Mimicking pregnancy as a strategy for breast cancer prevention

Treatment of women with BRCA mutation

The cumulative risk for breast and ovarian cancer is high in BRCA1 or BRCA2 mutation carriers. The lifetime risk of breast cancer by the age of 80 years is respectively up to 72% and 69% in BRCA1 and BRCA2 mutation carriers. The risk of ovarian cancer is higher (44%) in BRCA1 than in BRCA2 (17%) mutation carriers. Breast and ovarian cancers tend to arise earlier in BRCA1 mutation carriers. Breast cancers in BRCA1 mutation carriers are more frequently (up to 70%) triple negative while the majority (up to 80%) of breast cancers in BRCA2 mutation carriers are hormone sensitive. Many issues remain to be resolved. In daily practice we are often confronted with patients having BRCA mutations classified as variants of unknown significance, who do have breast cancer personally or have a strong family history of breast cancer. On the other hand, 30-40% of mutation carriers will not develop breast cancer. Moreover, it is very difficult to predict the age at which cancer will arise. In a multidisciplinary setting we need to offer BRCA and other mutation carriers a wide range of information, advice and support.

Recombinant human chorionic gonadotropin induces signaling pathways towards cancer prevention in the breast of BRCA1/2 mutation carriers

BACKGROUND

Strategies for breast cancer prevention in women with germline BRCA1/2 mutations are limited. We previously showed that recombinant human chorionic gonadotropin (r-hCG) induces mammary gland differentiation and inhibits mammary tumorigenesis in rats. The present study investigated hCG-induced signaling pathways in the breast of young nulliparous women carrying germline BRCA1/2 mutations.

METHODS

We performed RNA-sequencing on breast tissues from 25 BRCA1/2 mutation carriers who received r-hCG treatment for 3 months in a phase II clinical trial, we analyzed the biological processes, reactome pathways, canonical pathways, and upstream regulators associated with genes differentially expressed after r-hCG treatment, and validated genes of interest.

RESULTS

We observed that r-hCG induces remarkable transcriptomic changes in the breast of BRCA1/2 carriers, especially in genes related to cell development, cell differentiation, cell cycle, apoptosis, DNA repair, chromatin remodeling, and G protein-coupled receptor signaling. We revealed that r-hCG inhibits Wnt/β-catenin signaling, MYC, HMGA1 , and HOTAIR , whereas activates TGFB/TGFBR-SMAD2/3/4, BRCA1, TP53, and upregulates BRCA1 protein.

CONCLUSION

Our data suggest that the use of r-hCG at young age may reduce the risk of breast cancer in BRCA1/2 carriers by inhibiting pathways associated with stem/progenitor cell maintenance and neoplastic transformation, whereas activating genes crucial for breast epithelial differentiation and lineage commitment, and DNA repair.

NF-κB and Its Regulators During Pregnancy

The transcriptional factor NF-κB is a nuclear factor involved in both physiological and pathological processes. This factor can control the transcription of more than 400 genes, including cytokines, chemokines, and their modulators, immune and non-immune receptors, proteins involved in antigen presentation and cell adhesion, acute phase and stress response proteins, regulators of apoptosis, growth factors, other transcription factors and their regulators, as well as different enzymes; all these molecules control several biological processes. NF-κB is a tightly regulated molecule that has also been related to apoptosis, cell proliferation, inflammation, and the control of innate and adaptive immune responses during onset of labor, in which it has a crucial role; thus, early activation of this factor may have an adverse effect, by inducing premature termination of pregnancy, with bad outcomes for the mother and the fetus, including product loss. Reviews compiling the different activities of NF-κB have been reported. However, an update regarding NF-κB regulation during pregnancy is lacking. In this work, we aimed to describe the state of the art around NF-κB activity, its regulatory role in pregnancy, and the effect of its dysregulation due to invasion by pathogens like Trichomonas vaginalis and Toxoplasma gondii as examples.

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.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Early Parity Epigenetic Footprint of FOXA1 Gene Body in Normal Breast Tissue of Iranian Women

BACKGROUND

Young age at first full-term pregnancy (FFTP) is an important factor in breast cancer risk reduction. It is postulated that this protective effect is the result of stable molecular signatures imprinted by physiological process of pregnancy, but the molecular mechanism of this protective role is unclear. The aim of the current study was to identify the effect of early FFTP on methylation status of FOXA1 gene body. FOXA1 is an essential transcription factor for mammary gland development and estrogen responsiveness of breast tissue.

METHODS

Fresh frozen normal breast tissues (n = 51) were collected from Iranian women who underwent cosmetic mammoplasty (27 nulliparous women and 24 parous women who have experienced first pregnancy before the age of 25). DNA was extracted and then methylated DNA immunoprecipitation (MeDIP) real-time PCR was used to assess FOXA1 gene body methylation.

RESULTS

Our results revealed that FOXA1 methylation level is significantly higher in early parous compared with nulliparous group (p = 0.041).

