Genomic signature of parity in the breast of premenopausal women

Background

Full-term pregnancy (FTP) at an early age confers long-term protection against breast cancer. Previously, we reported that a FTP imprints a specific gene expression profile in the breast of postmenopausal women. Herein, we evaluated gene expression changes induced by parity in the breast of premenopausal women.

Methods

Gene expression profiling of normal breast tissue from 30 nulliparous (NP) and 79 parous (P) premenopausal volunteers was performed using Affymetrix microarrays. In addition to a discovery/validation analysis, we conducted an analysis of gene expression differences in P vs. NP women as a function of time since last FTP. Finally, a laser capture microdissection substudy was performed to compare the gene expression profile in the whole breast biopsy with that in the epithelial and stromal tissues.

Results

Discovery/validation analysis identified 43 differentially expressed genes in P vs. NP breast. Analysis of expression as a function of time since FTP revealed 286 differentially expressed genes (238 up- and 48 downregulated) comparing all P vs. all NP, and/or P women whose last FTP was less than 5 years before biopsy vs. all NP women. The upregulated genes showed three expression patterns: (1) transient: genes upregulated after FTP but whose expression levels returned to NP levels. These genes were mainly related to immune response, specifically activation of T cells. (2) Long-term changing: genes upregulated following FTP, whose expression levels decreased with increasing time since FTP but did not return to NP levels. These were related to immune response and development. (3) Long-term constant: genes that remained upregulated in parous compared to nulliparous breast, independently of time since FTP. These were mainly involved in development/cell differentiation processes, and also chromatin remodeling. Lastly, we found that the gene expression in whole tissue was a weighted average of the expression in epithelial and stromal tissues.

Conclusions

Genes transiently activated by FTP may have a role in protecting the mammary gland against neoplastically transformed cells through activation of T cells. Furthermore, chromatin remodeling and cell differentiation, represented by the genes that are maintained upregulated long after the FTP, may be responsible for the lasting preventive effect against breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1128-x) contains supplementary material, which is available to authorized users.

Incidence of Breast Cancer in Piedmont: 1979–1981

A population-based survey of histologically diagnosed breast cancer was carried out among residents in Piedmont. A total of 5267 incident cases occurring in 1979–1981 was collected, corresponding to an age-standardized (on the world population) incidence rate of 49.5/100,000 per year. Rates (standardized on the population of Piedmont in 1981) were highest in the city of Torino (112.4/100,000 per year) and lowest in the province of Cuneo (67.5), whereas in the other provinces they ranged between 85.3 and 90.0. Estimation of rates in the 54 Local Health Authorities of Piedmont detected up to 2-fold differences between adjacent areas. A correlation was found between rates and size of the population of town of residence. Comparison with age-specific incidence rates from the Cancer Registry of the nearby province of Varese suggested a loss of nonhistologically confirmed cases selectively in older age groups. The distribution of cases diagnosed in 1979 by histologic type is presented. The proportion of diagnoses reported in terms which were consistent with the 1978 WHO Histological Typing of Breast Tumours was 61.3%. It was highest among cases identified in Pathology Services located in University Hospitals and/or diagnosing more than 50 breast cancers per year.

Risk of Breast Cancer, Diet and Internal Migrations in Northern Italy

The protective effect of birth in southern Italy as opposed to other regions was evaluated in a population-based case-control study of diet and breast cancer among residents In the province of Vercelli. Cases were 250 women with breast cancer diagnosed during 1983-1984 and controls 499 women randomly selected from the general population. The crude relative risk of breast cancer for women born in the south was 0.76 (95% confidence interval, 0.43-1.3). After adjustment for dietary and other potential confounders in multivariate analyses, the protective effect of place of birth disappeared (RR 1.0; 95 % CI, 0.57-1.9). The study indicates that north-south differences in the incidence of breast cancer in Italy may in large part be attributed to different dietary habits.

Early pregnancy sex steroids during primiparous pregnancies and maternal breast cancer: a nested case-control study in the Northern Sweden Maternity Cohort

BACKGROUND

Pregnancy and parity are associated with subsequent breast cancer risk. Experimental and epidemiologic data suggest a role for pregnancy sex steroid hormones.

METHODS

We conducted a nested case-control study in the Northern Sweden Maternity Cohort (1975-2007). Eligible women had provided a blood sample in the first 20 weeks of gestation during a primiparous pregnancy leading to a term delivery. The current study includes 223 cases and 417 matched controls (matching factors: age at and date of blood collection). Estrogen receptor (ER) and progesterone receptor (PR) status was available for all cases; androgen receptor (AR) data were available for 41% of cases (n = 92). Sex steroids were quantified by high-performance liquid chromatography tandem mass spectrometry. Odds ratios (ORs) and 95% confidence intervals were estimated using conditional logistic regression.

RESULTS

Higher concentrations of circulating progesterone in early pregnancy were inversely associated with ER+/PR+ breast cancer risk (OR_log2: 0.64 (0.41-1.00)). Higher testosterone was positively associated with ER+/PR+ disease risk (OR_log2: 1.57 (1.13-2.18)). Early pregnancy estrogens were not associated with risk, except for relatively high estradiol in the context of low progesterone (split at median, relative to low concentrations of both; OR: 1.87 (1.11-3.16)). None of the investigated hormones were associated with ER-/PR- disease, or with AR+ or AR+/ER+/PR+ disease.

CONCLUSIONS

Consistent with experimental models, high progesterone in early pregnancy was associated with lower risk of ER+/PR+ breast cancer in the mother. High circulating testosterone in early pregnancy, which likely reflects nonpregnant premenopausal exposure, was associated with higher risk of ER+/PR+ disease.

Human Chorionic Gonadotropin Does Not Correlate with Risk for Maternal Breast Cancer: Results from the Finnish Maternity Cohort

Human chorionic gonadotropin (hCG) is necessary for the maintenance of early pregnancy and promotes normal breast cell differentiation. Administered hCG reduces risk of carcinogen-induced breast cancer in animal models, and higher circulating hCG concentrations were associated with significantly lower long-term risk of breast cancer in a prior nested case-control study. In this study, we investigated early-pregnancy hCG concentrations and subsequent breast cancer risk. We conducted a nested case-control study with 1,191 cases and 2,257 controls (matched on age and date at blood collection) in the Finnish Maternity Cohort, a cohort with serum samples from 98% of pregnancies registered in Finland since 1983. This study included women with a serum sample collected early (<140 days gestation) in their first pregnancy resulting in a live, term birth. Breast cancer cases were identified via the Finnish Cancer Registry. Age at breast cancer diagnosis ranged from 22 to 58 years (mean: 41 years). hCG was measured using a solid-phase competitive chemiluminescence assay. Odds ratios (OR) were calculated using conditional logistic regression. We observed no association between hCG and breast cancer risk, overall [Quartile 4 vs. 1, OR, 1.14; 95% confidence interval (CI), 0.94-1.39], by estrogen and progesterone receptor status, or by ages at first-term birth or diagnosis. Associations did not differ by time between pregnancy and diagnosis (e.g., <5 years, OR_{Q4 vs. Q1}, 1.10; 95% CI, 0.64-1.89; ≥15 years, OR_{Q4 vs. Q1}, 1.36; 95% CI, 0.86-2.13; p_{heterogeneity} = 0.62). This large prospective study does not support an inverse relationship between early pregnancy serum hCG concentrations and breast cancer risk. Cancer Res; 77(1); 134-41. ©2016 AACR.

Free β-human chorionic gonadotropin, total human chorionic gonadotropin and maternal risk of breast cancer

BACKGROUND

We investigated whether the free β-human chorionic gonadotropin (free β-hCG) would provide additional information to that provided by total hCG alone and thus be useful in future epidemiological studies relating hCG to maternal breast cancer risk.

MATERIALS & METHODS

Cases (n = 159) and controls (n = 286) were a subset of our previous study within the Northern Sweden Maternity Cohort on total hCG during primiparous pregnancy and breast cancer risk.

RESULTS

The associations between total hCG (hazard ratio: 0.79; 95% CI: 0.49-1.27), free β-hCG (hazard ratio: 0.85; 95% CI: 0.33-2.18) and maternal risk of breast cancer were very similar in all analyses and mutual adjustment for either one had minor effects on the risk estimates.

CONCLUSION

In the absence of a reliable assay on intact hCG, total hCG alone can be used in epidemiological studies investigating hCG and breast cancer risk, as free β-hCG does not appear to provide any additional information.

