective factor against breast cancer.

Genetic variants in TP53 and MDM2 associated with male infertility in Chinese population

The TP53, a transcriptional regulator and tumor suppressor, is functionally important in spermatogenesis. MDM2 is a key regulator of the p53 pathway and modulates p53 activity. Both proteins have been functionally linked to germ cell apoptosis, which may affect human infertility, but very little is known on how common polymorphisms in these genes may influence germ cell apoptosis and the risk of male infertility. Thus, this study was designed to test whether three previously described polymorphisms 72Arg>Pro (rs1042522) and the Ex2+19C>T (rs2287498) in TP53, and the 5' untranslated region (5' UTR) 309T>G (rs937283) in MDM2, are associated with idiopathic male infertility in a Chinese population. The three polymorphisms were genotyped using OpenArray assay in a hospital-based case-control study, including 580 infertile patients and 580 fertile controls. Our analyses revealed that TP53 Ex2+19C>T and MDM2 309T>G polymorphisms are associated with male infertility. Furthermore, we detected a nearly statistically significant additive interaction between TP53 rs2287498 and MDM2 rs937283 for the development of male infertility (P(interaction)=0.055). In summary, this study found preliminary evidence, demonstrating that genetic variants in genes of the TP53 pathway are risk factors for male infertility.

Individual and combined effects of MDM2 SNP309 and TP53 Arg72Pro on breast cancer risk: an updated meta-analysis

The tumor suppressor gene TP53 and its negative regulator murine double minute 2 are involved in multiple cellular pathways. Two potentially functional single nucleotide polymorphisms (SNPs) MDM2 SNP309 and TP53 R72P have been extensively investigated to be associated with breast cancer risk. However, the original studies as well as the subsequent meta-analysis, have yielded contradictory results for the individual effect of the two SNPs on breast cancer risk, plus that conflicting results also existed for the combined effects of MDM2 SNP309 and TP53 R72P on breast cancer risk. This meta-analysis aimed to clarify the individual and combined effects of these two genes on breast cancer risk. We performed a meta-analysis of publications with a total 9,563 cases and 9,468 controls concerning MDM2 SNP309 polymorphism and 19,748 cases and 19,962 controls concerning TP53 R72P. Odds ratios (ORs) with 95 % confidence intervals (CIs) were used to assess the strength of the association. In overall meta-analysis, individuals with the MDM2 SNP309TG genotype were associated with a borderline higher breast cancer risk than those with TT genotype (OR = 1.11, 95 % CI: 1.00-1.24, P (heterogeneity) = 0.007), whereas the TP53 R72P CC or GC genotype had no effects on breast cancer risk. In the stratified analyses, a significant association between MDM2 SNP309 and breast cancer risk were observed in Asian, but null significant association between TP53 R72P and breast cancer risk were found even in various subgroups. Moreover, no significant combined effects of MDM2 SNP309 and TP53 R72P were observed on breast cancer risk. The borderline association between MDM2 SNP309 and breast cancer risk in overall analysis should be treated with caution, and no significant combined effects for the two SNPs on breast cancer risk suggested functional investigations warranted to explore the molecular mechanism of the TP53-MDM2 circuit genes.

Evaluation of 19 susceptibility loci of breast cancer in women of African ancestry

Multiple breast cancer susceptibility loci have been identified in genome-wide association studies (GWAS) in populations of European and Asian ancestry using array chips optimized for populations of European ancestry. It is important to examine whether these loci are associated with breast cancer risk in women of African ancestry. We evaluated 25 single nucleotide polymorphisms (SNPs) at 19 loci in a pooled case-control study of breast cancer, which included 1509 cases and 1383 controls. Cases and controls were enrolled in Nigeria, Barbados and the USA; all women were of African ancestry. We found significant associations for three SNPs, which were in the same direction and of similar magnitude as those reported in previous fine-mapping studies in women of African ancestry. The allelic odds ratios were 1.24 [95% confidence interval (CI): 1.04-1.47; P = 0.018] for the rs2981578-G allele (10q26/FGFR2), 1.34 (95% CI: 1.10-1.63; P = 0.0035) for the rs9397435-G allele (6q25) and 1.12 (95% CI: 1.00-1.25; P = 0.04) for the rs3104793-C allele (16q12). Although a significant association was observed for an additional index SNP (rs3817198), it was in the opposite direction to prior GWAS studies. In conclusion, this study highlights the complexity of applying current GWAS findings across racial/ethnic groups, as none of GWAS-identified index SNPs could be replicated in women of African ancestry. Further fine-mapping studies in women of African ancestry will be needed to reveal additional and causal variants for breast cancer.

Clinical implication of p53 overexpression in breast cancer patients younger than 50 years with a triple-negative subtype who undergo a modified radical mastectomy

OBJECTIVE

The purpose of this study was to identify the clinicopathological characteristics and prognostic value of p53 overexpression in breast cancer patients treated with a modified radical mastectomy.

METHODS

The medical records of 197 patients who had undergone modified radical mastectomy between January 1991 and December 2008 were reviewed retrospectively. Breast cancer subtype and p53 overexpression were investigated using immunohistochemistry and/or fluorescent in situ hybridization analysis of surgical specimens.

