Synergistic effects of STK15 gene polymorphisms and endogenous estrogen exposure in the risk of breast cancer.

STK15 is a member of a family of serine/threonine kinases that act as key regulators of chromosome segregation and cytokinesis. Over expression of the STK15 gene leads to centrosome amplification, chromosomal instability, aneuploidy, and transformation. It has been reported that the 91T --> A (Phe --> Ile at codon 31) polymorphism in the STK15 gene affects the function of this gene. We hypothesized that this polymorphism may interact with endogenous estrogen exposure in the risk of breast cancer and evaluated this hypothesis in a population-based, case-control study conducted among Chinese women in Shanghai. Genotyping assays were completed for 1,102 incident cases and 1,186 community controls. Participation and blood donation rates were over 90% and 80%, respectively. Elevated risks of breast cancer were found to be associated with the Phe/Ile [odds ratio (OR), 1.3; 95% confidence interval (CI), 1.0-1.7] and Ile/Ile (OR, 1.2; 95% CI, 0.9-1.6) genotypes at codon 31 of the STK15 gene, although the ORs were not statistically significant. The risk associated with this polymorphism was modified by factors related to endogenous estrogen exposure, such as high body mass index (BMI), high waist-to-hip ratio, long duration of lifetime menstruation, or long duration of menstruation before first live birth. In particular, a statistically significant interaction was found between BMI and the STK15 Phe(31)Ile polymorphism (P = 0.02) and a positive association with breast cancer risk for the Ile allele was found only among overweight (BMI >/= 25 kg/m(2)) women with adjusted ORs (95% CIs) of 3.3 (1.4-7.7) and 4.1 (1.7-9.8) associated with the Phe/Ile and Ile/Ile genotypes (Pfor trend <0.01), respectively. The findings from this study are consistent with the evidence from invitro and in vivo experiments, implicating an etiologic role of the STK15 gene in human breast cancer, and provide evidence for the modifying effects of genetic background on human cancer risk.

Genetic polymorphisms in the human growth hormone-1 gene (GH1) and the risk of breast carcinoma.

BACKGROUND: In addition to possessing many physiologic functions, human growth hormone-1 (GH1) has been shown in recent in vitro and in vivo experiments to induce malignant disease, including breast carcinoma. The authors investigated the association of breast carcinoma with genetic polymorphisms in the GH1 gene in the Shanghai Breast Cancer Study. METHODS: Included in the current investigation were 1193 women with breast carcinoma (case patients) and 1310 healthy women from the same community (control patients) who completed in-person interviews and provided blood samples. Genetic polymorphisms in the proximal promoter region (nucleotide [nt] -162 to nt +148 relative to the transcription start site of the GH1 gene) were searched and confirmed by resequencing DNA samples from 43 study participants. A novel polymorphism, a transition from adenine to guanine at nt 69 (A69G), was identified. Samples from all participants were genotyped with TaqMan 5' nuclease assays for five common single-nucleotide polymorphisms (SNPs)-four in the proximal region (A-75G, G-57T, A-6G, and A69G) and one in intron 4 (T1169A). RESULTS: The frequencies of occurrence for the minor alleles in these polymorphic sites were 0.04, 0.60, 0.24, 0.03, and 0.34, respectively, in the control group; these frequencies were comparable to those observed in the case group. After adjusting for potential confounding factors, none of the SNPs investigated in this study showed a statistically significant association with breast carcinoma risk. This null association was found for both younger women (age < 45 years) and older women (age > or = 45 years). GH1 gene haplotypes were assessed using SNP data and were analyzed in relation to breast carcinoma risk. Again, none of the haplotypes were associated with breast carcinoma risk. CONCLUSIONS: The results of the current study suggest that genetic polymorphisms in the proximal promoter region and in the fourth intron of the GH1 gene are unrelated to breast carcinoma risk in Chinese women.

GSTM1 and GSTT1 polymorphisms and postmenopausal breast cancer risk.

Glutathione S-transferases (GSTs) are a family of important enzymes involved in the detoxification of a wide variety of known and suspected carcinogens, including potential mammary carcinogens identified in charred meats and tobacco smoke. A substantial proportion of the Caucasian population has a homozygous deletion (null) of the GSTMI or GSTT1 gene, which results in lack of production of these isoenzymes. We conducted a case-control study in a cohort of postmenopausal Iowa women who in 1986 completed a mailed questionnaire on lifestyle factors including information on cigarette smoking and breast cancer risk factors. DNA samples and information related to charred meat intake were obtained, in the case-control study, from breast cancer cases diagnosed during 1992-1994, and a random sample of cancer-free cohort members. Included in this study were 202 cases and 481 controls who were genotyped for GSTM1 or GSTT1 gene polymorphisms. Compared to women who had both GSTM1 and GSTT1 genes, a 60% elevated risk (95% CI = 1.0-2.5) was observed among those whose GSTM1 or GSTT1 gene was deleted. When stratified by meat eating habits, the risk of breast cancer associated with null GSTM1 or GSTT1 genotype was observed primarily among women who ate meats consistently well- or very well-done. Women who carried either one of the null genotypes and consumed meat consistently well- or very well-done had a 3.4-fold elevated risk of developing breast cancer (95% CI = 1.6-7.1). Cigarette smoking was not a risk factor for breast cancer among women who had either the GSTM1 or GSTT1 genes. Among those with the null GSTT1 genotype, however, a significantly elevated risk of breast cancer was associated with cigarette smoking (OR = 2.5, 95% CI = 1.1-5.4) and the association was stronger among former (OR = 4.4, 95% CI = 1.5-12.8) than current smokers (OR = 1.3, 95% CI = 0.4-4.1). This study suggests that certain null GST genotypes may be associated with an elevated risk of breast cancer and the association may be modified by charred meat intake and cigarette smoking.