The joint effect of smoking and AIB1 on breast cancer risk in BRCA1 mutation carriers

Alcohol Consumption, Cigarette Smoking, and Risk of Breast Cancer for BRCA1 and BRCA2 Mutation Carriers: Results from The BRCA1 and BRCA2 Cohort Consortium

BACKGROUND

Tobacco smoking and alcohol consumption have been intensively studied in the general population to assess their effects on the risk of breast cancer, but very few studies have examined these effects in BRCA1 and BRCA2 mutation carriers. Given the high breast cancer risk for mutation carriers and the importance of BRCA1 and BRCA2 in DNA repair, better evidence on the associations of these lifestyle factors with breast cancer risk is essential.

METHODS

Using a large international pooled cohort of BRCA1 and BRCA2 mutation carriers, we conducted retrospective (5,707 BRCA1 mutation carriers and 3,525 BRCA2 mutation carriers) and prospective (2,276 BRCA1 mutation carriers and 1,610 BRCA2 mutation carriers) analyses of alcohol and tobacco consumption using Cox proportional hazards models.

RESULTS

For both BRCA1 and BRCA2 mutation carriers, none of the smoking-related variables was associated with breast cancer risk, except smoking for more than 5 years before a first full-term pregnancy (FFTP) when compared with parous women who never smoked. For BRCA1 mutation carriers, the HR from retrospective analysis (HRR) was 1.19 [95% confidence interval (CI), 1.02-1.39] and the HR from prospective analysis (HRP) was 1.36 (95% CI, 0.99-1.87). For BRCA2 mutation carriers, smoking for more than 5 years before an FFTP showed an association of a similar magnitude, but the confidence limits were wider (HRR = 1.25; 95% CI, 1.01-1.55 and HRP = 1.30; 95% CI, 0.83-2.01). For both carrier groups, alcohol consumption was not associated with breast cancer risk.

CONCLUSIONS

The finding that smoking during the prereproductive years increases breast cancer risk for mutation carriers warrants further investigation.

IMPACT

This is the largest prospective study of BRCA mutation carriers to assess these important risk factors.

BRCA Mutations and Breast Cancer Prevention

Women who inherit a deleterious BRCA1 or BRCA2 mutation face substantially increased risks of developing breast cancer, which is estimated at 70%. Although annual screening with magnetic resonance imaging (MRI) and mammography promotes the earlier detection of the disease, the gold standard for the primary prevention of breast cancer remains bilateral mastectomy. In the current paper, I review the evidence regarding the management of healthy BRCA mutation carriers, including key risk factors and protective factors, and also discuss potential chemoprevention options. I also provide an overview of the key findings from the literature published to date, with a focus on data from studies that are well-powered, and preferably prospective in nature.

The association between smoking and cancer incidence in BRCA1 and BRCA2 mutation carriers

Tobacco smoke is an established carcinogen, but the association between tobacco smoking and cancer risk in BRCA mutation carriers is not clear. The aim of this study was to evaluate prospectively the association between tobacco smoking and cancer incidence in a cohort of BRCA1 and BRCA2 mutation carriers. The study population consisted of unaffected BRCA mutation carriers. Information on lifestyle including smoking histories, reproductive factors, and past medical histories was obtained through questionnaires. Incident cancers were updated biennially via follow-up questionnaires. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using time-dependent Cox regression models. There were 700 incident cancers diagnosed over 26,711 person-years of follow-up. The most frequent cancers seen in BRCA mutation carriers were breast (n = 428; 61%) and ovarian (n = 109; 15%) cancer. Compared to nonsmokers, (ever) smoking was associated with a modest increased risk of all cancers combined (HR = 1.17; 95%CI 1.01-1.37). Women in the highest group of total pack-years (4.3-9.8) had an increased risk of developing any cancer (HR = 1.27; 95%CI 1.04-1.56), breast cancer (HR = 1.33, 95%CI 1.02-1.75), and ovarian cancer (HR = 1.68; 95%CI 1.06-2.67) compared to never smokers. The associations between tobacco smoking and cancer did not differ by BRCA mutation type or by age at diagnosis. This prospective study suggests that tobacco smoking is associated with a modest increase in the risks of breast and ovarian cancer among women with BRCA1 or BRCA2 mutation.