RESULTS

The median follow-up after the modified radical mastectomy was 56.1 months (range, 14.7-232.7). The median age was 47 years (range, 31-72). p53 overexpression was noted in 73 patients (37.1%). Breast cancer-specific death rate (P = 0.011), cancer progression (P = 0.024), distant metastasis (P = 0.015), hormone receptor negativity (P < 0.001) and human epidermal growth factor receptor 2 positivity (P = 0.017) were detected more frequently in patients with p53 overexpression. The overall survival rates were significantly lower in the p53-overexpression group than in the non-p53-overexpression group (P = 0.021, log-rank test). In the multivariate analysis, p53 overexpression showed the strongest prognostic significance in patients aged <50 years (P = 0.039) and with the triple-negative subtype (P = 0.023).

CONCLUSIONS

p53 overexpression correlated with breast cancer-specific death rates and adverse prognostic factors in patients treated with modified radical mastectomy. p53 overexpression might be a more reliable prognosticator in patients aged <50 years and with the triple-negative subtype. More effective systemic treatments might be warranted for these patients exhibiting p53 overexpression. Further validation is required to make more definite conclusions.

Identification of the receptor tyrosine kinase AXL in breast cancer as a target for the human miR-34a microRNA

The identification of molecular features that contribute to the progression of breast cancer can provide valuable insight into the pathogenesis of this disease. Deregulated microRNA expression represents one type of molecular event that has been associated with many different human cancers. In order to identify a miRNA/mRNA regulatory interaction that is biologically relevant to the triple-negative breast cancer genotype/phenotype, we initially conducted a miRNA profiling experiment to detect differentially expressed miRNAs in cell line models representing triple-negative (MDA-MB-231), ER(+) (MCF7), and HER-2 overexpressed (SK-BR-3) histotypes. We identified human miR-34a expression as being >3-fold down (from its median expression value across all cell lines) in MDA-MB-231 cells, and identified AXL as a putative mRNA target using multiple miRNA/target prediction algorithms. The miR-34a/AXL interaction was functionally characterized through ectopic overexpression experiments with a miR-34a mimic in two independent triple-negative breast cancer cell lines. In reporter assays, miR-34a binds to its putative target site within the AXL 3'UTR to inhibit luciferase expression. We also observed degradation of AXL mRNA and decreased AXL protein levels, as well as cell signaling effects on AKT phosphorylation and phenotypic effects on cell migration. Finally, we present an inverse correlative trend in miR-34a and AXL expression for both cell line and patient tumor samples.

MDM2 SNP309 contributes to tumor susceptibility: a meta-analysis

The potentially functional polymorphism, SNP309, in the promoter region of MDM2 gene has been implicated in cancer risk, but individual published studies showed inconclusive results. To obtain a more precise estimate of the association between MDM2 SNP309 and risk of cancer, we performed a meta-analysis of 70 individual studies in 59 publications that included 26,160 cases with different types of tumors and 33,046 controls. Summary odds ratios (OR) and corresponding 95% confidence intervals (CIs) were estimated using fixed- and random-effects models when appropriate. Overall, the variant genotypes were associated with a significantly increased cancer risk for all cancer types in different genetic models (GG vs. TT: OR, 1.123; 95% CI, 1.056-1.193; GG/GT vs. TT: OR, 1.028; 95% CI, 1.006-1.050). In the stratified analyses, the increased risk remained for the studies of most types of cancers, Asian populations, and hospital- /population-based studies in different genetic models, whereas significantly decreased risk was found in prostate cancer (GG vs. TT: OR, 0.606; 95% CI, 0.407-0.903; GG/GT vs. TT: OR, 0.748; 95% CI, 0.579-0.968). In conclusion, the data of meta-analysis suggests that MDM2 SNP309 is a potential biomarker for cancer risk.

Combined effects of MDM2 SNP309 and TP53 R72P polymorphisms, and soy isoflavones on breast cancer risk among Chinese women in Singapore

The MDM2 oncoprotein regulates the p53 pathway and, while functional polymorphisms of the MDM2 and p53 genes have been investigated for association with breast cancer risk, results are largely null or non-conclusive. We have earlier reported that the increased intake of soy isoflavones reduces risk of postmenopausal breast cancer, and experimental studies suggest that dietary isoflavones can down-regulate the expression of the MDM2 oncoprotein. In this study, we investigated the association between the MDM2 SNP309 and TP53 R72P polymorphisms and breast cancer risk using a case-control study of 403 cases and 662 controls nested among 35,303 women in The Singapore Chinese Health Study, a population-based, prospective cohort of middle-aged and elderly men and women who have been continuously followed since 1993. The G allele of the TP53 R72P polymorphism and T allele of the MDM2 SNP309 polymorphism were putative high-risk alleles and exhibited a combined gene-dose-dependent joint effect on breast cancer risk that was more clearly observed in postmenopausal women. Among postmenopausal women, the simultaneous presence of G allele in TP53 and T allele in MDM2 polymorphisms was associated with an odds ratio (OR) of 2.42 [95% confidence interval (CI) 1.06-5.50]. Furthermore, the protective effect of dietary soy isoflavones on postmenopausal breast cancer was mainly confined to women homozygous for the high activity MDM2 allele (GG genotype). In this genetic subgroup, women consuming levels of soy isoflavones above the median level exhibited risk that was half of those with below median intake (OR 0.52; 95% CI 0.28-0.99). Our findings support experimental data implicating combined effects of MDM2 protein and the p53-mediated pathway in breast carcinogenesis, and suggest that soy isoflavones may exert protective effect via down-regulation of the MDM2 protein.

