Polymorphisms of TP53 codon 72 with breast carcinoma risk: evidence from 12226 cases and 10782 controls

Association Between the TP53 Polymorphisms and Breast Cancer Risk: An Updated Meta-Analysis

Background: The relationship of TP53 codons 72, IVS3 16 bp, and IVS6+62A > G polymorphisms with breast cancer (BC) risk has been analyzed in seventeen published meta-analyses. However, the credibility of statistically significant associations was ignored and many new studies have been reported on these themes.

Objectives: To explore whether TP53 codons 72, IVS3 16 bp, and IVS6+62A > G polymorphisms are associated with BC risk and the clinical phenomena.

Methods: To comprehensively search the data (through October 25, 2021), we provided a clear search strategy and reviewed the references of published meta-analyses. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) were used.

Results: The current meta-analysis had a larger sample size than the previous ones: 99 studies with 43,951 BC and 48,479 controls for TP53 codon 72 polymorphism, 35 studies with 8,705 BC and 7,516 controls for IVS3 16 bp polymorphism, and 25 studies with 12,222 BC and 12,895 controls for IVS6+62A > G polymorphism. Five gene models were used to explore the association between the three polymorphisms and BC risk, and partial positive results were similar to published meta-analyses results. However, a large number of significant results were considered to be unreliable after correcting with Bayesian false-discovery probability (BFDP), except for the association between TP53 IVS3 16 bp polymorphism and BC risk in overall analysis (GG vs. CC: BFDP = 0.738), matched studies (GG vs. CC: BFDP = 0.173; GG vs. CC + CG: BFDP = 0.447), and tumor size below 2 cm (GG vs. CC: BFDP = 0.088; GG + CG vs. CC: BFDP = 0.730; GG vs. CC + CG: BFDP = 0.311). These unreliable results were confirmed again without new solid results emerging in further sensitivity analysis (only studies in compliance with the quality assessment standard).

Conclusion: After considering the quality of the included studies and the reliability of the results, the present meta-analysis suggested that TP53 codons 72, IVS3 16 bp, and IVS6+62A > G polymorphisms were not significantly associated with the BC risk. Those results which prove that these three polymorphisms increase BC risk are more likely to be false-positive results due to various confounding factors.

Gene-Environment Interaction between Arg72Pro SNP and Selected Environmental Exposures among Brazilian Women Diagnosed with Benign Breast Disease

Background:

Benign breast disease (BBD) is a factor strongly associated with breast cancer worldwide. Arg72Pro SNP association with breast cancer is controversial due to the suggestion that environmental factors are required to modulate such risk. There are no studies evaluating these environmental interactions of the aforementioned SNP within BBD.

Aim:

To determine the frequency of SNP Arg72Pro in a cohort of women diagnosed with BBD; and to investigate gene-environmental interactions with environmental factors.

Results:

The genotype frequency was 44.6% for Arg/Pro, 39.3% for Arg/Arg genotype, and 16.3% for Pro/Pro homozygote. Gene-environment interaction analysis shows that when Arg/Arg is considered as reference, there is an ORinteraction with Arg/Pro and fabric exposure (OR=1.90;95%CI:1.04,3.48), solvents (OR=2.21;95%CI:1.01,4.83) and chlorine, bleaches, disinfectants, and liquid wax exposure (OR=2.52;95%CI:1.07,5.91). Analysis with Pro/Pro genotype as the reference showed an interaction between alcohol consumption and recessive model (OR=1.58;95%CI:1.00,2.51). Gene-environmental interactions were observed too between exposure to hair dyes, straighteners or relaxers and Arg/Arg (OR=3.26;95%CI:1.21,8.82).

Conclusion:

The Arg/Pro genotype was the most frequent in the BBD cohort. When compared with the Arg/Arg genotype, the presence of Arg/Pro genotype and solvents, fabric and cleaning products exposure increased the risk of BBD. When compared with Pro/Pro genotype, there were interactions between recessive model with alcohol consumption and exposure to hair products on the risk of BBD.

p.Arg72Pro polymorphism of P53 and breast cancer risk: a meta-analysis of case-control studies

Background

The effect of the p.Arg72Pro variant of the P53 gene on the risk of development ofbreast cancer remains variable in populations. However, the use ofstrategies such aspoolingage-matched controls with disease may provide a consistent meta-analysis. Our goal was to perform a meta-analysis in order to assess the association of p.Arg72Pro variant of P53 gene with the risk of breast cancer.

