Associations of breast cancer risk factors with tumor subtypes: a pooled analysis from the Breast Cancer Association Consortium studies

Obesity and breast cancer: a clinical biochemistry perspective

OBJECTIVES

To evaluate the laboratory diagnosis aspects of obesity-related health problems with special reference to postmenopausal breast cancer.

DESIGN AND METHODS

We conducted a systemic search of the literature primarily from the PubMed to obtain the relevant data.

RESULTS

Obesity is associated with the dysregulations of a number of body components such as blood constituents, extracellular matrix, and hormones/growth factors axes, which could be utilized for early diagnosis.

CONCLUSIONS

Obesity-related disorders including breast cancer have emerged as major health problems in almost all the nations. There is a need to elucidate different biochemical markers that are being used in the clinics or have the potential for such use. A precise understanding of the complex pathologies related with obesity is useful in prevention, early diagnosis and overall clinical management.

Advancements in the use of blood tests for cancer screening in women at high risk for endometrial and breast cancer

Several years ago, it was argued that the identification of serum biomarkers is one of the most promising approaches for the detection of early-stage malignant or even premalignant lesions. In this review, the need to establish better monitoring protocols is described for obese women who are at higher risk for the development of malignancies commonly associated with excess weight; specifically endometrial and postmenopausal breast cancer. These cancers have been chosen for this review article as our aim was to focus on female cancers that have been linked with obesity. Cancer screening is essential in detecting disease in its earliest stage in order to reduce morbidity and mortality; however, effective screening is not available for many cancer types. Even for cancers that have effective screening protocols available, there are barriers to screening in obese individuals, such as reduced mobility and embarrassment. These barriers often delay screening in these vulnerable population groups, leading to detection of the disease at a more advanced stage and ultimately leading to a poorer prognosis. As of today, biomarkers do not replace but augment imaging and other existing screening approaches. Future development of blood- or urine-based biomarkers as a way to screen individuals at high risk for certain cancers may prove to be an excellent method for overcoming the barriers that individuals at high risk are facing today. The overall purpose of this manuscript is to provide an overview of screening techniques and to identified barriers and alternate biomarker-based approaches for improvement of endometrial and breast cancer screening in obese women.

Evaluation of variation in the phosphoinositide-3-kinase catalytic subunit alpha oncogene and breast cancer risk

Background:

Somatic mutations in phosphoinositide-3-kinase catalytic subunit alpha (PIK3CA) are frequent in breast tumours and have been associated with oestrogen receptor (ER) expression, human epidermal growth factor receptor-2 overexpression, lymph node metastasis and poor survival. The goal of this study was to evaluate the association between inherited variation in this oncogene and risk of breast cancer.

Methods:

A single-nucleotide polymorphism from the PIK3CA locus that was associated with breast cancer in a study of Caucasian breast cancer cases and controls from the Mayo Clinic (MCBCS) was genotyped in 5436 cases and 5280 controls from the Cancer Genetic Markers of Susceptibility (CGEMS) study and in 30 949 cases and 29 788 controls from the Breast Cancer Association Consortium (BCAC).

Results:

Rs1607237 was significantly associated with a decreased risk of breast cancer in MCBCS, CGEMS and all studies of white Europeans combined (odds ratio (OR)=0.97, 95% confidence interval (CI) 0.95–0.99, P=4.6 × 10⁻³), but did not reach significance in the BCAC replication study alone (OR=0.98, 95% CI 0.96–1.01, P=0.139).

Conclusion:

Common germline variation in PIK3CA does not have a strong influence on the risk of breast cancer

Characteristics of triple-negative breast cancer in patients with a BRCA1 mutation: results from a population-based study of young women

PURPOSE

Triple-negative breast cancers (TNBCs) are tumors with low or no expression of estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2. These tumors have a poor prognosis, remain a clinical challenge, and are more common among women with BRCA1 mutations. We tested whether there are distinguishing features of TNBC after BRCA1 mutation status has been taken into account.

PATIENTS AND METHODS

We sequenced BRCA1 and BRCA2 genes in a population-based sample of 1,469 patients with incident breast cancer age 20 to 49 years from Los Angeles County (California). Information on tumor receptor status was available for 1,167 women. Clinical, pathologic, and hormone-related lifestyle characteristics were compared across patient subgroups defined by BRCA1 mutation status and triple-negative receptor status.

