Estrogen-induced immune changes within the normal mammary gland

Sex bias in tumor immunity: insights from immune cells

Significant sex disparities have been observed in cancer incidence, treatment response to immunotherapy, and susceptibility to adverse effects, affecting both reproductive and non-reproductive organ cancers. While lifestyle factors, carcinogenic exposure, and healthcare access contribute to these disparities, they do not fully explain the observed male-female variation in anti-tumor immunity. Despite the preferential expression of sex hormone receptors in immune cells, X chromosome also contains numerous genes involved in immune function, and its incomplete inactivation may enhance anti-tumor immune responses in females. In contrast, loss or downregulation of Y-linked genes in males has been associated with an increased cancer risk. Additionally, estrogen, progesterone and androgen signaling pathways influence both innate and adaptive immune responses, contributing to sex-specific outcomes in cancer progression and therapy. Sex-biased differences are also evident in the epigenetic regulation of gene expression, cellular senescence, microbiota composition, metabolism, and DNA damage response, all of which impact anti-tumor immunity and immunotherapy treatment efficacy. In general, the combination of sex chromosomes, sex hormones, and hormone receptors orchestrates the phenotype and function of various immune cells involved in tumor immunity. However, sex disparity in each specific immune cell are context and environment dependent, considering the preferential expression of hormone receptor in immune cell and sex hormone levels fluctuate significantly across different life stages. This review aims to outline the molecular, cellular, and epigenetic changes in T cells, B cells, NK cells, DCs, neutrophils, and macrophages driven by sex chromosomes and sex hormone signaling. These insights may inform the design of sex-specific targeted therapies and leading to more individualized cancer treatment strategies.

Estrogen promotes autophagy in the mammary epithelial cells of dairy sheep via the CXCL12/CXCR4 axis

Mammary gland development and lactation in dairy sheep are regulated by hormones and autophagy; however, the role of estrogen-mediated autophagy remains unclear. This study determined that estrogen enhances autophagy, promotes CXCR4 and CXCL12 gene expression, and increases the number of autolysosomes in sheep mammary epithelial cells. Co-treatment with a CXCR4 overexpression vector and the small-molecule alternative of CXCL12, NUCC-390, significantly upregulated ATG5 and LC3 gene expression, increased the abundance of the autophagy-associated protein ATG5 and the LC3II/I ratio, and increased the consumption of the autophagy substrate P62. These results suggest that CXCR4 and CXCL12 signaling promotes autophagy in mammary epithelial cells. Conversely, co-treatment with a CXCR4-specific blocker and estrogen inhibited autophagic changes in ATG5, P62, and LC3 levels, reducing the number of autophagosomes and autolysosomes. Overall, this study demonstrated that estrogen promotes autophagy in sheep mammary epithelial cells through the CXCL12/CXCR4 signaling axis, revealing the underlying mechanisms behind estrogen-mediated autophagy.

Loss of STING impairs lactogenic differentiation

Heightened energetic and nutrient demand during lactogenic differentiation of the mammary gland elicits upregulation of various stress responses to support cellular homeostasis. Here, we identify the stimulator of interferon genes (STING) as an immune supporter of the functional development of mouse mammary epithelial cells (MECs). An in vitro model of MEC differentiation revealed that STING is activated in a cGAS-independent manner to produce both type I interferons and proinflammatory cytokines in response to the accumulation of mitochondrial reactive oxygen species. Induction of STING activity was found to be dependent on the breast tumor suppressor gene single-minded 2 (SIM2). Using mouse models of lactation, we discovered that loss of STING activity results in early involution of #3 mammary glands, severely impairing lactational performance. Our data suggest that STING is required for successful functional differentiation of the mammary gland and bestows a differential lactogenic phenotype between #3 mammary glands and the traditionally explored inguinal 4|9 pair. These findings affirm unique development of mammary gland pairs that is essential to consider in future investigations into normal development and breast cancer initiation.

Sex as a biological variable in ageing: insights and perspectives on the molecular and cellular hallmarks

Sex-specific differences in lifespan and ageing are observed in various species. In humans, women generally live longer but are frailer and suffer from different age-related diseases compared to men. The hallmarks of ageing, such as genomic instability, telomere attrition or loss of proteostasis, exhibit sex-specific patterns. Sex chromosomes and sex hormones, as well as the epigenetic regulation of the inactive X chromosome, have been shown to affect lifespan and age-related diseases. Here we review the current knowledge on the biological basis of sex-biased ageing. While our review is focused on humans, we also discuss examples of model organisms such as the mouse, fruit fly or the killifish. Understanding these molecular differences is crucial as the elderly population is expected to double worldwide by 2050, making sex-specific approaches in the diagnosis, treatment, therapeutic development and prevention of age-related diseases a pressing need.

