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

Significant Association of the MDM2 T309G Polymorphism with Breast Cancer Risk in a Turkish Population

Background:

Breast cancer is a leading cause of death in women worldwide. Genetic polymorphisms have been reported to be important etiological factors. Murine double minute 2 (MDM2) T309G interacts with p53 and mutations in p53 are present in approximately 50% of all cancers. However, it has been reported that effect of the polymorphism on breast cancer risk may vary in different populations. Here, we therefore investigated whether there is an association between MDM2 T309G (rs2279744) polymorphism and breast cancer in a Turkish population.

Materials and Methods:

We analysed 110 patients with breast cancer and 138 matched? controls. For genotyping, polymerase chain reaction and restriction length fragment polymorphism methods were used.

Results:

A significant difference was observed between case and control groups with regard to the distribution of the MDM2 T309G polymorphism (p<0.05). There was a significantly higher frequency of the TT genotype in the control group (p=0.028; OR, 2.42; 95% CI, 1.09-5.37). However, we did not find any relationships among tumor grade and metastasis status and this polymorphism.

Conclusion:

This study indicates that the MDM2 T309G polymorphism GG genotype and the TG+GG combination may be risk factors for breast cancer in our Turkish population.

Association of rs2279744 and rs117039649 promoter polymorphism with the risk of gynecological cancer: A meta-analysis of case-control studies

BACKGROUND

Increasing evidence has suggested that rs2279744 is associated with rs117039649 polymorphism, which can increase the risk of gynecological cancers, including cervical, ovarian, breast, and endometrial cancer. The results are inconsistent so that we performed a meta-analysis of current literature to clarify the impacts of these polymorphisms on gynecological cancer.

METHODS

Eligible articles were identified through an exhaustive search of relevant databases including PubMed, Embase, Web of science, Springer Link, Chinese National Knowledge Infrastructure (CNKI), and Weipu database for the period up to July 2016. Data about the association between single nucleotide polymorphisms (SNPs) and cancer risk were refined from the selected articles as well as other information about cases and controls, and all of them were extracted by 2 independent researchers and pooled odds ratio with 95% confidence interval was calculated.

RESULTS

This analysis included 24 articles, 27 case-control studies of rs2279744 polymorphism and 3 case-control studies of rs117039649 polymorphism. Significant association with the risk of gynecological cancer was observed for both SNPs. Subgroup analysis by ethnicity and cancer type (cervical, ovarian, breast, and endometrial) also showed a positive relationship between rs2279744 polymorphism and gynecological cancer risk in Caucasian; and there was also a notable association between rs2279744 polymorphism and cervical cancer.

CONCLUSIONS

We found that rs2279744 (SNP309) and rs117039649 (SNP285) were both associated with the risk of gynecological cancers. Subgroup analysis showed that rs2279744 (SNP309) was associated with the risk of gynecological cancers in Caucasian and Asian according to the ethnicity and cancer type, especially for endometrial cancer.

Association between MDM2 rs 2279744 polymorphism and breast cancer susceptibility: a meta-analysis based on 9,788 cases and 11,195 controls

Purpose

Previous studies have suggested associations between MDM2 (mouse double minute 2 homolog) polymorphisms and cancer risk. The aim of this study was to evaluate the relationship between the MDM2 rs 2279744 polymorphism and the susceptibility of breast cancer.

Methods

We searched PubMed, Web of Knowledge, Embase, and the Chinese National Knowledge Infrastructure (CNKI) database for case–control studies published up to October 2013 that investigated MDM2 rs 2279744 polymorphism and breast cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of these associations.

Results

A total of 19 studies were identified for the meta-analysis, including 9,788 cases and 11,195 controls. The variant heterozygote (TG) was associated with breast cancer risk in the overall population (TG vs TT: OR =1.10, 95% CI =1.04–1.17, P=0.001, P=0.23 for heterogeneity test). In the subgroup analyses by ethnicity, a significantly increased risk was observed among Asians (G vs T: OR =1.12, 95% CI =1.02–1.23, P=0.02, P_het=0.04; GG vs TT: OR =1.29, 95% CI =1.06–1.56, P=0.01, P_het=0.04; TG vs TT: OR =1.36, 95% CI =1.15–1.60, P=0.0004, P_het=0.45; dominant model TG+GG vs TT: OR =1.21, 95% CI =1.03–1.41, P=0.02, P_het=0.07). However, among Caucasians, rs 2279744 was associated with breast cancer risk in only one genotype (TG vs TT: OR =1.09, 95% CI =1.00–1.18, P=0.04, P_het=0.37). No publication bias was found in the present study.