RESULTS

Forty-eight percent of BRCA1 mutation carriers had TNBC compared with only 12% of noncarriers. Within BRCA1 mutation carriers, as well as within noncarriers, triple-negative receptor status was associated with younger age at diagnosis and higher tumor grade. Among women without a BRCA1 mutation, we observed that women with TNBC had higher premenopausal body mass index and earlier age at first full-term pregnancy than those with non-TNBC. Age at menarche and other reproductive factors were not associated with triple-negative status regardless of BRCA1 mutation status. Within BRCA1 mutation carriers, Ashkenazi Jewish women were about five times more likely to have TNBC than non-Ashkenazi Jewish women.

CONCLUSION

Our results suggest that among BRCA1 mutation carriers, as among noncarriers, there are unique characteristics associated with the triple-negative subtype. The findings in Ashkenazi Jewish BRCA1 mutation carriers should be confirmed.

Normal breast tissue of obese women is enriched for macrophage markers and macrophage-associated gene expression

Activation of inflammatory pathways is one plausible mechanism underlying the association between obesity and increased breast cancer risk. However, macrophage infiltration and local biomarkers of inflammation in breast adipose tissue have seldom been studied in association with obesity. Gene expression profiles of normal breast tissue from reduction mammoplasty patients were evaluated by whole genome microarrays to identify patterns associated with obesity status (normal-weight, body mass index (BMI) <25; overweight, BMI 25-29.9; obese, BMI ≥30). The presence of macrophage-enriched inflammatory loci with immunopositivity for CD68 protein was evaluated by immunohistochemistry (IHC). After adjusting for confounding by age, 760 genes were differentially expressed (203 up and 557 down; FDR = 0.026) between normal-weight and obese women. Gene ontology analysis suggested significant enrichment for pathways involving IL-6, IL-8, CCR5 signaling in macrophages and RXRα and PPARα activation, consistent with a pro-inflammatory state and suggestive of macrophage infiltration. Gene set enrichment analysis also demonstrated that the genomic signatures of monocytes and macrophages were over-represented in the obese group with FDR of 0.08 and 0.13, respectively. Increased macrophage infiltration was confirmed by IHC, which showed that the breast adipose tissue of obese women had higher average macrophage counts (mean = 8.96 vs. 3.56 in normal-weight women) and inflammatory foci counts (mean = 4.91 vs. 2.67 in normal-weight women). Obesity is associated with local inflammation and macrophage infiltration in normal human breast adipose tissues. Given the role of macrophages in carcinogenesis, these findings have important implications for breast cancer etiology and progression.

A retrospective review of the metabolic syndrome in women diagnosed with breast cancer and correlation with estrogen receptor

Women diagnosed with obesity and breast cancer have an increased risk of recurrence and death (Protani et al., Breast Cancer Res Treat 123:627-635, 1). Obesity is associated with the metabolic syndrome--a pathophysiologically distinct inflammatory process comprised of central obesity, insulin resistance, hypertension, and atherogenic dyslipidemia. The relationship of obesity as a risk factor for breast cancer is complex with a protective effect for younger women in contrast to a risk for older women (Kabat et al., Cancer Epidemiol Biomarkers Prev 18:2046-2053, 2; Ursin et al., Epidemiology 6:137-141, 3). The metabolic syndrome has been associated with the risk of cancer, and pro-inflammatory circulating factors may be associated with risk of more aggressive breast cancer (Capasso et al., Cancer Biol Ther 10:1240-1243, 4; Healy et al., Clin Oncol (R Coll Radiol) 22:281-288, 5; Laukkanen et al., Cancer Epidemiol Biomarkers Prev 13:1646-1650, 6). We conducted a retrospective review of 860 breast cancer patients to determine the relationship between estrogen receptor status and the metabolic syndrome. We collected the relevant metabolic diagnoses, medications, physical findings, and laboratory values and adapted the National Cholesterol Education Program criteria to define the metabolic syndrome retrospectively. No relationship was found between estrogen receptor status and the individual components of the metabolic syndrome. Based on findings in the medical records, 15% of the women with breast cancer had the metabolic syndrome, and 26% of the women were considered obese, 16% hyperglycemic, 54% hypertensive, and 30% dyslipidemic. The metabolic syndrome was associated with advanced age and African-American race (P < 0.001). When adjusted for age, race, and stage, the metabolic syndrome was marginally associated with estrogen receptor-positive tumors (P = 0.054). Our findings do not support the concern that the metabolic syndrome may contribute to more biologically aggressive breast cancer.