Early pregnancy sex steroids and maternal breast cancer: a nested case-control study

Pregnancy, parity, and circulating steroid hormone levels are associated with risk of breast cancer, but little is known about hormone concentrations during pregnancy and subsequent breast cancer risk. We evaluated early pregnancy (<140 days gestation) serum estradiol, estrone, progesterone, and testosterone and breast cancer risk in a nested case-control study in the Finnish Maternity Cohort. The cohort includes 98% of pregnancies registered in Finland since 1983. Individuals with samples collected in the first pregnancy leading to a live birth were eligible. Breast cancer cases (n = 1,199) were identified through linkage with the Finnish Cancer Registry; 2,281 matched controls were selected using incidence density sampling. ORs were calculated using conditional logistic regression. Hormone concentrations were not associated with breast cancer overall. Estradiol was positively associated with risk of breast cancer diagnosed age <40 [4th vs. 1st quartile OR 1.60 (1.07-2.39); Ptrend = 0.01], and inversely associated with breast cancer diagnosed at age ≥40 [4th vs. 1st quartile OR 0.71 (0.51-1.00); Ptrend = 0.02]. Elevated concentrations of the steroid hormones were associated with increased risk of estrogen receptor (ER)- and progesterone receptor (PR)-negative tumors in women age <40 at diagnosis. We observed no association between steroid hormones and ER(+)/PR(+) disease. These data suggest a positive association between high concentrations of early pregnancy steroid hormones and risk of ER(-)/PR(-) breast cancer in women diagnosed age <40, and an inverse association for overall breast cancer diagnosed age ≥40. Further research on pregnancy hormones and risk of steroid receptor-negative cancers is needed to further characterize this association.

Abstract 1480: Long noncoding RNAs in the postmenopausal breast and their role in cancer prevention

Our initial transcriptomic analysis in the normal breast of parous and nulliparous women reveals that long non-coding RNA genes (lncRNAs) such as nuclear paraspeckle assembly transcript 1 (NEAT1), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), and X inactive specific transcript (XIST) are up-regulated in the parous breast [Cancer Prev Res 4 1457-1464, 2011, BMC Medical Genomics. 5:46. 2012 and Int. J. Cancer: 131, 1059-1070, 2012]. This novel observation provides a new paradigm in our understanding of the role of lncRNAs in the regulation of transcription and its potential function in pregnancy's preventive effect in reducing the lifetime risk of developing breast cancer. In the present work, we performed RNA sequencing of healthy postmenopausal breast tissue biopsies from 8 parous (P) and 8 nulliparous (NP) women using Illumina TruSeq for the library preparation and Illumina HiSeq 2000 (Illumina Inc., San Diego, CA) for RNA sequencing (RNAseq). The 16 sequenced samples (8P, 8NP) satisfied quality control thresholds. The sequencing results show that 140 genes were differentially expressed in the parous vs. the nulliparous breast tissue with fold change of two and a p-value of 0.05. Also, using t-statistics with p-value less than 0.01 and fold-change of at least two as criteria of significance, we identified 42 differentially expressed lncRNAs between P and NP women. Of these, 21 lncRNAs were up-regulated and 21 were down-regulated. We also identified 10 lncRNAs that show strong Pearson correlation of the differentially expressed lncRNA and its corresponding gene, for example lnc-CDH5-1 (long non-coding CDH5, transcript variant 1) and its corresponding gene CDH5 (cadherin 5, type 2) show a correlation p- value of 0.017 and a correlation estimate of -0.59. These results provide not only novel information on the hormonal regulation of lncRNAs induced by pregnancy in breast cells, but also place lncRNAs as potential key regulators in breast differentiation. These results begin to render a comprehensive picture of the differentiation of the human breast at the transcriptomic level, findings that will lead to the identification of the role played by lncRNAs in the prevention of breast cancer. (The sample collection was supported by Avon Foundation for Women Breast Cancer Research Program grant 02-2010-117 and the RNA sequencing studies by NIH core grant CA06927 to Fox Chase Cancer Center).

Citation Format: Maria Barton, Julia Santucci-Pereira, Ricardo Lopez de Cicco, Irma H. Russo, Eric A. Ross, Michael Slifker, Suraj Peri, Pal Bordas, Per Lenner, Göran Hallmans, Paolo Toniolo, Jose Russo. Long noncoding RNAs in the postmenopausal breast and their role in cancer prevention. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1480. doi:10.1158/1538-7445.AM2014-1480

Abstract 2360: Gene expression profile induced by pregnancy in the breast of premenopausal women

We previously reported that having completed a full term pregnancy (FTP) confers specific gene expression patterns in the breast of healthy postmenopausal women [Belitskaya-Levy, I. et al. 2011, Peri, S. et al. 2012 and Russo, J. 2012]. In the present work, we report on gene expression differences in the breast of parous versus nulliparous healthy premenopausal women. Using Affymetrix Human Genome U133 Plus 2.0 microarrays, we analyzed the gene expression profile of breast tissue from 30 nulliparous (NP) and 79 parous (P) premenopausal volunteers between the ages of 30 and 47 years who were free of breast pathology. Because of the known short-term increase in breast cancer risk preceding the long-term protective effect of FTP, we also examined gene expression differences in P vs. NP women as a function of time since last FTP. Through multiple regression analysis, controlling for confounders, we found 416 probesets differentially expressed (fold-change ≥ 1.2 and false discovery rate &lt; 10%) comparing all P vs. all NP, and/or, P women whose last FTP was less than 5 years before biopsy vs. all NP women. Among these, 352 probesets, representing 238 genes, were up-regulated, while 64 probesets, representing 48 genes, were down-regulated in parous compared to nulliparous breast. Of interest is that among the up-regulated genes, we observed three expression patterns: 1) transient: genes up-regulated after FTP but whose expression levels rapidly returned to nulliparous levels. These genes were mainly related to immune response (CCL5, CD48, IL7R); 2) long-term changing: genes up-regulated following FTP, whose expression levels decreased with increasing time since last FTP but did not return to nulliparous levels. These genes included genes related to immune response (CD38, CXCL10) and development (DKK3, LAMA2); 3) long-term constant: genes that remained up-regulated in parous compared to nulliparous breast, independent of time since last FTP. These genes were mainly involved in developmental processes (BHLHE22, FZD8, KRT5), cell differentiation (RASGRP1, DSC3) and chromatin remodeling (NAP1L2). This study shows that a FTP induces long-term expression changes in genes related to the processes of development, cell differentiation and chromatin remodeling as we also found in the parous postmenopausal breast. Additionally, the transiently activated genes related to immune response during the first five years after FTP may play a role in the short-term increase of breast cancer risk following FTP. A better understanding of the molecular effects of parity on the breast may help the development of novel strategies for preventing breast cancer. (This work was supported by Avon Foundation for Women Breast Cancer Research Program grant 02-2010-117 and by NIH core grant CA06927 to Fox Chase Cancer Center).

Citation Format: Julia Santucci-Pereira, Anne Zeleniuch-Jacquotte, Yelena Afanasyeva, Hua Zhong, Eric A. Ross, Michael Slifker, Suraj Peri, Ricardo López de Cicco, Yubo Zhai, Irma H. Russo, Theresa Nguyen, Fathima Sheriff, Alan A. Arslan, Pal Bordas, Per Lenner, Janet Åhman, Anna-Stina L. Eriksson, Robert Johansson, Göran Hallmans, Paolo Toniolo, Jose Russo. Gene expression profile induced by pregnancy in the breast of premenopausal women. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2360. doi:10.1158/1538-7445.AM2014-2360

Abstract 2294: Pregnancy changes the DNA methylation profile of the breast in postmenopausal women

Recently, we have described that the breast of parous postmenopausal women exhibits a specific gene expression profile induced by full term pregnancy (FTP) [Belitskaya-Levy, I. et al. 2011 and Peri, S. et al. 2012], which is centered on chromatin remodeling [Russo, J. 2012]. In order to better understand the molecular mechanism of gene regulation induced by FTP, we have investigated the DNA methylation profile in breast core needle biopsies of five nulliparous (NP) and five parous (P) postmenopausal women between the ages of 50 and 69. DNA was extracted from core needle biopsies and highly methylated fragments of the DNA were separated from the un-methylated DNA using MBD-Capture. The hypermethylated DNA was then sequenced using the Illumina system. Image analysis and base calling were performed with the standard Illumina pipeline, and the reads were aligned to human reference genome (hg18). Differentially methylated regions (DMR) were identified by comparing the differences of averaged methylation values between P and NP samples using Student's t-test (P&lt;0.01). 583 genes were differently methylated between P and NP, of which, 455 genes were hypermethylated in the P breast and 128 genes were hypermethylated in the NP. Additional visual analyses of the sequencing results were performed in these 583 genes using Integrative Genomics Viewer (IGV), of which, 53 genes with DMRs were identified. Analysis and research into the functions of these genes identified seven genes (DACT1, PPP2CA, GSK3B, ROBO1, INPP4B, IL6ST, FZD1) that have been described to interact with each other in either the Wnt signaling pathway or its controlling PI3K/AKT/mTOR pathways. The evaluation of these interactions suggests that beta-catenin, a downstream gene of the Wnt signaling pathway, is being inhibited in the P women. Wnt signaling plays different roles during the stages of the mammary gland development, and it is suggested that lowered beta-catenin expression is essential for proper mammary involution. This observed molecular machinery, leading to a decrease in beta-catenin production and accumulation, may be a leftover effect from mammary involution, last process that the parous mammary gland undergone and it may be, at least partially, responsible for their decreased risk of cancer. The pathways identified in this specific population are of the great importance and could represent a safeguard mechanism mediating the protection of the breast conferred by full term pregnancy. (The sample collection was supported by Avon Foundation for Women Breast Cancer Research Program grant 02-2010-117 and the methylation studies by NIH core grant CA06927 to Fox Chase Cancer Center).