CONCLUSION

Our study provides new hint about the association between early FFTP and epigenetic modifications within gene body of FOXA1 in normal breast tissue. More investigation is required for clarifying molecular mechanisms underlying this association in order to develop breast cancer prevention strategies.

The importance of hCG in human endometrial adenocarcinoma and breast cancer

Human chorionic gonadotropin (hCG) is a peptide hormone which plays an important role during pregnancy. But its impact is not limited to pregnancy; it also influences tumor formation and metastatic outgrowth, especially in endometrial adenocarcinoma and breast cancer. This review summarizes what has been written in the literature about the role of hCG as a tumor marker in these 2 gynecological malignancies and also about the signal transduction pathways in which hCG is involved. HCG can, on the one hand, be a marker for the progression of a malignant disease, and on the other hand, it may be a point for therapeutical intervention, so further research into this molecule would be very much worthwhile.

Two controls of cell proliferation underlie cancer relapse

Much progress has been made in understanding the basis of cancer. Current therapies can effectively shrink tumors. But they frequently relapse, metastasize to other locations, and are lethal. Effective therapies are very much needed for preventing this relapse. Creation of a eukaryotic organism commences with one original stem cell, a fertilized egg, which multiplies and differentiates. Mutations of normal stem cells can produce cancer stem cells (CSC). These cells may resist chemotherapy, proliferate, and produce new tumors. Human chorionic gonadotrophin (hCG) is composed of two proteins (alpha and beta) that bind to the cell membrane and activate a number of intracellular pathways. hCG has been shown to activate the proliferation of cancer stem cells. Cyclin dependent regulation of the adult cells is created in normal differentiation and replaces the hCG regulation of stem cells. To selectively kill the cancer stem cells conventional cancer therapies could be followed with a therapy based on inactivating human chronic gonadotrophin (HCG). For example chemically modified prostaglandins like RU486 prevent binding of the unmodified steroid to hCG and inactivate hCG.

Good Guy or Bad Guy? The Duality of Wild-Type p53 in Hormone-Dependent Breast Cancer Origin, Treatment, and Recurrence

"Lactation is at one point perilously near becoming a cancerous process if it is at all arrested", Beatson, 1896. Most breast cancers arise from the milk-producing cells that are characterized by aberrant cellular, molecular, and epigenetic translation. By understanding the underlying molecular disruptions leading to the origin of cancer, we might be able to design novel strategies for more efficacious treatments or, ambitiously, divert the cancerous process. It is an established reality that full-term pregnancy in a young woman provides a lifetime reduction in breast cancer risk, whereas delay in full-term pregnancy increases short-term breast cancer risk and the probability of latent breast cancer development. Hormonal activation of the p53 protein (encode by the TP53 gene) in the mammary gland at a critical time in pregnancy has been identified as one of the most important determinants of whether the mammary gland develops latent breast cancer. This review discusses what is known about the protective influence of female hormones in young parous women, with a specific focus on the opportune role of wild-type p53 reprogramming in mammary cell differentiation. The importance of p53 as a protector or perpetrator in hormone-dependent breast cancer, resistance to treatment, and recurrence is also explored.

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.

The controversial role of human chorionic gonadotropin in the development of breast cancer and other types of tumors

INTRODUCTION

Breast cancer is the most often diagnosed tumor of women and one of the leading cause of cancer related death. Due to different known risk factors there are epidemiological differences. Beside genetic disorders and patient's age it is especially the age of the first full-term pregnancy and in this context the pregnancy hormone human chorionic gonadotropin that seems to play an important role.

METHODS

This review is based on a PubMed research in publications of the last 20 years. Only articles in English language were considered.

RESULTS

The effect of human chorionic gonadotropin on development of cancer is controversial. In fact, for breast cancer there is evidence that this hormone has a protective effect against tumorigenesis due the differentiation of the mammary tissue after a full term pregnancy through the downregulation of estrogen receptors.

CONCLUSION

Human chorionic gonadotropin has among promoting pregnancy important controversial functions especially in tumor development. The mechanisms that explain the pro- and anti-carcinogenic effects are not fully understood yet. It seems to have a protective effect on breast cancer through increasing differentiation and hereby decreasing susceptibility of the mammary tissue for toxicants. This knowledge might help developing a preventive agent in the next future that uses the anti-carcinogenic effect of human chorionic gonadotropin and thereby decrease the mortality out of breast cancer.

Reproduction and breast cancer risk

Reproduction is doubtlessly one of the main biological meanings of life. It is therefore not surprising that various aspects of reproduction impact on breast cancer risk. Various developmental levels may become targets of breast tumorigenesis. This review follows the chronologic sequence of events in the life of a female at risk, starting with the intrauterine development. Furthermore, the influence of both contraceptive measures and fertility treatment on breast cancer development is dealt with, as well as various pregnancy-associated factors, events, and perinatal outcomes. Finally, the contribution of breast feeding to a reduced breast cancer risk is discussed.

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.

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.