Defining the genomic signature of the parous breast

Associations of reproductive breast cancer risk factors with expression of stem cell markers in benign breast tissue

Background

We investigated the associations of reproductive factors known to influence breast cancer risk with the expression of breast stem cell markers CD44, CD24, and ALDH1A1 in benign breast biopsy samples.

Methods

We included 439 cancer-free women with biopsy-confirmed benign breast disease within the Nurses' Health Study (NHS) and NHSII. The data on reproductive and other breast cancer risk factors were obtained from biennial questionnaires. Immunohistochemistry (IHC) was performed on tissue microarrays. For each core, the IHC expression was assessed using a semi-automated platform and expressed as % of cells that stained positive for a specific marker out of the total cell count. Generalized linear regression was used to examine the associations of reproductive factors with a log-transformed expression of each marker (in epithelium and stroma), adjusted for other breast cancer risk factors.

Results

In multivariate analysis, the time between menarche and age at first birth was inversely associated with CD44 in epithelium (β per 5 years = -0.38, 95% CI -0.69; -0.06). Age at first birth and the time between menarche and age at first birth were inversely associated with ALDH1A1 (stroma: β per 5 years = -0.43, 95% CI -0.76; -0.10 and β = -0.47, 95% CI -0.79; -0.15, respectively; epithelium: β = -0.15, 95% CI -0.30; -0.01 and β = -0.17, 95% CI -0.30; -0.03, respectively). Time since last pregnancy was inversely associated with stromal ALDH1A1 (β per 5 years = -0.55, 95% CI -0.98; -0.11). No associations were found for CD24. The observed associations were similar in premenopausal women. In postmenopausal women, lifetime duration of breastfeeding was inversely associated with stromal ALDH1A1 expression (β for ≥24 vs. 0 to <1 months = -2.24, 95% CI 3.96; -0.51, p-trend = 0.01).

Conclusion

Early-life reproductive factors may influence CD44 and ALDH1A1 expression in benign breast tissue.

Cold-Inducible RNA Binding Protein Impedes Breast Tumor Growth in the PyMT Murine Model for Breast Cancer

RNA binding proteins (RBPs) post-transcriptionally regulate gene expression by associating with regulatory sequences in the untranslated regions of mRNAs. Cold-inducible RBP (CIRP) is a stress-induced RBP that was recently shown to modulate inflammation in response to cellular stress, where it increases or decreases pro-tumorigenic (proinflammatory) cytokines in different contexts. CIRP expression is altered in several cancers, including breast cancer, but the effects of CIRP on inflammation in breast cancer is not known. Here, we investigate if CIRP alters growth and the inflammatory profile of breast tumors. Transgenic mice overexpressing CIRP in the mammary epithelium were crossed with the PyMT mouse model of breast cancer, and the effects on both early and late tumorigenesis and inflammation were assessed. The effects of CIRP knockdown were also assessed in Py2T cell grafts. Overexpression of CIRP led to decreased tumorigenesis in the PyMT mouse model. Conversely, the knockdown of CIRP in Py2T cell grafts led to increased tumor growth. Luminex cytokine assays assessed the effects on the inflammatory environment. CIRP/PyMT mammary glands/mammary tumors and serum had decreased cytokines that promote inflammation, angiogenesis, and metastasis compared to PyMT mammary glands and serum, documenting a shift towards an environment less supportive of tumorigenesis. CIRP overexpression also decreased CD4+ helper T cells and increased CD8+ cytotoxic T cells in mammary tumors. Overall, these data support a role for CIRP as a potent antitumor molecule that suppresses both local and systemic pro-tumorigenic inflammation.

DNA methylation and gene expression changes in mouse mammary tissue during successive lactations: part II - the impact of lactation rank

Mastitis is among the main reasons women cease breastfeeding. In farm animals, mastitis results in significant economic losses and the premature culling of some animals. Nevertheless, the effect of inflammation on the mammary gland is not completely understood. This article discusses the changes to DNA methylation in mouse mammary tissue caused by lipopolysaccharide-induced inflammation after in vivo intramammary challenges and the differences in DNA methylation between 1^st and 2^nd lactations. Lactation rank induces 981 differential methylations of cytosines (DMCs) in mammary tissue. Inflammation in 1^st lactation compared to inflammation in 2^nd lactation results in the identification of 964 DMCs. When comparing inflammation in 1^st vs. 2^nd lactations with previous inflammation history, 2590 DMCs were identified. Moreover, Fluidigm PCR data show changes in the expression of several genes related to mammary function, epigenetic regulation, and the immune response. We show that the epigenetic regulation of two successive physiological lactations is not the same in terms of DNA methylation and that the effect of lactation rank on DNA methylation is stronger than that of the onset of inflammation. The conditions presented here show that few DMCs are shared between comparisons, suggesting a specific epigenetic response depending on lactation rank, the presence of inflammation, and even whether the cells had previously suffered inflammation. In the long term, this information could lead to a better understanding of the epigenetic regulation of lactation in both physiological and pathological conditions.Abbreviations: RRBS, reduced representation bisulphite sequencing; RT-qPCR, real-time quantitative polymerase chain reaction; MEC, mammary epithelial cells; MaSC, mammary stem cell; TSS, transcription start site; TTS, transcription termination site; UTR, untranslated region; SINE, short interspersed nuclear element; LINE, long interspersed nuclear element; CGI, CpG island; DEG, differentially expressed gene; DMC, differentially methylated cytosine; DMR, differentially methylated region; GO term, gene ontology term; MF, molecular function; BP, biological process.

Mass spectrometry-based phosphoproteomics in clinical applications

Protein phosphorylation is an essential post-translational modification that regulates many aspects of cellular physiology, and dysregulation of pivotal phosphorylation events is often responsible for disease onset and progression. Clinical analysis on disease-relevant phosphoproteins, while quite challenging, provides unique information for precision medicine and targeted therapy. Among various approaches, mass spectrometry (MS)-centered characterization features discovery-driven, high-throughput and in-depth identification of phosphorylation events. This review highlights advances in sample preparation and instrument in MS-based phosphoproteomics and recent clinical applications. We emphasize the preeminent data-independent acquisition method in MS as one of the most promising future directions and biofluid-derived extracellular vesicles as an intriguing source of the phosphoproteome for liquid biopsy.