Modifiers of breast and ovarian cancer risks for BRCA1 and BRCA2 mutation carriers

Pathogenic mutations in BRCA1 and BRCA2 are associated with high risks of breast and ovarian cancer. However, penetrance estimates for mutation carriers have been found to vary substantially between studies, and the observed differences in risk are consistent with the hypothesis that genetic and environmental factors modify cancer risks for women with these mutations. Direct evidence that this is the case has emerged in the past decade, through large-scale international collaborative efforts. Here, we describe the methodological challenges in the identification and characterisation of these risk-modifying factors, review the latest evidence on genetic and lifestyle/hormonal risk factors that modify breast and ovarian cancer risks for women with BRCA1 and BRCA2 mutations and outline the implications of these findings for cancer risk prediction. We also review the unresolved issues in this area of research and identify strategies of clinical implementation so that women with BRCA1 and BRCA2 mutations are no longer counselled on the basis of 'average' risk estimates.

Effect of lifestyle and reproductive factors on the onset of breast cancer in female BRCA 1 and 2 mutation carriers

BACKGROUND

The birth year-dependent onset of breast cancer (BC) in BRCA1/2 mutation carriers suggests a risk-modifying role for reproductive and life style factors. We therefore examined possible associations between these factors and age at diagnosis.

METHODS

Cox regression analysis and log-Rank testing were used to estimate the effect of potential life style factors on the onset of BC in 197 BRCA mutation carriers.

RESULTS

Nulliparous BRCA mutation carriers developed BC earlier than those who had delivered (36.4 vs. 40.9; P = 0.001). Similarly, smokers and women who had used oral contraceptives experienced an earlier cancer onset (39.0 vs. 41.4; P = 0.05 and 39.3 vs. 44.9; P = 0.0001, respectively). In multivariate analysis, oral contraceptive use (HR: 1.7; P = 0.006) and birth cohort (< vs. ≥1965 HR: 4.5; P = 0.001) were associated with an earlier BC onset, while previous pregnancies led to a delay (HR: 0.2; P = 0.04). Mutation carriers born ≥1965 were less likely to have experienced pregnancies and more likely to have used oral contraceptives, and consequently developed BC at an earlier age (median age: 42 vs. 58; P < 0.0001 log-Rank test).

CONCLUSION

We here demonstrate that in BRCA1/2 mutation carriers the birth cohort-associated differences in the onset of BC are profound and influenced by reproductive factors.

Dose-response effects of aerobic exercise on estrogen among women at high risk for breast cancer: a randomized controlled trial

Medical and surgical interventions for elevated breast cancer risk (e.g., BRCA1/2 mutation, family history) focus on reducing estrogen exposure. Women at elevated risk may be interested in less aggressive approaches to risk reduction. For example, exercise might reduce estrogen, yet has fewer serious side effects and less negative impact than surgery or hormonal medications. Randomized controlled trial. Increased risk defined by risk prediction models or BRCA mutation status. Eligibility: Age 18-50, eumenorrheic, non-smokers, and body mass index (BMI) between 21 and 50 kg/m(2). 139 were randomized. Treadmill exercise: 150 or 300 min/week, five menstrual cycles. Control group maintained exercise <75 min/week.