Methods

Databases such as PubMed, Genetics Medical Literature, Harvard University Library, Web of Science and Genesis Library were used to search articles. Case-control studies with age-matched on breast cancer havingevaluated the genotype frequencies of the TP53 p.Arg72Pro polymorphism were selected. The fixed and random effects (Mantel-Haenszel) were calculated using pooled odds ratio of 95% CI to determine the risk of disease. Inconsistency was calculated to determine heterogeneity among the studies. The publication bias was estimated using the funnel plot.

Results

Twenty-one publications with 7841 cases and 8876 controls were evaluated in this meta-analysis. Overall, our results suggested that TP53 p.Arg72Pro was associated with the risk of breast cancer for the dominant model (OR = 1.09, 95% CI = 1.02–1.16, P = 0.01) and the additive model (OR = 1.09, 95% CI = 1.01–1.17, P = 0.03), but not for the recessive model (OR = 1.07, 95% CI = 0.97–1.18, P = 0.19). According to the ethnic group analysis, Pro allele was associated with the risk of breast cancer in Caucasians for the dominant model and additive model (P = 0.02), and Africans for the recessive model and additive model (P = 0.03).

Conclusions

This meta-analysis found a significant association between TP53 p.Arg72Pro polymorphism and the risk of breast cancer. Individuals carrying at least one Pro allele were more likely to have breast cancer than individuals harboring the Arg allele.

Association of Single-Nucleotide Polymorphisms in Monoubiquitinated FANCD2-DNA Damage Repair Pathway Genes With Breast Cancer in the Chinese Population

Objective:

The aim of the study was to estimate breast cancer risk conferred by individual single-nucleotide polymorphisms of breast cancer susceptibility genes.

Methods:

We analyzed the 48 tagging single-nucleotide polymorphisms of 8 breast cancer susceptibility genes involved in the monoubiquitinated FANCD2–DNA damage repair pathway in 734 Chinese women with breast cancer and 672 age-matched healthy controls.

Results:

Forty-five tagging single-nucleotide polymorphisms were successfully genotyped by SNPscan, and the call rates for each tagging single-nucleotide polymorphisms were above 98.9%. We found that 13 tagging single-nucleotide polymorphisms of 5 genes (Parter and localizer of Breast cancer gene2 (PALB2), Tumour protein 53 (TP53), Nijmegen breakage syndrome 1, Phosphatase and tensin homolog deleted from chromosome 10 (PTEN), and Breast cancer gene 1 (BRCA1-interacting protein 1)) were significantly associated with breast cancer risk. A total of 5 tagging single-nucleotide polymorphisms (rs2299941 of PTEN, rs2735385, rs6999227, rs1805812, and rs1061302 of Nijmegen breakage syndrome 1) were tightly associated with breast cancer risk in sporadic cases, and 5 other tagging single-nucleotide polymorphisms (rs1042522 of TP53, rs2735343 of PTEN, rs7220719, rs16945628, and rs11871753 of BRCA1-interacting protein 1) were tightly associated with breast cancer risk in familial and early-onset cases.

Conclusions:

Some of the tagging single-nucleotide polymorphisms of 5 genes (PALB2, TP53, Nijmegen breakage syndrome 1, PTEN, and BRCA1-interacting protein 1) involved in the monoubiquitinated FANCD2–DNA damage repair pathway were significantly associated with breast cancer risk.

Association between polymorphisms in TP53 and MDM2 genes and susceptibility to prostate cancer

Tumor protein 53 (TP53), a tumor suppressor gene, is a vital cellular cancer suppressor in multicellular organisms. Murine double minute-2 (MDM2) is an oncoprotein that inhibits TP53 activity. A number of studies have examined the association of TP53 and MDM2 polymorphisms with the risk of common forms of cancer, but the findings remain inconclusive. The present study aimed to evaluate the impact of the 40-bp insertion/deletion (I/D) polymorphism (rs3730485) in the MDM2 promoter region and the 16-bp I/D polymorphism (rs17878362) in TP53 on the susceptibility of prostate cancer (PCa) in a sample of the Iranian population. This case-control study included 103 patients with pathologically confirmed PCa and 142 patients with benign prostatic hyperplasia. The MDM2 40-bp I/D and TP53 16-bp I/D polymorphism was determined using polymerase chain reaction analysis. The results demonstrated that the MDM2 40-bp I/D polymorphism increased the risk of PCa in a co-dominant inheritance model [odds ratio (OR)=1.88; 95% confidence interval (CI)=1.11-3.19; P=0.023, D/D vs. I/I], while this variant marginally increased the risk of PCa in a dominant model (OR=1.69; 95% CI=1.00-2.83; P=0.051, I/D+D/D vs. I/I). No significant association was observed between the TP53 16-bp I/D polymorphism and PCa. In conclusion, the present study demonstrated that the 40-bp I/D polymorphism in the MDM2 promoter increased the risk of PCa in an Iranian population. Further investigations with diverse ethnicities and larger sample sizes are required to verify these results.