Citation Format: Julia Santucci-Pereira, Colleen O'Malley, Ricardo López de Cicco, Nameer B. Kirma, Tim H. Huang, Joseph Liu, Eric A. Ross, Michael Slifker, Suraj Peri, Irma H. Russo, Pal Bordas, Per Lenner, Göran Hallmans, Paolo Toniolo, Jose Russo. Pregnancy changes the DNA methylation profile of the breast in postmenopausal women. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2294. doi:10.1158/1538-7445.AM2014-2294

Circulating estrogen metabolites and risk of breast cancer in postmenopausal women

BACKGROUND

It has been hypothesized that predominance of the 2-hydroxylation estrogen metabolism pathway over the 16α-hydroxylation pathway may be inversely associated with breast cancer risk.

METHODS

We examined the associations of invasive breast cancer risk with circulating 2-hydroxyestrone (2-OHE1), 16α-hydroxyestrone (16α-OHE1), and the 2-OHE1:16α-OHE1 ratio in a case-control study of postmenopausal women nested within two prospective cohorts: the New York University Women's Health Study (NYUWHS) and the Northern Sweden Mammary Screening Cohort (NSMSC), with adjustment for circulating levels of estrone, and additional analyses by tumor estrogen receptor (ER) status. Levels of 2-OHE1 and 16α-OHE1 were measured using ESTRAMET 2/16 assay in stored serum or plasma samples from 499 incident breast cancer cases and 499 controls, who were matched on cohort, age, and date of blood donation.

RESULTS

Overall, no significant associations were observed between breast cancer risk and circulating levels of 2-OHE1, 16α-OHE1, or their ratio in either cohort and in combined analyses. For 2-OHE1, there was evidence of heterogeneity by ER status in models adjusting for estrone (P ≤ 0.03). We observed a protective association of 2-OHE1 with ER+ breast cancer [multivariate-adjusted OR for a doubling of 2-OHE1, 0.67 (95% confidence interval [CI], 0.48-0.94; P = 0.02)].

CONCLUSIONS

In this study, higher levels of 2-OHE1 were associated with reduced risk of ER+ breast cancer in postmenopausal women after adjustment for circulating estrone.

IMPACT

These results suggest that taking into account the levels of parent estrogens and ER status is important in studies of estrogen metabolites and breast cancer.

Early pregnancy sex steroids and maternal risk of epithelial ovarian cancer

Well-established associations between reproductive characteristics and epithelial ovarian cancer (EOC) support an involvement of sex steroid hormones in the etiology of EOC. Limited previous studies have evaluated circulating androgens and the risk of EOC, and estrogens and progesterone have been investigated in only one of the previous studies. Furthermore, there is little data on potential heterogeneity in the association between circulating hormones and EOC by histological subgroup. Therefore, we conducted a nested case-control study within the Finnish Maternity Cohort and the Northern Sweden Maternity Cohort to investigate the associations between circulating pre-diagnostic sex steroid concentrations and the histological subtypes of EOC. We identified 1052 EOC cases among cohort members diagnosed after recruitment (1975-2008) and before March 2011. Up to three controls were individually matched to each case (n=2694). Testosterone, androstenedione, 17-hydroxyprogesterone (17-OHP), progesterone, estradiol (E2), and sex hormone-binding globulin levels were measured in serum samples collected during the last pregnancy before EOC diagnosis. We used conditional logistic regression to estimate odds ratios (ORs) and 95% CIs. Associations between hormones and EOC differed with respect to tumor histology and invasiveness. Sex steroid concentrations were not associated with invasive serous tumors; however, doubling of testosterone and 17-OHP concentration was associated with approximately 40% increased risk of borderline serous tumors. A doubling of androgen concentrations was associated with a 50% increased risk of mucinous tumors. The risk of endometrioid tumors increased with higher E2 concentrations (OR: 1.89 (1.20-2.98)). This large prospective study in pregnant women supports a role of sex steroid hormones in the etiology of EOC arising in the ovaries.

Circulating levels of 25-hydroxyvitamin D and risk of breast cancer: a nested case-control study

Introduction

Experimental evidence suggests a protective role for circulating 25-hydroxyvitamin D (25(OH)D) in breast cancer development, but the results of epidemiological studies have been inconsistent.

Methods

We conducted a case-control study nested within two prospective cohorts, the New York University Women's Health Study and the Northern Sweden Mammary Screening Cohort. Blood samples were collected at enrollment, and women were followed up for breast cancer ascertainment. In total, 1,585 incident breast cancer cases were individually-matched to 2,940 controls. Of these subjects, 678 cases and 1,208 controls contributed two repeat blood samples, at least one year apart. Circulating levels of 25(OH)D were measured, and multivariate odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression.

Results

No association was observed between circulating levels of 25(OH)D and overall breast cancer risk (multivariate-adjusted model OR = 0.94, 95% CI = 0.76-1.16 for the highest vs. lowest quintile, p_trend = 0.30). The temporal reliability of 25(OH)D measured in repeat blood samples was high (intraclass correlation coefficients for season-adjusted 25(OH)D > 0.70). An inverse association between 25(OH)D levels and breast cancer risk was observed among women who were ≤ 45 years of age (OR_Q5-Q1 = 0.48, 95% CI = 0.30-0.79, p_trend = 0.01) or premenopausal at enrollment (OR_Q5-Q1 = 0.67, 95% CI = 0.48-0.92, p_trend = 0.03).

Conclusions

Circulating 25(OH)D levels were not associated with breast cancer risk overall, although we could not exclude the possibility of a protective effect in younger women. Recommendations regarding vitamin D supplementation should be based on considerations other than breast cancer prevention.

Circulating carotenoids and risk of breast cancer: pooled analysis of eight prospective studies

BACKGROUND

Carotenoids, micronutrients in fruits and vegetables, may reduce breast cancer risk. Most, but not all, past studies of circulating carotenoids and breast cancer have found an inverse association with at least one carotenoid, although the specific carotenoid has varied across studies.

METHODS

We conducted a pooled analysis of eight cohort studies comprising more than 80% of the world's published prospective data on plasma or serum carotenoids and breast cancer, including 3055 case subjects and 3956 matched control subjects. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels to a common standard by reassaying 20 plasma or serum samples from each cohort together at the same laboratory. Using conditional logistic regression, adjusting for several breast cancer risk factors, we calculated relative risks (RRs) and 95% confidence intervals (CIs) using quintiles defined among the control subjects from all studies. All P values are two-sided.

RESULTS

Statistically significant inverse associations with breast cancer were observed for α-carotene (top vs bottom quintile RR = 0.87, 95% CI = 0.71 to 1.05, P(trend) = .04), β-carotene (RR = 0.83, 95% CI = 0.70 to 0.98, P(trend) = .02), lutein+zeaxanthin (RR = 0.84, 95% CI = 0.70 to 1.01, P(trend) = .05), lycopene (RR = 0.78, 95% CI = 0.62 to 0.99, P(trend) = .02), and total carotenoids (RR = 0.81, 95% CI = 0.68 to 0.96, P(trend) = .01). β-Cryptoxanthin was not statistically significantly associated with risk. Tests for heterogeneity across studies were not statistically significant. For several carotenoids, associations appeared stronger for estrogen receptor negative (ER(-)) than for ER(+) tumors (eg, β-carotene: ER(-): top vs bottom quintile RR = 0.52, 95% CI = 0.36 to 0.77, P(trend) = .001; ER(+): RR = 0.83, 95% CI = 0.66 to 1.04, P(trend) = .06; P(heterogeneity) = .01).

CONCLUSIONS

This comprehensive prospective analysis suggests women with higher circulating levels of α-carotene, β-carotene, lutein+zeaxanthin, lycopene, and total carotenoids may be at reduced risk of breast cancer.

Abstract B75: Pregnancy hormones and maternal risk of hormone receptor-defined breast cancer

Introduction: Hormonal exposure during pregnancy is believed to be associated with subsequent maternal risk of breast cancer, but so far limited epidemiological data are available.

Study design: A case-control study (223 cases and 417 controls) was nested within the Northern Sweden Maternity Cohort to explore the associations between pregnancy concentrations of sex steroid hormones and insulin-like growth factor I (IGF-I) with maternal risk of breast cancer by hormone receptor (HR) expression of the tumors. The study included women who had donated a blood sample during the first trimester of their first full-term pregnancy. Most cases had HR-positive disease: 171 (77%) estrogen receptor-positive (ER+), 157 (70%) progesterone receptor-positive (PR+) and 152 (68%) ER+/PR+ tumors. Estradiol, estrone, progesterone and testosterone were measured by high-performance liquid chromatography tandem mass spectrometry. Sex hormone-binding globulin (SHBG) and insulin-like growth factor I (IGF-I) were measured by immunoassays. For each hormone, the difference (residual) between the actual assay value for each subject and the estimated mean determined for the day of gestation when the sample was drawn was computed by local linear regression. Conditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).