PRIMARY OUTCOME

Area under curve (AUC) for urinary estrogen. Secondary measures: urinary progesterone, quantitative digitized breast dynamic contrast-enhanced magnetic resonance imaging background parenchymal enhancement. Mean age 34 years, mean BMI 26.8 kg/m(2). A linear dose-response relationship was observed such that every 100 min of exercise is associated with 3.6 % lower follicular phase estrogen AUC (linear trend test, p = 0.03). No changes in luteal phase estrogen or progesterone levels. There was also a dose-response effect noted: for every 100 min of exercise, there was a 9.7 % decrease in background parenchymal enhancement as measured by imaging (linear trend test, p = 0.009). Linear dose-response effect observed to reduce follicular phase estrogen exposure measured via urine and hormone sensitive breast tissue as measured by imaging. Future research should explore maintenance of effects and extent to which findings are repeatable in lower risk women. Given the high benefit to risk ratio, clinicians can inform young women at increased risk that exercise may blunt estrogen exposure while considering whether to try other preventive therapies.

Modifiers of cancer risk in BRCA1 and BRCA2 mutation carriers: systematic review and meta-analysis

BACKGROUND

There is substantial variability in cancer risk in women who have inherited a BRCA1 or BRCA2 (BRCA1/2) mutation. Numerous factors have been hypothesized to modify these risks, but studies are of variable quality, and it remains unclear which of these may be of value in clinical risk assessment.

METHODS

PubMed and Web of Science databases were searched for articles published through September 2013. Fixed effects meta-analysis was done using the hazard ratios and/or odds ratios to estimate the pooled effect estimates (ES) and 95% confidence intervals (CIs) to identify factors that are associated with cancer risk modification in BRCA1/2 mutation carriers.

RESULTS

We identified 44 nonoverlapping studies that met predefined quality criteria. Sufficient evidence is available to make clinically relevant inferences about a number of cancer risk modifiers. The only variable examined that produced a probable association was late age at first live birth, a meta-analysis showed a decrease in the risk of breast cancer in BRCA1 mutation carriers with women aged 30 years or older vs. women younger than 30 years (ES = 0.65; 95% CI =0.42 to 0.99). The same was shown for women aged 25 to 29 years versus those aged less than 25 years (ES = 0.69; 95% CI = 0.48 to 0.99). Breastfeeding and tubal ligation were associated with reduced ovarian cancer risk in BRCA1 mutation carriers; oral contraceptives were associated with reduced risk among BRCA1/2 mutation carriers. Smoking was associated with increased breast cancer risk in BRCA2 mutation carriers only.

CONCLUSIONS

Data assessing many potential risk modifiers are inadequate, and many have not been externally validated. Although additional studies are required to confirm some associations, sufficient information is available for some risk factors to be used in risk counseling or lifestyle modification to minimize cancer risk in BRCA1/2 mutation carriers

Relationship of early-onset baldness to prostate cancer in African-American men

BACKGROUND

Early-onset baldness has been linked to prostate cancer; however, little is known about this relationship in African-Americans who are at elevated prostate cancer risk.

METHODS

We recruited 219 African-American controls and 318 African-American prostate cancer cases. We determined age-stratified associations of baldness with prostate cancer occurrence and severity defined by high stage (T3/T4) or high grade (Gleason 7+.) Associations of androgen metabolism genotypes (CYP3A4, CYP3A5, CYP3A43, AR-CAG, SRD5A2 A49T, and SRD5A2 V89L), family history, alcohol intake, and smoking were examined by baldness status and age group by using multivariable logistic regression models.

RESULTS

Baldness was associated with odds of prostate cancer [OR = 1.69; 95% confidence interval (CI), 1.05-2.74]. Frontal baldness was associated with high-stage (OR = 2.61; 95% CI, 1.10-6.18) and high-grade (OR = 2.20; 95% CI, 1.05-4.61) tumors. For men diagnosed less than the age of 60 years, frontal baldness was associated with high stage (OR = 6.51; 95% CI, 2.11-20.06) and high grade (OR = 4.23; 95% CI, 1.47-12.14). We also observed a suggestion of an interaction among smoking, median age, and any baldness (P = 0.02).