Breastfeeding reduces the risk of breast cancer: A call for action in high-income countries with low rates of breastfeeding

Women in the UK have a 15% lifetime risk of developing breast cancer. Like other high-income countries, women in the UK are having children later in life which increases their risk. The risk of breast cancer is reduced by 4.3% for every 12 months of breastfeeding, this is in addition to the 7.0% decrease in risk observed for each birth. Breastfeeding reduces the risk of Triple-Negative Breast Cancer (20%) and in carriers of BRCA1 mutations (22-55%). The mechanisms of reduced risk as a result of pregnancy are related to changes in RNA processing and cellular differentiation. The UK has a low rate of breastfeeding (81%) and this is contrasted to countries with higher (Sweden, Australia) and lower rates (Ireland). The low UK rate is in part due to a lack of experience in the population, todays grandmothers have less experience with breastfeeding (62%) than their daughters. An estimated 4.7% of breast cancer cases in the UK are caused by not breastfeeding. The UK only has 43% of maternity services with full Baby-Friendly accreditation which promotes compliance with the WHO 'Ten Steps to Successful Breast Feeding'. Legislation in the UK and Europe is far short of the WHO Guidance on restricting the advertising of formula milk. Expansion of the Baby-Friendly Hospital Initiative, stricter laws on the advertising of formula milk and legislation to support nursing mothers in the workplace have the potential to increase breastfeeding in the UK. Women with a family history of breast cancer should particularly be supported to breastfeed as a way of reducing their risk.

Associations of breast cancer related exposures and gene expression profiles in normal breast tissue-The Norwegian Women and Cancer normal breast tissue study

BACKGROUND

Normal breast tissue is utilized in tissue-based studies of breast carcinogenesis. While gene expression in breast tumor tissue is well explored, our knowledge of transcriptomic signatures in normal breast tissue is still incomplete. The aim of this study was to investigate variability of gene expression in a large sample of normal breast tissue biopsies, according to breast cancer related exposures (obesity, smoking, alcohol, hormone therapy, and parity).

METHODS

We analyzed gene expression profiles from 311 normal breast tissue biopsies from cancer-free, post-menopausal women, using Illumina bead chip arrays. Principal component analysis and K-means clustering was used for initial analysis of the dataset. The association of exposures and covariates with gene expression was determined using linear models for microarrays.

RESULTS

Heterogeneity of the breast tissue and cell composition had the strongest influence on gene expression profiles. After adjusting for cell composition, obesity, smoking, and alcohol showed the highest numbers of associated genes and pathways, whereas hormone therapy and parity were associated with negligible gene expression differences.

CONCLUSION

Our results provide insight into associations between major exposures and gene expression profiles and provide an informative baseline for improved understanding of exposure-related molecular events in normal breast tissue of cancer-free, post-menopausal women.

Translational proteomics and phosphoproteomics: Tissue to extracellular vesicles

We are currently experiencing a rapidly developing era in terms of translational and clinical medical sciences. The relatively mature state of nucleic acid examination has significantly improved our understanding of disease mechanism and therapeutic potential of personalized treatment, but misses a large portion of phenotypic disease information. Proteins, in particular phosphorylation events that regulates many cellular functions, could provide real-time information for disease onset, progression and treatment efficacy. The technical advances in liquid chromatography and mass spectrometry have realized large-scale and unbiased proteome and phosphoproteome analyses with disease relevant samples such as tissues. However, tissue biopsy still has multiple shortcomings, such as invasiveness of sample collection, potential health risk for patients, difficulty in protein preservation and extreme heterogeneity. Recently, extracellular vesicles (EVs) have offered a great promise as a unique source of protein biomarkers for non-invasive liquid biopsy. Membranous EVs provide stable preservation of internal proteins and especially labile phosphoproteins, which is essential for effective routine biomarker detection. To aid efficient EV proteomic and phosphoproteomic analyses, recent developments showcase clinically-friendly EV techniques, facilitating diagnostic and therapeutic applications. Ultimately, we envision that with streamlined sample preparation from tissues and EVs proteomics and phosphoproteomics analysis will become routine in clinical settings.

Understanding Breast Cancers through Spatial and High-Resolution Visualization Using Imaging Technologies

Breast cancer is the most common cancer affecting women worldwide. Although many analyses and treatments have traditionally targeted the breast cancer cells themselves, recent studies have focused on investigating entire cancer tissues, including breast cancer cells. To understand the structure of breast cancer tissues, including breast cancer cells, it is necessary to investigate the three-dimensional location of the cells and/or proteins comprising the tissues and to clarify the relationship between the three-dimensional structure and malignant transformation or metastasis of breast cancers. In this review, we aim to summarize the methods for analyzing the three-dimensional structure of breast cancer tissue, paying particular attention to the recent technological advances in the combination of the tissue-clearing method and optical three-dimensional imaging. We also aimed to identify the latest methods for exploring the relationship between the three-dimensional cell arrangement in breast cancer tissues and the gene expression of each cell. Finally, we aimed to describe the three-dimensional imaging features of breast cancer tissues using noninvasive photoacoustic imaging methods.

Mapping hormone-regulated cell-cell interaction networks in the human breast at single-cell resolution

The rise and fall of estrogen and progesterone across menstrual cycles and during pregnancy regulates breast development and modifies cancer risk. How these hormones impact each cell type in the breast remains poorly understood because they act indirectly through paracrine networks. Using single-cell analysis of premenopausal breast tissue, we reveal a network of coordinated transcriptional programs representing the tissue-level response to changing hormone levels. Our computational approach, DECIPHER-seq, leverages person-to-person variability in breast composition and cell state to uncover programs that co-vary across individuals. We use differences in cell-type proportions to infer a subset of programs that arise from direct cell-cell interactions regulated by hormones. Further, we demonstrate that prior pregnancy and obesity modify hormone responsiveness through distinct mechanisms: obesity reduces the proportion of hormone-responsive cells, whereas pregnancy dampens the direct response of these cells to hormones. Together, these results provide a comprehensive map of the cycling human breast.

Expression and functions of long non-coding RNA NEAT1 and isoforms in breast cancer

NEAT1 is a highly abundant nuclear architectural long non-coding RNA. There are two overlapping NEAT1 isoforms, NEAT1_1 and NEAT1_2, of which the latter is an essential scaffold for the assembly of a class of nuclear ribonucleoprotein bodies called paraspeckles. Paraspeckle formation is elevated by a wide variety of cellular stressors and in certain developmental processes, either through transcriptional upregulation of the NEAT1 gene or through a switch from NEAT1_1 to NEAT1_2 isoform production. In such conditions, paraspeckles modulate cellular processes by sequestering proteins or RNA molecules. NEAT1 is abnormally expressed in many cancers and a growing body of evidence suggests that, in many cases, high NEAT1 levels are associated with therapy resistance and poor clinical outcome. Here we review the current knowledge of NEAT1 expression and functions in breast cancer, highlighting its established role in postnatal mammary gland development. We will discuss possible isoform-specific roles of NEAT1_1 and NEAT1_2 in different breast cancer subtypes, which critically needs to be considered when studying NEAT1 and breast cancer.