Results: For HR-positive tumors, a significant direct association was observed with circulating concentrations of testosterone (e.g. OR for ER+ in the top versus bottom tertile of 1.8 (1.1-3.0), p&lt;0.02) and IGF-I (e.g. OR for ER+ in the top versus bottom tertile of 2.0 (1.2-3.3), p&lt;0.01). For HR-negative disease, risk estimates for a doubling of estrogens, progesterone and SHBG concentrations were above unity, but did not reach statistical significance with the exception of progesterone for PR-negative tumors (OR 2.0 (1.0-3.9), p&lt;0.04). In analyses limited to ER-negative tumors diagnosed up to age 50 (n=38), these associations were stronger, but only of borderline significance. For PR-negative tumors diagnosed up to age 50 (n=49), the associations were significant for estradiol (OR 1.8 (1.0-3.1), p&lt;0.04), progesterone (OR 2.6 (1.1-6.1), p&lt;0.03) and SHBG (OR 1.8 (1.0-3.0), p&lt;0.04). Adjustments for maternal height, weight, smoking, hypertension during pregnancy, child's sex, weight and length had negligible effect on risk estimates. Associations were similar by combined ER/PR tumor status or when limited to cases diagnosed ≥10 years after blood donation.

Conclusions: In this nested case-control study hormone concentrations during early pregnancy were associated with risk of maternal breast cancer but the associations differed by hormone receptor expression of the tumors. For hormones with placental contribution to circulating concentrations (estrogens and progesterone), there were indications for positive associations with risk of maternal HR-negative breast cancer. For hormones, with similar concentrations during early pregnancy and in the non-pregnant state (testosterone and IGF-I), direct associations with HR-positive breast cancer were observed, in line with most available epidemiological data in non-pregnant women. Larger studies are necessary to characterize the association of pregnancy hormones with risk of hormone-defined maternal breast cancer.

Citation Format: Annekatrin Lukanova, Egle Tolockiene, Helena Schock, Kjell Grankvist, Hans Ake Lakso, Helja Marja Surcel, Goran Wadell, Anne Zelenuich-Jacquotte, Paolo Toniolo, Eva Lundin. Pregnancy hormones and maternal risk of hormone receptor-defined breast cancer. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B75.

Defining the genomic signature of the parous breast

Background

It is accepted that a woman's lifetime risk of developing breast cancer after menopause is reduced by early full term pregnancy and multiparity. This phenomenon is thought to be associated with the development and differentiation of the breast during pregnancy.

Methods

In order to understand the underlying molecular mechanisms of pregnancy induced breast cancer protection, we profiled and compared the transcriptomes of normal breast tissue biopsies from 71 parous (P) and 42 nulliparous (NP) healthy postmenopausal women using Affymetrix Human Genome U133 Plus 2.0 arrays. To validate the results, we performed real time PCR and immunohistochemistry.

Results

We identified 305 differentially expressed probesets (208 distinct genes). Of these, 267 probesets were up- and 38 down-regulated in parous breast samples; bioinformatics analysis using gene ontology enrichment revealed that up-regulated genes in the parous breast represented biological processes involving differentiation and development, anchoring of epithelial cells to the basement membrane, hemidesmosome and cell-substrate junction assembly, mRNA and RNA metabolic processes and RNA splicing machinery. The down-regulated genes represented biological processes that comprised cell proliferation, regulation of IGF-like growth factor receptor signaling, somatic stem cell maintenance, muscle cell differentiation and apoptosis.

Conclusions

This study suggests that the differentiation of the breast imprints a genomic signature that is centered in the mRNA processing reactome. These findings indicate that pregnancy may induce a safeguard mechanism at post-transcriptional level that maintains the fidelity of the transcriptional process.

Selected polymorphisms in sex hormone-related genes, circulating sex hormones and risk of endometrial cancer

BACKGROUND

The role of estrogen and progesterone in the development of endometrial cancer is well documented. Few studies have examined the association of genetic variants in sex hormone-related genes with endometrial cancer risk.

METHODS

We conducted a case-control study nested within three cohorts to examine the association of endometrial cancer risk with polymorphisms in hormone-related genes among 391 cases (92% postmenopausal at diagnosis) and 712 individually-matched controls. We also examined the association of these polymorphisms with circulating levels of sex hormones and SHBG in a cross-sectional analysis including 596 healthy postmenopausal women at blood donation (controls from this nested case-control study and from a nested case-control study of breast cancer in one of the three cohorts).

RESULTS

Adjusting for endometrial cancer risk factors, the A allele of rs4775936 in CYP19 was significantly associated (OR(per allele)=1.22, 95% CI=1.01-1.47, p(trend)=0.04), while the T allele of rs10046 was marginally associated with increased risk of endometrial cancer (OR(per allele)=1.20, 95% CI=0.99-1.45, p(trend)=0.06). PGR rs1042838 was also marginally associated with risk (OR(per allele)=1.25, 95% CI=0.96-1.61, p(trend)=0.09). No significant association was found for the other polymorphisms, i.e. CYP1B1 rs1800440 and rs1056836, UGT1A1 rs8175347, SHBG rs6259 and ESR1 rs2234693. Rs8175347 was significantly associated with postmenopausal levels of estradiol, free estradiol and estrone and rs6259 with SHBG and estradiol.

CONCLUSION

Our findings support an association between genetic variants in CYP19, and possibly PGR, and risk of endometrial cancer.

Premenopausal serum androgens and breast cancer risk: a nested case-control study

INTRODUCTION

Prospective epidemiologic studies have consistently shown that levels of circulating androgens in postmenopausal women are positively associated with breast cancer risk. However, data in premenopausal women are limited.

METHODS

A case-control study nested within the New York University Women's Health Study was conducted. A total of 356 cases (276 invasive and 80 in situ) and 683 individually-matched controls were included. Matching variables included age and date, phase, and day of menstrual cycle at blood donation. Testosterone, androstenedione, dehydroandrosterone sulfate (DHEAS) and sex hormone-binding globulin (SHBG) were measured using direct immunoassays. Free testosterone was calculated.

RESULTS

Premenopausal serum testosterone and free testosterone concentrations were positively associated with breast cancer risk. In models adjusted for known risk factors of breast cancer, the odds ratios for increasing quintiles of testosterone were 1.0 (reference), 1.5 (95% confidence interval (CI), 0.9 to 2.3), 1.2 (95% CI, 0.7 to 1.9), 1.4 (95% CI, 0.9 to 2.3) and 1.8 (95% CI, 1.1 to 2.9; Ptrend = 0.04), and for free testosterone were 1.0 (reference), 1.2 (95% CI, 0.7 to 1.8), 1.5 (95% CI, 0.9 to 2.3), 1.5 (95% CI, 0.9 to 2.3), and 1.8 (95% CI, 1.1 to 2.8, Ptrend = 0.01). A marginally significant positive association was observed with androstenedione (P = 0.07), but no association with DHEAS or SHBG. Results were consistent in analyses stratified by tumor type (invasive, in situ), estrogen receptor status, age at blood donation, and menopausal status at diagnosis. Intra-class correlation coefficients for samples collected from 0.8 to 5.3 years apart (median 2 years) in 138 cases and 268 controls were greater than 0.7 for all biomarkers except for androstenedione (0.57 in controls).

CONCLUSIONS

Premenopausal concentrations of testosterone and free testosterone are associated with breast cancer risk. Testosterone and free testosterone measurements are also highly reliable (that is, a single measurement is reflective of a woman's average level over time). Results from other prospective studies are consistent with our results. The impact of including testosterone or free testosterone in breast cancer risk prediction models for women between the ages of 40 and 50 years should be assessed. Improving risk prediction models for this age group could help decision making regarding both screening and chemoprevention of breast cancer.

Pregnancy-induced chromatin remodeling in the breast of postmenopausal women

Early pregnancy and multiparity are known to reduce the risk of women to develop breast cancer at menopause. Based on the knowledge that the differentiation of the breast induced by the hormones of pregnancy plays a major role in this protection, this work was performed with the purpose of identifying what differentiation-associated molecular changes persist in the breast until menopause. Core needle biopsies (CNB) obtained from the breast of 42 nulliparous (NP) and 71 parous (P) postmenopausal women were analyzed in morphology, immunocytochemistry and gene expression. Whereas in the NP breast, nuclei of epithelial cells were large and euchromatic, in the P breast they were small and hyperchromatic, showing strong methylation of histone 3 at lysine 9 and 27. Transcriptomic analysis performed using Affymetrix HG_U133 oligonucleotide arrays revealed that in CNB of the P breast, there were 267 upregulated probesets that comprised genes controlling chromatin organization, transcription regulation, splicing machinery, mRNA processing and noncoding elements including XIST. We concluded that the differentiation process induced by pregnancy is centered in chromatin remodeling and in the mRNA processing reactome, both of which emerge as important regulatory pathways. These are indicative of a safeguard step that maintains the fidelity of the transcription process, becoming the ultimate mechanism mediating the protection of the breast conferred by full-term pregnancy.