CONCLUSIONS

We observed significant associations between early-onset baldness and prostate cancer in African-American men. Interactions with age and smoking were suggested in these associations. Studies are needed to investigate the mechanisms influencing the relationship between baldness and prostate cancer in African-American men.

IMPACT

African-American men present with unique risk factors including baldness patterns that may contribute to prostate cancer disparities.

Polymorphic repeat length in the AIB1 gene and breast cancer risk in BRCA1 and BRCA2 mutation carriers: a meta-analysis of observational studies

OBJECTIVES

We carried out a meta-analysis focusing on the relationship between length of AIB1 gene poly-Q repeat domain as a modifier of breast cancer (BC) susceptibility in patients with BRCA1 and BRCA2 mutation carriers.

DATA SOURCES

We searched MEDLINE and EMBASE for all medical literature published until February, 2012.

STUDY ELIGIBILITY CRITERIA

Studies were included in the meta-analysis if they met all the predetermined criteria, such as: (a) case-control or cohort studies; (b) the primary outcome was clearly defined as BC; (c) the exposure of interest measured was AIB1 polyglutamine repeat length genotype; (d) provided relative risk (RR) or odds ratio (OR) estimates and their 95% confidence intervals (CIs). SYNTHESIS METHODS: Two of the authors independently evaluated the quality of the studies included and extracted the data. Meta-analyses were performed for case-control and cohort studies separately. Heterogeneity was examined and the publication bias was assessed with a funnel plot for asymmetry.

RESULT

7 studies met our predetermined inclusion criteria and were included in the meta-analysis. Overall quality ratings of the studies varied from 0.36 to 0.77, with a median of 0.5. The overall RR estimates of 29/29 poly-Q repeats on risk of BC in BRCA1/2, BRCA1, and BRCA2, were always greater than 1.00; however, this effect was not statistically significant. In the meta-analysis of studies reporting the effect of 28/28 poly-Q repeats on risk of BC in BRCA1/2, BRCA1, and BRCA2, the overall RR decreased below 1.00; however, this effect was not statistically significant. Similar estimates were shown for at least 1 allele of ≤26 repeats.

CONCLUSIONS

Genotypes of AIB1 polyglutamine polymorphism analyzed do not appear to be associated to a modified risk of BC development in BRCA1 and BRCA2 mutation carriers. Future research on length of poly-Q repeat domain and BC susceptibility should be discouraged and more promising potential sources of penetrance variation among BRCA1 and BRCA2 mutation carriers should be investigated.

AIB1 polymorphisms with breast cancer susceptibility: a pooled analysis of variation in BRCA1/2 mutation carriers and non-carriers

The AIB1 gene (amplified in breast cancer 1), coding for a member of steroid receptor co-activator p160 protein family is involved in regulation of estrogen receptor transactivation influencing the estrogen-dependent gene expression. It contains a glutamine repeat polymorphism and several single nucleotide polymorphisms that may alter the transcriptional activation of the receptor and affect susceptibility to breast cancer. Previous studies have shown that these polymorphisms may modify the breast cancer risk in women carrying BRCA1/2 mutations. However, the results remained controversial. This meta-analysis of literatures was performed to derive a more precise estimation of the relationship. A total of 22 studies were identified, including 3,742 cases and 3,491 controls for AIB1 polyglutamine repeat polymorphism, 2,170 cases and 3,309 controls for Q586H polymorphism, and 2,183 cases and 3,319 controls for T960T polymorphism. Overall, we found no evidence of association for individuals who carried at least one AIB1 allele of 28 or 29 or more repeat with breast cancer risk. But we found increased breast cancer risk in BRCA1/2 mutation carriers for individuals with both alleles ≥29 polyglutamine repeat (OR, 1.64; 95% CI 1.24-2.17). And reduced risk was found to be associated with the Q586H polymorphism among the variant homozygote genotype carriers (OR, 0.42; 95% CI 0.23-0.77). Our results do not support the direct association of AIB1 polyglutamine repeat length and breast cancer. However, we found that BRCA1/2 mutation carriers with both alleles ≥29 repeats have a higher risk of breast cancer.