The Evaluation of p53 Polymorphism at Codon 72 and Association With Breast Cancer in Iran: A Systematic Review and Meta-analysis

Background

Breast cancer is the most common cancer among women in Iran and the world. Multiple environmental factors and genetic variations such as genetic polymorphisms are of its main causes. p53 gene plays an important role in conserving and sustaining the genome as a tumor suppressing gene. Change and polymorphism at codon 72 of p53 gene are correlated with increased risk of lung, mouth, endometrial, prostate, and colorectal cancers, and could be considered an indicator of susceptibility to breast cancer.

Methods

Twelve studies (1,190 cases and 1,145 control studies with evaluation of three types of Arg/Arg, Arg/Pro, and Pro/Pro genotypes) have been conducted using keywords, such as polymorphism at codon 72, gene p53 polymorphisms, and the relation between polymorphisms and breast cancer, from databases in Iran, including Magiran, Medlibe, Sid, and Iranmedex, as well as Latin databases such as PubMed, Google Scholar, Science Direct, and Scopus.

Results

The OR for Arg/Arg is 1.58 (95% CI: 2.45 to 1.01), the OR for Arg/Pro is 0.75 (95% CI: 1.10 to 0.51), and the OR for Pro/Pro is 0.62 (95% CI: 0.93 to 0.42). p53 gene polymorphism at codon 72 is statistically significant in Arg/Arg and Pro/Pro genotypes.

Conclusions

Arg/Arg genotype can be considered as a risk factor for breast cancer, and Pro/Pro genotype can be accounted for as a protective factor against breast cancer.

Evaluation of polymorphic variants in apoptotic genes and their role in susceptibility and clinical progression to systemic lupus erythematosus

Background Systemic lupus erythematosus (SLE) is an autoimmune disease marked by the disruption of the immune homeostasis. Patients exhibit a wide range of clinical manifestations, and environmental and genetic factors are involved in SLE pathogenesis. Evidence suggests that abnormalities in the cellular and molecular events that coordinate apoptosis may favour the generation of autoantigens involved in autoimmunity. In this way, the apoptotic deregulation may be affected by polymorphic variants in apoptotic-related genes. Methods We analyzed FAS, FASL, BCL-2 and BAX polymorphisms in order to correlate to SLE susceptibility and clinical features. A total of 427 SLE patients from the Hospital de Clínicas de Porto Alegre and 543 controls from southern Brazil were evaluated. Results We observed higher frequencies of the FASL -844CC genotype and -844C allele, as well as of the FASL-844C/IVS2nt-124A haplotype in African-derived SLE patients when compared to controls ( P < 0.001). FASL -844C, which is related to high FasL expression, could contribute to increased apoptosis and to the breakdown of immunological tolerance, favouring autoantibody production and inflammation. On the other hand, the BAX -248GA genotype and the -248A allele , related to low protein expression, were observed as a protective factor against SLE in this same population. The rate of apoptosis and cell death was evaluated in peripheral lymphocytes, and SLE patients presented a higher percentage of dead lymphocytes (CD3⁺Annexin V⁺ 7-AAD⁺) compared to the control group. Conclusion Our data support a role for apoptosis in SLE susceptibility.