Mutations of mitochondrial DNA as potential biomarkers in breast cancer

BACKGROUND

Alterations of mitochondrial DNA (mtDNA) have been found in cancer patients, therefore informative mtDNA mutations could serve as biomarkers for the disease.

MATERIALS AND METHODS

The two hypervariable regions HVR1 and HVR2 in the D-Loop region were sequenced in ten paired tissue and plasma samples from breast cancer patients.

RESULTS

MtDNA mutations were found in all patients' samples, suggesting a 100% detection rate. Examining germline mtDNA mutations, a total of 85 mutations in the D-loop region were found; 31 of these mutations were detected in both tissues and matched plasma samples, the other 54 germline mtDNA mutations were found only in the plasma samples. Regarding somatic mtDNA mutations, a total of 42 mutations in the D-loop region were found in breast cancer tissues.

CONCLUSION

Somatic mtDNA mutations in the D-loop region were detected in breast cancer tissues but not in the matched plasma samples, suggesting that more sensitive methods will be needed for such detection to be of clinical utility.

Postmenopausal circulating levels of 2- and 16α-hydroxyestrone and risk of endometrial cancer

Background:

It has been suggested that the relative importance of oestrogen-metabolising pathways may affect the risk of oestrogen-dependent tumours including endometrial cancer. One hypothesis is that the 2-hydroxy pathway is protective, whereas the 16α-hydroxy pathway is harmful.

Methods:

We conducted a case–control study nested within three prospective cohorts to assess whether the circulating 2-hydroxyestrone : 16α-hydroxyestrone (2-OHE1 : 16α-OHE1) ratio is inversely associated with endometrial cancer risk in postmenopausal women. A total of 179 cases and 336 controls, matching cases on cohort, age and date of blood donation, were included. Levels of 2-OHE1 and 16α-OHE1 were measured using a monoclonal antibody-based enzyme assay.

Results:

Endometrial cancer risk increased with increasing levels of both metabolites, with odds ratios in the top tertiles of 2.4 (95% CI=1.3, 4.6; P_trend=0.007) for 2-OHE1 and 1.9 (95% CI=1.1, 3.5; P_trend=0.03) for 16α-OHE1 in analyses adjusting for endometrial cancer risk factors. These associations were attenuated and no longer statistically significant after further adjustment for oestrone or oestradiol levels. No significant association was observed for the 2-OHE1 : 16α-OHE1 ratio.

Conclusion:

Our results do not support the hypothesis that greater metabolism of oestrogen via the 2-OH pathway, relative to the 16α-OH pathway, protects against endometrial cancer.

Circulating sex hormones and breast cancer risk factors in postmenopausal women: reanalysis of 13 studies

Background:

Breast cancer risk for postmenopausal women is positively associated with circulating concentrations of oestrogens and androgens, but the determinants of these hormones are not well understood.

Methods:

Cross-sectional analyses of breast cancer risk factors and circulating hormone concentrations in more than 6000 postmenopausal women controls in 13 prospective studies.

Results:

Concentrations of all hormones were lower in older than younger women, with the largest difference for dehydroepiandrosterone sulphate (DHEAS), whereas sex hormone-binding globulin (SHBG) was higher in the older women. Androgens were lower in women with bilateral ovariectomy than in naturally postmenopausal women, with the largest difference for free testosterone. All hormones were higher in obese than lean women, with the largest difference for free oestradiol, whereas SHBG was lower in obese women. Smokers of 15+ cigarettes per day had higher levels of all hormones than non-smokers, with the largest difference for testosterone. Drinkers of 20+ g alcohol per day had higher levels of all hormones, but lower SHBG, than non-drinkers, with the largest difference for DHEAS. Hormone concentrations were not strongly related to age at menarche, parity, age at first full-term pregnancy or family history of breast cancer.

Conclusion:

Sex hormone concentrations were strongly associated with several established or suspected risk factors for breast cancer, and may mediate the effects of these factors on breast cancer risk.

Assessing the value of CAN-gene mutations using MALDI-TOF MS

PURPOSE

To identify cancer-linked genes, Sjöblom et al. and Wood et al. performed a genome-wide mutation screening in human breast and colorectal cancers. 140 CAN-genes were found in breast cancer, which in turn contained overall 334 mutations. These mutations could prove useful for diagnostic and therapeutic purposes.

METHODS

We used a MALDI-TOF MS 40-plex assay for testing 40 loci within 21 high-ranking breast cancer CAN-genes. To confirm mutations, we performed single-plex assays and sequencing.

RESULTS

In general, the mutation rate of the analyzed loci in our sample cohort was very low. No mutation from the 40 loci analyzed could be found in the 6 cell lines. In tissue samples, a single breast cancer tissue sample showed heterozygosity at locus c.5834G>A within the ZFYVE26 gene (Zinc finger FYVE domain-containing gene 26).

CONCLUSIONS

Sjöblom et al./Wood et al. already showed that the vast majority of CAN-genes are mutated at very low frequency. Due to the fact that we only found one mutation in our cohort, we therefore assume that at the selected loci, mutations might be low-frequency events and therefore, more rarely detectable. However, further evaluation of the CAN-gene mutations in larger cohorts should be the aim of further studies.

Circulating insulin-like growth factor-I in pregnancy and maternal risk of breast cancer

BACKGROUND

Elevated serum concentrations of insulin-like growth factor (IGF)-I have been associated with increased risk of developing breast cancer. Previously, we reported a similar association in samples obtained during pregnancy. This study was conducted to further characterize the association of IGF-I during pregnancy with maternal breast cancer risk.

METHODS

A case-control study was nested within the Finnish Maternity Cohort. The study was limited to primiparous women younger than 40 years, who donated blood samples during early (median, 12 weeks) pregnancy and delivered a single child at term. Seven hundred nineteen women with invasive breast cancer were eligible. Two controls (n = 1,434) were matched with each case on age and date at blood donation. Serum IGF-I concentration was measured using an Immulite 2000 analyzer. Conditional logistic regression was used to estimate ORs and 95% CIs.

RESULTS

No significant associations were observed between serum IGF-I concentrations and breast cancer risk in both the overall analysis (OR, 1.08; 95% CI, 0.80-1.47) and in analyses stratified by histologic subtype, lag time to cancer diagnosis, age at pregnancy, or age at diagnosis.

CONCLUSION

There was no association between IGF-I and maternal breast cancer risk during early pregnancy in this large nested case-control study.

IMPACT

Serum IGF-I concentrations during early pregnancy may not be related to maternal risk of developing breast cancer.

Endogenous hormones and coronary heart disease in postmenopausal women

The association between serum levels of endogenous estrogens in postmenopausal women and the subsequent risk of coronary heart disease (CHD) was examined in a prospective case-control study nested within the New York University Women's Health Study (NYUWHS). The NYUWHS is a prospective cohort study of 14,274 healthy women enrolled between 1985 and 1991. A total of 99 women who were postmenopausal and free of cardiovascular disease at enrollment and who subsequently experienced CHD, defined as non-fatal myocardial infarction (MI), fatal CHD, percutaneous transluminal coronary angioplasty (PTCA), or coronary artery bypass grafting (CABG), were matched 1:2 by baseline age, blood sampling date, and postmenopausal status to controls who remained free of CHD as of the date of diagnosis of the matching case. Biochemical analyses for total estradiol, estrone, percent free estradiol, percent estradiol bound to sex hormone-binding globulin (SHBG), and SHBG were performed on pre-diagnostic stored serum samples. Participants had not used any hormone medications in the 6 months prior to blood collection. In the model adjusting only for matching factors, the risk of CHD in the top tertile of calculated bioavailable estradiol was elevated compared with the bottom tertile (OR=2.10; 95% CI=1.13-3.90, P for trend=0.03), and the risk in the top tertile of SHBG was reduced (OR=0.50, 95% CI=0.28-0.92, P for trend<0.01). However, these associations disappeared after adjusting for baseline hypertension status, body mass index, and serum cholesterol levels. These findings suggest that circulating estradiol and SHBG are not associated with CHD risk in postmenopausal women beyond what can be explained by the variation in hypertension status, BMI, and cholesterol.