Variation in breast cancer risk with mutation position, smoking, alcohol, and chest X-ray history, in the French National BRCA1/2 carrier cohort (GENEPSO)

Germline mutations in BRCA1/2 confer a high risk of breast cancer (BC), but the magnitude of this risk varies according to various factors. Although controversial, there are data to support the hypothesis of allelic-risk heterogeneity. We assessed variation in BC risk according to the location of mutations recorded in the French study GENEPSO. Since the women in this study were selected from high-risk families, oversampling of affected women was eliminated by using a weighted Cox-regression model. Women were censored at the date of diagnosis when affected by any cancer, or the date of interview when unaffected. A total of 990 women were selected for the analysis: 379 were classified as affected, 611 as unaffected. For BRCA1, there was some evidence of a central region where the risk of BC is lower (codons 374-1161) (HR = 0.59, P = 0.04). For BRCA2, there was a strong evidence for a region at decreased risk (codons 957-1827) (HR = 0.35, P = 0.005) and for one at increased risk (codons 2546-2968) (HR = 3.56, P = 0.01). Moreover, we found an important association between radiation exposure from chest X-rays and BC risk (HR = 4.29, P < 10(-3)) and a positive association between smoking more than 21 pack-years and BC risk (HR = 2.09, P = 0.04). No significant variation in BC risk associated with chest X-ray exposure, smoking, and alcohol consumption was found according to the location of the mutation in BRCA1 and BRCA2. Our findings are consistent with those suggesting that the risk of BC is lower in the central regions of BRCA1/2. A new high-risk region in BRCA2 is described. Taking into account environmental and lifestyle modifiers, the location of mutations might be important in the clinical management of BRCA mutation carriers.

The AIB1 gene polyglutamine repeat length polymorphism and the risk of breast cancer development

PURPOSE

Carriers of BRCA1/2 mutations are at high lifetime risk of breast cancer (BC); however, the BC onset broadly vary in individual patients. Recently, polyglutamine (poly-Q) repeat length polymorphism of the amplified in breast cancer 1 (AIB1) gene was analyzed as a risk factor influencing BC onset in BRCA1/2 mutation carriers with contradictory results.

METHODS

We genotyped AIB1 poly-Q repeat in 243 BRCA1/2 mutation carriers, 61 patients with familial BC (negatively tested for the presence of BRCA1/2 mutation), 221 patients with sporadic BC, and 176 non-cancer controls using denaturing high-performance liquid chromatography and statistically evaluated the effect of AIB1 poly-Q repeat length polymorphism on BC onset.

RESULTS

Having used previously published statistical analyses of AIB1 poly-Q repeat length (≥28 and ≥29 repeat cutpoints or analysis of AIB1 poly-Q repeat length as continuous variable), we did not find any association between AIB1 poly-Q repeat length and BC development in analyzed BC groups. However, the analysis of individual genotypes revealed that AIB1 genotype consisting of 28/28 glutamine repeats served as a protective factor in BRCA1 mutation carriers (HR = 0.64; 95% CI 0.41-0.99; P = 0.045) and as a risk factor in carriers of mutation in exon 11 of the BRCA2 gene (HR = 3.50; 95% CI 1.25-9.78; P = 0.017).

CONCLUSIONS

Our results confirm that AIB1 poly-Q repeat length polymorphism does not influence the BC risk in general but suggest that the specific AIB1 genotypes should be considered in patients with BC carrying mutation in the BRCA1/2 genes.

