Intrinsic breast cancer subtypes defined by estrogen receptor signalling-prognostic relevance of progesterone receptor loss

The majority of luminal type breast carcinomas are slowly growing tumors with an overall favorable prognosis. However, a proportion of cases (luminal B tumors) are characterized by coactivation of growth factor receptors or non-canonical ER signaling and a poorer clinical outcome. The aim of our study was to evaluate whether the expression of proteins that are part of the ER signaling network may be used to distinguish low-risk from high-risk luminal tumors. Unsupervised hierarchical clustering of a set of proteins either involved in estrogen receptor signaling or associated with resistance to endocrine therapy was performed in a series of 443 postmenopausal breast carcinomas. Using this approach, we were able to reproduce the established classification with two distinct groups of luminal (estrogen receptor positive) tumors, one group of HER2-associated tumors and a group of triple-negative tumors. However, neither proliferation nor the expression of one or more of the ER-co-factors or resistance-associated factors, but PR-expression was identified as the most important stratifier distinguishing between the two luminal groups. In fact, not only the four identified clusters were shown to be significantly associated with patient outcome, PR-expression alone or in combination with Ki-67-stains stratified ER-positive tumors into a low-risk and a high-risk group. Our data indicate that defining luminal B tumors by the presence of high-risk criteria (loss of PR-expression or increased proliferation) provides a robust and highly significant stratification of ER-positive breast carcinomas into luminal A and B.

The UGT1A6_19_GG genotype is a breast cancer risk factor

Validation of an association between the UGT1A6_19_T>G (rs6759892) polymorphism and overall breast cancer risk. A pilot study included two population-based case-control studies from Germany (MARIE-GENICA). An independent validation study comprised four independent breast cancer case-control studies from Finland (KBCP, OBCS), Germany (BBCC), and Sweden (SASBAC). The pooled analysis included 7418 cases and 8720 controls from all six studies. Participants were of European descent. Genotyping was done by MALDI-TOF MS and statistical analysis was performed by logistic regression adjusted for age and study. The increased overall breast cancer risk for women with the UGT1A6_19_GG genotype which was observed in the pilot study was confirmed in the set of four independent study collections (OR 1.13, 95% CI 1.05–1.22; p = 0.001). The pooled study showed a similar effect (OR 1.09, 95% CI 1.04–1.14; p = 0.001). The risk effect on the basis of allele frequencies was highly significant, the pooled analysis showed an OR of 1.11 (95% CI 1.06–1.16; p = 5.8 × 10⁻⁶). We confirmed the association of UGT1A6_19_GG with increased overall breast cancer risk and conclude that our result from a well powered multi-stage study adds a novel candidate to the panel of validated breast cancer susceptibility loci.

Association of pre-diagnosis physical activity with recurrence and mortality among women with breast cancer

Evidence is emerging that physical activity (PA) may improve overall survival after breast cancer diagnosis. However, the effect of PA on breast cancer recurrence and on cause-specific mortality is less investigated. We assessed the association of pre-diagnosis PA with recurrence, overall and cause-specific survival in a prospective cohort study in Germany including 3,393 non-metastatic breast cancer patients aged 50-74 years. Cox proportional hazards models were calculated adjusted for relevant prognostic factors. During a median follow-up of 5.6 years, 367 patients deceased. Overall mortality was significantly inversely associated with pre-diagnosis recreational PA. However, this effect was mainly attributed to deaths due to causes other than breast cancer. Multiple fractional polynomial analyses yielded a nonlinear association with markedly increased non-breast cancer mortality for women who did not engage in any sports or cycling in the years before the breast cancer diagnosis with a hazard ratio (HR, none vs. any) of 1.71, 95% confidence interval (1.16, 2.52). There were no further risk reductions with increasing activity levels. The association with breast cancer-specific mortality showed a similar dose-response but was far less pronounced with HR (none vs. any) = 1.22 (0.91, 1.64). In contrast, regarding cancer recurrence the dose-response was linear. However, this association was restricted to estrogen/progesterone receptor-negative (ER-/PR-) cases (p interaction = 0.033) with HR (highest vs. no recreational PA) = 0.53 (0.24, 1.16), p trend = 0.0045. Thus, breast cancer patients with a physically inactive lifestyle pre-diagnosis may decease prematurely irrespective of their cancer prognosis. Higher levels of exercise may reduce the risk of recurrence of ER-/PR- breast tumors.