Conclusion

This meta-analysis provides evidence for the association between the MDM2 rs 2279744 polymorphism and breast cancer susceptibility. The results suggest that the MDM2 rs 2279744 polymorphism plays an important role in breast cancer, especially in Asians.

Significance of MDM2-309 polymorphisms and induced corresponding plasma MDM2 levels in susceptibility to laryngeal squamous cell carcinoma

The tumor suppressor p53 plays a crucial role in maintaining genomic stability and tumor prevention. Murine double-minute 2 (MDM2) oncoprotein plays a pivotal role in regulating p53, and the single-nucleotide polymorphism (SNP) 309T/G SNP in the promoter region of Mdm2 has been shown to be associated with increased risk of cancer. We investigated the association between Mdm2-309 promoter polymorphism, plasma MDM2 levels, and risk of laryngeal squamous cell carcinoma (LSCC). In this case-control study, 146 patients with LSCC, 61 patients with vocal leukoplakia, and 212 healthy controls were genotyped for the Mdm2-309 T/G gene using pyrosequencing. Plasma MDM2 levels were also analyzed by enzyme-linked immunosorbent assay (ELISA). Patients with LSCC had a significantly lower frequency of GT at Mdm2-309 (odds ratio [OR]=0.50, p=0.02) than controls. The proportion of GT heterozygotes in advanced stage cases were less than that in the initial stage patients (OR: 0.36 vs. 0.63; p=0.007 and 0.16). The same result was found between cases with and without lymph node metastases (OR: 0.45 vs. 0.52; p=0.075 and 0.04). Moreover, the plasma Mdm2 concentrations of LSCC patients (343.36±14.8 pg/mL) were significantly higher than those in controls (255.76±8.2 pg/mL; p<0.01) and vocal leukoplakia patients (301.42±8.6 pg/mL; p<0.05). Patients in advanced stages and with lymph node metastasis had higher plasma MDM2 levels, while the GT genotypes (308.06±18.9 pg/mL; p=0.037) had lower MDM2 plasma levels than the TT genotypes (369.00±25.2 pg/mL). The Mdm2 SNP309 G allele is implicated as an important LSCC and a vocal leukoplakia protective factor in the Chinese Han Population, and the proportion of GT genotype was lower in advanced LSCC patients and lymph node metastasis patients. Moreover, Mdm2-309 GT genotype patients had a lower plasma MDM2 level than the TT genotypes.

Functional MDM4 rs4245739 genetic variant, alone and in combination with P53 Arg72Pro polymorphism, contributes to breast cancer susceptibility

The oncoprotein MDM4 plays an essential role in P53 tumor suppressor pathway through negative regulation of P53 function. It has been reported that the rs4245739 A > C polymorphism located in the MDM4 3'-untranslated region creates a miR-191 target site and results in decreased MDM4 expression. Therefore, we investigated the association of the MDM4 rs4245739 polymorphism as well as the P53 Arg72Pro genetic variant with the breast cancer risk. Genotypes were determined in two independent case-control sets consisting of 1100 breast cancer cases and 1400 controls from two regions of China. Odds ratios (ORs) and 95 % confidence intervals (CIs) were estimated by logistic regression. Our results demonstrated that the MDM4 rs4245739 AC and CC genotypes were significantly associated with decreased breast cancer risk compared to the AA genotype in both the case-control sets (Jinan set: OR = 0.55, 95 % CI 0.40-0.76, P = 2.3 × 10(-4); Huaian set: OR = 0.41, 95 % CI 0.25-0.67, P = 3.1 × 10(-4)). The P53 Arg/Pro genotype or Pro/Pro genotype was significantly associated with an increased risk of developing breast cancer, compared to the P53 Arg/Arg genotype in both the case-control sets (all P < 0.05). Interestingly, we observed a combinational effect between MDM4 rs4245739 and P53 Arg72Pro variants in attenuating breast cancer risk, highlighting the importance of the P53 tumor suppressor pathway genes during malignant transformation. Our results also support the hypothesis that genetic variants interrupting miRNA-mediated gene regulation might be important genetic modifiers of breast cancer risk.