Smoking and colorectal cancer in Lynch syndrome: results from the Colon Cancer Family Registry and the University of Texas M.D. Anderson Cancer Center

PURPOSE

Lynch syndrome family members with inherited germline mutations in DNA mismatch repair (MMR) genes have a high risk of colorectal cancer (CRC), and cases typically have tumors that exhibit a high level of microsatellite instability (MSI). There is some evidence that smoking is a risk factor for CRCs with high MSI; however, the association of smoking with CRC among those with Lynch syndrome is unknown.

EXPERIMENTAL DESIGN

A multicentered retrospective cohort of 752 carriers of pathogenic MMR gene mutations was analyzed, using a weighted Cox regression analysis, adjusting for sex, ascertainment source, the specific mutated gene, year of birth, and familial clustering.

RESULTS

Compared with never smokers, current smokers had a significantly increased CRC risk [adjusted hazard ratio (HR), 1.62; 95% confidence interval (95% CI), 1.01-2.57] and former smokers who had quit smoking for 2 or more years were at decreased risk (HR, 0.53; 95% CI, 0.35-0.82). CRC risk did not vary according to age at starting. However, light smoking (<10 cigarettes per day) and shorter duration of smoking (<10 years) were associated with decreased CRC risk (HR, 0.51; 95% CI, 0.29-0.91 and HR, 0.52; 95% CI, 0.30-0.89, respectively). For former smokers, CRC risk decreased with years since quitting (P trend <0.01).

CONCLUSIONS

People with Lynch syndrome may be at increased risk of CRC if they smoke regularly. Although our data suggest that former smokers, short-term smokers, and light smokers are at decreased CRC risk, these findings need further confirmation, preferably using prospective designs.

Application of OMICS technologies in occupational and environmental health research; current status and projections

OMICS technologies are relatively new biomarker discovery tools that can be applied to study large sets of biological molecules. Their application in human observational studies (HOS) has become feasible in recent years due to a spectacular increase in the sensitivity, resolution and throughput of OMICS-based assays. Although, the number of OMICS techniques is ever expanding, the five most developed OMICS technologies are genotyping, transcriptomics, epigenomics, proteomics and metabolomics. These techniques have been applied in HOS to various extents. However, their application in occupational environmental health (OEH) research has been limited. Here, we will discuss the opportunities these new techniques provide for OEH research. In addition we will address difficulties and limitations to the interpretation of the data that is generated by OMICS technologies. To illustrate the current status of the application of OMICS in OEH research, we will provide examples of studies that used OMICS technologies to investigate human health effects of two well-known toxicants, benzene and arsenic.

The roles and action mechanisms of p160/SRC coactivators and the ANCCA coregulator in cancer

Chromosomal aberrations involving genes encoding members of the p160/SRC transcriptional coactivator family such as AIB1/ACTR and TIF2 implicated the coactivators in malignancy of human cells. Significant progress has been made in the last decade toward uncovering their roles in the development and progression of solid tissue tumors as well as leukemia and understanding of the underlying molecular mechanisms. Here, we review their genetic aberrations and dysregulation in expression in breast cancer, prostate cancer, and other nonhormone-responsive cancers. The experimental evidence gathered from studies using cell culture and animal models strongly supports a critical and, in some circumstances, their oncogenic function. We summarize results that the SRCs may contribute to tumorigenesis and disease progression through transcription factors such as E2F, PEA3, and AP-1 and through an intimate control of signaling pathways of growth factors-Akt and the receptor tyrosine kinases. The finding that a recently identified nuclear receptor coregulator ANCCA, like the SRCs, is frequently overexpressed in many types of cancers again underscores their broader roles in cancer.