Association of rs1219648 in FGFR2 and rs1042522 in TP53 with premenopausal breast cancer in an Iranian Azeri population

Breast cancer is the most common cancer among women in the world. In Iran, the incidence of breast cancer is on the increase. We here studied the association of rs1219648 in FGFR2 and rs1042522 in TP53 and their interaction in development of early onset sporadic breast cancer in Iranian Azeri population to evaluate epistatic effects on the risk of mammary neoplasia. We genotyped the two polymorphisms in 100 women with early onset breast cancer and 100 healthy women by PCR-RFLP. Allele frequency differences were tested using chi2-test with 95% confident intervals. Our results indicated a statistically significant association (p<0.05) between rs1219648, but not rs1042522, and risk of breast cancer. We also found that the combination of FGFR2 major genotype and TP53 hetero genotype had protective effects against breast cancer , while the hetero allele of FGFR2 in combination with the minor genotype of TP53 was associated with a high risk. This study revealed an important crosstalk between two polymorphisms in FGFR2 and TP53 in development of breast cancer. These candidates risk variants should be further evaluated in studies with a larger sample size.

Effect of TP53 16-bp and β-TrCP 9-bp INS/DEL polymorphisms in relation to risk of breast cancer

P53 as a tumor suppressor and an apoptosis modulator, is the regulator of the cell cycle and apoptosis, and contributes to mammary gland development and breast cancer (BC) progression. BTRC gene (Homo sapiens beta-transducing repeat containing E3 ubiquitin protein ligase) encoded protein, β-TrCP, is a novel regulator of p53. The current study aimed to assess the possible effects of TP53 IVS3 16 bp (rs17878362) and β-TrCP 9 bp (rs16405) INS/DEL polymorphisms on BC risk in an Iranian population. A total of 439 women including 236 BC patients and 203 healthy women were recruited. The TP53 and β-TrCP INS/DEL polymorphisms were genotyped by allele-specific polymerase chain reaction method. Our data demonstrated that the TP53 16-bp INS/DEL variation was associated with an increased risk of BC in codominant (INS/INS vs.

DEL/DEL

OR=1.82; 95% CI=1.02-3.23; P=0.042) and dominant (Del/INS+INS/INS vs.

DEL/DEL

OR=1.48; 95% CI=1.03-2.21; P=0.044) models. Additionally, the variant allele (INS) of TP53 DEL/INS polymorphism with a relatively higher frequency in cases than in controls (35.6 vs. 27.8) was a risk factor for BC (OR=1.43; 95% CI=1.06-1.93; P=0.017). With respect to β-TrCP INS/DEL polymorphism, our study failed to find any difference in allele and genotype distribution between BC patients and controls in codominant, dominant and recessive tested inheritance models (P>0.05). Furthermore, no significant association among the β-TrCP and TP53 genotype distribution and clinical characteristics of BC patients were found (P>0.05). Our findings suggest that the TP53 16-bp INS/INS and DEL/INS+INS/INS genotypes as well as the INS allele could be genetic factors related to BC risk.

Association of Two Polymorphic Codons in P53 and ABCC1 Promoter with Prostate Cancer

BACKGROUND

In prostate cancer, mutated p53 alleles typically contain missense single-base substitution in codon 72 that resides within exons 5-8. Stable p53 proteins in tumor cell nuclei have been associated with malignancy. A role of p53 is the regulation of drug transporters like ABCC1 (MRP1) by an effect on promoter region.

OBJECTIVES

The objective of this study was to identify association of mutations of p53 at codon 72 and 282 and promoter region of ABCC1 with increased risks of prostate cancer.

MATERIALS AND METHODS

Formalin fixed, paraffin-embedded malignant tissues of 45 patients and 45 control samples were evaluated. PCR-RFLP using BstUI for codon 72 and HpaII restriction enzyme for codon 282 p53 gene, and G-1666A promoter region of ABCC1 gene was performed. To assess the frequency of these mutations and to detect new mutations in cancerous samples, PCR-SSCP analysis was performed.

RESULTS

The frequencies of CC, GC and GG genotypes of codon 72 of p53 were 33.33%, 46.67% and 20.00% in patients with cancer and 15.56%, 48.89% and 35.55% in controls, respectively. The relative allele frequencies of ABCC1 promoter polymorphism were 60.00% A and 40.00% G in patients as opposed to 37.78% for A and 62.22% for G in controls. Genotypic frequencies of p53 codon 72 and G1666A of ABCC1 in patients vs. Controls were statistically significant(p<0.05). The study of these samples with PCR-SSCP displayed some new banding patterns.

CONCLUSIONS

The present findings suggest that CC homozygosity in codon 72 of p53 gene and AA genotype in G-1666A of ABCC1 gene may play a role in combination in prostate cancer and increased susceptibility for this malignancy in the Iranian Kurdish population.