Polymorphisms in oxidative stress-related genes and mortality in breast cancer patients--potential differential effects by radiotherapy?

We assessed whether variants in 22 oxidative stress-related genes are associated with mortality of breast cancer patients and whether the associations differ according to radiotherapy. Using a prospective cohort of 1348 postmenopausal breast cancer patients, we estimated hazard ratios (HR) and 95% confidence intervals (CI) for 109 single nucleotide polymorphisms (SNPs) using Cox proportional hazards regression. Validation of results was attempted using two Scandinavian studies. Eleven SNPs in MT2A, NFE2L2, NQO1, PRDX1, and PRDX6 were significantly associated with overall mortality after a median follow-up of 5.7 years. Three SNPs in NQO1 (rs2917667) and in PRDX6 (rs7314, rs4916362) were consistently associated with increased risk of dying across all three study populations (pooled: HRNQO1_rs2917667 1.20, 95% CI 1.00-1.44, p = 0.051; HRPRDX6_rs7314 1.16, 95% CI 1.00-1.35, p = 0.056, HRPRDX6_rs4916362 1.14 95% CI 1.00-1.32, p = 0.062). Potential effect modification by radiotherapy was found for CAT_rs769218. In conclusion, genetic variants in NQO1 and PRDX6 may modify breast cancer prognosis.

A genome-wide association study to identify genetic susceptibility loci that modify ductal and lobular postmenopausal breast cancer risk associated with menopausal hormone therapy use: a two-stage design with replication

Menopausal hormone therapy (MHT) is associated with an elevated risk of breast cancer in postmenopausal women. To identify genetic loci that modify breast cancer risk related to MHT use in postmenopausal women, we conducted a two-stage genome-wide association study (GWAS) with replication. In stage I, we performed a case-only GWAS in 731 invasive breast cancer cases from the German case-control study Mammary Carcinoma Risk Factor Investigation (MARIE). The 1,200 single nucleotide polymorphisms (SNPs) showing the lowest P values for interaction with current MHT use (within 6 months prior to breast cancer diagnosis), were carried forward to stage II, involving pooled case-control analyses including additional MARIE subjects (1,375 cases, 1,974 controls) as well as 795 cases and 764 controls of a Swedish case-control study. A joint P value was calculated for a combined analysis of stages I and II. Replication of the most significant interaction of the combined stage I and II was performed using 5,795 cases and 5,390 controls from nine studies of the Breast Cancer Association Consortium (BCAC). The combined stage I and II yielded five SNPs on chromosomes 2, 7, and 18 with joint P values <6 × 10(-6) for effect modification of current MHT use. The most significant interaction was observed for rs6707272 (P = 3 × 10(-7)) on chromosome 2 but was not replicated in the BCAC studies (P = 0.21). The potentially modifying SNPs are in strong linkage disequilibrium with SNPs in TRIP12 and DNER on chromosome 2 and SETBP1 on chromosome 18, previously linked to carcinogenesis. However, none of the interaction effects reached genome-wide significance. The inability to replicate the top SNP × MHT interaction may be due to limited power of the replication phase. Our study, however, suggests that there are unlikely to be SNPs that interact strongly enough with MHT use to be clinically significant in European women.

