Normal Breast Physiology: The Reasons Hormonal Contraceptives and Induced Abortion Increase Breast-Cancer Risk

2009 ◽  
Vol 76 (3) ◽  
pp. 236-249 ◽  
Author(s):  
Angela Lanfranchi
Keyword(s):  
Breast Cancer ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Breast Tissue ◽  
Induced Abortion ◽  
Normal Breast ◽  
Increase Breast Cancer Risk ◽  
Hormonal Contraceptives ◽  
Proliferative Effect ◽  
Breast Physiology

A woman gains protection from breast cancer by completing a full-term pregnancy. In utero, her offspring produce hormones that mature 85 percent of the mother's breast tissue into cancer-resistant breast tissue. If the pregnancy ends through an induced abortion or a premature birth before thirty-two weeks, the mother's breasts will have only partially matured, retaining even more cancer-susceptible breast tissue than when the pregnancy began. This increased amount of immature breast tissue will leave the mother with more sites for cancer initiation, thereby increasing her risk of breast cancer. Hormonal contraceptives increase breast-cancer risk by their proliferative effect on breast tissue and their direct carcinogenic effects on DNA. Hormonal contraceptives include estrogen-progestin combination drugs prescribed in any manner of delivery: orally, transdermally, vaginally, or intrauterine. This article provides the detailed physiology and data that elucidate the mechanisms through which induced abortion and hormonal contraceptives increase breast-cancer risk.

scholarly journals DNA Methylation and Breast Cancer Risk: An Epigenome-Wide Study of Normal Breast Tissue and Blood

Cancers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3088 ◽  
Author(s):  
Kaoutar Ennour-Idrissi ◽  
Dzevka Dragic ◽  
Elissar Issa ◽  
Annick Michaud ◽  
Sue-Ling Chang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dna Methylation ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Breast Tissue ◽  
Normal Breast Tissue ◽  
Normal Breast ◽  
Breast Epithelium ◽  
Normal Breast Epithelium ◽  
Differentially Methylated Genes

Differential DNA methylation is a potential marker of breast cancer risk. Few studies have investigated DNA methylation changes in normal breast tissue and were largely confounded by cancer field effects. To detect methylation changes in normal breast epithelium that are causally associated with breast cancer occurrence, we used a nested case–control study design based on a prospective cohort of patients diagnosed with a primary invasive hormone receptor-positive breast cancer. Twenty patients diagnosed with a contralateral breast cancer (CBC) were matched (1:1) with 20 patients who did not develop a CBC on relevant risk factors. Differentially methylated Cytosine-phosphate-Guanines (CpGs) and regions in normal breast epithelium were identified using an epigenome-wide DNA methylation assay and robust linear regressions. Analyses were replicated in two independent sets of normal breast tissue and blood. We identified 7315 CpGs (FDR < 0.05), 52 passing strict Bonferroni correction (p < 1.22 × 10−7) and 43 mapping to known genes involved in metabolic diseases with significant enrichment (p < 0.01) of pathways involving fatty acids metabolic processes. Four differentially methylated genes were detected in both site-specific and regions analyses (LHX2, TFAP2B, JAKMIP1, SEPT9), and three genes overlapped all three datasets (POM121L2, KCNQ1, CLEC4C). Once validated, the seven differentially methylated genes distinguishing women who developed and who did not develop a sporadic breast cancer could be used to enhance breast cancer risk-stratification, and allow implementation of targeted screening and preventive strategies that would ultimately improve breast cancer prognosis.

scholarly journals Progesterone and Breast Cancer

2019 ◽  
Vol 41 (2) ◽  
pp. 320-344 ◽  
Author(s):  
Britton Trabert ◽  
Mark E Sherman ◽  
Nagarajan Kannan ◽  
Frank Z Stanczyk
Keyword(s):  
Breast Cancer ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Normal Breast ◽  
Cancer Etiology ◽  
Progesterone Metabolites ◽  
Breast Physiology ◽  
Independent Effects ◽  
The Individual

Abstract Synthetic progestogens (progestins) have been linked to increased breast cancer risk; however, the role of endogenous progesterone in breast physiology and carcinogenesis is less clearly defined. Mechanistic studies using cell culture, tissue culture, and preclinical models implicate progesterone in breast carcinogenesis. In contrast, limited epidemiologic data generally do not show an association of circulating progesterone levels with risk, and it is unclear whether this reflects methodologic limitations or a truly null relationship. Challenges related to defining the role of progesterone in breast physiology and neoplasia include: complex interactions with estrogens and other hormones (eg, androgens, prolactin, etc.), accounting for timing of blood collections for hormone measurements among cycling women, and limitations of assays to measure progesterone metabolites in blood and progesterone receptor isotypes (PRs) in tissues. Separating the individual effects of estrogens and progesterone is further complicated by the partial dependence of PR transcription on estrogen receptor (ER)α-mediated transcriptional events; indeed, interpreting the integrated interaction of the hormones may be more essential than isolating independent effects. Further, many of the actions of both estrogens and progesterone, particularly in “normal” breast tissues, are driven by paracrine mechanisms in which ligand binding to receptor-positive cells evokes secretion of factors that influence cell division of neighboring receptor-negative cells. Accordingly, blood and tissue levels may differ, and the latter are challenging to measure. Given conflicting data related to the potential role of progesterone in breast cancer etiology and interest in blocking progesterone action to prevent or treat breast cancer, we provide a review of the evidence that links progesterone to breast cancer risk and suggest future directions for filling current gaps in our knowledge.