Smoking and the risk of breast cancer in BRCA1 and BRCA2 carriers: an update

Among women with a mutation in BRCA1 or BRCA2, the risk of breast cancer is high, but it may be modified by exogenous and endogenous factors. There is concern that exposure to carcinogens in cigarette smoke may increase the risk of cancer in mutation carriers. We conducted a matched case-control study of 2,538 cases of breast cancer among women with a BRCA1 (n = 1,920) or a BRCA2 (n = 618) mutation. One non-affected mutation carrier control was selected for each case, matched on mutation, country of birth, and year of birth. Odds ratios were calculated using conditional logistic regression, adjusted for oral contraceptive use and parity. Ever-smoking was not associated with an increased breast cancer risk among BRCA1 carriers (OR = 1.09; 95% CI 0.95-1.24) or among BRCA2 carriers (OR = 0.81; 95% CI 0.63-1.05). The result did not differ when cases were restricted to women who completed the questionnaire within two years of diagnosis. A modest, but significant increase in risk was seen among BRCA1 carriers with a past history of smoking (OR = 1.27; 95% CI 1.06-1.50), but not among current smokers (OR = 0.95; 0.81-1.12). There appears to be no increase in the risk of breast cancer associated with current smoking in BRCA1 or BRCA2 carriers. There is a possibility of an increased risk of breast cancer among BRCA1 carriers associated with past smoking. There may be different effects of carcinogens in BRCA mutation carriers, depending upon the timing of exposure.

Variation in breast cancer risk in BRCA1 and BRCA2 mutation carriers

Genetic testing for BRCA1 and BRCA2 (BRCA1/2) mutations can provide important information for women who are concerned about their breast and ovarian cancer risks and need to make relevant prevention and medical management decisions. However, lifetime risks of breast cancer in individual BRCA1/2 mutation carriers have been confusing to apply in clinical decision-making. Published risk estimates vary significantly and are very dependent on the characteristics of the population under study. Recently, Begg and colleagues estimated cancer risks in a population-based study of BRCA1/2 mutation carriers. Here, we discuss the clinical decision-making implications of this research in the context of risk factors that may influence risk estimates in BRCA1/2 mutation carriers.

Endocrinology of the wild and mutant BRCA1 gene and types of hormonal carcinogenesis

Information related to the BRCA1 gene has increasingly become a subject for analysis by endocrinologists. For example, it is hard to dismiss the fact that, in BRCA1 mutation carriers, tumors develop predominantly in such estrogen-dependent organs as the mammary glands and ovaries but not in the endometrium. Another characteristic feature is that although BRCA1 mutants and knock-downs are unable to inhibit the transcriptional activity of estrogen receptor-alpha, in BRCA1 mutation carriers breast cancers are often estrogen receptor-negative and originate from the basal rather than the luminal epithelium. The latter, together with other data, suggests that BRCA1-positive breast neoplasms could be considered to be a consequence of the genotoxic variant of hormonal carcinogenesis (that is, associated with DNA damaging rather then with pure hormonal/physiological properties of hormones or their derivatives). Of indisputable significance are the data demonstrating that knocking down of the BRCA1 gene is accompanied by aromatase overexpression and the abolishment of IGF-1 receptor expression suppression, thus increasing both steroid and insulin signaling. Importantly, the endocrine-genotoxic 'liberation' found upon transfer from the wild-type to the mutant BRCA1 provides grounds to regard BRCA1 as a modulator of endocrine-genotoxic switching (predominantly into a direction of DNA-damaging hormone effects) and also to ask whether this is a property of only this or some other tumor suppressor's.

Smoking and risk of breast cancer in carriers of mutations in BRCA1 or BRCA2 aged less than 50 years

BACKGROUND

Cigarette smoke contains compounds that may damage DNA, and the repair of damage may be impaired in women with germline mutations in BRCA1 or BRCA2. However, the effect of cigarette smoking on breast cancer risk in mutation carriers is the subject of conflicting reports. We have examined the relation between smoking and breast cancer risk in non-Hispanic white women under the age of 50 years who carry a deleterious mutation in BRCA1 or BRCA2.