CD24 polymorphisms in breast cancer: impact on prognosis and risk

Overexpression of CD24 has a negative impact on breast cancer prognosis. We have recently reported that the CD24 codon 57 Val/Val genotype (rs52812045) is associated with pathologic complete response after neoadjuvant chemotherapy for primary breast cancer and correlates with intratumoral lymphocyte infiltrates. This study was performed to investigate the influence of CD24 polymorphisms on breast cancer prognosis and risk. A total of 2,514 patients and 4,858 controls recruited as part of the MARIE study, a population-based case-control study, were genotyped for two CD24 polymorphisms (rs52812045, rs3838646) using TaqMan custom genotyping assays. Associations with overall and breast cancer-specific survival were assessed using uni- and multivariable Cox regression models stratified by age at diagnosis and adjusted for prognostic factors. Conditional logistic regression analysis adjusted for major risk factors was used to estimate multivariable odds ratios for risk of putative allele carriers compared to wildtype carriers. CD24 Ala/Val was significantly associated with breast cancer prognosis [Val/Val hazard ratio (HR)(adjusted) = 1.52; 95 % confidence interval (CI): 1.00-2.30, p = 0.05 and HR(adjusted) = 1.83; 95 % CI: 1.10-3.05, p = 0.018 for all-cause and breast cancer-specific mortality, respectively). The association was significant only in patients with a BMI <25 and in those who received adjuvant chemotherapy. None of the CD24 alleles was associated with breast cancer risk. These results provide further evidence of the CD24 Val/Val genotype influencing outcome in primary breast cancer. Together with previous data of CD24 overexpression as a poor prognostic marker, the findings underline the biological importance of CD24 for breast cancer.

CD24 polymorphisms in breast cancer: impact on prognosis and risk

Overexpression of CD24 has a negative impact on breast cancer prognosis. We have recently reported that the CD24 codon 57 Val/Val genotype (rs52812045) is associated with pathologic complete response after neoadjuvant chemotherapy for primary breast cancer and correlates with intratumoral lymphocyte infiltrates. This study was performed to investigate the influence of CD24 polymorphisms on breast cancer prognosis and risk. A total of 2,514 patients and 4,858 controls recruited as part of the MARIE study, a population-based case-control study, were genotyped for two CD24 polymorphisms (rs52812045, rs3838646) using TaqMan custom genotyping assays. Associations with overall and breast cancer-specific survival were assessed using uni- and multivariable Cox regression models stratified by age at diagnosis and adjusted for prognostic factors. Conditional logistic regression analysis adjusted for major risk factors was used to estimate multivariable odds ratios for risk of putative allele carriers compared to wildtype carriers. CD24 Ala/Val was significantly associated with breast cancer prognosis [Val/Val hazard ratio (HR)(adjusted) = 1.52; 95 % confidence interval (CI): 1.00-2.30, p = 0.05 and HR(adjusted) = 1.83; 95 % CI: 1.10-3.05, p = 0.018 for all-cause and breast cancer-specific mortality, respectively). The association was significant only in patients with a BMI <25 and in those who received adjuvant chemotherapy. None of the CD24 alleles was associated with breast cancer risk. These results provide further evidence of the CD24 Val/Val genotype influencing outcome in primary breast cancer. Together with previous data of CD24 overexpression as a poor prognostic marker, the findings underline the biological importance of CD24 for breast cancer.

Individual patient data meta-analysis shows no association between the SNP rs1800469 in TGFB and late radiotherapy toxicity

BACKGROUND AND PURPOSE

Reported associations between risk of radiation-induced normal tissue injury and single nucleotide polymorphisms (SNPs) in TGFB1, encoding the pro-fibrotic cytokine transforming growth factor-beta 1 (TGF-β1), remain controversial. To overcome publication bias, the international Radiogenomics Consortium collected and analysed individual patient level data from both published and unpublished studies.

MATERIALS AND METHODS

TGFB1 SNP rs1800469 c.-1347T>C (previously known as C-509T) genotype, treatment-related data, and clinically-assessed fibrosis (measured at least 2years after therapy) were available in 2782 participants from 11 cohorts. All received adjuvant breast radiotherapy. Associations between late fibrosis or overall toxicity, reported by STAT (Standardised Total Average Toxicity) score, and rs1800469 genotype were assessed.

RESULTS

No statistically significant associations between either fibrosis or overall toxicity and rs1800469 genotype were observed with univariate or multivariate regression analysis. The multivariate odds ratio (OR), obtained from meta-analysis, for an increase in late fibrosis grade with each additional rare allele of rs1800469 was 0.98 (95% Confidence Interval (CI) 0.85-1.11). This CI is sufficiently narrow to rule out any clinically relevant effect on toxicity risk in carriers vs. non-carriers with a high probability.

CONCLUSION

This meta-analysis has not confirmed previous reports of association between fibrosis or overall toxicity and rs1800469 genotype in breast cancer patients. It has demonstrated successful collaboration within the Radiogenomics Consortium.