scholarly journals Estrogen receptor subtypes dictate the proliferative nature of the mammary gland

2018 ◽  
Vol 237 (3) ◽  
pp. 323-336 ◽  
Author(s):  
Genevieve V Dall ◽  
Samuel Hawthorne ◽  
Yashar Seyed-Razavi ◽  
Jessica Vieusseux ◽  
Wanfu Wu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Breast Cancer Diagnosis ◽  
Normal Breast ◽  
Breast Development ◽  
Receptor Subtypes ◽  
Breast Cancers ◽  
Proliferative Effect

Estrogen induces proliferation of breast epithelial cells and is responsible for breast development at puberty. This tightly regulated control is lost in estrogen-receptor-positive (ER+) breast cancers, which comprise over 70% of all breast cancers. Currently, breast cancer diagnosis and treatment considers only the α isoform of ER; however, there is a second ER, ERβ. Whilst ERα mediates estrogen-driven proliferation of the normal breast in puberty and breast cancers, ERβ has been shown to exert an anti-proliferative effect on the normal breast. It is not known how the expression of each ER (alone or in combination) correlates with the ability of estrogen to induce proliferation in the breast. We assessed the levels of each ER in normal mouse mammary glands subdivided into proliferative and non-proliferative regions. ERα was most abundant in the proliferative regions of younger mice, with ERβ expressed most abundantly in old mice. We correlated this expression profile with function by showing that the ability of estrogen to induce proliferation was reduced in older mice. To show that the ER profile associated with breast cancer risk, we assessed ER expression in parous mice which are known to have a reduced risk of developing ERα breast cancer. ERα expression was significantly decreased yet co-localization analysis revealed ERβ expression increased with parity. Parous mice had less unopposed nuclear ERα expression and increased levels of ERβ. These changes suggest that the nuclear expression of ERs dictates the proliferative nature of the breast and may explain the decreased breast cancer risk with parity.

scholarly journals Rho GTPase transcriptional activity and breast cancer risk: A Mendelian randomization analysis

2020 ◽  
Author(s):  
Nabila Kazmi ◽  
Tim Robinson ◽  
Jie Zheng ◽  
Siddhartha Kar ◽  
Richard M Martin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Gene Expression ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Rho Gtpases ◽  
Breast Tissue ◽  
Rho Gtpase ◽  
Normal Breast Tissue ◽  
Normal Breast

AbstractBackgroundRho GTPases are a family of 20 intracellular signalling proteins that influence cytoskeletal dynamics, cell migration and cell cycle progression. Rho GTPases are implicated in breast cancer progression but their role in breast cancer aetiology is unknown. As aberrant Rho GTPase activity could be associated with breast cancer, we aimed to determine the potential for a causal role of Rho GTPase gene expression in breast cancer risk, using two-sample Mendelian randomization (MR).MethodsMR was undertaken in 122,977 breast cancer cases and 105,974 controls, including 69,501 estrogen receptor positive (ER+) cases and 105,974 controls, and 21,468 ER negative (ER-) cases and 105,974 controls. Single nucleotide polymorphisms (SNPs) underlying expression quantitative trait loci (eQTLs) obtained from normal breast tissue, breast cancer tissue and blood were used as genetic instruments for Rho GTPase expression. Colocalisation was performed as a sensitivity analysis to examine whether findings reflected shared causal variants or genomic confounding.ResultsWe identified genetic instruments for 14 of the 20 human Rho GTPases. Using eQTLs obtained from normal breast tissue and normal blood, we identified evidence of a causal role of RHOD in overall and ER+ breast cancers (overall breast cancer: odds ratio (OR) per standard deviation (SD) increase in expression level 1.06; (95% confidence interval (CI): 1.03, 1.09; P=5.65×10-5) and OR 1.22 (95% CI: 1.11, 1.35; P=5.22×10−5) in normal breast tissue and blood respectively). The direction of association was consistent for ER- breast cancer, although the effect-estimate was imprecisely estimated. Using eQTLs from breast cancer tissue and normal blood there was some evidence that CDC42 was inversely associated with overall and ER+ breast cancer risk. The evidence from colocalization analyses strongly supported the MR results particularly for RHOD.ConclusionsOur study suggests a potential causal role of increased RHOD gene expression, and a potential protective role for CDC42 gene expression, in overall and ER+ breast cancers. These finding warrant validation in independent samples and further biological investigation to assess whether they may be suitable targets for drug targeting.