ERK1/2‐RSK regulation of oestrogen homeostasis

The molecular mechanisms regulating oestrogen homeostasis have been primarily studied in the mammary gland, which is the focus of this review. In the non-pregnant adult, the mammary gland undergoes repeated cycles of proliferation and apoptosis in response to the fluctuating levels of oestrogen that occur during the reproductive stage. Oestrogen actions are mediated through the steroid hormone receptors, oestrogen receptor α and β and through a G-protein coupled receptor. In the mammary gland, ERα is of particular importance and thus will be highlighted. Mechanisms regulating oestrogen-induced responses through ERα are necessary to maintain homeostasis given that the signalling pathways that are activated in response to ERα-mediated transcription can also induce transformation. ERK1/2 and its downstream effector, p90 ribosomal S6 kinase (RSK), control homeostasis in the mammary gland by limiting oestrogen-mediated ERα responsiveness. ERK1/2 drives degradation coupled ERα-mediated transcription, whereas RSK2 acts as a negative regulator of ERK1/2 activity to limit oestrogen responsiveness. Moreover, RSK2 acts as a positive regulator of translation. Thus, RSK2 provides both positive and negative signals to maintain oestrogen responsiveness. In addition to transmitting signals through tyrosine kinase receptors, ERK1/2-RSK engages with hedgehog signalling to maintain oestrogen levels and with the HIPPO pathway to regulate ERα-mediated transcription. Additionally, ERK1/2-RSK controls the progenitor populations within the mammary gland to maintain the ERα-positive population. RSK2 is involved in increased breast cancer risk in individuals taking oral contraceptives and in parity-induced protection against breast cancer. RSK2 and ERα may also co-operate in diseases in tissues outside of the mammary gland.

Controversial roles of cold‑inducible RNA‑binding protein in human cancer (Review)

Cold‑inducible RNA‑binding protein (CIRBP) is a cold‑shock protein comprised of an RNA‑binding motif that is induced by several stressors, such as cold shock, UV radiation, nutrient deprivation, reactive oxygen species and hypoxia. CIRBP can modulate post‑transcriptional regulation of target mRNA, which is required to control DNA repair, circadian rhythms, cell growth, telomere integrity and cardiac physiology. In addition, the crucial function of CIRBP in various human diseases, including cancers and inflammatory disease, has been reported. Although CIRBP is primarily considered to be an oncogene, it may also serve a role in tumor suppression. In the present study, the controversial roles of CIRBP in various human cancers is summarized, with a focus on the interconnectivity between CIRBP and its target mRNAs involved in tumorigenesis. CIRBP may represent an important prognostic marker and therapeutic target for cancer therapy.

Prolonged recombinant pregnancy hormone use in BRCA1 and BRCA2 mutation carriers

BACKGROUND

An early first full-time pregnancy substantially reduces the risk of developing breast cancer later in life. Extensive studies indicate that this protective effect is mediated by the pregnancy hormone human chorionic gonadotrophin (hCG).

METHODS

In this proof-of-concept study 33 women with a BRCA mutation received recombinant-hCG (r-hCG). A 4-mm breast biopsy was obtained before (T1) and after 12 weeks of r-hCG injections (T2), as well as 6 months later (T3). The tissue was examined using RNA-sequencing methodology to determine if the 'high-risk' transcriptomic signature was converted to a 'low-risk' signature as in an early first full-time pregnancy. A stringent clinical safety monitoring was performed.

RESULTS

The r-hCG administration was well tolerated in all participants. No clinically relevant changes were observed. In 25 women, the RNA quality was good for RNA sequencing in all three breast tissue biopsies. In response to the r-hCG, we observed 1907 differentially expressed genes (DEGs) (1032 up, 875 down) at T2 vs. T1 and 1065 DEGs (897 up, 168 down) at T3 vs. T1 in the group of women (n = 11) not using any hormonal contraceptives during the study. There was no response at T2 vs. T1 and a small number of DEGs, 260 (214 up, 46 down) at T3 vs. T1 in the group of 14 women using contraceptives.

CONCLUSIONS

In summary, r-hCG has a remarkable effect on the gene expression profile of breast tissues from BRCA1/2 carriers who did not use any contraception. This opens an opportunity for a novel preventive strategy to reduce the incidence of breast cancer.

The role of gene to gene interaction in the breast's genomic signature of pregnancy

Full-term pregnancy at an early age confers long-term protection against breast cancer. Published data shows a specific transcriptomic profile controlling chromatin remodeling that could play a relevant role in the pregnancy-induced protection. This process of chromatin remodeling, induced by the breast differentiation caused by the first full-term pregnancy, has mainly been measured by the expression level of genes individually considered. However, genes equally expressed during the process of chromatin remodeling may behave differently in their interaction with other genes. These changes at the gene cluster level could constitute an additional dimension of chromatin remodeling and therefore of the pregnancy-induced protection. In this research, we apply Information and Graph Theories, Differential Co-expression Network Analysis, and Multiple Regression Analysis, specially designed to examine structural and informational aspects of data sets, to analyze this question. Our findings demonstrate that, independently of the changes in the gene expression at the individual level, there are significant changes in gene-gene interactions and gene cluster behaviors. These changes indicate that the parous breast, through the process of early full-term pregnancy, generates more modules in the networks, with higher density, and a genomic structure performing additional and more complex functions than those found in the nulliparous breast.

Emerging roles of N6-methyladenosine (m6A) modification in breast cancer

N6-Methyladenosine (m6A) is the most abundant, dynamic, and reversible epigenetic RNA modification that is found in coding and non-coding RNAs. Emerging studies have shown that m6A and its regulators affect multiple steps in RNA metabolism and play broad roles in various cancers. Worldwide, breast cancer is the most prevalent cancer in female. It is a very heterogeneous disease characterized by genetic and epigenetic variations in tumor cells. Increasing evidence has shown that the dysregulation of m6A-related effectors, as methyltransferases, demethylases, and m6A binding proteins, is pivotal in breast cancer pathogenesis. In this review, we have summarized the most up-to-date research on the biological functions of m6A modification in breast cancer and have discussed the potential clinical applications and future directions of m6A modification as a biomarker as well as a therapeutic target of breast cancer.

Pregnancy-Associated Breast Cancer: A Multidisciplinary Approach

The diagnosis of breast cancer (BC) during pregnancy is uncommon. It has varied among different studies from 1:10,000 to 1:3000 of all pregnancies, with a median age of 33 years. Pregnancy-associated BC represents a challenge in terms of clinical management to guarantee both maternal and fetal security in choosing the right treatment. This situation is complex and requires a multidisciplinary approach, including the surgeon, anesthesiologist, oncologist, radiotherapist, psychologist, and maternal-fetal medicine specialist. In the present review, we examined the management of pregnancy-associated BC, focusing on pathophysiologic background, risk factors, diagnosis, staging procedures, anesthesia, surgical management, and systemic treatment.