Association of the germline TP53 R72P and MDM2 SNP309 variants with breast cancer survival in specific breast tumor subgroups

The tumor suppressor gene TP53 and its regulator MDM2 are both important players in the DNA-damage repair "TP53 response pathway". Common germline polymorphisms in these genes may affect outcome in patients with tumors characterized by additional somatic changes in the same or a related pathway. To evaluate this hypothesis, we determined the effect of the common germline TP53 R72P and MDM2 SNP309 polymorphisms on breast cancer survival in a consecutive cohort of breast cancer patients (age at diagnosis <53 years, n = 295) with gene expression data available. Patients were classified in subgroups according to their tumor TP53 mutation status and three gene expression profiles; a TP53 mutation status expression signature, a PTEN/PI3K pathway signature and the 70-gene prognosis profile. Survival analyses were performed using Cox regression models adjusting for clinico-pathological characteristics and treatment. An increase in breast cancer-specific mortality was observed for carriers of the germline MDM2 SNP309 rare GG-genotype (range hazard ratios: 2-3) or TP53 R72P heterozygous GC-genotype (range hazard ratios: 1-2) compared to those having the common genotypes within subgroups of tumors displaying a "more aggressive phenotype" gene expression profile. There was no evidence of such an effect on survival within the TP53-mutated tumor group for TP53 R72P carriers but a suggestion of an effect for MDM2 SNP309 carriers (GG vs. TT-genotype HR 2.99, P = 0.06). These results indicate that common polymorphisms in specific pathways may add to the worse prognosis of patients with tumors in which these pathways are affected by somatic alterations.

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

Background

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

Methods

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

Results

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

Conclusions

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

Predictive and prognostic impact of TP53 mutations and MDM2 promoter genotype in primary breast cancer patients treated with epirubicin or paclitaxel

Background

TP53 mutations have been associated with resistance to anthracyclines but not to taxanes in breast cancer patients. The MDM2 promoter single nucleotide polymorphism (SNP) T309G increases MDM2 activity and may reduce wild-type p53 protein activity. Here, we explored the predictive and prognostic value of TP53 and CHEK2 mutation status together with MDM2 SNP309 genotype in stage III breast cancer patients receiving paclitaxel or epirubicin monotherapy.

Experimental Design

Each patient was randomly assigned to treatment with epirubicin 90 mg/m² (n = 109) or paclitaxel 200 mg/m² (n = 114) every 3rd week as monotherapy for 4–6 cycles. Patients obtaining a suboptimal response on first-line treatment requiring further chemotherapy received the opposite regimen. Time from last patient inclusion to follow-up censoring was 69 months. Each patient had snap-frozen tumor tissue specimens collected prior to commencing chemotherapy.

Principal Findings

While TP53 and CHEK2 mutations predicted resistance to epirubicin, MDM2 status did not. Neither TP53/CHEK2 mutations nor MDM2 status was associated with paclitaxel response. Remarkably, TP53 mutations (p = 0.007) but also MDM2 309TG/GG genotype status (p = 0.012) were associated with a poor disease-specific survival among patients having paclitaxel but not patients having epirubicin first-line. The effect of MDM2 status was observed among individuals harbouring wild-type TP53 (p = 0.039) but not among individuals with TP53 mutated tumors (p>0.5).

Conclusion

TP53 and CHEK2 mutations were associated with lack of response to epirubicin monotherapy. In contrast, TP53 mutations and MDM2 309G allele status conferred poor disease-specific survival among patients treated with primary paclitaxel but not epirubicin monotherapy.

Functional polymorphisms associated with disease-free survival in resected carcinoma of the esophagus

PURPOSE

The aim of this study was to determine whether clinical outcome after surgical resection of esophageal adenocarcinoma (EAC) or esophageal squamous cell carcinoma (ESCC) could be predicted by functional polymorphisms in different proto-oncogenes and tumor suppressor genes.

EXPERIMENTAL DESIGN

Six single nucleotide polymorphisms (SNPs) in the AURKA (rs2273535), ERBB2 (rs1136201), MDM2 (rs2279744), CDH1 (rs5030625), CDKN2A (rs11515), and TP73 (rs2273953) genes were genotyped in a consecutive cohort of 346 esophageal cancer patients, who had underwent surgical resection with curative intent. Associations with disease-free survival (DFS) were analyzed with Kaplan-Meier curves and Cox regression, adjusting for potential confounders.