scholarly journals DNA methylation differences at regulatory elements are associated with the cancer risk factor age in normal breast tissue

2017 ◽  
Author(s):  
Kevin C. Johnson ◽  
E. Andres Houseman ◽  
Jessica E. King ◽  
Brock C. Christensen
Keyword(s):  
Breast Cancer ◽  
Risk Factors ◽  
Dna Methylation ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Breast Tissue ◽  
Normal Breast ◽  
Cancer Risk Factors ◽  
Age Related ◽  
Breast Cancer Risk Factors

AbstractBackgroundThe underlying biological mechanisms through which epidemiologically defined breast cancer risk factors contribute to disease risk remain poorly understood. Identification of the molecular changes associated with cancer risk factors in normal tissues may aid in determining the earliest events of carcinogenesis and informing cancer prevention strategies.ResultsHere we investigated the impact cancer risk factors have on the normal breast epigenome by analyzing DNA methylation genome-wide (Infinium 450K array) in cancer-free women from the Susan G. Komen Tissue Bank (n = 100). We tested the relation of established breast cancer risk factors: age, body mass index, parity, and family history of disease with DNA methylation adjusting for potential variation in cell-type proportions. We identified 787 CpG sites that demonstrated significant associations (Q-value < 0.01) with subject age. Notably, DNA methylation was not strongly associated with the other evaluated breast cancer risk factors. Age-related DNA methylation changes are primarily increases in methylation enriched at breast epithelial cell enhancer regions (P = 7.1E-20), and binding sites of chromatin remodelers (MYC and CTCF). We validated the age-related associations in two independent populations of normal breast tissue (n = 18) and normal-adjacent to tumor tissue (n = 97). The genomic regions classified as age-related were more likely to be regions altered in cancer in both pre-invasive (n = 40, P=3.0E-03) and invasive breast tumors (n = 731, P=1.1E-13).ConclusionsDNA methylation changes with age occur at regulatory regions, and are further exacerbated in cancer suggesting that age influences breast cancer risk in part through its contribution to epigenetic dysregulation in normal breast tissue.

scholarly journals Aberrant epigenetic and transcriptional events associated with breast cancer risk

2021 ◽  
Author(s):  
Natascia Marino ◽  
Rana German ◽  
Ram Podicheti ◽  
Douglas B. Rush ◽  
Pam Rockey ◽  
...  
Keyword(s):  
Breast Cancer ◽  
High Risk ◽  
Breast Cancer Risk ◽  
Epithelial Cells ◽  
Cancer Risk ◽  
Breast Tissue ◽  
Cancer Susceptibility ◽  
Breast Cancer Susceptibility ◽  
Normal Breast ◽  
Breast Tissues

ABSTRACTBackgroundGenome-wide association studies have identified several breast cancer susceptibility loci. However, biomarkers for risk assessment are still missing. Here, we investigated cancer-related molecular changes detected in tissues from women at high risk for breast cancer prior to disease manifestation. Disease-free breast tissue cores donated by healthy women (N=146, median age=39 years) were processed for both methylome (MethylCap) and transcriptome (Illumina’s HiSeq4000) sequencing. Analysis of tissue microarray and primary breast epithelial cells was used to confirm gene expression dysregulation.ResultsTranscriptomic analysis identified 69 differentially expressed genes between women at either high and those at average risk of breast cancer (Tyrer-Cuzick model) at FDR<0.05 and fold change≥2. The majority of the identified genes were involved in DNA damage checkpoint, cell cycle, and cell adhesion. Two genes, FAM83A and NEK2, were overexpressed in tissue sections (FDR<0.01) and primary epithelial cells (p<0.05) from high-risk breasts. Moreover, 1698 DNA methylation aberrations were identified in high-risk breast tissues (FDR<0.05), partially overlapped with cancer-related signatures and correlated with transcriptional changes (p<0.05, r≤0.5). Finally, among the participants, 35 women donated breast biopsies at two time points, and age-related molecular alterations enhanced in high-risk subjects were identified.ConclusionsNormal breast tissue from women at high risk of breast cancer bears molecular aberrations that may contribute to breast cancer susceptibility. This study is the first molecular characterization of the true normal breast tissues and provides an opportunity to investigate molecular markers of breast cancer risk, which may lead to new preventive approaches.

scholarly journals Androgen receptor expression in normal breast tissue and subsequent breast cancer risk

2018 ◽  
Vol 4 (1) ◽  
Author(s):  
Kevin H. Kensler ◽  
Francisco Beca ◽  
Gabrielle M. Baker ◽  
Yujing J. Heng ◽  
Andrew H. Beck ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Androgen Receptor ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Breast Tissue ◽  
Normal Breast Tissue ◽  
Normal Breast ◽  
Receptor Expression ◽  
Androgen Receptor Expression
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