p53 codon 72 polymorphism and breast cancer risk: A meta-analysis

p53 is a tumor suppressor gene and plays important roles in the etiology of breast cancer. Studies have produced conflicting results concerning the role of p53 codon 72 polymorphism (G>C) on the risk of breast cancer; therefore, a meta-analysis was performed to estimate the association between the p53 codon 72 polymorphism and breast cancer. Screening of the PubMed database was conducted to identify relevant studies. Studies containing available genotype frequencies of the p53 codon 72 polymorphism were selected and a pooled odds ratio (OR) with 95% confidence interval (CI) was used to assess the association. Sixty-one published studies, including 28,539 breast cancer patients and 32,788 controls were identified. The results suggest that variant genotypes are not associated with breast cancer risk (Pro/Pro + Arg/Pro vs. Arg/Arg: OR=1.016, 95% CI=0.931–1.11, P=0.722). The symmetric funnel plot, Egger’s test (P=0.506) and Begg’s test (P=0.921) were all suggestive of the lack of publication bias. This meta-analysis suggests that the p53 codon 72 Pro/Pro + Arg/Pro genotypes are not associated with an increased risk of breast cancer. To validate the association between the p53 codon 72 polymorphism and breast cancer, further studies with larger numbers of participants worldwide are required.

Soy products in the management of breast cancer

PURPOSE OF REVIEW

Meta-analyses of epidemiological studies of soy consumption and breast cancer risk have demonstrated modest protective effects, usually attributed to isoflavones. Concern has been expressed, however, that the estrogenic activity of isoflavones may have adverse effects on breast cancer recurrence.

RECENT FINDINGS

The review covers epidemiological studies that have investigated the impact of soy consumption in breast cancer patients on recurrence and mortality. There are preliminary data to suggest that soy has differential effects on recurrence in human epidermal growth factor receptor-2 positive and human epidermal growth factor receptor-2 negative tumours. Recent studies on mechanisms of action of soy in breast cancer provide insights into epigenetic effects and the interaction of isoflavones with IGF-1 and with a number of polymorphisms of genes associated with breast cancer risk such as MDM2 and CYP1B1.

SUMMARY

Overall, these studies indicate that soy foods consumed at levels comparable to those in Asian populations have no detrimental effects on risk of breast cancer recurrence and in some cases significantly reduce the risk. Importantly, soy does not appear to interfere with tamoxifen or anastrozole therapy. Recent research suggests that women who are at increased risk of breast cancer due to polymorphisms in genes associated with the disease may especially benefit from high soy isoflavone intake.

Breast cancer research in Asia: adopt or adapt Western knowledge?

The incidence and mortality of breast cancer continues to rise rapidly in Asian countries. However, most of our current knowledge on breast cancer has been generated in Western populations. As the socio-economic profile, life style and culture of Asian and Western women are substantially different, and genetic backgrounds vary to some extent, we need to answer the question on whether to 'adopt' or 'adapt' Western knowledge before applying it in the Asian setting. It is generally accepted that breast cancer risk factors, which have mainly been studied in Western populations are similar worldwide. However, the presence of gene-environment or gene-gene interactions may alter their importance as causal factors across populations. Diagnostic and prognostic study findings, including breast cancer prediction rules, are increasingly shown to be 'setting specific' and must therefore be validated in Asian women before implementing them in clinical care in Asia. Interventional research findings from Caucasian patients may not be applicable in patients in Asia due to differences in tumour biology/profiles, metabolism of drugs and also health beliefs which can influence treatment acceptance and adherence. While breast cancer research in Asia is warranted in all domains of medical research, it is felt that for Asian breast cancer patients, needs are highest for diagnostic and prognostic studies. International clinical trials meanwhile need to include breast cancer patients from various Asian settings to provide an insight into the effectiveness of new treatment modalities in this part of the world.

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.