BC200 overexpression contributes to luminal and triple negative breast cancer pathogenesis

Background

Long non coding RNAs (lncRNAs) are RNA molecules longer than 200 nucleotides that are not translated into proteins, but regulate the transcription of genes involved in different cellular processes, including cancer. Epidemiological analyses have demonstrated that parous women have a decreased risk of developing breast cancer in postmenopausal years if they went through a full term pregnancy in their early twenties. We here provide evidence of the role of BC200 in breast cancer and, potentially, in pregnancy’s preventive effect in reducing the lifetime risk of developing breast cancer.

Methods

Transcriptome analysis of normal breast of parous and nulliparous postmenopausal women revealed that several lncRNAs are differentially expressed in the parous breast. RNA sequencing of healthy postmenopausal breast tissue biopsies from eight parous and eight nulliparous women showed that there are 42 novel lncRNAs differentially expressed between these two groups. Screening of several of these 42 lncRNAs by RT-qPCR in different breast cancer cell lines, provided evidence that one in particular, lncEPCAM (more commonly known as BC200), was a strong candidate involved in cancer progression. Proliferation, migration, invasion and xerograph studies confirmed this hypothesis.

Results

The poorly studied oncogenic BC200 was selected to be tested in vitro and in vivo to determine its relevance in breast cancer and also to provide us with an understanding of its role in the increased susceptibility of the nulliparous women to cancer. Our results show that BC200 is upregulated in nulliparous women, and breast cancer cells and tissue. The role of BC200 is not completely understood in any of the breast cancer subtypes. We here provide evidence that BC200 has a role in luminal breast cancer as well as in the triple negative breast cancer subtype.

Conclusion

When overexpressed in luminal and triple negative breast cancer cell lines, BC200 shows increased proliferation, migration, and invasion in vitro. In vivo, overexpression of BC200 increased tumor size. Although treatment for cancer using lncRNAs as targets is in its infancy, the advancement in knowledge and technology to study their relevance in disease could lead to the development of novel treatment and preventive strategies for breast cancer.

Loss of Cirbp expression is correlated with the malignant progression and poor prognosis in nasopharyngeal carcinoma

Purpose: The correlation of cold-inducible RNA-binding protein (Cirbp) expression with clinicopathological features including patient prognosis in nasopharyngeal carcinoma (NPC) was investigated.

Methods: The expression of Cirbp in NPC cell lines and tissue specimens was examined by qRT-PCR or immunohistochemistry (IHC).

Results: Immunohistochemistry (IHC) results showed that high Cirbp expression was detected in 61 of 61 non-cancerous nasopharyngeal squamous epithelial biopsies, whereas the significantly reduced expression of Cirbp was observed in NPC specimens. In addition, IHC assay for Cirbp protein illustrated that the cells of 177 NPC samples and nasopharyngeal squamous epithlial cells displayed strong signals in nuclei and faint signals in cytoplasm, whereas Cirbp protein is mainly detected in the cell’s cytoplasm in many other cancers. More importantly, TNM classification displayed that the low expression of Cirbp was more frequently observed in T3-T4, N2-N3, M1 and III-IV NPC biopsies, and undifferentiated carcinoma (UDC) than T1-T2, N0-N1, M0 and I-II tumors, and differentiated nonkeratinizing carcinoma (DNKC), suggesting that Cirbp loss is a key molecular event in advanced cases of NPC. Kaplan–Meier survival analysis indicated that NPC patients showing lower Cirbp expression had a significantly shorter overall survival time than those with high Cirbp expression. Multivariate analysis suggested that the level of Cirbp expression was an independent prognostic indicator for NPC survival. Finally, we revealed a significant positive association between Cirbp expression and E-cadherin, and a notable negative correlation between Cirbp expression and Ki67 labeling index in NPC biopsies.

Conclusion: Collectively, these findings demonstrate that loss of Cirbp expression is correlated with malignant progression and poor prognosis in NPC.

Integrative analysis of rare copy number variants and gene expression data in alopecia areata implicates an aetiological role for autophagy

Alopecia areata (AA) is a highly prevalent autoimmune disease that attacks the hair follicle and leads to hair loss that can range from small patches to complete loss of scalp and body hair. Our previous linkage and genome-wide association studies (GWAS) generated strong evidence for aetiological contributions from inherited genetic variants at different population frequencies, including both rare mutations and common polymorphisms. Additionally, we conducted gene expression (GE) studies on scalp biopsies of 96 patients and controls to establish signatures of active disease. In this study, we performed an integrative analysis on these two datasets to test the hypothesis that rare CNVs in patients with AA could be leveraged to identify drivers of disease in our AA GE signatures. We analysed copy number variants (CNVs) in a case-control cohort of 673 patients with AA and 16 311 controls independent of the case-control cohort of 96 research participants used in our GE study. Using an integrative computational analysis, we identified 14 genes whose expression levels were altered by CNVs in a consistent direction of effect, corresponding to gene expression changes in lesional skin of patients. Four of these genes were affected by CNVs in three or more unrelated patients with AA, including ATG4B and SMARCA2, which are involved in autophagy and chromatin remodelling, respectively. Our findings identified new classes of genes with potential contributions to AA pathogenesis.

HNRNPA2/B1 is upregulated in endocrine-resistant LCC9 breast cancer cells and alters the miRNA transcriptome when overexpressed in MCF-7 cells

MicroRNAs are dysregulated in breast cancer. Heterogeneous Nuclear Ribonucleoprotein A2/B1 (HNRNPA2/B1) is a reader of the N(6)-methyladenosine (m6A) mark in primary-miRNAs (pri-miRNAs) and promotes DROSHA processing to precursor-miRNAs (pre-miRNAs). We examined the expression of writers, readers, and erasers of m6A and report that HNRNPA2/B1 expression is higher in tamoxifen-resistant LCC9 breast cancer cells as compared to parental, tamoxifen-sensitive MCF-7 cells. To examine how increased expression of HNRNPA2/B1 affects miRNA expression, HNRNPA2/B1 was transiently overexpressed (~5.4-fold) in MCF-7 cells for whole genome miRNA profiling (miRNA-seq). 148 and 88 miRNAs were up- and down-regulated, respectively, 48 h after transfection and 177 and 172 up- and down-regulated, respectively, 72 h after transfection. MetaCore Enrichment analysis identified progesterone receptor action and transforming growth factor β (TGFβ) signaling via miRNA in breast cancer as pathways downstream of the upregulated miRNAs and TGFβ signaling via SMADs and Notch signaling as pathways of the downregulated miRNAs. GO biological processes for mRNA targets of HNRNPA2/B1-regulated miRNAs included response to estradiol and cell-substrate adhesion. qPCR confirmed HNRNPA2B1 downregulation of miR-29a-3p, miR-29b-3p, and miR-222 and upregulation of miR-1266-5p, miR-1268a, miR-671-3p. Transient overexpression of HNRNPA2/B1 reduced MCF-7 sensitivity to 4-hydroxytamoxifen and fulvestrant, suggesting a role for HNRNPA2/B1 in endocrine-resistance.