RAD51 135G>C and TP53 Arg72Pro polymorphisms and susceptibility to breast cancer in Serbian women

Breast cancer is a complex disease with both genetic and environmental factors involved in its etiology. An important role of polymorphisms in genes involved in DNA repair has been reported related to breast cancer risk. We conducted a case-control study in order to investigate the association of RAD51 135G>C and TP53 Arg72Pro polymorphisms with breast cancer in Serbian women.48 BRCA negative women with breast cancer and family history of breast/ovarian cancer (hereditary group), 107 women with breast cancer but without family history of the disease (sporadic group) and 114 healthy women without a history of the disease (control group) were included. Restriction fragment length polymorphism was used for genotyping. Genotype and allelic frequencies, the odds ratio (OR) and the 95 % confidence interval (CI) were calculated as an estimate of relative risk. The Hardy-Weinberg equilibrium was tested using χ(2) test. Significance was considered for p < 0.05. RAD51 135G>C showed statistically significant association of CC genotype and increased breast cancer risk (OR 10.28, 95 % CI 1.12-94.5) in hereditary group of patients compared to the control group. Regarding the TP53 Arg72Pro, we showed statistical significance for ProPro + ProArg comparing to ArgArg (OR 2.34, 95 %, CI 1.17-4.70) in hereditary compared to sporadic group. RAD51 135G>C contributes to hereditary breast cancer in Serbian population, with CC genotype as a risk factor. We also found that carriers of Pro allele of TP53 codon 72 is related to hereditary cancer comparing to sporadic one, which indicates it as a potential risk factor for hereditary form of disease.

Association of the TP53 codon 72 polymorphism and breast cancer risk: a meta-analysis

This study was conducted in order to investigate the implications of the R72P polymorphism in the TP53 gene in breast cancer risk. The enlightenment of this matter might provide a piece of information about the potential implications of this polymorphism in patient risk. A meta-analysis was conducted considering a large sample size from studies with conflicting results on the R72P polymorphism in breast cancer patients. Relevant studies were selected from PubMed and SciELO databases for data extraction and statistical analysis. Database was built according to the continent and considering the genotype frequencies, sample size and genotyping methodology. The dominant models (RR vs RP + PP and RR + RP vs. PP), homozygous (RR vs. PP), heterozygous (RR vs. RP and RP vs. PP) and the allele (R vs. P) were used. Genotype frequencies were summarized and evaluated by χ² test of heterogeneity in 2×2 contingency tables with 95% CIs. Odds Ratios (OR) were calculated with a fixed-effect model (Mantel-Haenszel) or a random-effect model (DerSimonian-Laird) if the studies were considered homogeneous (P > 0.05) or heterogeneous (P < 0.05), respectively, using BioEstat® 5.0 software. Supported by a large sample size composed by 25,629 cases and 26,633 controls from 41 studies, we found significant association between the R72P polymorphism in the TP53 gene and the breast cancer risk. The overall data shows an increased risk due to the P allele dominant model, but not in Asia where the risk was associated with the R allele and R dominant model.

Assessment of changes in the BRCA2 and P53 genes in breast invasive ductal carcinoma in northeast Brazil

Background

BRCA protein interacts with at least 13 different proteins that have been implicated with cancer susceptibility and loss of BRCA function is correlated to sensitivity to DNA crosslinking agents in preclinical models.

Results

BRCA2 methylation frequency was 44%, p53 Pro22 allele frequency was 32% and heterozygous frequency of Arg/Pro72 genotype was 60% which could be associated as risk factor for metastasis (p = 0.046 OR = 4.190). Regarding to polymorphism of codon 249 the frequency of Arg249 allele presented 82% which was considered not statistically significant.

Conclusions

There was not statistical significance to BRCA2 promoter methylation with any parameters chosen. However, our findings suggest that patients who present heterozygous genotype at codon 72 of p53 gene may have a major susceptibility to any type of metastasis and this could serve as potential auxiliary biomarker for poor prognosis.