RESULTS

Univariate analysis showed no significant associations between the tested polymorphisms and DFS in patients with EAC or ESCC. However, in a multivariate analysis, patients with EAC carrying the heterozygous MDM2 (rs2279744) T/G genotype had significantly improved DFS compared with patients carrying the wild-type genotype (adjusted hazard ratio (AHR), 0.63; 95% confidence interval (CI) [0.45-0.88]). Patients with EAC harboring the homozygous CDH1 (rs5030625) GA/GA genotype had a significantly reduced survival as compared with patients carrying the wild-type genotype AHR 4.0, 95% CI [1.4-11].

CONCLUSIONS

In a large cohort of esophageal cancer patients, the MDM2 T/G and CDH1 GA/GA genotype confer risk of death in patients with EAC. These data suggest that inter-individual differences in germ-line DNA have an impact on DFS in patients with EAC.

COX-2 activation is associated with Akt phosphorylation and poor survival in ER-negative, HER2-positive breast cancer

Background

Inducible cyclooxgenase-2 (COX-2) is commonly overexpressed in breast tumors and is a target for cancer therapy. Here, we studied the association of COX-2 with breast cancer survival and how this association is influenced by tumor estrogen and HER2 receptor status and Akt pathway activation.

Methods

Tumor COX-2, HER2 and estrogen receptor α (ER) expression and phosphorylation of Akt, BAD, and caspase-9 were analyzed immunohistochemically in 248 cases of breast cancer. Spearman's correlation and multivariable logistic regression analyses were used to examine the relationship between COX-2 and tumor characteristics. Kaplan-Meier survival and multivariable Cox proportional hazards regression analyses were used to examine the relationship between COX-2 and disease-specific survival.

Results

COX-2 was significantly associated with breast cancer outcome in ER-negative [Hazard ratio (HR) = 2.72; 95% confidence interval (CI), 1.36-5.41; comparing high versus low COX-2] and HER2 overexpressing breast cancer (HR = 2.84; 95% CI, 1.07-7.52). However, the hazard of poor survival associated with increased COX-2 was highest among patients who were both ER-negative and HER2-positive (HR = 5.95; 95% CI, 1.01-34.9). Notably, COX-2 expression in the ER-negative and HER2-positive tumors correlated significantly with increased phosphorylation of Akt and of the two Akt targets, BAD at Ser136 and caspase-9 at Ser196.

Conclusions

Up-regulation of COX-2 in ER-negative and HER2-positive breast tumors is associated with Akt pathway activation and is a marker of poor outcome. The findings suggest that COX-2-specific inhibitors and inhibitors of the Akt pathway may act synergistically as anticancer drugs in the ER-negative and HER2-positive breast cancer subtype.

Increased NOS2 predicts poor survival in estrogen receptor-negative breast cancer patients

Inducible nitric oxide synthase (NOS2) is involved in wound healing, angiogenesis, and carcinogenesis. NOS2 upregulation and increased nitric oxide (NO) production affect the redox state of cells and can induce protein, lipid, and DNA modifications. To investigate whether NOS2 levels influence survival of breast cancer patients, we examined NOS2 expression and its association with tumor markers and survival in 248 breast tumors. In multivariable survival analysis, increased NOS2 predicted inferior survival in women with estrogen receptor α-negative (ER-negative) tumors. Microdissected tumor epithelium from ER-negative tumors with high NOS2 had increased IL-8 and a gene expression signature characteristic of basal-like breast cancer with poor prognosis. In cell culture, NO only induced selected signature genes in ER-negative breast cancer cells. ER transgene expression in ER-negative cells inhibited NO-induced upregulation of the stem cell marker CD44 and other proteins encoded by signature genes, but not of IL-8. Exposure to NO also enhanced cell motility and invasion of ER-negative cells. Last, pathway analysis linked the tumor NOS2 gene signature to c-Myc activation. Thus, NOS2 is associated with a basal-like transcription pattern and poor survival of ER-negative patients.

MDM2 polymorphism increases susceptibility to childhood acute myeloid leukemia: a report from the Children's Oncology Group

BACKGROUND

The variant polymorphism in the gene MDM2, SNP309, leads to increased level of mdm2 protein and subsequent downregulation of p53 tumor suppressor pathway. Presence of this single nucleotide polymorphism (SNP) has been associated with earlier tumorigenesis in patients with Li-Fraumeni syndrome, as well as decreased survival in patients with CLL. In addition, cells homozygous (G/G) for SNP 309 were found to have 10-fold increase resistance to topoisomerase II inhibitors in vitro.

PROCEDURE

We genotyped children (n = 575) with de novo acute myeloid leukemia (AML) treated on three Children's Oncology Group protocols (CCG 2941/2961/AAML 03P1) for the presence of SNP309. Healthy blood donors were genotyped as control population.

RESULTS

The variant G/G genotype was associated with an increased susceptibility to AML (OR 1.5; P = 0.049). However, the presence of the variant allele at SNP309 did not modify disease response or toxicity in children treated on CCG protocols 2941/2961.

CONCLUSIONS

The variant SNP 309 influences susceptibility to pediatric AML, but does not impact overall response to therapy.