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.

Imprint of parity and age at first pregnancy on the genomic landscape of subsequent breast cancer

Background

Although parity and age at first pregnancy are among the most known extrinsic factors that modulate breast cancer risk, their impact on the biology of subsequent breast cancer has never been explored in depth. Recent data suggest that pregnancy-induced tumor protection is different according to breast cancer subtypes, with parity and young age at first pregnancy being associated with a marked reduction in the risk of developing luminal subtype but not triple negative breast cancer. In this study, we investigated the imprint of parity and age at first pregnancy on the pattern of somatic mutations, somatic copy number alterations, transcriptomic profiles, and tumor immune microenvironment by assessing tumor-infiltrating lymphocytes (TILs) levels of subsequent breast cancer.

Methods

A total of 313 patients with primary breast cancer with available whole genome, RNA sequencing, and TILs data were included in this study. We used a multivariate analysis adjusted for age at diagnosis, pathological stage, molecular subtypes, and histological subtypes. We compared nulliparous vs. parous, late parous vs. early parous, and nulliparous vs. pregnancy-associated breast cancer (PABC) patients. Late and early parous patients were grouped by using the median age at first pregnancy. PABC was defined as patients diagnosed up to 10 years postpartum.

Results

Genomic alterations of breast cancer were associated with age at first pregnancy but not with parity status alone. Independently of clinicopathological features, early parous patients developed tumors characterized by a higher number of Indels (P_adj = 0.002), a lower frequency of CDH1 mutations (1.2% vs. 12.7%; P_adj = 0.013), a higher frequency of TP53 mutations (50% vs. 22.5%; P_adj = 0.010), and MYC amplification (28% vs. 7%; P_adj = 0.008). PABC were associated with increased TILs infiltration (P_adj = 0.0495).

Conclusions

These findings highlight an unprecedented link between reproductive history and the genomic landscape of subsequent breast cancer. We further hypothesize that TP53-mutant premalignant lesions could be less susceptible to the protective effect of an early parity, which might explain the difference of parity-induced protection according to breast cancer subtypes. This work also advocates that reproductive history should be routinely collected in future large-scale genomic studies addressing the biology of female cancers.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1111-6) contains supplementary material, which is available to authorized users.

Breast cancer-linked lncRNA u-Eleanor is upregulated in breast of healthy women with lack or short duration of breastfeeding

Recently, it has been revealed that estrogen-related reproductive factors are linked with some early gene expression lesions associated with malignancy in clinically healthy breasts. Accordingly, the aim of the current study was to evaluate the association of expression levels of estrogen-related long noncoding RNAs (lncRNAs) upstream Eleanor (u-Eleanor) and HOX antisense intergenic RNA (HOTAIR) with the different patterns of reproductive factors in breast tissue of healthy women. The subjects of this study were 98 cancer-free women who had undergone cosmetic mammoplasty. The expression levels of u-Eleanor and HOTAIR were measured using quantitative real-time polymerase chain reaction. The results of the current study showed that the women without a history of breastfeeding had a high-level expression of u-Eleanor compared with the women with a breastfeeding duration greater than 6 to 24 months (P = 0.03) as well as the women with a breastfeeding duration of more than 24 months (P = 0.005). Furthermore, a higher expression of u-Eleanor was found in the women with a short breastfeeding duration for 1 to 6 months than that in the women with a breastfeeding duration of greater than 24 months (P = 0.02). In the same way, the results of correlation test (r = -0.258; P = 0.036) and multivariate regression model (β = -0.321; P = 0.023) are indicative of a significant relationship of elevated expression of u-Eleanor with decreasing breastfeeding duration in the women. These findings could be important to identify the molecular mechanisms behind the relationship between a lack or short duration of the breastfeeding and the risk of breast cancer, which has previously been reported by epidemiological studies.

Histology and Transcriptome Profiles of the Mammary Gland across Critical Windows of Development in Sprague Dawley Rats

Breast development occurs through well-defined stages representing 'windows of susceptibility' to adverse environmental exposures that potentially modify breast cancer risk. Systematic characterization of morphology and transcriptome during normal breast development lays the foundation of our understanding of cancer etiology. We examined mammary glands in female Sprague Dawley rats across six developmental stages - pre-pubertal, peri-pubertal, pubertal, lactation, adult parous and adult nulliparous. We investigated histology by Hematoxylin and Eosin and Mallory's Trichrome stain, proliferative and apoptotic rate by immunohistochemistry and whole-transcriptome by microarrays. We identified differentially expressed genes between adjacent developmental stages by linear models, underlying pathways by gene ontology analysis and gene networks and hubs active across developmental stages by coexpression network analysis. Mammary gland development was associated with large-scale changes in the transcriptome; particularly from pre-pubertal to peri-pubertal period and the lactation period were characterized by distinct patterns of gene expression with unique biological functions such as immune processes during pre-pubertal development and cholesterol biosynthesis during lactation. These changes were reflective of the shift in mammary gland histology, from a rudimentary organ during early stages to a secretory organ during lactation followed by regression with age. Hub genes within mammary gene networks included metabolic genes such as Pparg during the pre-pubertal stage and tight junction-related genes claudins and occludins in lactating mammary glands. Transcriptome profile paired with histology enhanced our understanding of mammary development, which is fundamental in understanding the etiologic mechanism of breast cancer, especially pertaining to windows of susceptibility to environmental exposures that may alter breast cancer risk.

A link between expression level of long-non-coding RNA ZFAS1 in breast tissue of healthy women and obesity

BACKGROUND

Epidemiological and experimental literature indicates that the risk of breast cancer incidence is strongly linked to hormone-dependent factors, including reproductive history and obesity. However, the molecular mechanisms underlying the association between these factors and breast cancer risk are poorly understood. The aim of this study, therefore, was to determine whether obesity and reproductive history are associated with expression levels of two breast cancer-related long non-coding RNAs (lncRNAs), namely ZFAS1 and SRA1 in cancer-free breast tissues of women.

METHODS

In the current research, 145 healthy women were recruited, and the quantitative expression levels of the two lncRNAs were determined through qPCR assay after gathering the mammoplasty breast tissue samples.

