Microenvironmental control of cell fate decisions in mammary gland development and cancer

FOXO4-SP6 axis controls surface epithelium commitment by mediating epigenomic remodeling

Proper development of surface epithelium (SE) is a requisite for the normal development and function of ectodermal appendages; however, the molecular mechanisms underlying SE commitment remain largely unexplored. Here, we developed a KRT8 reporter system and utilized it to identify FOXO4 and SP6 as novel, essential regulators governing SE commitment. We found that the FOXO4-SP6 axis governs SE fate and its abrogation markedly impedes SE fate determination. Mechanistically, FOXO4 regulates SE initiation by shaping the SE chromatin accessibility landscape and regulating the deposition of H3K4me3. SP6, as a novel effector of FOXO4, activates SE-specific genes through modulating the H3K27ac deposition across their super-enhancers. Our work highlights the regulatory function of the FOXO4-SP6 axis in SE development, contributing to an improved understanding of SE fate decisions and providing a research foundation for the therapeutic application of ectodermal dysplasia.

Triple-positive breast cancer: navigating heterogeneity and advancing multimodal therapies for improving patient outcomes

Triple-positive breast cancer (TPBC), a unique subtype of luminal breast cancer, is characterized by concurrent positivity for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Owing to the crosstalk between the ER and HER2 signaling pathways, the standard of care and drug resistance of this particular subtype are difficult challenges. Recent research and clinical trials have indicated a shift in the treatment paradigm for TPBC from single-target therapies to multi-pathway, multitarget strategies aiming to comprehensively modulate intricate signaling networks, thereby overcoming resistance and enhancing therapeutic outcomes. Among multiple strategies, triple-drug therapy has emerged as a promising treatment modality, demonstrating potential efficacy in patients with TPBC. Moving forward, there is a critical need to perform in-depth analyses of specific mechanisms of cancer pathogenesis and metastasis, decipher the complex interactions between different genes or proteins, and identify concrete molecular targets, thus paving the way for the development of tailored therapeutic strategies to combat TPBC effectively.

Breast Morphogenesis: From Normal Development to Cancer

The human breast gland is composed of branching epithelial ducts that culminate in milk-producing units known as terminal duct lobular units (TDLUs). The epithelial compartment comprises an inner layer of luminal epithelial cells (LEP) and an outer layer of contractile myoepithelial cells (MEP). Both LEP and MEP arise from a common stem cell population. The epithelial compartment undergoes dynamic branching morphogenesis and remodelling, which expands the surface area for milk production. The epithelial remodelling that starts at the onset of menarche is largely under hormonal control, first and foremost by estrogen and progesterone from ovaries, the production of which is stimulated by pituitary-derived hormones. Menopause leads to a significant decline in estrogen and progesterone levels, resulting in involution and senescence of the breast epithelium. The branching morphogenesis involves developmental events such as epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET). EMT and MET confer plasticity to the epithelial compartment enabling the migration of epithelial cells through the stroma and restoration of the epithelial phenotype. In the normal breast, the stroma, including the basement membrane (BM), collagen-rich extracellular matrix, and various stromal cells, supports the correct histoarchitecture of the glandular tree. However, in cancer, the stroma can acquire tumour-promoting properties and is referred to as the tumour microenvironment. This chapter will explore the developmental processes including branching morphogenesis in the normal breast gland and discuss the lineage relationship between LEPS and MEPs and their interactions with the surrounding stroma in the normal and neoplastic breast gland. Finally, we will review various in vitro and in vivo models employed in mammary gland research.

Sympathetic nerve signals: orchestrators of mammary development and stem cell vitality

The mammary gland is a dynamic organ that undergoes significant changes at multiple stages of postnatal development. Although the roles of systemic hormones and microenvironmental cues in mammary homeostasis have been extensively studied, the influence of neural signals, particularly those from the sympathetic nervous system, remains poorly understood. Here, using a mouse mammary gland model, we delved into the regulatory role of sympathetic nervous signaling in the context of mammary stem cells and mammary development. Our findings revealed that depletion of sympathetic nerve signals results in defective mammary development during puberty, adulthood, and pregnancy, accompanied by a reduction in mammary stem cell numbers. Through in vitro three-dimensional culture and in vivo transplantation analyses, we demonstrated that the absence of sympathetic nerve signals hinders mammary stem cell self-renewal and regeneration, while activation of sympathetic nervous signaling promotes these capacities. Mechanistically, sympathetic nerve signals orchestrate mammary stem cell activity and mammary development through the extracellular signal-regulated kinase signaling pathway. Collectively, our study unveils the crucial roles of sympathetic nerve signals in sustaining mammary development and regulating mammary stem cell activity, offering a novel perspective on the involvement of the nervous system in modulating adult stem cell function and organ development.