Dietary patterns and survival in German postmenopausal breast cancer survivors

BACKGROUND

Research on the association between dietary patterns and breast cancer survival is very limited.

METHODS

A prospective follow-up study was conducted in Germany, including 2522 postmenopausal breast cancer patients diagnosed in 2001-2005 with available food frequency questionnaire data. Vital status, causes of death, and recurrences were verified through the end of 2009. Principle component factor analysis was used to identify pre-diagnostic dietary patterns. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated with Cox proportional hazards models.

RESULTS

Two major dietary patterns were identified: 'healthy' (high intakes of vegetables, fruits, vegetable oil, sauces/condiments, and soups/bouillons) and 'unhealthy' (high intakes of red meat, processed meat, and deep-frying fat). Increasing consumption of an 'unhealthy' dietary pattern was associated with an increased risk of non-breast cancer mortality (highest vs lowest quartile: HR, 3.69; 95% CI, 1.66-8.17; P-trend <0.001). No associations with breast cancer-specific mortality and breast cancer recurrence were found. The 'healthy' dietary pattern was inversely associated with overall mortality (HR, 0.74; 95% CI, 0.47-1.15; P-trend=0.02) and breast cancer recurrence (HR, 0.71; 95% CI, 0.48-1.06; P-trend=0.02) in stage I-IIIa patients only.

CONCLUSION

Increasing intake of an 'unhealthy' pre-diagnostic dietary pattern may increase the risk of non-breast cancer mortality, whereas increasing intake of a 'healthy' pattern may reduce the risk of overall mortality and breast cancer recurrence.

A replicated association between polymorphisms near TNFα and risk for adverse reactions to radiotherapy

BACKGROUND

Response to radiotherapy varies between individuals both in terms of efficacy and adverse reactions. Finding genetic determinants of radiation response would allow the tailoring of the treatment, either by altering the radiation dose or by surgery. Despite a growing number of studies in radiogenomics, there are no well-replicated genetic association results.

METHODS

We carried out a candidate gene association study and replicated the result using three additional large cohorts, a total of 2036 women scored for adverse reactions to radiotherapy for breast cancer.

RESULTS

Genetic variation near the tumour necrosis factor alpha gene is shown to affect several clinical endpoints including breast induration, telangiectasia and overall toxicity. In the combined analysis homozygosity for the rare allele increases overall toxicity (P=0.001) and chance of being in the upper quartile of risk with odds ratio of 2.46 (95% confidence interval 1.52-3.98).

CONCLUSION

We have identified that alleles of the class III major histocompatibility complex region associate with overall radiotherapy toxicity in breast cancer patients by using internal replication through a staged design. This is the first well-replicated report of a genetic predictor for radiotherapy reactions.

Germline variants of base excision repair genes and breast cancer: A polymorphism in DNA polymerase gamma modifies gene expression and breast cancer risk

Base excision repair (BER) removes DNA damage induced by endogenous reactive oxygen species or ionizing radiation, important breast cancer risk factors. Genetic variation associated with impaired BER might thus increase breast cancer risk. Therefore, we assessed risk associations of 123 common single nucleotide polymorphisms (SNPs) in 19 BER genes in 1,639 postmenopausal breast cancer cases and 1,967 controls from the German population-based case-control study MARIE. SNPs were tagging SNPs representing genetic variation across the gene together with potentially functional SNPs. Risk associations were assessed using conditional logistic regression, adjusted for potential breast cancer risk factors. Significant associations between polymorphisms and breast cancer risk were found for one SNP in PARP2 and three SNPs in the mitochondrial DNA polymerase gamma, POLG. A SNP in the promoter region of POLG (rs2856268, A>G) showed a protective effect for homozygous GG carriers (odds ratio 0.81, 95% confidence intervals 0.65-1.00). Joint analysis of an enlarged sample set and haplotype analysis supported the results for POLG. Quantification of POLG mRNA expression in lymphocytes of 148 breast cancer patients revealed higher mRNA levels for rs2856268 GG carriers (p value = 0.038). A luciferase promoter assay showed significant differences between constructs harboring the respective alleles. Taken together, our results suggest that genetic variation in the POLG promoter region affects DNA polymerase gamma levels in mitochondria. This could contribute to the reported increase in mitochondrial mutation frequency resulting in dysfunction and altered breast cancer risk. Risk effects and the functional impact of the POLG promoter variant require further confirmation.

