Association of genetic markers in the BCL-2 family of apoptosis-related genes with endometrial cancer risk in a Chinese population

Background

In vitro studies have demonstrated the role of the BCL-2 family of genes in endometrial carcinogenesis. The role of genetic variants in BCL-2 genes and their interactions with non-genetic factors in the development of endometrial cancer has not been investigated in epidemiological studies.

Patients and Methods

We examined the relationship between BCL-2 gene family variants and endometrial cancer risk among 1,028 patients and 1,922 age-matched community controls from Shanghai, China. We also investigated possible interactions between genetic variants and established risk factors (demographic, lifestyle and clinical). Individuals were genotyped for 86 tagging single nucleotide polymorphisms (SNPs) in the BCL2, BAX, BAD and BAK1 genes.

Results

Significant associations with endometrial cancer risk were found for 9 SNPs in the BCL2 gene (P trend<0.05 for all). For SNPs rs17759659 and rs7243091 (minor allele for both: G), the associations were independent. The odds ratio was 1.27 (95% CI: 1.04–1.53) for women with AG genotype for the SNP rs17759659 and 1.82 (95% CI: 1.21–2.73) for women with the GG genotype for the SNP rs7243091. No interaction between these two SNPs and established non-genetic risk factors of endometrial cancer was noticed.

Conclusion

Genetic polymorphisms in the BCL2 gene may be associated with the risk of endometrial cancer in Chinese women.

Abstract 1900: Age at last birth and endometrial cancer risk: Pooled analysis in the Epidemiology of Endometrial Cancer Consortium

Some studies show that childbearing at older age is associated with lower risk of endometrial cancer, but whether the association is independent of number of children or other factors still requires clarification. We pooled individual-level data from epidemiologic studies in the Epidemiology of Endometrial Cancer Consortium (E2C2). Data on age at last birth and/or last pregnancy were available from 14 studies: 11 case-control studies and 3 cohort studies; the latter were analyzed using a nested case-control design. A total of 9,613 endometrial cancer cases and 17,112 controls were included in the analysis. The majority of women were White (82%) and older than 55 years (69%). We estimated the effects of age at last birth using data from 12 studies and age at last pregnancy using data from 10 studies on the risk of endometrial cancer by calculating odds ratios (OR) and 95% confidence intervals (95% CI) using logistic regression models. Potential confounders included in the analysis were race, body mass index, parity, age at menarche, age at first birth, oral contraceptive use, postmenopausal hormone use, smoking status, and report of diabetes. After adjusting for potential confounders, a reduction in endometrial cancer risk was observed in women with increasing age at last birth (P trend &lt;0.0001) and age at last pregnancy (P trend &lt;0.0001). The OR per five-year increase in age at last birth and age at last pregnancy was 0.90 (95%CI: 0.86, 0.94) and 0.91 (95% CI: 0.87, 0.95), respectively. Women who had their last child at an age &gt;40 years were at a 34% decreased risk compared with women who had their last child at an age &lt;25 years (95% CI: 0.52, 0.82). Compared to women with age at last pregnancy &lt;25 years, those with age at last pregnancy &gt;40 years had a 30% decreased risk of endometrial cancer (95%CI: 0.57, 0.86). Inverse associations were observed for Whites and Asians in race-specific analysis and also in analysis restricted to women with at least 2 births. In this large pooled analysis, we show that late age at last birth or last pregnancy is a strong and independent protective factor for endometrial cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1900. doi:10.1158/1538-7445.AM2011-1900

Making epidemiologic studies responsive to the needs of participants and communities: the Carolina Breast Cancer Study experience

In this report, we present the results of surveys administered to participants and nonparticipants in the Carolina Breast Cancer Study (CBCS). Surveys and structured interviews were administered to determine women's concerns regarding participation in research studies, access to health care, and beliefs regarding causes of breast cancer. Survey results showed the highest concern for the growing number of women diagnosed with breast cancer in North Carolina and potential environmental agents that may cause breast cancer. Negative responses were noted for time constraints related to participation and lack of familiarity with epidemiologic research; another concern noted was the lack of centralized information regarding breast cancer treatment. These issues were addressed by (1) developing a web site that provided background information about the CBCS, summaries of published study results, and information about the etiology of breast cancer; and (2) creating a statewide, comprehensive breast cancer resource directory for women who need information about breast cancer diagnosis, treatment, and support. These two projects were carried out in collaboration with breast cancer advocates, and demonstrate the important role that advocates can play in making epidemiologic research more responsive to the needs of communities.

Myc/p53 interactions in transgenic mouse mammary development, tumorigenesis and chromosomal instability

We have examined defects in mammary development and tumorigenesis in a transgenic model expressing the c-myc gene under the MMTV-LTR promoter. The stochastic tumors which arise from hyperplastic ductal and lobular lesions in this model are characterized by high rates both of apoptosis and of chromosomal instability. Since the p53 gene product is thought to be central in the maintenance of genomic integrity, in part due to its ability to induce apoptosis in cells harboring DNA damage, we examined its expression and possible mutation. Initially, we observed that unmutated p53 is strongly expressed in premalignant mammary glands and in mammary tumors derived from the MMTV-c-myc strain. We then mated the MMTV-myc strain to a p53-deficient strain as a means of examining the effect of this lesion on mammary development and tumorigenesis in the context of c-myc overexpression. A lack of both p53 alleles in the presence of c-myc overexpression resulted in a dramatic hyerplastic alteration in mammary gland development. Specifically, in female bitransgenic MMTV-c-myc/p53 null mice (MMTV-myc/p53(-/-)), lobular hyperplasias were observed at almost every ductal end bud as early as 32 days of age. In contrast, only mild ductal and lobular hyperplasias were seen in MMTV-myc mice that contained both p53 alleles (MMTV-myc/p53(+/+)); an intermediate phenotype occurred in mice with a single intact (MMTV-myc/p53(+/-)) p53 allele. Mammary carcinomas arose with a high frequency in MMTV-myc/p53(+/-) mice; the tumors were comparable in frequency, histology and apoptotic index to the tumors in MMTV-myc/p53(+/+) mice. Also, as previously observed (Elson et al., 1995), lymphomas arose with extremely short latency in MMTV-myc/p53(-/-) mice, precluding study of the fate of their hyperplastic mammary lesions in situ. The frequency of p53 mutations in MMTV-myc/p53(+/+) and MMTV-myc/p53(+/-) mammary tumors and in cell lines derived from these tumors was examined by direct sequencing. No point mutations or deletions in p53 were observed in mammary tumors or cell lines from either genotype. Finally, a detailed chromosomal analysis using multicolor spectral karyotyping (SKY) revealed that there were multiple chromosomal alterations in the c-myc-overexpressing cells that contained either one or two unmutated p53 alleles. Variable ploidy changes, a common translocation of chromosome 11, and other chromosomal aberrations were observed. Our data thus support an interaction between c-Myc and p53 in mammary development, but suggest that loss of p53 is required neither for c-myc-dependent tumorigenesis nor for c-myc-dependent chromosomal instability.