Characterization of a genomic signature of pregnancy identified in the breast

The objective of this study was to comprehensively compare the genomic profiles in the breast of parous and nulliparous postmenopausal women to identify genes that permanently change their expression following pregnancy. The study was designed as a two-phase approach. In the discovery phase, we compared breast genomic profiles of 37 parous with 18 nulliparous postmenopausal women. In the validation phase, confirmation of the genomic patterns observed in the discovery phase was sought in an independent set of 30 parous and 22 nulliparous postmenopausal women. RNA was hybridized to Affymetrix HG_U133 Plus 2.0 oligonucleotide arrays containing probes to 54,675 transcripts, scanned and the images analyzed using Affymetrix GCOS software. Surrogate variable analysis, logistic regression, and significance analysis of microarrays were used to identify statistically significant differences in expression of genes. The false discovery rate (FDR) approach was used to control for multiple comparisons. We found that 208 genes (305 probe sets) were differentially expressed between parous and nulliparous women in both discovery and validation phases of the study at an FDR of 10% and with at least a 1.25-fold change. These genes are involved in regulation of transcription, centrosome organization, RNA splicing, cell-cycle control, adhesion, and differentiation. The results provide initial evidence that full-term pregnancy induces long-term genomic changes in the breast. The genomic signature of pregnancy could be used as an intermediate marker to assess potential chemopreventive interventions with hormones mimicking the effects of pregnancy for prevention of breast cancer.

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.

Abstract 3672: Defining the genomic signature of the parous breast

Epidemiological data have consistently shown that a pregnancy early in life confer mothers lifetime protection against breast cancer, which is enhanced by subsequent pregnancies. Previous studies have demonstrated that the protection conferred by pregnancy is mediated by the differentiation of the breast, which is expressed as a specific genomic profile detectable in breast cells of postmenopausal parous women that serves as a biomarker indicative of reduced cancer risk. For further confirming these observations we designed a multidisciplinary study for determining whether the pattern of gene expression differed between nulliparous and parous postmenopausal women from an ethnically homogeneous population residing in Norrbotten County, Sweden; the study was approved by the IRB/Ethical Board of the University of Umeå, Sweden. Volunteer women from 50-69 years of age, belonging to one of the following categories based on reproductive history: parous (G≥1/P≥1), nulligravida nullipara (G0/P0) or gravida nullipara (G≥1/P0). The subjects signed an informed consent to participate in the study and donated core needle biopsies (CNB) of breast. CNB were taken from the upper outer quadrant of the breast and divided for 70% ethanol fixation for histopathological analysis and RNA extraction for subsequent genomic analysis. Total RNA was isolated using the Qiagen Allprep RNA/DNA Mini Kit. RNA quantity and quality were determined and the GeneChip Expression 3’-Amplification Two-Cycle cDNA Synthesis Kit (Affymetrix, Santa Clara, CA) was used to prepare the cRNA for hybridization; samples were hybridized to Affymetrix HG_U133 Plus 2.0 oligonucleotide arrays; 71 parous and 42 nulliparous satisfied quality control thresholds based on standard Affymetrix quality control measures. Probesets for which the proportion of Present calls was less than 75% in both samples were filtered out. A variance filter was also applied, removing all probesets whose variance across all samples fell below the first quartile, remaining 18,694 probesets for further analysis using both a p-value of 0.001 from the empirical Bayes moderated t-statistics, and a minimum log2 fold-change of 0.3 threshold as criteria of significance. Two hundred and eight genes were found to be differentially expressed between parous and nulliparous women. Gene ontology and pathway analyses revealed enrichment of biological processes related to regulation of transcription, RNA splicing, cell cycle control, adhesion and differentiation. IGF-like growth factor signaling and somatic stem cell maintenance were significantly downregulated. These results demonstrated that the breast of parous postmenopausal women exhibits a transcriptomic profile that differs from that of nulliparous women, representing a genomic signature induced by full term pregnancy that is indicative of breast differentiation.

Work supported by Avon Foundation Women Breast Cancer Research Program grant 02-2008-034.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3672. doi:10.1158/1538-7445.AM2011-3672

Circulating sex steroids during pregnancy and maternal risk of non-epithelial ovarian cancer

BACKGROUND

Sex steroid hormones have been proposed to play a role in the development of non-epithelial ovarian cancers (NEOC) but so far no direct epidemiologic data are available.

METHODS

A case-control study was nested within the Finnish Maternity Cohort, the world's largest biorepository of serum specimens from pregnant women. Study subjects were selected among women who donated a blood sample during a singleton pregnancy that led to the birth of their last child preceding diagnosis of NEOC. Case subjects were 41 women with sex cord stromal tumors (SCST) and 21 with germ cell tumors (GCT). Three controls, matching the index case for age, parity at the index pregnancy, and date at blood donation were selected (n = 171). OR and 95% CI associated with concentrations of testosterone, androstenedione, 17-OH-progesterone, progesterone, estradiol, and sex hormone-binding globulin (SHBG) were estimated through conditional logistic regression.

RESULTS

For SCST, doubling of testosterone, androstenedione, and 17-OH-progesterone concentrations were associated with about 2-fold higher risk of SCST [ORs and 95% CI of 2.16 (1.25-3.74), 2.16 (1.20-3.87), and 2.62 (1.27-5.38), respectively]. These associations remained largely unchanged after excluding women within 2-, 4-, or 6-year lag time between blood donation and cancer diagnosis. Sex steroid hormones concentrations were not related to maternal risk of GCT.

CONCLUSIONS

This is the first prospective study providing initial evidence that elevated androgens play a role in the pathogenesis of SCST.

IMPACT

Our study may note a particular need for larger confirmatory investigations on sex steroids and NEOC.

Abstract A90: Plasma carotenoids and risk of breast cancer: Pooled analysis of eight prospective cohorts

Carotenoids, prominent micronutrients in fruits and vegetables that act as antioxidants, may reduce the risk of breast cancer. Several studies of plasma carotenoids and breast cancer have been conducted and most, but not all, have found an inverse association with at least one carotenoid although the specific carotenoid has varied across studies. We conducted a pooled analysis of eight cohort studies comprising &gt;95% of the world's published prospective data on plasma carotenoids and breast cancer. The studies included 3,055 cases and 3,955 matched controls from the Columbia Missouri Breast Cancer Serum Bank; MSP/VIP/MONICA cohorts in Umea, Sweden; Johns Hopkins University CLUE I and II; Nurses’ Health Study; Women's Health Study; New York University Women's Health Study; Shanghai Women's Health Study; and Multiethnic Cohort Study. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels by re-assaying 20 plasma samples from each cohort together at the same laboratory. Recalibration data are currently available for seven of the eight cohorts; recalibration data from the 8th cohort are being incorporated. Using conditional logistic regression, adjusted for several breast cancer risk factors, we first calculated relative risks (RRs) and 95% confidence intervals (CIs) from each study, using study-specific quintiles, and pooled the estimates using a random effects model weighted by the inverse variances. Next we recalibrated carotenoid levels from each study to a common standard and conducted conditional logistic regression on the pooled data using quintiles defined among the controls from all studies. Levels of carotenoids differed across cohorts (e.g., median recalibrated lycopene ranged from 17.9 (Umea) to 41.9 (NHS) μg/dL) as did the primary contributor to total carotenoids (ß-carotene, lutein/zeaxanthin, or lycopene). Total carotenoids were suggestively inversely associated with breast cancer risk when study-specific RRs were pooled (top vs. bottom study-specific quintile RR=0.72,95% CI (0.51 −1.01), p-trend=0.07), but with significant heterogeneity across studies (p=0.002). Using recalibrated carotenoid levels and common quintiles, significant inverse associations with breast cancer were observed for α-carotene (top vs. bottom common quintile RR=0.82,95% CI (0.68-0.99), p-trend=0.01), ß-carotene (comparable RR=0.75,95% CI (0.62-0.90), p-trend=0.002), lutein/zeaxanthin (comparable RR=0.80,95% CI (0.67-0.97), p-trend=0.03), and total carotenoids (comparable RR=0.79,95% CI (0.65-0.97), p-trend=0.01). ß-cryptoxanthin (comparable RR=0.93,95% CI (0.76-1.13), p-trend=0.07) and lycopene (comparable RR=0.91,95% CI (0.74-1.12), p-trend=0.18) were not significantly associated with breast cancer risk. Tests for heterogeneity using recalibrated data were not significant. This comprehensive prospective analysis suggests women with higher plasma levels of a-carotene, ß-carotene, lutein/zeaxanthin, and total carotenoids may be at reduced risk of breast cancer.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):A90.

Pooled analyses of 13 prospective cohort studies on folate intake and colon cancer

OBJECTIVE

Studies of folate intake and colorectal cancer risk have been inconsistent. We examined the relation with colon cancer risk in a series of 13 prospective studies.

METHODS

Study- and sex-specific relative risks (RRs) were estimated from the primary data using Cox proportional hazards models and then pooled using a random-effects model.

RESULTS

Among 725,134 participants, 5,720 incident colon cancers were diagnosed during follow-up. The pooled multivariate RRs (95% confidence interval [CI]) comparing the highest vs. lowest quintile of intake were 0.92 (95% CI 0.84-1.00, p-value, test for between-studies heterogeneity = 0.85) for dietary folate and 0.85 (95% CI 0.77-0.95, p-value, test for between-studies heterogeneity = 0.42) for total folate. Results for total folate intake were similar in analyses using absolute intake cutpoints (pooled multivariate RR = 0.87, 95% CI 0.78-0.98, comparing ≥ 560 mcg/days vs. <240 mcg/days, p-value, test for trend = 0.009). When analyzed as a continuous variable, a 2% risk reduction (95% CI 0-3%) was estimated for every 100 μg/day increase in total folate intake.