Family history of breast cancer in relation to tumor characteristics and mortality in a population-based study of young women with invasive breast cancer

BACKGROUND

Inherited predisposition may be associated with distinctive breast cancer phenotypes and/or mortality. Past studies have had inconsistent results and little is known about the contributions of screening and treatment.

METHODS

Within a population-based cohort of 1,260 women diagnosed with invasive breast cancer before age 46, we assessed how family history of breast cancer relates to mortality and tumor characteristics. Analyses were repeated excluding BRCA1/BRCA2 carriers. Medical records were reviewed for treatment history and tumors were centrally reviewed and tested. Cox proportional hazard modeling was used to assess the risk of dying in relation to family history; logistic regression was used to assess the association of family history to tumor characteristics.

RESULTS

Compared with women with no family history, women with first-degree family history of breast cancer had a 40% reduction (95% CI: 0.5-0.8) in the risk of dying. Mortality in women with only a second-degree family history was similar to those with no family history. The risk of dying was further reduced in those with a greater number of affected relatives. These relationships did not seem to be attributable to differences in screening, detection method, or treatment. Tumors in women with a first-degree family history had generally more favorable prognostic profiles.

CONCLUSION

Our findings suggest that breast cancer patients with a first-degree family history, compared with their counterparts without such a profile, may have a better prognosis.

IMPACT

These findings support the need for future research directed at replicating these results and identifying factors underlying this possible relationship.

Parity and lactation in relation to estrogen receptor negative breast cancer in African American women

BACKGROUND

Estrogen receptor (ER)-negative breast tumors and progesterone receptor (PR)-negative breast tumors occur more commonly in women of African ancestry. Recent research indicates that the effects of reproductive factors may differ by hormone receptor status. We assessed the relation of parity and lactation to incidence of ER(-)/PR(-) and ER(+)/PR(+) breast cancer in a cohort of African American women.

METHODS

From 1995-2009, 457 incident cases of ER(+)/PR(+) and 318 cases of ER(-)/PR(-) breast cancer were confirmed by review of pathology data among 59,000 African American women followed in the Black Women's Health Study through biennial questionnaires. HRs and two-sided 95% CIs for the incidence of breast cancer subtypes were derived from proportional hazards regression models that controlled for age, reproductive variables, and breast cancer risk factors.

RESULTS

Higher parity was associated with an increased risk of ER(-)/PR(-) breast cancer (HR = 1.48, 95% CI: 0.98-1.84 for 3+ versus 0 births, P(trend) = 0.009), and with a reduced risk of ER(+)/PR(+) cancer (HR = 0.53, 95% CI: 0.39-0.73 for 3+ versus 0 births, P(trend) = 0.0002). Among women who had breastfed, high parity was no longer associated with increased incidence of ER(-)/PR(-) breast, but the inverse association with ER(+)/PR(+) cancer persisted.

CONCLUSIONS

The higher incidence of ER(-)/PR(-) breast cancer in African American women may be explained in part by their higher parity and lower prevalence of breastfeeding relative to white women.

IMPACT

Increased breastfeeding may lead to a reduction in the incidence of this breast cancer subtype.

Genetic and environmental predictors, endogenous hormones and growth factors, and risk of estrogen receptor-positive breast cancer in Japanese women