RESULTS

It was found that women with body mass index (BMI)≥30 kg/m² and BMI 25-29 kg/m² show a low expression of ZFAS1 compared to the BMI<25 kg/m² (P=0.031 and P=0.027, respectively). Then, the correlation analysis disclosed a negative correlation of ZFAS1 low expression with increasing BMI (r=-0.194, P=0.019). Interestingly, this analysis demonstrated a negative correlation between low expression of the ZFAS1 and high BMI in women with menarche age below 14 (r=-221; P=0.028). Lastly, it was also revealed that there was a negative association of the low expression level of ZFAS1 with increasing BMI in women through regression models (B=-0.048, P=0.019).

CONCLUSIONS

These findings suggest interesting clues about the links between high BMI and the expression levels of ZFAS1 in non-diseased breasts that may help us better understand the underlying mechanisms through which obesity contributes to breast carcinogenesis. However, such results need more validations in future research.

The serum protein profile of early parity which induces protection against breast cancer

Early parity reduces the risk of breast cancer in women while nulliparity and late parity increase the risk of breast cancer. In order to translate this protection to women where early pregnancy is not feasible, much work has focused on understanding how parity confers protection against breast cancer, the molecular mechanisms by which this occurs is still not well understood. Healthy parous and nulliparous women were recruited for this study. We assessed serum protein profiles of early parous, late parous, and nulliparous women using the Phospho Explorer antibody array. Significantly altered proteins identified were validated by Western blot analysis. In silico analysis was performed with the data obtained. Our findings indicate increased phosphorylation levels of CDK1, AKT1 and Epo-R increased cell cycle and cell proliferation in late/nulliparous women. Increased levels of LIMK1, paxillin, caveolin-1, and tyrosine hydroxylase in late/nulliparous women demonstrate enhanced cell stress while decreased activity of p-p53 and pRAD51 in late/nulliparous women indicates decreased apoptosis and increased genomic instability. Further, increased levels of pFAK, pCD3zeta, pSTAT5B, MAP3K8 in early parous women favor enhanced innate/adaptive immunity. Overall, we have identified a unique protein signature that is responsible for the decreased risk of breast cancer and these proteins can also serve as biomarkers to predict the risk of breast cancer.

Cold-inducible RNA binding protein in cancer and inflammation

RNA binding proteins (RBPs) play key roles in RNA dynamics, including subcellular localization, translational efficiency and metabolism. Cold-inducible RNA binding protein (CIRP) is a stress-induced protein that was initially described as a DNA damage-induced transcript (A18 hnRNP), as well as a cold-shock domain containing cold-stress response protein (CIRBP) that alters the translational efficiency of its target messenger RNAs (mRNAs). This review summarizes recent work on the roles of CIRP in the context of inflammation and cancer. The function of CIRP in cancer appeared to be solely driven though its functions as an RBP that targeted cancer-associated mRNAs, but it is increasingly clear that CIRP also modulates inflammation. Several recent studies highlight roles for CIRP in immune responses, ranging from sepsis to wound healing and tumor-promoting inflammation. While modulating inflammation is an established role for RBPs that target cytokine mRNAs, CIRP appears to modulate inflammation by several different mechanisms. CIRP has been found in serum, where it binds the TLR4-MD2 complex, acting as a Damage-associated molecular pattern (DAMP). CIRP activates the NF-κB pathway, increasing phosphorylation of Iκκ and IκBα, and stabilizes mRNAs encoding pro-inflammatory cytokines. While CIRP promotes higher levels of pro-inflammatory cytokines in certain cancers, it also decreases inflammation to accelerate wound healing. This dichotomy suggests that the influence of CIRP on inflammation is context dependent and highlights the importance of detailing the mechanisms by which CIRP modulates inflammation. WIREs RNA 2018, 9:e1462. doi: 10.1002/wrna.1462 This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Proof of region-specific multipotent progenitors in human breast epithelia

We have devised a culture system with conditions that allow primary breast myoepithelial cells (MEPs) to be passaged in a manner that sustains either nonmyodifferentiated or myodifferentiated cell populations without permitting contaminating luminal cells to grow. We show that progenitor activity and potency of MEPs to generate luminal cells in culture and in vivo rely on maintenance of myodifferentiation. Specific isolation and propagation of topographically distinct MEPs reveal the existence of multipotent progenitors in terminal duct lobular units. These findings have important implications for our understanding of the emergence of candidate luminal precursor cells to human breast cancer.

The human breast parenchyma consists of collecting ducts and terminal duct lobular units (TDLUs). The TDLU is the site of origin of most breast cancers. The reason for such focal susceptibility to cancer remains poorly understood. Here, we take advantage of a region-specific heterogeneity in luminal progenitors to interrogate the differentiation repertoire of candidate stem cells in TDLUs. We show that stem-like activity in serial passage culture and in vivo breast morphogenesis relies on the preservation of a myoepithelial phenotype. By enrichment for region-specific progenitors, we identify bipotent and multipotent progenitors in ducts and TDLUs, respectively. We propose that focal breast cancer susceptibility, at least in part, originates from region-specific myoepithelial progenitors.

Pregnancy and Breast Cancer

Breast cancer is the most commonly diagnosed type of cancer among women worldwide. The majority of breast cancers are sporadic and the etiology is not well understood. Several factors have been attributed to altering the risk of breast cancer. A full-term pregnancy is a crucial factor in altering the risk. Early full-term pregnancy has been shown to reduce the lifetime risk of breast cancer, while a later first full-term pregnancy increases breast cancer risk. Epidemiological and experimental data demonstrate that spontaneous or induced abortions do not significantly alter the risk of breast cancer. In this study, we briefly discuss the different types and stages of breast cancer, various risk factors, and potential mechanisms involved in early full-term pregnancy-induced protection against breast cancer. Understanding how early full-term pregnancy induces protection against breast cancer will help design innovative preventive and therapeutic strategies. This understanding can also help in the development of molecular biomarkers that can be of tremendous help in predicting the risk of breast cancer in the general population.

Phosphoproteins in extracellular vesicles as candidate markers for breast cancer

The state of protein phosphorylation can be a key determinant of cellular physiology such as early-stage cancer, but the development of phosphoproteins in biofluids for disease diagnosis remains elusive. Here we demonstrate a strategy to isolate and identify phosphoproteins in extracellular vesicles (EVs) from human plasma as potential markers to differentiate disease from healthy states. We identified close to 10,000 unique phosphopeptides in EVs isolated from small volumes of plasma samples. Using label-free quantitative phosphoproteomics, we identified 144 phosphoproteins in plasma EVs that are significantly higher in patients diagnosed with breast cancer compared with healthy controls. Several biomarkers were validated in individual patients using paralleled reaction monitoring for targeted quantitation. This study demonstrates that the development of phosphoproteins in plasma EV as disease biomarkers is highly feasible and may transform cancer screening and monitoring.