NOTCH2 in breast cancer: association of SNP rs11249433 with gene expression in ER-positive breast tumors without TP53 mutations

Background

A recent genome-wide association study (GWAS) has identified a single nucleotide polymorphism (SNP) rs11249433 in the 1p11.2 region as a novel genetic risk factor for breast cancer, and this association was stronger in patients with estrogen receptor (ER)⁺ versus ER^- cancer.

Results

We found association between SNP rs11249433 and expression of the NOTCH2 gene located in the 1p11.2 region. Examined in 180 breast tumors, the expression of NOTCH2 was found to be lowest in tumors with TP53 mutations and highest in TP53 wild-type/ER⁺ tumors (p = 0.0059). In the latter group, the NOTCH2 expression was particularly increased in carriers of the risk genotypes (AG/GG) of rs11249433 when compared to the non-risk AA genotype (p = 0.0062). Similar association between NOTCH2 expression and rs11249433 was observed in 60 samples of purified monocytes from healthy controls (p = 0.015), but not in total blood samples from 302 breast cancer patients and 76 normal breast tissue samples. We also identified the first possible dominant-negative form of NOTCH2, a truncated version of NOTCH2 consisting of only the extracellular domain.

Conclusion

This is the first study to show that the expression of NOTCH2 differs in subgroups of breast tumors and by genotypes of the breast cancer-associated SNP rs11249433. The NOTCH pathway has key functions in stem cell differentiation of ER⁺ luminal cells in the breast. Therefore, increased expression of NOTCH2 in carriers of rs11249433 may promote development of ER⁺ luminal tumors. Further studies are needed to investigate possible mechanisms of regulation of NOTCH2 expression by rs11249433 and the role of NOTCH2 splicing forms in breast cancer development.

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.

ARLTS1, MDM2 and RAD51 gene variations are associated with familial breast cancer

Genetic factors that contribute to the risk of breast cancer are largely not known and association studies have revealed several genes with low penetrance risk alleles for breast cancer. Analysis of these genes may provide important information on the risk factors affecting carcinogenesis. Variations in the ARLTS1, RAD51 and MDM2 genes have been associated with increased risk of different cancer types but for breast cancer the results are not consistent. In this study we investigated the role of the allelic variants in candidate genes acting in the tumor suppressor, DNA repair and p53 pathways as risk factors for familial breast cancer in 147 patients displaying characteristics of familial disease. Presence of the polymorphic variants were investigated by amplification of the corresponding regions and restriction fragment length polymorphism analysis. Genotype and allele frequencies in the patients were significantly different for all three variants. Our results indicate that the polymorphic variants might affect individual susceptibility towards breast cancer.

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.

Germline analysis of thymidine/guanidine polymorphism at position 309 of the Mdm2 promoter in malignant melanoma patients

p53 is a major tumor suppressor gene, frequently mutated in human cancer, but rarely mutated in malignant melanoma (MM). Mdm2, the major negative regulator of p53, is overexpressed in 50-60% of MM patients, by an unknown mechanism. Single nucleotide polymorphism at position 309 of the Mdm2 promoter correlates with increased Mdm2 levels and reduced p53 activation. We speculated that guanine at position 309 (G309) of the Mdm2 promoter might be a cause of Mdm2 overexpression in MM patients, and associated with increased risk of MM. We aimed to estimate the prevalence of G309 in MM patients. Genomic DNA was collected from a cohort of 28 MM patients of various clinical stages. The relevant DNA stretch was sequenced and thymidine/guanidine polymorphism at position 309 of Mdm2 promoter was examined. We compared the resultant frequencies with the frequencies reported in the literature for the general population. The G allele frequency in the cohort of MM patients was 0.518. This frequency is high compared with the reported frequency of 0.351 in Caucasian healthy populations (odds ratio=1.98, P=0.014). It is also higher than a G allele frequency of 0.464 reported for Ashkenazi Jewish women, although this comparison was not statistically significant (odds ratio=1.14, P=0.76). These results suggest that the single nucleotide polymorphism G309 in the Mdm2 promoter might be an important genetic predisposing factor, and possibly indicate a molecular mechanism of disease regarding MM. These results must be confirmed in a larger cohort of MM patients and controls.

When mutants gain new powers: news from the mutant p53 field

Ample data indicate that mutant p53 proteins not only lose their tumour suppressive functions, but also gain new abilities that promote tumorigenesis. Moreover, recent studies have modified our view of mutant p53 proteins, portraying them not as inert mutants, but rather as regulated proteins that influence the cancer cell transcriptome and phenotype. This influence is clinically manifested as association of TP53 mutations with poor prognosis and drug resistance in a growing array of malignancies. Here, we review recent studies on mutant p53 regulation, gain-of-function mechanisms, transcriptional effects and prognostic association, with a focus on the clinical implications of these findings.