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades. We have recently shown that this marked increase is mostly due to an increase in the estrogen receptor (ER)-positive subtype. It is necessary to establish risk factors capable of predicting the risk of ER-positive breast cancer that will enable the efficient selection of candidates for preventive therapy. We analyzed genetic factors, including 14 single nucleotide polymorphisms (SNPs), environmental risk factors (body mass index, age at menarche, pregnancy, age at first birth, breastfeeding, family history of breast cancer, age at menopause, use of hormone replacement therapy, alcohol intake, and smoking), serum hormones and growth factors (estradiol, testosterone, prolactin, insulin-like growth factor 1 [IGF1] and IGF binding protein 3 [IGFBP3]), and mammographic density in 913 women with breast cancer and 278 disease-free controls. To identify important risk factors, risk prediction models for ER-positive breast cancer in both pre- and postmenopausal women were created by logistic regression analysis. In premenopausal women, one SNP (CYP19A1-rs10046), age, pregnancy, breastfeeding, alcohol intake, serum levels of prolactin, testosterone, and IGFBP3 were considered to be risk predictors. In postmenopausal women, one SNP (TP53-rs1042522), age, body mass index, age at menopause, serum levels of testosterone, and IGF1 were identified as risk predictors. Risk factors may differ between women of different menopausal status, and inclusion of common genetic variants and serum hormone measurements as well as environmental factors might improve risk assessment models. Further validation studies will clarify appropriate risk groups for preventive therapy.

Low penetrance breast cancer susceptibility loci are associated with specific breast tumor subtypes: findings from the Breast Cancer Association Consortium

Breast cancers demonstrate substantial biological, clinical and etiological heterogeneity. We investigated breast cancer risk associations of eight susceptibility loci identified in GWAS and two putative susceptibility loci in candidate genes in relation to specific breast tumor subtypes. Subtypes were defined by five markers (ER, PR, HER2, CK5/6, EGFR) and other pathological and clinical features. Analyses included up to 30 040 invasive breast cancer cases and 53 692 controls from 31 studies within the Breast Cancer Association Consortium. We confirmed previous reports of stronger associations with ER+ than ER- tumors for six of the eight loci identified in GWAS: rs2981582 (10q26) (P-heterogeneity = 6.1 × 10(-18)), rs3803662 (16q12) (P = 3.7 × 10(-5)), rs13281615 (8q24) (P = 0.002), rs13387042 (2q35) (P = 0.006), rs4973768 (3p24) (P = 0.003) and rs6504950 (17q23) (P = 0.002). The two candidate loci, CASP8 (rs1045485, rs17468277) and TGFB1 (rs1982073), were most strongly related with the risk of PR negative tumors (P = 5.1 × 10(-6) and P = 4.1 × 10(-4), respectively), as previously suggested. Four of the eight loci identified in GWAS were associated with triple negative tumors (P ≤ 0.016): rs3803662 (16q12), rs889312 (5q11), rs3817198 (11p15) and rs13387042 (2q35); however, only two of them (16q12 and 2q35) were associated with tumors with the core basal phenotype (P ≤ 0.002). These analyses are consistent with different biological origins of breast cancers, and indicate that tumor stratification might help in the identification and characterization of novel risk factors for breast cancer subtypes. This may eventually result in further improvements in prevention, early detection and treatment.

Cancer stem cells in the human mammary gland and regulation of their differentiation by estrogen

The identification and characterization of normal and breast cancer stem cells have provided a new vision of breast tumorigenesis. Cancer stem cells may be responsible for breast tumor initiation, progression and development of resistance to therapy. Most breast cancers express the estrogen receptor, and several studies have linked long-term estrogen exposure to enhanced breast cancer risk; however, estrogen receptor-positive tumors usually present a better prognosis than estrogen receptor-negative ones. The finding that estrogen reduces the pool of human breast stem cells may explain the more differentiated phenotype observed in estrogen receptor-positive tumors. In this article, our current understanding of the complex role of estrogen in human breast stem cells is discussed in the context of breast malignancy.

Identification of human triple-negative breast cancer subtypes and preclinical models for selection of targeted therapies

Triple-negative breast cancer (TNBC) is a highly diverse group of cancers, and subtyping is necessary to better identify molecular-based therapies. In this study, we analyzed gene expression (GE) profiles from 21 breast cancer data sets and identified 587 TNBC cases. Cluster analysis identified 6 TNBC subtypes displaying unique GE and ontologies, including 2 basal-like (BL1 and BL2), an immunomodulatory (IM), a mesenchymal (M), a mesenchymal stem-like (MSL), and a luminal androgen receptor (LAR) subtype. Further, GE analysis allowed us to identify TNBC cell line models representative of these subtypes. Predicted "driver" signaling pathways were pharmacologically targeted in these cell line models as proof of concept that analysis of distinct GE signatures can inform therapy selection. BL1 and BL2 subtypes had higher expression of cell cycle and DNA damage response genes, and representative cell lines preferentially responded to cisplatin. M and MSL subtypes were enriched in GE for epithelial-mesenchymal transition, and growth factor pathways and cell models responded to NVP-BEZ235 (a PI3K/mTOR inhibitor) and dasatinib (an abl/src inhibitor). The LAR subtype includes patients with decreased relapse-free survival and was characterized by androgen receptor (AR) signaling. LAR cell lines were uniquely sensitive to bicalutamide (an AR antagonist). These data may be useful in biomarker selection, drug discovery, and clinical trial design that will enable alignment of TNBC patients to appropriate targeted therapies.