CONCLUSION

These data support the hypothesis that higher folate intake is modestly associated with reduced risk of colon cancer.

Human chorionic gonadotropin in pregnancy and maternal risk of breast cancer

Full-term pregnancies are associated with long-term reductions in maternal risk of breast cancer, but the biological determinants of the protection are unknown. Experimental observations suggest that human chorionic gonadotropin (hCG), a major hormone of pregnancy, could play a role in this association. A case-control study (242 cases and 450 controls) nested within the Northern Sweden Maternity Cohort included women who had donated a blood sample during the first trimester of a first full-term pregnancy. Total hCG was determined on Immulite 2000 analyzer. Odds ratios (OR) and 95% confidence intervals (CI) were estimated through conditional logistic regression. Maternal breast cancer risk decreased with increasing hCG (upper tertile OR, 0.67; CI, 0.46-0.99), especially for pregnancies before age 25 (upper tertile OR, 0.41; CI, 0.21-0.80). The association diverged according to age at diagnosis: risk was reduced after age 40 (upper tertile OR, 0.60; CI, 0.39-0.91) and seemed to increase before age 40 (upper tertile OR, 1.78; CI, 0.72-4.38). Risk was reduced among those diagnosed 10 years or longer after blood draw (upper tertile OR, 0.60; CI, 0.40-0.90), but not so among those diagnosed within 10 years (upper tertile OR, 4.33; CI, 0.86-21.7). These observations suggest that the association between pregnancy hCG and subsequent maternal risk of breast cancer is modified by age at diagnosis. Although the hormone seems to be a determinant of the reduced risk around or after age 50, it might not confer protection against, or it could even increase the risk of, cancers diagnosed in the years immediately following pregnancy.

Methylation profile of TP53 regulatory pathway and mtDNA alterations in breast cancer patients lacking TP53 mutations

The present study investigated promoter hypermethylation of TP53 regulatory pathways providing a potential link between epigenetic changes and mitochondrial DNA (mtDNA) alterations in breast cancer patients lacking a TP53 mutation. The possibility of using the cancer-specific alterations in serum samples as a blood-based test was also explored. Triple-matched samples (cancerous tissues, matched adjacent normal tissues and serum samples) from breast cancer patients were screened for TP53 mutations, and the promoter methylation profile of P14(ARF), MDM2, TP53 and PTEN genes was analyzed as well as mtDNA alterations, including D-loop mutations and mtDNA content. In the studied cohort, no mutation was found in TP53 (DNA-binding domain). Comparison of P14(ARF) and PTEN methylation patterns showed significant hypermethylation levels in tumor tissues (P < 0.05 and <0.01, respectively) whereas the TP53 tumor suppressor gene was not hypermethylated (P < 0.511). The proportion of PTEN methylation was significantly higher in serum than in the normal tissues and it has a significant correlation to tumor tissues (P < 0.05). mtDNA analysis revealed 36.36% somatic and 90.91% germline mutations in the D-loop region and also significant mtDNA depletion in tumor tissues (P < 0.01). In addition, the mtDNA content in matched serum was significantly lower than in the normal tissues (P < 0.05). These data can provide an insight into the management of a therapeutic approach based on the reversal of epigenetic silencing of the crucial genes involved in regulatory pathways of the tumor suppressor TP53. Additionally, release of significant aberrant methylated PTEN in matched serum samples might represent a promising biomarker for breast cancer.

Circulating estrogen metabolites and risk for breast cancer in premenopausal women

BACKGROUND

It has been proposed that a shift toward 2-hydroxyestrone from 16alpha-hydroxyestrone metabolic pathway may be inversely associated with breast cancer risk because 2-hydroxyestrone is thought to be less genotoxic and estrogenic than 16alpha-hydroxyestrone.

METHODS

We examined the associations of invasive breast cancer risk with circulating 2-hydroxyestrone, 16alpha-hydroxyestrone, and the 2-hydroxyestrone:16alpha-hydroxyestrone ratio in a case-control study on premenopausal women nested within a prospective cohort the New York University Women's Health Study. The serum levels of 2-hydroxyestrone and 16alpha-hydroxyestrone were measured in 377 incident premenopausal breast cancer cases and 377 premenopausal controls, who were matched on age at enrollment, number and dates of blood donations, and day and phase of menstrual cycle.

RESULTS

Overall, no significant associations were observed between breast cancer risk and serum levels of 2-hydroxyestrone, 16alpha-hydroxyestrone, or their ratio. The 2-hydroxyestrone:16alpha-hydroxyestrone ratio was positively associated with risk for estrogen receptor-positive breast cancer in the analyses controlling for matching factors. However, the association was attenuated and not significant after adjustment for potential confounders (odds ratio for the highest versus the lowest quartile, 2.15; 95% CI, 0.88-5.27; P(trend) = 0.09).

CONCLUSIONS

The results of the current study do not support the hypothesis that a metabolic shift from 16alpha-hydroxyestrone toward 2-hydroxyestrone in premenopausal women is associated with reduced risk for breast cancer. The association between the 2-hydroxy:16alpha-hydroxyestrone ratio and estrogen receptor-positive breast cancer needs to be explored in future studies.

IGF-I during primiparous pregnancy and maternal risk of breast cancer

Previously, we reported that insulin-like growth factor (IGF)-I during early pregnancy is positively associated with maternal risk of breast cancer. To further explore this association, we designed a new study limited to women who donated a blood sample during their first pregnancy ending with childbirth. A case-control study was nested within the Northern Sweden Maternity Cohort in which repository since 1975, serum specimens remaining after early pregnancy screening for infectious diseases had been preserved. Study subjects were selected among women who donated a blood sample during the full-term pregnancy that led to the birth of their first child. Two hundred and forty-four women with invasive breast cancer were eligible. Two controls, matching the index case for age and date at blood donation were selected (n = 453). IGF-I was measured in serum samples on an Immulite 2000 analyzer. Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals. A significant positive association of breast cancer with IGF-I was observed, with OR of 1.73 (95% CI: 1.14-2.63) for the top tertile, P < 0.009. Subgroup analyses did not indicate statistical heterogeneity of the association by ages at sampling and diagnosis or by lag time to cancer diagnosis, although somewhat stronger associations with risk were observed in women < or = age 25 at index pregnancy and for cases diagnosed within 15 years of blood donation. The results of the study add further evidence for an adverse effect of elevated IGF-I concentrations during early reproductive life on risk of breast cancer.

C-reactive protein and ovarian cancer: a prospective study nested in three cohorts (Sweden, USA, Italy)

OBJECTIVES

Inflammatory processes may influence the risk of epithelial ovarian cancer, but available epidemiological evidence is limited and indirect. Circulating C-reactive protein (CRP), a sensitive marker of inflammation, may serve as a direct biological marker of an underlying association.

METHODS

The association between ovarian cancer risk and pre-diagnostic circulating CRP was tested in a case-control study nested within three prospective cohorts from Sweden, USA, and Italy. The study included 237 cases and 427 individually matched controls. CRP was measured in stored blood samples by high-sensitivity immunoturbidimetric assay. Odds ratios (OR) and 95% confidence intervals (CI) were calculated by conditional logistic regression.

RESULTS

Overall, CRP was not related to risk of ovarian cancer. However, a marked increase in risk was observed for CRP concentrations >10 mg/l: OR (95% CI) 4.4 (1.8-10.9), which remained significant after limiting analyses to cases diagnosed more than two or five years after blood donation (OR 3.0 (1.2-8.0) and 3.6 (1.0-13.2), respectively). Risk of mucinous tumors increased with high CRP, but the number of cases in this analysis was small.

CONCLUSION

Study results offer additional support to the concept that chronic inflammation plays a role in epithelial ovarian cancer.

Reproducibility of serum pituitary hormones in women

Endogenous pituitary hormones are commonly used in clinical and epidemiologic studies and some of them are thought to influence the risk of several diseases in women. In most studies, endogenous levels of pituitary hormones are usually assessed at a single point in time, assuming that this single measurement represents the long-term biomarker status of the individual. Such an assumption is rarely tested and may not always be valid. This study examined the reproducibility of the following pituitary hormones: adrenocorticotropic hormone (ACTH), growth hormone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and prolactin, measured using the Luminex xMap method in sera of healthy premenopausal and postmenopausal women. The study included 30 premenopausal women with three yearly samples and 35 postmenopausal women with two repeated yearly samples randomly selected from an existing prospective cohort. Analysis of intraclass correlation coefficients suggested higher reproducibility in postmenopausal women compared with premenopausal women for the following hormones: FSH (0.72 and 0.37, respectively), LH (0.83 and 0.44, respectively), and growth hormone (0.60 and 0.35, respectively). The intraclass correlation coefficients were relatively high and similar between postmenopausal and premenopausal women for ACTH (0.95 and 0.94, respectively), TSH (0.85 and 0.85, respectively), and prolactin (0.72 and 0.69, respectively). This study found that serum concentrations of FSH, LH, and growth hormone are stable in postmenopausal women and that ACTH, TSH, and prolactin are stable in both premenopausal and postmenopausal women, suggesting that a single measurement may reliably categorize average levels over at least a 2-year period.

