Association between MDM2 SNP309 and skin cancer: A meta-analysis of case–control studies

The complementary effect of rs1042522 in TP53 and rs1805007 in MC1R is associated with an elevated risk of cutaneous melanoma in Latvian population

Genetic factors serve important roles in melanoma susceptibility. Although much genetic variation has been associated with cutaneous melanoma (CM), little is known about the interactions between genetic variants. The current study investigated the joint effect of rs1042522 in the tumour protein 53 (TP53) gene, rs2279744 in the murine double minute-2 (MDM2) gene and several single nucleotide polymorphisms (SNPs) in the melanocortin 1 receptor (MC1R) gene. All of these genes are interconnected in a single signalling pathway that regulates pigmentation. The current study included 479 individuals, of which, 255 were patients with CM and 224 were controls from the Latvian population. Multifaceted analyses of potential interactions between SNPs were performed, whilst taking into account the pigmentation phenotypes of individuals and tumour characteristics (Breslow thickness and ulceration). Univariate analyses revealed a borderline significant association between rs1042522 in the TP53 gene and CM risk. The results also confirmed a known association with rs1805007 in the MC1R gene. The rs1042522 was also selected as a CM risk factor in multivariate models, suggesting an effect that is independent from and complementary to that of rs1805007. The results indicated that these SNPs need to be taken into account when determining melanoma risk. A strong association between CM and red hair was identified for rs1805007, and rs1805008 in the MC1R gene was mainly associated with red hair. An association was also determined between rs2279744 in the MDM2 gene and brown eye colour. No convincing associations were identified between the analysed SNPs and Breslow thickness of tumours or ulcerations.

Associations Between IL-10 Polymorphisms and Susceptibility to Melanoma, Basal Cell Carcinoma, and Squamous Cell Carcinoma: A Meta-Analysis

BACKGROUND

According to relevant reports, interleukin-10 (IL-10), as a multifunctional anti-inflammatory cytokine, has a critical influence in cancer development. A meta-analysis was carried out regarding the relationships among the -592 A/C, -1082 G/A, and -819 T/C polymorphisms as well as the susceptibility to skin squamous cell carcinoma (sSCC), melanoma, and basal cell carcinoma (BCC).

MATERIALS AND METHODS

A meta-analysis was carried out on the inter-relationships among the -592 A/C, IL-10-1082 G/A, and -819 T/C polymorphisms as well as the susceptibility to sSCC, melanoma, and BCC.

RESULTS

In this analysis, a total of 11 researches, involving 2149 controls and 2128 cases, were included. No association was found between skin cancer risk and the -592A/C or IL-10-1082G/A polymorphisms in any of the analyses. However, a moderately decreased skin cancer risk was found in the -819 TC versus CC model (odds ratio [OR] = 0.81 and 95% confidence interval [CI] = 0.67-0.99, p = 0.04). From the subgroup analysis, a decreased risk was found between the studies of nonmelanoma skin cancers and IL-10-819T/C in the dominant model (OR = 0.60, 95% CI = 0.43-0.85, p = 0.004 for TT+TC vs. CC). Egger's and Begg's tests demonstrated that there was no significant publication bias.

CONCLUSION

This meta-analysis showed that the -592A/C and 1082G/A IL-10 polymorphisms might not be risk factors for melanoma or for BCC and sSCC patients, but we obtained a correlation between skin cancer risk and the IL-10 -819T/C polymorphism.

Contrasting effects of an Mdm2 functional polymorphism on tumor phenotypes

MDM2, an E3 ubiquitin ligase, is a potent inhibitor of the p53 tumor suppressor and is elevated in many human cancers that retain wild-type p53. MDM2 SNP309G is a functional polymorphism that results in elevated levels of MDM2 (due to enhanced SP1 binding to the MDM2 promoter) thus decreasing p53 activity. Mdm2^SNP309G/G mice are more prone to spontaneous tumor formation than Mdm2^SNP309T/T mice, providing direct evidence for the impact of this SNP in tumor development. We asked whether environmental factors impact SNP309G function and show that SNP309G cooperates with ionizing radiation to exacerbate tumor development. Surprisingly, ultraviolet B light or Benzo(a)pyrene exposure of skin shows that SNP309G allele actually protects against squamous cell carcinoma susceptibility. These contrasting differences led us to interrogate the mechanism by which Mdm2 SNP309 regulates tumor susceptibility in a tissue-specific manner. Although basal Mdm2 levels were significantly higher in most tissues in Mdm2^SNP309G/G mice compared with Mdm2^SNP309T/T mice, they were significantly lower in Mdm2^SNP309G/G keratinocytes, the cell-type susceptible to squamous cell carcinoma. The assessment of potential transcriptional regulators in ENCODE ChIP-seq database identified transcriptional repressor E2F6 as a possible negative regulator of MDM2 expression. Our data show that E2F6 suppresses Mdm2 expression in cells harboring the SNP309G allele but not the SNP309T allele. Thus, Mdm2 SNP309G exhibits tissue-specific regulation and differentially impacts cancer risk.

Genetic variants in cell cycle control pathway confer susceptibility to aggressive prostate carcinoma

BACKGROUND

Because a significant number of patients with prostate cancer (PCa) are diagnosed with disease unlikely to cause harm, genetic markers associated with clinically aggressive PCa have potential clinical utility. Since cell cycle checkpoint dysregulation is crucial for the development and progression of cancer, we tested the hypothesis that common germ-line variants within cell cycle genes were associated with aggressive PCa.

METHODS

Via a two-stage design, 364 common sequence variants in 88 genes were tested. The initial stage consisted of 258 aggressive PCa patients and 442 controls, and the second stage added 384 aggressive PCa Patients and 463 controls. European-American and African-American samples were analyzed separately. In the first stage, SNPs were typed by Illumina Goldengate assay while in the second stage SNPs were typed by Pyrosequencing assays. Genotype frequencies between cases and controls were compared using logistical regression analysis with additive, dominant and recessive models.

RESULTS

Eleven variants within 10 genes (CCNC, CCND3, CCNG1, CCNT2, CDK6, MDM2, SKP2, WEE1, YWHAB, YWHAH) in the European-American population and nine variants in 7 genes (CCNG1, CDK2, CDK5, MDM2, RB1, SMAD3, TERF2) in the African-American population were found to be associated with aggressive PCa using at least one model. Of particular interest, CCNC (rs3380812) was associated with risk in European-American cohorts from both institutions. CDK2 (rs1045435) and CDK5 (rs2069459) were associated with risk in the African-American cohorts from both institutions. Lastly, variants within MDM2 and CCNG1 were protective for aggressive PCa in both ethnic groups.

CONCLUSIONS

This study confirms that polymorphisms within cell cycle genes are associated with clinically aggressive PCa. Validation of these markers in additional populations is necessary, but these markers may help identify patients at risk for potentially lethal carcinoma.