Polymorphism Thr160Thr in SRD5A1, involved in the progesterone metabolism, modifies postmenopausal breast cancer risk associated with menopausal hormone therapy

Menopausal hormone therapy (MHT) is associated with an increased breast cancer risk in postmenopausal women, with combined estrogen-progestagen therapy posing a greater risk than estrogen monotherapy. However, few studies focused on potential effect modification of MHT-associated breast cancer risk by genetic polymorphisms in the progesterone metabolism. We assessed effect modification of MHT use by five coding single nucleotide polymorphisms (SNPs) in the progesterone metabolizing enzymes AKR1C3 (rs7741), AKR1C4 (rs3829125, rs17134592), and SRD5A1 (rs248793, rs3736316) using a two-center population-based case-control study from Germany with 2,502 postmenopausal breast cancer patients and 4,833 matched controls. An empirical-Bayes procedure that tests for interaction using a weighted combination of the prospective and the retrospective case-control estimators as well as standard prospective logistic regression were applied to assess multiplicative statistical interaction between polymorphisms and duration of MHT use with regard to breast cancer risk assuming a log-additive mode of inheritance. No genetic marginal effects were observed. Breast cancer risk associated with duration of combined therapy was significantly modified by SRD5A1_rs3736316, showing a reduced risk elevation in carriers of the minor allele (p (interaction,empirical-Bayes) = 0.006 using the empirical-Bayes method, p (interaction,logistic regression) = 0.013 using logistic regression). The risk associated with duration of use of monotherapy was increased by AKR1C3_rs7741 in minor allele carriers (p (interaction,empirical-Bayes) = 0.083, p (interaction,logistic regression) = 0.029) and decreased in minor allele carriers of two SNPs in AKR1C4 (rs3829125: p (interaction,empirical-Bayes) = 0.07, p (interaction,logistic regression) = 0.021; rs17134592: p (interaction,empirical-Bayes) = 0.101, p (interaction,logistic regression) = 0.038). After Bonferroni correction for multiple testing only SRD5A1_rs3736316 assessed using the empirical-Bayes method remained significant. Postmenopausal breast cancer risk associated with combined therapy may be modified by genetic variation in SRD5A1. Further well-powered studies are, however, required to replicate our finding.

Coffee consumption modifies risk of estrogen-receptor negative breast cancer

Introduction

Breast cancer is a complex disease and may be sub-divided into hormone-responsive (estrogen receptor (ER) positive) and non-hormone-responsive subtypes (ER-negative). Some evidence suggests that heterogeneity exists in the associations between coffee consumption and breast cancer risk, according to different estrogen receptor subtypes. We assessed the association between coffee consumption and postmenopausal breast cancer risk in a large population-based study (2,818 cases and 3,111 controls), overall, and stratified by ER tumour subtypes.

Methods

Odds ratios (OR) and corresponding 95% confidence intervals (CI) were estimated using the multivariate logistic regression models fitted to examine breast cancer risk in a stratified case-control analysis. Heterogeneity among ER subtypes was evaluated in a case-only analysis, by fitting binary logistic regression models, treating ER status as a dependent variable, with coffee consumption included as a covariate.

Results

In the Swedish study, coffee consumption was associated with a modest decrease in overall breast cancer risk in the age-adjusted model (OR_{> 5 cups/day} compared to OR_{≤ 1 cup/day}: 0.80, 95% CI: 0.64, 0.99, P trend = 0.028). In the stratified case-control analyses, a significant reduction in the risk of ER-negative breast cancer was observed in heavy coffee drinkers (OR_{> 5 cups/day} compared to OR_{≤ 1 cup/day} : 0.43, 95% CI: 0.25, 0.72, P trend = 0.0003) in a multivariate-adjusted model. The breast cancer risk reduction associated with higher coffee consumption was significantly higher for ER-negative compared to ER-positive tumours (P heterogeneity (age-adjusted) = 0.004).

Conclusions

A high daily intake of coffee was found to be associated with a statistically significant decrease in ER-negative breast cancer among postmenopausal women.