Human chorionic gonadotropin and alpha-fetoprotein concentrations in pregnancy and maternal risk of breast cancer: a nested case-control study

Pregnancy hormones are believed to be involved in the protection against breast cancer conferred by pregnancy. The authors explored the association of maternal breast cancer with human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP). In 2001, a case-control study was nested within the Northern Sweden Maternity Cohort, an ongoing study in which blood samples have been collected from first-trimester pregnant women since 1975. Cases (n = 210) and controls (n = 357) were matched for age, parity, and date of blood donation. Concentrations of hCG and AFP were measured by immunoassay. No overall significant association of breast cancer with either hCG or AFP was observed. However, women with hCG levels in the top tertile tended to be at lower risk of breast cancer than women with hCG levels in the lowest tertile in the whole study population and in subgroups of age at sampling, parity, and age at cancer diagnosis. A borderline-significant decrease in risk with high hCG levels was observed in women who developed breast cancer after the median lag time to cancer diagnosis (> or =14 years; odds ratio = 0.53, 95% confidence interval: 0.27, 1.03; P = 0.06). These findings, though very preliminary, are consistent with a possible long-term protective association of breast cancer risk with elevated levels of circulating hCG in the early stages of pregnancy.

Vitamin D receptor polymorphisms and risk of epithelial ovarian cancer

The vitamin D receptor (VDR) is a critical mediator of the cellular effects of vitamin D. The associations between four common VDR polymorphisms (BSMI, APAI, TAQI, and FOKI) and risk of epithelial ovarian cancer (EOC) were assessed in a case-control study nested within two prospective cohorts. One hundred seventy incident cases of EOC and 323 individually matched controls were genotyped. Overall, no associations were observed in genotype analyses. Haplotypes combining three SNPs in high linkage disequilibrium (BSMI, APAI, and TAQI) were also not associated with risk. These observations do not support a role for BSMI, APAI, TAQI, and FOKI polymorphisms in epithelial ovarian cancer in a predominantly Caucasian population.

Effect of long-term storage on hormone measurements in samples from pregnant women: the experience of the Finnish Maternity Cohort

Validity of biobank studies on hormone associated cancers depend on the extent the sample preservation is affecting the hormone measurements. We investigated the effect of long-term storage (up to 22 years) on immunoassay measurements of three groups of hormones and associated proteins: sex-steroids [estradiol, progesterone, testosterone, dihydroepiandrosterone sulphate (DHEAS), sex hormone-binding globulin (SHBG)], pregnancy-specific hormones [human chorionic gonadotropin (hCG), placental growth hormone (pGH), alpha-fetoprotein (AFP)], and insulin-like growth factor (IGF) family hormones exploiting the world largest serum bank, the Finnish Maternity Cohort (FMC). Hormones of interest were analyzed in a random sample of 154 Finnish women in the median age (29.5 years, range 25 to 34 years) of their first pregnancy with serum samples drawn during the first trimester. All hormone measurements were performed using commercial enzyme-linked- or radio-immunoassays. Storage time did not correlate with serum levels of testosterone, DHEAS, hCG, pGH and total IGFBP-1. It had a weak or moderate negative correlation with serum levels of progesterone (Spearman's ranked correlation coefficient (r(s))=- 0.36), IGF-I (r(s)=-0.23) and IGF binding protein (BP)-3 (r(s)=-0.38), and weak positive correlation with estradiol (r(s)=0.23), SHBG (r(s)=0.16), AFP (r(s)=0.20) and non-phosphorylated IGF binding protein (BP)-1 (r(s)=0.27). The variation of all hormone levels studied followed the kinetics reported for early pregnancy. Bench-lag time (the time between sample collection and freezing for storage) did not materially affect the serum hormone levels. In conclusion, the stored FMC serum samples can be used to study hormone-disease associations, but close matching for storage time and gestational day are necessary design components of all related biobank studies.

Effects of parity on pregnancy hormonal profiles across ethnic groups with a diverse incidence of breast cancer

Epidemiologic evidence suggests that a full-term pregnancy may affect maternal risk of breast cancer later in life. The objective of this cross-sectional study was to compare circulating levels of maternal hormones affecting breast differentiation (human chorionic gonadotropin and prolactin) and proliferation [alpha-fetoprotein, insulin-like growth factor I (IGF-I), and estradiol] between women at a low to moderate risk (Asians and Hispanics), as compared with women at a high risk for breast cancer (Caucasians and African-Americans). Between May 2002 and December 2004, a total of 586 pregnant women were approached during a routine prenatal visit. Among them, 450 women (206 Caucasian, 126 Asian, 88 Hispanic, and 30 African-American) met the inclusion criteria and signed the informed consent. Only singleton pregnancies were considered. Blood samples were drawn during the second trimester of pregnancy. Laboratory analyses were done using the IMMULITE 2000 immunoassay system. Gestational age standardized mean levels of estradiol, IGF-I, and prolactin were significantly higher in Hispanic women compared with Caucasian women. Mean concentration of IGF-I was significantly higher in African-American women compared with Caucasian and Asian women. No significant differences in pregnancy hormone levels were observed between Caucasian and Asian (predominantly second-generation Chinese) women in this study. Irrespective of ethnicity, women who had their first pregnancy had substantially higher mean levels of alpha-fetoprotein, human chorionic gonadotropin, estradiol, and prolactin compared with women who previously had at least one full-term pregnancy. These data suggest that circulating pregnancy hormone levels may explain some of the ethnic differences in breast cancer risk.

Reliability of serum assays of iron status in postmenopausal women

PURPOSE

The aim of the study is to determine the reliability during a 2-year period of several newly developed iron-related assays to assess their potential for use in prospective epidemiologic studies.

METHODS

We assessed the temporal reliability of several iron-related assays by using three serum samples collected at yearly intervals from 50 postmenopausal participants in a large prospective study.

RESULTS

We observed high reliability coefficients for ferritin (0.78; 95% confidence interval [CI], 0.67-0.86), soluble transferrin receptor (sTfR; 0.79; 95% CI, 0.69-0.87), sTfR/ferritin ratio (0.74; 95% CI, 0.62-0.83), and hepcidin (0.89; 95% CI, 0.84-0.94). In a subset of 30 women, lower reliability was observed for serum iron (0.50; 95% CI, 0.29-0.70), unsaturated iron-binding capacity (0.55; 95% CI, 0.34-0.73), total iron-binding capacity (0.60; 95% CI, 0.40-0.76), and serum transferrin saturation rate (0.44; 95% CI, 0.22-0.65). The reliability of anti-5-hydroxymethyl-2'-deoxyuridine autoantibody titers, a biomarker of oxidized DNA damage, one of the mechanisms by which iron is thought to impact disease risk, was very high (0.97, 95% CI, 0.5-0.99).

CONCLUSIONS

Our results show that some newly developed iron-related assays could be useful tools to assess iron-disease associations in prospective cohorts that collect a single blood sample.

Insulin-like Growth Factor I in Pregnancy and Maternal Risk of Breast Cancer

BACKGROUND

The role of insulin-like growth factor (IGF)-I in breast cancer remains controversial, despite numerous reports on the association of the hormone with breast cancer or high-risk mammographic densities. We hypothesized that exposure to elevated IGF-I during early pregnancy, a period characterized by intense cell proliferation in the breasts and in the presence of high concentrations of sex steroids, will be associated with increased maternal risk to develop a breast malignancy.

METHODS

The Northern Sweden Maternity Cohort is an ongoing prospective study, collecting blood samples from first-trimester-pregnant women since 1975 as part of screening for infectious diseases. A case-control study (212 cases and 369 controls) was nested among Northern Sweden Maternity Cohort members who delivered singleton babies. RIA was used to measure IGF-I and IGF-II levels. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Breast cancer risk increased with increasing IGF-I (top tertile OR, 1.7; 95% CI, 1.1-2.7). The association was stronger among the primiparous (OR, 2.2; 95% CI, 1.1-4.4) than in the nonprimiparous women (OR, 1.4; 95% CI, 0.7-2.8). Upper-tertile risks seemed to decrease within the <28-, 28 to 33, and >33-year groups of age at sampling, from 2.5 (0.9-7.6) to 2.1 (0.9-5.0) and 1.2 (0.5-2.5), respectively. There was no association of breast cancer with first-trimester-pregnancy IGF-II.

CONCLUSIONS

The study offers further evidence that IGF-I is important in breast cancer. Our findings suggest that the adverse effect of IGF-I on the breast may be stronger before the remodeling of the gland induced by a first pregnancy.