Recent advances in validating MDM2 as a cancer target

The MDM2 oncogene is overexpressed in various human cancers. Its expression correlates with the phenotypes of high-grade, late-stage, and more resistant tumors. The auto-regulatory loop between MDM2 and the tumor suppressor p53 has long been considered the epitome of a rational target for cancer therapy. As such, many novel agents have been generated to interfere with the interaction of the two proteins, which results in the activation of p53. Among these agents are several small molecule inhibitors synthesized based upon the crystal structures of the MDM2-p53 complex. With use of high-throughput screening, several specific and effective agents for inhibition of the protein-protein interaction were discovered. Recent investigations, however, have demonstrated that many proteins regulate the MDM2-p53 interaction, and that MDM2 may have p53-independent oncogenic functions. In order for novel MDM2 inhibitors to be translated to the clinic, it is necessary to obtain a better understanding of the regulation of MDM2 and of the MDM2-p53 interaction. In particular, the implications of various interactions between certain regulator(s) and MDM2/p53 under different circumstances need to be elucidated to determine which pathway(s) represent the best targets for therapy. Targeting both MDM2 itself and regulators of MDM2 and the MDM2-p53 interaction, or use of MDM2 inhibitors in combination with conventional treatments, may improve prospects for tumor eradication.

Polymorphisms in p53 and the p53 pathway: roles in cancer susceptibility and response to treatment

The p53 tumour suppressor protein lies at the crossroads of multiple cellular response pathways that control the fate of the cell in response to endogenous or exogenous stresses and inactivation of the p53 tumour suppressor signalling pathway is seen in most human cancers. Such aberrant p53 activity may be caused by mutations in the TP53 gene sequence producing truncated or inactive mutant proteins, or by aberrant production of other proteins that regulate p53 activity, such as gene amplification and overexpression of MDM2 or viral proteins that inhibit or degrade p53. Recent studies have also suggested that inherited genetic polymorphisms in the p53 pathway influence tumour formation, progression and/or response to therapy. In some cases, these variants are clearly associated with clinico-pathological variables or prognosis of cancer, whereas in other cases the evidence is less conclusive. Here, we review the evidence that common polymorphisms in various aspects of p53 biology have important consequences for overall tumour susceptibility, clinico-pathology and prognosis. We also suggest reasons for some of the reported discrepancies in the effects of common polymorphisms on tumourigenesis, which relate to the complexity of effects on tumour formation in combination with other oncogenic changes and other polymorphisms. It is likely that future studies of combinations of polymorphisms in the p53 pathway will be useful for predicting tumour susceptibility in the human population and may serve as predictive biomarkers of tumour response to standard therapies.

No evidence for association of the MDM2-309 T/G promoter polymorphism with prostate cancer outcomes

OBJECTIVES

Mouse double-minute 2 (MDM2) SNP309 polymorphism (T>G) has been correlated with an increased risk of cancer in multiple tumor types. MDM2 overexpression has shown to be weakly associated with distant tumor metastases, and down-regulation of MDM2 via antisense oligonucleotides in vitro has resulted in the radiosensitization of prostate cancer cell lines. Based on these results, we decided to evaluate the role of MDM2 SNP309 in the context of histopathologic parameters and clinical outcomes in prostate cancer tumors.

MATERIALS AND METHODS

The population consisted of 212 consecutive prostate cancer patients who underwent radical prostatectomy between 1997 and 1999 at Vanderbilt University Medical Center. Two hundred eight of the samples were successfully genotyped for the MDM2 SNP309 polymorphism. Correlations between the polymorphism, recurrence, and survival data were analyzed using univariate and multivariate genetic models.

RESULTS

The only prognostic factor predictive of overall survival in our study was Gleason score (P<0.005). Using χ(2) analysis, we determined that the MDM2 SNP309 polymorphism had no significant association with race (P=0.7512), patient's age at diagnosis (P=0.6820), pre-prostatectomy PSA level (P=0.8606), Gleason's score (P=0.4839), surgical margin status (P=1.0000), extracapsular extension (P=0 .6175), and disease stage (P=0.4945). In addition, there was no significant difference in 3-year recurrence-free survival (P=0.218), or 8-year overall survival (P=0.376).

CONCLUSIONS

Our study finds no evidence for association of the MDM2 SNP309 polymorphism with clinicopathologic variables, recurrence risk, and overall survival outcome in prostate cancer.

A mitochondrial target sequence polymorphism in manganese superoxide dismutase predicts inferior survival in breast cancer patients treated with cyclophosphamide

PURPOSE

Manganese superoxide dismutase protects against oxidative damage and modulates the efficacy of chemotherapeutic drugs. A functional single-nucleotide polymorphism in codon 16 of SOD2 (rs4880), which encodes manganese superoxide dismutase, results in a substitution of valine by alanine (Val16Ala). We hypothesized that this single-nucleotide polymorphism affects breast cancer survival of patients receiving chemotherapy.

EXPERIMENTAL DESIGN

Two patient populations from the United States (n = 248) and Norway (n = 340) were genotyped for Val16Ala. Kaplan-Meier survival and Cox proportional hazards regression analyses were used to examine the relationship between Val16Ala and disease-specific survival.