Risk factors for breast cancer: epidemiological evidence from Japanese studies

Although our understanding of the etiology of breast cancer has improved, many well-known risk factors are not modifiable and present knowledge has proved insufficient to allow the disease to be overcome. Indeed, incidence and mortality among Japanese women have increased over the past three decades. Here, we review epidemiological evidence from our cohort and case-control studies among Japanese women in comparison with other published findings. Our studies confirm the important role of established factors derived primarily from Western populations, such as menstrual and reproductive factors, anthropometric factors, physical activity, and alcohol intake, in the development of breast cancer. In addition, we provide further evidence to better understand the role of traditional Japanese foods in the etiology of breast cancer. Our cohort study found that a higher intake of isoflavone and higher levels of plasma genistein, but not daidzein, were associated with a decreased risk of breast cancer. Our case-control studies reveal a dose-response pattern for these compounds; specifically, decreased risk as women move from "no" to "moderate" intake and leveling off thereafter. In addition, gene-environment interactions have been revealed in the effects of isoflavones. The evidence reviewed suggests that isoflavone has a protective effect against breast cancer in Asian populations. Conversely, our cohort study did not observe an inverse association between breast cancer risk and the intake of green tea and/or the plasma level of tea polyphenols, but we did find an association between increased risk and active and passive smoking. In conclusion, based on current knowledge, primary prevention according to individual lifestyle modification should focus on alcohol intake, weight control, physical activity, and tobacco smoking.

Pathological characteristics of BRCA-associated breast cancers in Hispanics

The immunophenotype of BRCA-associated breast cancer has been studied in predominantly non-Hispanic whites (NHW). We evaluated the pathological characteristics of BRCA-associated invasive breast cancer in Hispanics. A case-control study was conducted on breast cancers from Hispanic and NHW women who enrolled in an IRB-approved registry and underwent BRCA gene analysis. BRCA negative controls (41 Hispanic, 39 NHW) were matched on age and ethnicity to BRCA positive cases (39 Hispanic, 35 NHW). A tissue array was constructed to characterize the expression of estrogen receptor (ER), progesterone receptor (PR), HER2, Ki-67 and p53 by immunohistochemistry. Mean age at diagnosis was 37.1 years (range 24-59) for Hispanics (80% with Mexican ancestry) and 40.1 years (range 21-63) for NHW (P = 0.03). Hispanic BRCA1 cases were more likely than BRCA negative controls to have tumors that were ER-negative (P < 0.001) and PR-negative (P = 0.001), had higher levels of Ki-67 (P = 0.001) and p53 expression, and lower levels of HER2 overexpression. When stratified by genes, there were no significant differences in expression of ER, Ki-67, HER2, and p53 by ethnicity among mutation carriers. However, a significantly higher proportion of BRCA-positive Hispanics had PR-negative tumors compared to BRCA-positive NHW (80 vs. 57%, OR = 2.9, 95% CI 1.0-8.1, P = 0.04). Hispanic BRCA-associated breast cancers were found to have the unique immunophenotype associated with BRCA mutations; however, there was a trend toward a difference in PR expression among Hispanic BRCA1 and BRCA2 cases. Additional research on the molecular mechanisms involved in the loss of PR in this population is warranted as it could have important implications for the treatment and prevention of breast cancer in Hispanics.

Plasma biomarker profiles differ depending on breast cancer subtype but RANTES is consistently increased

BACKGROUND

Current biomarkers for breast cancer have little potential for detection. We determined whether breast cancer subtypes influence circulating protein biomarkers.