Immune Cell Contribution to Mammary Gland Development

Postpartum breast cancer (PPBC) is a unique subset of breast cancer, accounting for nearly half of the women diagnosed during their postpartum years. Mammary gland involution is widely regarded as being a key orchestrator in the initiation and progression of PPBC due to its unique wound-healing inflammatory signature. Here, we provide dialogue suggestive that lactation may also facilitate neoplastic development as a result of sterile inflammation. Immune cells are involved in all stages of postnatal mammary development. It has been proposed that the functions of these immune cells are partially directed by mammary epithelial cells (MECs) and the cytokines they produce. This suggests that a more niche area of exploration aimed at assessing activation of innate immune pathways within MECs could provide insight into immune cell contributions to the developing mammary gland. Immune cell contribution to pubertal development and mammary gland involution has been extensively studied; however, investigations into pregnancy and lactation remain limited. During pregnancy, the mammary gland undergoes dramatic expansion to prepare for lactation. As a result, MECs are susceptible to replicative stress. During lactation, mitochondria are pushed to capacity to fulfill the high energetic demands of producing milk. This replicative and metabolic stress, if unresolved, can elicit activation of innate immune pathways within differentiating MECs. In this review, we broadly discuss postnatal mammary development and current knowledge of immune cell contribution to each developmental stage, while also emphasizing a more unique area of study that will be beneficial in the discovery of novel therapeutic biomarkers of PPBC.

Distribution of Inflammatory Infiltrate in Feline Mammary Lesions: Relationship With Clinicopathological Features

Inflammation is a frequent finding in feline mammary neoplasms. Recent research suggests that the presence and location of tumour-associated immune cells might play a significant role in the clinical outcome of feline mammary carcinomas. The present study aimed to characterise the overall inflammatory infiltrates in healthy, hyperplastic/dysplastic, benign and malignant lesions of the feline mammary gland, and to evaluate its association with clinicopathological features. Perilesional and intralesional inflammatory foci were evaluated in 307 lesions from 185 queens, and categorised according to its distribution and intensity. The presence, location and density of tertiary lymphoid structures were also assessed. A control group included 24 queens without mammary changes. The presence of intralesional and perilesional inflammatory infiltrate was observed in a majority of the lesions (80.8% and 90.2%, respectively), but differed according to the type of mammary lesion, being more remarkable in malignant neoplasms. Only scarce individual cells were observed in 28.1% of the normal mammary glands. Data analysis revealed statistically significant associations (p < 0.05) between the presence of a more prominent intralesional and perilesional inflammatory reaction and several clinicopathological features associated with worse prognosis, including clinical stage, tumour size, mitotic count, lymphovascular invasion and lymph node metastasis. Furthermore, tertiary lymphoid structures were significantly more frequent in tumours with an infiltrative growth and lymph node metastasis. According to our results, the inflammatory reaction present in different types of feline mammary lesions is associated with the development of more aggressive tumours.

Estrogen receptor regulation of the immune microenvironment in breast cancer

Breast cancer (BCa) is the most common cancer in women and the estrogen receptor (ER)+ subtype is increasing in incidence. There are numerous therapy options available for patients that target the ER, however issues such as innate and acquired treatment resistance, and treatment related side effects justify research into alternative therapeutic options for these patients. Patients of many solid tumour types have benefitted from immunotherapy, however response rates have been generally low in ER+ BCa. We summarise the recent work assessing CDK4/6 inhibitors for ER+ BCa and how they have been shown to prime anti-tumour immune cells and achieve impressive results in preclinical models. A great example of how the immune system might be activated against ER+ BCa. We review the role of estrogen signalling in immune cells, and explore recent data highlighting the hormonal regulation of the immune microenvironment of normal breast, BCa and immune disorders. As recent data has indicated that macrophages are particularly susceptible to estrogen signalling, we highlight macrophage phagocytosis as a key potential target for priming the tumour immune microenvironment. We challenge the generally accepted paradigm that ER+ BCa are "immune-cold" - advocating instead for research into therapies that could be used in combination with targeted therapies and/or immune checkpoint blockade to achieve durable antitumour responses in ER+ BCa.

Influence of tumor microenvironment on the different breast cancer subtypes and applied therapies

Despite the significant improvements made in breast cancer therapy during the last decades, this disease still has increasing incidence and mortality rates. Different targets involved in general processes, like cell proliferation and survival, have become alternative therapeutic options for this disease, with some of them already used in clinic, like the CDK4/6 inhibitors for luminal A tumors treatment. Nevertheless, there is a demand for novel therapeutic strategies focused not only on tumor cells, but also on their microenvironment. Tumor microenvironment (TME) is a very complex and dynamic system that, more than surrounding and supporting tumor cells, actively participates in tumor development and progression. During the last decades, it has become clear that the cellular and acellular components of TME differ between the various breast cancer subtypes and shape the differences regarding their severity and prognosis. The pivotal role of the TME in controlling tumor growth and influencing responses to therapy represents a potential source for novel targets and therapeutic strategies. In this review, we present a description of the multiple therapeutic options used for different breast cancer subtypes, as well as the influence that the TME may exert on the development of the disease and on the response to the distinct therapies, which in some cases may explain their failure by the occurrence of relapses and resistance. Furthermore, the ongoing studies focused on the use of TME components for developing potential cancer treatments are described.