P53 (Pro72Arg) polymorphism associated with the risk of oral squamous cell carcinoma in gutka, niswar and manpuri addicted patients of Pakistan

OBJECTIVES

The chewing habit of paan, chhaliya, and tobacco is common in the traditional culture of Pakistan. Currently, niswar, gutka and manpuri are also commercially available in the Pakistani market. Epidemiologic evidences and increased rate of oral squamous cell carcinoma (OSCC) cases may indicate a direct relationship of these chewing habits with oral carcinogenesis. The p53 gene has been known to be a tumor suppressor gene that is found mutated in common human cancers. The p53 gene contains a single nucleotide polymorphism at codon 72 of exon 4 which encodes either proline (Pro) or arginine (Arg). The aim of the present study was to investigate association of p53 gene codon 72 polymorphism with patients of oral squamous cell carcinoma consuming these carcinogenic chewable materials.

MATERIALS AND METHODS

Blood and tissue samples of 260 OSCC patients were collected with informed consent from the local hospitals of Karachi. The patients were compared with controls of similar age and sex. The exon 4 of p53 gene was examined by PCR-SSCP. The tumor samples showing mobility shift were purified and sequenced.

RESULTS

The C>G missense mutation at nucleotide position 215 of the coding sequence was identified which substitutes proline with arginine at codon 72 of p53 protein. When the data for CCC72CGC polymorphism was analyzed statistically, a significant difference was observed between OSCC and control samples. The Pro allelic frequencies were significantly higher in OSCC patients as compare to controls. The current study indicated the Pro form of p53 codon 72 increases the risk of developing OSCC in Pakistani population. The risk ratio for Pro allele was 1.5004 (95% confidence interval: 1.2559 to 1.7924) and odds ratio of Pro allele was 2.389 (95% confidence interval: 1.5591 to 2.8137) in comparison with the Arg and Pro alleles in the OSCC group.

CONCLUSION

These evidences suggest that there may be specific genetic targets with these chewing ingredients that are responsible for causing OSCC. The p53 codon 72 polymorphism is associated with OSCC at somatic cell level but the polymorphism was not associated at inherited level.

TP53 codon 72 polymorphism in pigmentary phenotypes

The p53 protein exerts different cellular functions, and recent findings have demonstrated its influence on the cascade of skin pigmentation during UV exposure. Among TP53 gene polymorphisms, the most studied is the G to C transversion in exon 4 at codon 72, which results in three distinct genotypes, Arg/Arg, Pro/Pro and Arg/Pro, each one encoding different p53 isoforms. Therefore, this study aimed to determine the relationship between TP53 codon 72 polymorphism and skin protection against sunburn. Genomic DNA was extracted from peripheral blood samples and genotyping was performed by PCR and confirmed by restriction enzyme digestion. The genotype frequency was 50% for Arg/Arg and 14.6% for Pro/Pro genotype. The frequency of heterozygous subjects was 35.4%. In our population, p53 genotypes were in Hardy-Weinberg (HW) equilibrium (X2 HM less than 3.84), showing a predominance of arginine allele (total Arg allele frequency of 68%). No significant association between p53 genotype and skin colour, hair or eye colour and susceptibility to sun exposure was found. However, further analysis demonstrated a significant association between the genotype Pro/Pro and blue/green eyes among participants who presented redness (P=0.016). Our findings indicate susceptibility to sun exposure when this phenotype (eye colour) occurs simultaneously with Pro/Pro genotype.

Coordination of TP53 abnormalities in breast cancer: data from analysis of TP53 polymorphisms, loss of heterozygosity, methylation, and mutations

AIMS

We have studied whether TP53 rs1042522, rs17878362, and rs1625895 alleles having a protective effect against breast cancer (BC) will be lost in tumors, whereas those allowing disease development will be retained.

METHODS

Analysis of TP53 polymorphisms was performed in blood leukocytes and tumors from 80 Caucasian BC patients. In addition, TP53 loss of heterozygosity (LOH), methylation, and mutations were studied in tumor DNA of BC individuals with loss of alleles of TP53 polymorphisms.

RESULTS

In breast tumors of patients heterozygous for TP53 polymorphisms, we detected loss of rs1042522 C and G and rs17878362 A2 alleles; however, the loss of the C allele was preferential. We found that loss of TP53 alleles, namely rs1042522 C, has been caused by an LOH mechanism, namely TP53 deletions, whereas TP53 point mutations frequently occurred in the retained G allele (p=0.03). In addition, we showed that BC patients with rs1042522 CC genotype were characterized by only unifocal tumors and decreased frequency of lymph node metastases (p=0.03).