METHODS

A sandwich ELISA microarray platform was used to evaluate 23 candidate biomarkers in plasma samples that were obtained from subjects with either benign breast disease or invasive breast cancer. All plasma samples were collected at the time of biopsy, after a referral due to a suspicious screen (e.g., mammography). Cancer samples were evaluated on the basis of breast cancer subtypes, as defined by the HER2 and estrogen receptor statuses.

RESULTS

Ten proteins were statistically altered in at least one breast cancer subtype, including four epidermal growth factor receptor ligands, two matrix metalloproteases, two cytokines, and two angiogenic factors. Only one cytokine, RANTES, was significantly increased (P < 0.01 for each analysis) in all four subtypes, with areas under the curve (AUC) for receiver operating characteristic values that ranged from 0.76 to 0.82, depending on cancer subtype. The best AUC values were observed for analyses that combined data from multiple biomarkers, with values ranging from 0.70 to 0.99, depending on the cancer subtype. Although the results for RANTES are consistent with previous publications, the multi-assay results need to be validated in independent sample sets.

CONCLUSIONS

Different breast cancer subtypes produce distinct biomarker profiles, and circulating protein biomarkers have potential to differentiate between true- and false-positive screens for breast cancer.

IMPACT

Subtype-specific biomarker panels may be useful for detecting breast cancer or as an adjunct assay to improve the accuracy of current screening methods.

Circulating estrogens and progesterone during primiparous pregnancies and risk of maternal breast cancer

Pregnancy reduces maternal risk of breast cancer in the long term, but the biological determinants of the protection are unknown. Animal experiments suggest that estrogens and progesterone could be involved, but direct human evidence is scant. A case-control study (536 cases and 1,049 controls) was nested within the Finnish Maternity Cohort. Eligible were primiparous women who delivered at term a singleton offspring before age 40. For each case, two individually matched controls by age (± 6 months) and date of sampling (± 3 months) were selected. Estradiol, estrone and progesterone in first-trimester serum were measured by high-performance liquid chromatography tandem mass spectrometry and sex-hormone binding globulin (SHBG) by immunoassay. Odds ratios (OR) and 95% confidence intervals (CI) were estimated through conditional logistic regression. In the whole study population there was no association of breast cancer with any of the studied hormones. In analyses stratified by age at diagnosis, however, estradiol concentrations were positively associated with risk of breast cancer before age 40 (upper quartile OR, 1.81; CI, 1.08-3.06), but inversely associated with risk in women who were diagnosed ≥ age 40 (upper quartile OR, 0.64; CI, 0.40-1.04), p(interaction) 0.004. Risk estimates for estrone mirrored those for estradiol but were less pronounced. Progesterone was not associated with risk of subsequent breast cancer. Our results provide initial evidence that concentrations of estrogens during the early parts of a primiparous pregnancy are associated with maternal risk of breast cancer and suggest that the effect may differ for tumors diagnosed before and after age 40.

Interactions among genes, tumor biology and the environment in cancer health disparities: examining the evidence on a national and global scale

Cancer incidence and mortality rates show great variations across nations and between population groups. These variations are largely explained by differences in age distribution, diet and lifestyle, access to health care, cultural barriers and exposure to carcinogens and pathogens. Cancers caused by infections are significantly more common in developing than developed countries, and they overproportionally affect immigrant populations in the USA and other countries. The global pattern of cancer is not stagnant. Instead, it is dynamic because of fluctuations in the age distribution of populations, improvements in cancer prevention and early detection in affluent countries and rapid changes in diet and lifestyle in parts of the world. For example, increased smoking rates have caused tobacco-induced cancers to rise in various Asian countries, whereas reduced smoking rates have caused these cancers to plateau or even begin to decline in Western Europe and North America. Some population groups experience a disproportionally high cancer burden. In the USA and the Caribbean, cancer incidence and mortality rates are excessively high in populations of African ancestry when compared with other population groups. The causes of this disparity are multifaceted and may include tumor biological and genetic factors and their interaction with the environment. In this review, we will discuss the magnitude and causes of global cancer health disparities and will, with a focus on African-Americans and selected cancer sites, evaluate the evidence that genetic and tumor biological factors contribute to existing cancer incidence and outcome differences among population groups in the USA.