Host response during unresolved urinary tract infection alters female mammary tissue homeostasis through collagen deposition and TIMP1

Exposure to pathogens throughout a lifetime influences immunity and organ function. Here, we explore how the systemic host-response to bacterial urinary tract infection (UTI) induces tissue-specific alterations to the mammary gland. Utilizing a combination of histological tissue analysis, single cell transcriptomics, and flow cytometry, we identify that mammary tissue from UTI-bearing mice displays collagen deposition, enlarged ductal structures, ductal hyperplasia with atypical epithelial transcriptomes and altered immune composition. Bacterial cells are absent in the mammary tissue and blood of UTI-bearing mice, therefore, alterations to the distal mammary tissue are mediated by the systemic host response to local infection. Furthermore, broad spectrum antibiotic treatment resolves the infection and restores mammary cellular and tissue homeostasis. Systemically, unresolved UTI correlates with increased plasma levels of the metalloproteinase inhibitor, TIMP1, which controls extracellular matrix remodeling and neutrophil function. Treatment of nulliparous and post-lactation UTI-bearing female mice with a TIMP1 neutralizing antibody, restores mammary tissue normal homeostasis, thus providing evidence for a link between the systemic host response during UTI and mammary gland alterations.

Single-Cell Transcription Mapping of Murine and Human Mammary Organoids Responses to Female Hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Hormone Receptor Signaling and Breast Cancer Resistance to Anti-Tumor Immunity

Breast cancers regroup many heterogeneous diseases unevenly responding to currently available therapies. Approximately 70-80% of breast cancers express hormone (estrogen or progesterone) receptors. Patients with these hormone-dependent breast malignancies benefit from therapies targeting endocrine pathways. Nevertheless, metastatic disease remains a major challenge despite available treatments, and relapses frequently ensue. By improving patient survival and quality of life, cancer immunotherapies have sparked considerable enthusiasm and hope in the last decade but have led to only limited success in breast cancers. In addition, only patients with hormone-independent breast cancers seem to benefit from these immune-based approaches. The present review examines and discusses the current literature related to the role of hormone receptor signaling (specifically, an estrogen receptor) and the impact of its modulation on the sensitivity of breast cancer cells to the effector mechanisms of anti-tumor immune responses and on the capability of breast cancers to escape from protective anti-cancer immunity. Future research prospects related to the possibility of promoting the efficacy of immune-based interventions using hormone therapy agents are considered.

Single-cell transcription mapping of murine and human mammary organoids responses to female hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Effects of Atractylodes Macrocephala Rhizoma polysaccharide on intestinal microbiota composition in rats with mammary gland hyperplasia

BACKGROUND

In recent years, mammary gland hyperplasia (MGH) has been considered to be one of the diseases caused by endocrine disorders. It has been shown that diseases caused by endocrine disorders can be treated by regulating intestinal microbial. As a commonly used medicine in clinical practice, Atractylodes Macrocephala Rhizoma has good functions in regulating intestinal homeostasis. Therefore, this paper studied the effect of Atractylodes Macrocephala Rhizoma polysaccharide (AMP) on the intestinal flora of MGH rats, providing a new idea for polysaccharide treatment of MGH.

MATERIALS AND METHODS

Eighteen female SD rats were selected and randomly divided into three groups: blank control group (Con), model control group (Mod), and AMP group, six rats in each group. MGH rat models were established by estradiol-progesterone combination and treated with AMP gastric infusion. The levels of E₂, P, and PRL in the serum of rats were measured, the intestinal contents were collected, and 16s rRNA high- throughput sequencing technology was analyzed the changes of intestinal flora in the MGH rats.

RESULTS

AMP has good therapeutic effects on MGH rats, decreasing estradiol (E₂) and prolactin (PRL) levels and increasing progesterone (P) levels; at the same time, it can regulate the abundance and diversity of intestinal flora of MGH rats, improve the disorder of intestinal flora caused by MGH, and change the community structure, increase the abundance of beneficial flora, and decrease the abundance of pathogenic flora.

CONCLUSION

AMP can improve the intestinal microbiological environment of MGH rats, maintain the microecological balance of intestinal microbial, and improve MGH symptoms.