METHODS

We conducted a case-control study using data from carriers of mutations in BRCA1 (195 cases and 302 controls) and BRCA2 (128 cases and 179 controls). Personal information, including smoking history, was collected using a common structured questionnaire by eight recruitment sites in four countries. Odds-ratios (OR) for breast cancer risk according to smoking were adjusted for age, family history, parity, alcohol use, and recruitment site.

RESULTS

Compared to non-smokers, the OR for risk of breast cancer for women with five or more pack-years of smoking was 2.3 (95% confidence interval 1.6-3.5) for BRCA1 carriers and 2.6 (1.8-3.9) for BRCA2 carriers. Risk increased 7% per pack-year (p<0.001) in both groups.

CONCLUSIONS

These results indicate that smoking is associated with increased risk of breast cancer before age 50 years in BRCA1 and BRCA2 mutation carriers. If confirmed, they provide a practical way for carriers to reduce their risks. Previous studies in prevalent mutation carriers have not shown smoking to increase risk of breast cancer, but are subject to bias, because smoking decreases survival after breast cancer.

Cancer genetics of epigenetic genes

The cancer epigenome is characterised by specific DNA methylation and chromatin modification patterns. The proteins that mediate these changes are encoded by the epigenetics genes here defined as: DNA methyltransferases (DNMT), methyl-CpG-binding domain (MBD) proteins, histone acetyltransferases (HAT), histone deacetylases (HDAC), histone methyltransferases (HMT) and histone demethylases. We review the evidence that these genes can be targeted by mutations and expression changes in human cancers.

Regulation of SRC family coactivators by post-translational modifications

Initially identified as a group of auxiliary protein factors involved in transcriptional regulation by steroid hormone receptors as well as by other members of the nuclear receptor superfamily, the steroid receptor coactivators (SRCs) have since then been implicated in the transcriptional regulation of other transcription factors which are important components of very different signaling pathways. Members of the SRC family have been shown to interact with myogenin, MEF-2, transcriptional enhancer factor (TEF), NF-kappaB, AP-1, STAT, p53, and E2F1, suggesting that SRC coactivators participate in diverse cellular processes. Recent evidence indicates that various post-translational modifications play critical roles in determining the final transcriptional output and specificity of SRC coactivators. In this review, we summarized the current knowledge concerning post-translational modifications, dynamic interplay between different modifications, and patho-physiological relevance of the modifications of SRC proteins.

Is the association between cigarette smoking and breast cancer modified by genotype? A review of epidemiologic studies and meta-analysis

Epidemiologic studies have examined the association between cigarette smoking and breast cancer risk according to genotype with increasing frequency, commensurate with the growing awareness of the roles genes play in detoxifying or activating chemicals found in cigarette smoke and in preventing or repairing the damage caused by those compounds. To date, approximately 50 epidemiologic studies have examined the association between smoking and breast cancer risk according to variation in genes related to carcinogen metabolism, modulation of oxidative damage, and DNA repair. Some of the findings presented here suggest possible effect modification by genotype. In particular, 14 epidemiologic studies have tended to show positive associations with long-term smoking among NAT2 slow acetylators, especially among postmenopausal women. Summary analyses produced overall meta-relative risk (RR) estimates for smoking of 1.2 [95% confidence interval (95% CI), 1.0-1.5] for rapid acetylators and 1.5 (95% CI, 1.2-1.8) for slow acetylators. After stratification by menopausal status, the meta-RR for postmenopausal slow acetylators was 2.4 (95% CI, 1.7-3.3), whereas similar analyses for the other categories showed no association. In addition, summary analyses produced meta-RRs for smoking of 1.1 (95% CI, 0.8-1.4) when GSTM1 was present and 1.5 (95% CI, 1.1-2.1) when the gene was deleted. Overall, however, interpretation of the available literature is complicated by methodologic limitations, including small sample sizes, varying definitions of smoking, and difficulties involving single nucleotide polymorphism selection, which likely have contributed to the inconsistent findings. These methodologic issues should be addressed in future studies to help clarify the association between smoking and breast cancer.