CONCLUSIONS

Taken together, we showed the preferential loss of the rs1042522 C allele, which is protective against BC progression, in breast tumors. Also, the loss of the C allele, which encodes p53 protein with the best DNA repair capability according to literature data, may create prerequisites for mutations, but not for methylation in a retained G variant, as we found here. However, these results need to be confirmed because of the limited statistical power of the present study and the small sampling.

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.

Genome-based prediction of breast cancer risk in the general population: a modeling study based on meta-analyses of genetic associations

BACKGROUND

Genome-wide association studies identified novel breast cancer susceptibility variants that could be used to predict breast cancer in asymptomatic women. This review and modeling study aimed to investigate the current and potential predictive performance of genetic risk models.

METHODS

Genotypes and disease status were simulated for a population of 10,000 women. Genetic risk models were constructed from polymorphisms from meta-analysis including, in separate scenarios, all polymorphisms or statistically significant polymorphisms only. We additionally investigated the magnitude of the odds ratios (OR) for 1 to 100 hypothetical polymorphisms that would be needed to achieve similar discriminative accuracy as available prediction models [modeled range of area under the receiver operating characteristic curve (AUC) 0.70-0.80].

RESULTS

Of the 96 polymorphisms that had been investigated in meta-analyses, 41 showed significant associations. AUC was 0.68 for the genetic risk model based on all 96 polymorphisms and 0.67 for the 41 significant polymorphisms. Addition of 50 additional variants, each with risk allele frequencies of 0.30, requires per-allele ORs of 1.2 to increase this AUC to 0.70, 1.3 to increase AUC to 0.75, and 1.5 to increase AUC to 0.80. To achieve AUC of 0.80, even 100 additional variants would need per-allele ORs of 1.3 to 1.7, depending on risk allele frequencies.

CONCLUSION

The predictive ability of genetic risk models in breast cancer has the potential to become comparable to that of current breast cancer risk models.

IMPACT

Risk prediction based on low susceptibility variants becomes a realistic tool in prevention of nonfamilial breast cancer.

Tp53 codon-72 polymorphisms identify different radiation sensitivities to g2-chromosome breakage in human lymphoblast cells

Both the G2 chromosomal radiosensitivity assay and allelic differences in TP53 codon-72 have been associated with cancer predisposition. The relationship between the two endpoints was determined in 56 human EBV-transformed lymphoblastoid cell lines. Although there were overlapping distributions of sensitivity for the different genotypes, cell lines that were homozygous for the proline coding allele were more likely to be resistant to chromatid break formation than those containing two arginine coding alleles, whereas cell lines expressing both the proline and arginine codon were either resistant like proline-proline lines or sensitive like arginine-arginine lines. The results support an important role of the TP53 codon-72 polymorphism in modifying G2-chromosome radiosensitivity. Distinguishing the effect of TP53 codon-72 variations from other modifiers of G2-chromosome radiosensitivity might aid in identifying new markers of cancer risk.

Association between TP53 gene ARG72PRO polymorphism and chromosome aberrations in human cancers

It is well known that the TP53 gene considerably influences on DNA repair processes. Polymorphisms in the TP53 gene, particularly the well-known Arg72Pro in codon 72 of exon 4 (Ex4+119 G>C; rs1042522), can modify the functionality of the p53 protein and activation of DNA repair. Actually, polymorphic variants Arg and Pro were found to have different properties of regulation of TP53-dependent DNA repair target genes, that can effect various levels of chromosome aberrations in cancer patients with these genotypes. Here, we studied frequency of chromatid breaks (CB), chromosome-type aberrations (CTA) and aberrant cells (AC) in cancer patients (n = 102) with various Arg72Pro genotypes. It was shown that the Arg variant of TP53 gene is associated with high frequency of AC and chromatid breaks. That is Arg/Arg carriers have more different chromosome aberrations in comparison to individuals with Arg/Pro and Pro/Pro genotypes (P < 0.05). Conversely, the lowest level of AC and chromatid breaks were detected in cancer patients with the Pro/Pro genotype. A completely unexpected result was that women with Arg/Arg genotype had the most high frequency of CB and AC in comparison to Arg/Pro and Pro/Pro women carriers (P < 0.001). In the group of male patients we did not show any differences in chromosome aberrations between carriers of Arg72Pro genotypes. In conclusion, the TP53 gene Arg72Pro polymorphism appreciably influence on occurrence of chromosome aberrations in cancer.