RESULTS

Val16Ala was significantly associated with breast cancer outcome in both patient populations. Carriers of the Ala allele had inferior survival rates in the multivariate analysis [hazard ratio (HR), 2.44 and 95% confidence interval (95% CI), 1.11-5.37 in U.S. cohort; HR, 1.91 and 95% CI, 1.06-3.45 in Norway cohort for Ala/Ala versus Val/Val]. In an analysis of the combined cohorts, this association was significant for patients receiving adjuvant therapy (HR, 2.47; 95% CI, 1.46-4.19), but not for patients without it (HR, 1.47; 95% CI, 0.57-3.74). After further stratification by type of chemotherapy, the effect of the Ala allele was mostly restricted to cyclophosphamide-containing chemotherapy regimens (HR, 22.0; 95% CI, 5.22-92.9; Ala/Ala versus Val/Val).

CONCLUSION

The Val16Ala polymorphism affects survival of patients receiving cyclophosphamide-containing chemotherapy. The findings provide the first evidence pointing toward a mechanism for cyclophosphamide resistance in breast cancer patients.

p53 Arg72Pro and MDM2 T309G polymorphisms, histology, and esophageal cancer prognosis

PURPOSE

This study aimed to evaluate the prognostic significance of two functional single nucleotide polymorphisms (SNP) in the p53 pathway (p53 Arg72Pro and MDM2 T309G) in patients with esophageal cancer, and to determine the importance of histologic subtype in the SNP-outcome relationships.

EXPERIMENTAL DESIGN

A cohort of 371 patients with esophageal carcinoma enrolled in Boston, USA from 1999 to 2004 were genotyped for the p53 and MDM2 SNPs. Associations between genotypes and overall survival (OS; the primary outcome) and progression-free survival (PFS) were assessed using the Kaplan-Meier method. Cox proportional hazard models, adjusted for age, stage, performance status, and smoking were developed. Interaction analyses were done for histology (adenocarcinoma versus squamous cell carcinoma).

RESULTS

At the median follow-up of 33 months, median survival (MS) and PFS were 29.1 and 15.7 months, respectively. p53 Pro/Pro was strongly associated with shorter survival in the entire cohort (MS of 11.8 versus 29.1 months, P < 0.0001; adjusted hazard ratio for death, 2.05; 95% confidence interval, 1.30-3.24; P = 0.002 for Pro/Pro versus Arg/Arg). MDM2 G/G was associated with markedly reduced survival in squamous cell carcinoma (MS of 10.3 versus 49.4 months; adjusted hazard ratio for death, 7.9; 95% confidence interval, 2.4-26.0; P = 0.0007 for G/G versus T/T) but not in adenocarcinoma (SNP-histology interaction P = 0.004).

CONCLUSIONS

In a large prospective cohort, p53 Arg72Pro Pro/Pro was associated with a 2-fold increased risk of death in all esophageal cancers, whereas MDM2 T309G G/G was associated with a 7-fold increased risk of death in squamous cell carcinoma.

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.

p53 polymorphisms: cancer implications

The normal functioning of p53 is a potent barrier to cancer. Tumour-associated mutations in TP53, typically single nucleotide substitutions in the coding sequence, are a hallmark of most human cancers and cause dramatic defects in p53 function. By contrast, only a small fraction, if any, of the >200 naturally occurring sequence variations (single nucleotide polymorphisms, SNPs) of TP53 in human populations are expected to cause measurable perturbation of p53 function. Polymorphisms in the TP53 locus that might have cancer-related phenotypical manifestations are the subject of this Review. Polymorphic variants of other genes in the p53 pathway, such as MDM2, which might have biological consequences either individually or in combination with p53 variants are also discussed.

Results based on 124 cases of breast cancer and 97 controls from Taiwan suggest that the single nucleotide polymorphism (SNP309) in the MDM2 gene promoter is associated with earlier onset and increased risk of breast cancer

Background

It has been suggested that the single nucleotide polymorphism 309 (SNP309, T -> G) in the promoter region of the MDM2 gene is important for tumor development; however, with regards to breast cancer, inconsistent associations have been reported worldwide. It is speculated that these conflicting results may have arisen due to different patient subgroups and ethnicities studied. For the first time, this study explores the effect of the MDM2 SNP309 genotype on Taiwanese breast cancer patients.

Methods

Genomic DNA was obtained from the whole blood of 124 breast cancer patients and 97 cancer-free healthy women living in Taiwan. MDM2 SNP309 genotyping was carried out by restriction fragment length polymorphism (RFLP) assay. The multivariate logistic regression and the Kaplan-Meier method were used for analyzing the risk association and significance of age at diagnosis among different MDM2 SNP309 genotypes, respectively.

Results

Compared to the TT genotype, an increased risk association with breast cancer was apparent for the GG genotype (OR = 3.05, 95% CI = 1.04 to 8.95), and for the TG genotype (OR = 2.12, 95% CI = 0.90 to 5.00) after adjusting for age, cardiovascular disease/diabetes, oral contraceptive usage, and body mass index, which exhibits significant difference between cases and controls. Furthermore, the average ages at diagnosis for breast cancer patients were 53.6, 52 and 47 years for those harboring TT, TG and GG genotypes, respectively. A significant difference in median age of onset for breast cancer between GG and TT+TG genotypes was obtained by the log-rank test (p = 0.0067).

Conclusion

Findings based on the current sample size suggest that the MDM2 SNP309 GG genotype may be associated with both the risk of breast cancer and an earlier age of onset in Taiwanese women.