LncRNA SNHG12 promotes cell growth and inhibits cell apoptosis in colorectal cancer cells

Several long non-coding RNA (lncRNA) might be correlated with the prognosis of colorectal cancer (CRC) and serve as a diagnostic and prognostic biomarker. However, the exact expression pattern of small nucleolar RNA host gene 12 (SNHG12) in colorectal cancer and its clinical significance remains unclear. The level of SNHG12 was detected by qRT-PCR in CRC tissues and CRC cells. MTT assay and colony formation assay were performed to examine the cell proliferation of CRC cells transfected with pcDNA-SNHG12 or si-SNHG12. Flow cytometry technology was used to detect cell cycle and cell apoptosis of CRC cells transfected with pcDNA-SNHG12 or si-SNHG12. The protein level of cell cycle progression-related molecules, including cyclin-dependent kinases (CDK4, CDK6), cyclin D1 (CCND1) and cell apoptosis-related molecule caspase 3 was detected by western blot. The effect of SNHG12 knockdown was examined in vivo. Increased levels of SNHG12 were observed in CRC tissues and in CRC cells. SNHG12 promoted the cell proliferation of CRC cells. In addition, SNHG12 overexpression boosted the cell cycle progression of SW480 cells transfected with pcDNA-SNHG12 and SNHG12 knockdown inhibited the cell cycle progression of HT29 cells transfected with si-SNHG12. SNHG12 also inhibited the cell apoptosis of CRC cells. We also found that SNHG12 increased the expression of cell cycle-related proteins and suppressed the expression of caspase 3. Our results suggest that SNHG12 promoted cell growth and inhibited cell apoptosis in CRC cells, indicating that SNHG12 might be a useful biomarker for colorectal cancer.

Cold-inducible RNA binding protein in mouse mammary gland development

RNA binding proteins (RBPs) regulate gene expression by controlling mRNA export, translation, and stability. When altered, some RBPs allow cancer cells to grow, survive, and metastasize. Cold-inducible RNA binding protein (CIRP) is overexpressed in a subset of breast cancers, induces proliferation in breast cancer cell lines, and inhibits apoptosis. Although studies have begun to examine the role of CIRP in breast and other cancers, its role in normal breast development has not been assessed. We generated a transgenic mouse model overexpressing human CIRP in the mammary epithelium to ask if it plays a role in mammary gland development. Effects of CIRP overexpression on mammary gland morphology, cell proliferation, and apoptosis were studied from puberty through pregnancy, lactation and weaning. There were no gross effects on mammary gland morphology as shown by whole mounts. Immunohistochemistry for the proliferation marker Ki67 showed decreased proliferation during the lactational switch (the transition from pregnancy to lactation) in mammary glands from CIRP transgenic mice. Two markers of apoptosis showed that the transgene did not affect apoptosis during mammary gland involution. These results suggest a potential in vivo function in suppressing proliferation during a specific developmental transition.

Tamoxifen therapy benefit predictive signature coupled with prognostic signature of post-operative recurrent risk for early stage ER+ breast cancer

Two types of prognostic signatures for predicting recurrent risk of ER+ breast cancer patients have been developed: one type for patients accepting surgery only and another type for patients receiving post-operative tamoxifen therapy. However, the first type of signature cannot distinguish high-risk patients who cannot benefit from tamoxifen therapy, while the second type of signature cannot identify patients who will be at low risk of recurrence even if they accept surgery only. In this study, we proposed to develop two coupled signatures to solve these problems based on within-sample relative expression orderings (REOs) of gene pairs. Firstly, we identified a prognostic signature of post-operative recurrent risk using 544 samples of ER+ breast cancer patients accepting surgery only. Then, applying this drug-free signature to 840 samples of patients receiving post-operative tamoxifen therapy, we recognized 553 samples of patients who would have been at high risk of recurrence if they had accepted surgery only and used these samples to develop a tamoxifen therapy benefit predictive signature. The two coupled signatures were validated in independent data. The signatures developed in this study are robust against experimental batch effects and applicable at the individual levels, which can facilitate the clinical decision of tamoxifen therapy.

Potential Mechanisms underlying the Protective Effect of Pregnancy against Breast Cancer: A Focus on the IGF Pathway

A first full-term birth at an early age protects women against breast cancer by reducing lifetime risk by up to 50%. The underlying mechanism resulting in this protective effect remains unclear, but many avenues have been investigated, including lobular differentiation, cell fate, and stromal composition. A single pregnancy at an early age protects women for 30-40 years, and this long-term protection is likely regulated by a relatively stable yet still modifiable method, such as epigenetic reprograming. Long-lasting epigenetic modifications have been shown to be induced by pregnancy and to target the IGF pathway. Understanding how an early first full-term pregnancy protects against breast cancer and the role of epigenetic reprograming of the IGF system may aid in developing new preventative strategies for young healthy women in the future.

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.

Reproductive history and breast cancer prevention

The hormonal milieu of an early full-term pregnancy induces lobular development, completing the cycle of differentiation of the breast. This process induces a specific genomic signature in the mammary gland that is represented by the stem cell containing a heterochomatin condensed nucleus (HTN). Even though differentiation significantly reduces cell proliferation in the mammary gland, the mammary epithelium remains capable of responding with proliferation to given stimuli, such as a new pregnancy. The stem cell HTN is able to metabolize the carcinogen and repair the induced DNA damage more efficiently than the stem cell containing an euchromatinic structure (EUN), as it has been demonstrated in the rodent experimental system. The basic biological concept is that pregnancy shifts the stem cell EUN to the stem cell HTN that is refractory to carcinogenesis. Data generated by the use of cDNA micro array techniques have allowed to demonstrate that while lobular development regressed after pregnancy and lactation, programmed cell death genes, DNA repair genes, chromatin remodeling, transcription factors and immune-surveillance gene transcripts all of these genes are upregulated and are part of the genomic signature of pregnancy that is associated with the preventive effect of this physiological process.

Targeted DNA Methylation Screen in the Mouse Mammary Genome Reveals a Parity-Induced Hypermethylation of Igf1r That Persists Long after Parturition

The most effective natural prevention against breast cancer is an early first full-term pregnancy. Understanding how the protective effect is elicited will inform the development of new prevention strategies. To better understand the role of epigenetics in long-term protection, we investigated parity-induced DNA methylation in the mammary gland. FVB mice were bred or remained nulliparous and mammary glands harvested immediately after involution (early) or 6.5 months following involution (late), allowing identification of both transient and persistent changes. Targeted DNA methylation (109 Mb of Ensemble regulatory features) analysis was performed using the SureSelectXT Mouse Methyl-seq assay and massively parallel sequencing. Two hundred sixty-nine genes were hypermethylated and 128 hypomethylated persistently at both the early and late time points. Pathway analysis of the persistently differentially methylated genes revealed Igf1r to be central to one of the top identified signaling networks, and Igf1r itself was one of the most significantly hypermethylated genes. Hypermethylation of Igf1r in the parous mammary gland was associated with a reduction of Igf1r mRNA expression. These data suggest that the IGF pathway is regulated at multiple levels during pregnancy and that its modification might be critical in the protective role of pregnancy. This supports the approach of lowering IGF action for prevention of breast cancer, a concept that is currently being tested clinically.