Association of HDM2 transcript levels with age of onset and prognosis in soft tissue sarcomas

The p53 stress response is crucial for the prevention of tumor formation. The oncogene HDM2 is one of the key negative regulators of p53 and is a central node in the p53 pathway. P53 and HDM2 form an oscillating feedback loop. HDM2 expression is regulated by different promoters. To evaluate its clinical relevance, we determined the levels of HDM2 transcripts originating from the constitutive P1 and p53-sensitive P2 promoter in 133 soft tissue sarcomas and correlated the results with the age of diagnosis and the patients' outcome. We show that only high levels of the HDM2-P1 transcript but not the P2 transcript are associated with an 11-year earlier age of onset (50.5 years) compared with low P1 levels (61.5 years; P < 0.0001, t test). In addition, low P1 and P2 mRNA expression levels were independent predictors of poor outcome for patients with soft tissue sarcomas (low P1: relative risk, 3.7; P < 0.0001; low P2: relative risk, 2.5; P = 0.001). A change in the expression levels of the HDM2 transcripts originating from the two HDM2 promoters could disrupt the oscillating P53-HDM2 feedback loop in a way that elevated levels of HDM2-P1 transcript are associated with an earlier age of tumor onset and that reduced levels of HDM2-P1 or HDM2-P2 transcripts are correlated with poor prognosis of patients with soft tissue sarcomas.

Mutations in p53, p53 protein overexpression and breast cancer survival

p53 is an important tumour suppressor gene that encodes p53 protein, a molecule involved in cell cycle regulation and has been inconsistently linked to breast cancer survival. Using archived tumour tissue from a population-based sample of 859 women diagnosed with breast cancer between 1996 and 1997, we determined p53 mutations in exons 5–8 and p53 protein overexpression. We examined the association of p53 mutations with overexpression and selected tumour clinical parameters. We assessed whether either p53 marker was associated with survival through 2002, adjusting for other tumour markers and prognostic factors. The prevalence of protein overexpression in the tumour was 36% (307/859) and of any p53 mutation was 15% (128/859). p53 overexpression was positively associated with the presence of any p53 mutation (odds ratio [OR]= 2.2, 95% confidence interval [CI]= 1.5–3.2), particularly missense mutations (ER = 7.0, 95% CI = 3.6–13.7). Negative oestrogen and progesterone receptor (ER/PR) status was positively associated with both p53 protein overexpression (= 2.6, 95% CI = 1.7–4.0) and p53 mutation (OR = 3.9, 95% CI = 2.4–6.5). Any p53 mutation and missense mutations, but not p53 protein overexpression, were associated with breast cancer-specific mortality (hazard ratio [HR]= 1.7, 95% CI = 1.0–2.8; HR = 2.0, 95% CI = 1.1–3.6, respectively) and all-cause mortality (HR = 1.5, 95% CI = 1.0–2.4; HR = 2.0, 95% CI = 1.2–3.4, respectively); nonsense mutations were associated only with breast cancer-specific mortality (HR = 3.0, 95% CI = 1.1–8.1). These associations however did not remain after adjusting for ER/PR status. Thus, in this population-based cohort of women with breast cancer, although p53 protein overexpression and p53 mutations were associated with each other, neither independently impacted breast cancer-specific or all-causing mortality, after considering ER/PR status.

MDM2 SNP309 is associated with high grade node positive breast tumours and is in linkage disequilibrium with a novel MDM2 intron 1 polymorphism

INTRODUCTION

A functional polymorphism within MDM2, SNP309 T>G, has been linked to early onset cancer. This study examined clinical associations of breast cancer with SNP309 in a Scottish Caucasian population and investigated additional MDM2 intron 1 polymorphisms.

METHODS

Intron 1 of MDM2 was PCR amplified and directly sequenced from 299 breast cancer patients and 275 cancer free controls and compared with clinical and pathological parameters.

RESULTS

SNP309 was observed, for the control and breast cancer cohorts respectively, at frequencies of: T/T = 44.7% and 39.5%; G/T = 42.2% and 47.2%; G/G = 13.1% and 13.4%, indicating that SNP309 is not a predisposing factor for breast cancer. The 309G/G genotype was associated with high grade tumours (OR = 1.64, 95%CI = 1.06-2.53, p = 0.025) and greater nodal involvement (OR = 2.51, 95%CI = 1.26-4.98, p = 0.009). SNP309 was not associated with an earlier age of cancer diagnosis. No association was observed between genotype and age of breast cancer diagnosis when patients were stratified by menopausal status and estrogen receptor status. Three additional low frequency SNPs were identified: 344T>A, 285G>C and 443G>T, the latter two novel. SNP285 was in complete linkage disequilibrium with SNP309 (D' = 1.0) with the minor alleles being in phase with each other. Moreover, the 285C/C, 309G/G double homozygous genotype was only observed in the breast cancer cohort.

CONCLUSION

SNP309G/G is associated with poor prognostic breast cancer features in the Scottish population. Additionally, a novel SNP, SNP285, that is in linkage disequilibrium with SNP309, may also have a role in breast tumorigenesis.

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.