Molecular Phenotype of Breast Cancer According to Time Since Last Pregnancy in a Large Cohort of Young Women

BACKGROUND

The increase in breast cancer risk during pregnancy and postpartum is well known; however, the molecular phenotype of breast cancers occurring shortly after pregnancy has not been well studied. Given this, we investigated whether nulliparity and the time interval since pregnancy among parous women affects the breast cancer phenotype in young women.

MATERIALS AND METHODS

We examined molecular phenotype in relation to time since pregnancy in a prospective cohort of 707 young women (aged ≤40 years) with breast cancer. Parity was ascertained from study questionnaires. Using tumor histologic grade on central review and biomarker expression, cancers were categorized as luminal A- or B-like, HER2 enriched, and triple negative.

RESULTS

Overall, 32% were luminal A-like, 41% were luminal B-like, 9% were HER2 enriched, and 18% were triple negative. Although, numerically, patients diagnosed >5 years after pregnancy had more luminal A-like subtypes than women with shorter intervals since pregnancy, there was no evidence of a relationship between these intervals and molecular subtypes once family history of breast cancer and age at diagnosis were considered.

CONCLUSION

Distribution of breast cancer molecular phenotype did not differ significantly among young women by parity or time interval since parturition when important predictors of tumor phenotype such as age and family history were considered.

IMPLICATIONS FOR PRACTICE

Distribution of breast cancer molecular phenotype did not differ among parous young women by time interval since pregnancy. The implication of these findings for clinical practice suggests that pregnancy-associated breast cancers may be seen up to 5 years beyond parturition.

Relation between parity and pregnancy-related hormones and breast cancer control

SUMMARY 

Epidemiological research has indicated the beneficial effects of full-term pregnancy at an early age for a reduction in breast cancer risk. Experimental data have shown that pregnancy and pregnancy-related hormones, such as estrogen plus progesterone, estrogen alone and human chorionic gonadotropin, are involved in parity-induced protection. Pregnancy and short-duration treatment of a young host with pregnancy-related hormones to mimic the pregnancy environment provide mammary cancer protection by making cells refractory to carcinogenic stimuli and causing growth arrest and programmed cell death. Experimental data concerning pregnancy and pregnancy-related hormones are reviewed in relation to intrinsic subtypes of mammary cancer.

Parity-related molecular signatures and breast cancer subtypes by estrogen receptor status

INTRODUCTION

Relationships of parity with breast cancer risk are complex. Parity is associated with decreased risk of postmenopausal hormone receptor-positive breast tumors, but may increase risk for basal-like breast cancers and early-onset tumors. Characterizing parity-related gene expression patterns in normal breast and breast tumor tissues may improve understanding of the biological mechanisms underlying this complex pattern of risk.

METHODS

We developed a parity signature by analyzing microRNA microarray data from 130 reduction mammoplasty (RM) patients (54 nulliparous and 76 parous). This parity signature, together with published parity signatures, was evaluated in gene expression data from 150 paired tumors and adjacent benign breast tissues from the Polish Breast Cancer Study, both overall and by tumor estrogen receptor (ER) status.

RESULTS

We identified 251 genes significantly upregulated by parity status in RM patients (parous versus nulliparous; false discovery rate = 0.008), including genes in immune, inflammation and wound response pathways. This parity signature was significantly enriched in normal and tumor tissues of parous breast cancer patients, specifically in ER-positive tumors.

CONCLUSIONS

Our data corroborate epidemiologic data, suggesting that the etiology and pathogenesis of breast cancers vary by ER status, which may have implications for developing prevention strategies for these tumors.

The genomic signature of breast cancer prevention

The breast of parous postmenopausal women exhibits a specific signature that has been induced by a full term pregnancy. This signature is centered in chromatin remodeling and the epigenetic changes induced by methylation of specific genes which are important regulatory pathways induced by pregnancy. Through the analysis of the genes found to be differentially methylated between women of varying parity, multiple positions at which beta-catenin production and use is inhibited were recognized. The biological importance of the pathways identified in this specific population cannot be sufficiently emphasized because they could represent a safeguard mechanism mediating the protection of the breast conferred by full term pregnancy.

Molecular pathways involved in pregnancy-induced prevention against breast cancer

Pregnancy produces a protective effect against breast cancer in women who had their first full term pregnancy (FTP) in their middle twenties. The later in life the first delivery occurs, the higher the risk of breast cancer development. Also, transiently during the postpartum period, the risk of developing breast cancer increases. This transient increased risk is taken over by a long-lasting protective period. The genomic profile of parous women has shown pregnancy induces a long-lasting "genomic signature" that explains the preventive effect on breast cancer. This signature reveals that chromatin remodeling is the driver of the differentiation process conferred by FTP. The chromatin remodeling process may be the ultimate step mediating the protection of the breast against developing breast cancer in post-menopausal years.

Mimicking pregnancy as a strategy for breast cancer prevention

Pregnancy and its effects on breast cancer risk have been widely investigated; there is consensus among researchers that early pregnancy confers protection against breast cancer later in life, whereas nulliparity and late-age parity have been associated with increased risk of developing breast cancer. The answer to the question of how pregnancy reduces breast cancer risk has been elusive; however, pregnancy, like breast cancer, is a similar hormone-dependent entity under direct control of estrogen, progesterone and, of particular importance, human chorionic gonadotropin (hCG). In this report, we emphasize the main changes, previously described by our laboratory, in morphology and gene expression levels of the mammary gland of Sprague-Dawley rats exposed to known cancer-preventative conditions (pregnancy, hCG and progesterone + estrogen). In addition, we postulate a protective mechanism induced by hCG that could reduce the cell's potential to be transformed by carcinogens.

Pregnancy protection of breast cancer: new insights reveal unanswered questions

The recent paper by Meier-Abt and colleagues on pregnancy protection of breast cancer development takes a different approach to the problem and focused on the effect of parity on the cell subpopulations of the mouse mammary gland. Their results demonstrate that parity decreases the cell number of the hormone receptor-positive luminal cells (that is, luminal Sca1+) but not the basal stem/progenitor cells (CD24lo/CD49hi). Additionally, microarray studies demonstrate that wnt4 expression from the luminal Sca1+ cells is markedly reduced as is the wnt signaling pathway in basal cells. One important implication from these results is that targeting the wnt signaling pathway might be a feasible prevention approach in humans.