Synergistic effects of photodynamic therapy and chemotherapy: Activating the intrinsic/extrinsic apoptotic pathway of anoikis for triple-negative breast cancer treatment

Triple-negative breast cancer (TNBC) is a highly invasive and metastatic subtype of breast cancer that often recurs after surgery. Herein, we developed a cyclodextrin-based tumor-targeted nano delivery system that incorporated the photosensitizer chlorin e6 (Ce6) and the chemotherapeutic agent lonidamine (LND) to form the R6RGD-CMβCD-se-se-Ce6/LND nanoparticles (RCC/LND NPS). This nanosystem could target cancer cells, avoid lysosomal degradation and further localize within the mitochondria. The RCC/LND NPS had pH and redox-responsive to control the release of Ce6 and LND. Consequently, the nanosystem had a synergistic effect by effectively alleviating hypoxia, enhancing the production of cytotoxic reactive oxygen species (ROS) and amplifying the efficacy of photodynamic therapy (PDT). Furthermore, the RCC/LND NPS + light weakened anoikis resistance, disrupted extracellular matrix (ECM), activated both the intrinsic apoptotic pathway (mitochondrial pathway) and extrinsic apoptotic pathway (receptor death pathway) of anoikis. In addition, the nanosystem showed significant anti-TNBC efficacy in vivo. These findings collectively demonstrated that RCC/LND NPS + light enhanced the anticancer effects, induced anoikis and inhibited tumor cell migration and invasion through a synergistic effect of chemotherapy and PDT. Overall, this study highlighted the promising potential of the RCC/LND NPS + light for the treatment of TNBC.

Dual role of pregnancy in breast cancer risk

Reproductive history is one of the strongest risk factors for breast cancer in women. Pregnancy can promote short-term breast cancer risk, but also reduce a woman's lifetime risk of breast cancer. Changes in hormone levels before and after pregnancy are one of the key factors in breast cancer risk. This article summarizes the changes in hormone levels before and after pregnancy, and the roles of hormones in mammary gland development and breast cancer progression. Other factors, such as changes in breast morphology and mammary gland differentiation, changes in the proportion of mammary stem cells (MaSCs), changes in the immune and inflammatory environment, and changes in lactation before and after pregnancy, also play key roles in the occurrence and development of breast cancer. This review discusses the dual effects and the potential mechanisms of pregnancy on breast cancer risk from the above aspects, which is helpful to understand the complexity of female breast cancer occurrence.

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.

The prognostic implications and tumor-suppressive functions of CYR61 in estrogen receptor-positive breast cancer

Due to the therapeutic resistance of endocrine therapy and the limited efficacy of immune checkpoint inhibitors in estrogen receptor (ER)-positive breast cancer (BRCA), there is an urgent need to develop novel prognostic markers and understand the regulation of the tumor immune microenvironment (TIME). As a matricellular protein, CYR61 has been shown to either promote or suppress cancer progression depending on cancer types. However, how CYR61 functions in ER-positive BRCA remains elusive. In this study, we comprehensively analyzed the expression of CYR61 in BRCA based on the TCGA and METABRIC databases. Our findings showed that the expression of CYR61 is downregulated in different subtypes of BRCA, which is associated with elevated promoter methylation levels and predicts bad clinical outcomes. By comparing the high or low CYR61 expression groups of ER-positive BRCA patients, we found that CYR61 is intimately linked to the expression of genes involved in tumor-suppressive pathways, such as the TGF-β and TNF signaling pathways, and genes related to cytokine-receptor interaction that may regulate cancer immunity. Moreover, reduced CYR61 expression is associated with an altered TIME that favors cancer progression. Finally, experimental analyses ascertained that CYR61 is downregulated in clinical BRCA tissues compared to matched normal breast tissues. Furthermore, CYR61 is able to impede the proliferation and colony formation of ER-positive BRCA cells. In summary, our study reveals that CYR61 could serve as a novel prognostic marker for ER-positive BRCA, and function as an inhibitor of cancer progression by both acting on cancer cells and remodeling the TIME.

Additively manufactured bioceramic scaffolds based on triply periodic minimal surfaces for bone regeneration

The study focused on the effects of a triply periodic minimal surface (TPMS) scaffolds, varying in porosity, on the repair of mandibular defects in New Zealand white rabbits. Four TPMS configurations (40%, 50%, 60%, and 70% porosity) were fabricated with β-tricalcium phosphate bioceramic via additive manufacturing. Scaffold properties were assessed through scanning electron microscopy and mechanical testing. For proliferation and adhesion assays, mouse bone marrow stem cells (BMSCs) were cultured on these scaffolds. In vivo, the scaffolds were implanted into rabbit mandibular defects for 2 months. Histological staining evaluated osteogenic potential. Moreover, RNA-sequencing analysis and RT-qPCR revealed the significant involvement of angiogenesis-related factors and Hippo signaling pathway in influencing BMSCs behavior. Notably, the 70% porosity TPMS scaffold exhibited optimal compressive strength, superior cell proliferation, adhesion, and significantly enhanced osteogenesis and angiogenesis. These findings underscore the substantial potential of 70% porosity TPMS scaffolds in effectively promoting bone regeneration within mandibular defects.

The Role of the Tumor Microenvironment in Triple-Positive Breast Cancer Progression and Therapeutic Resistance

Breast cancer (BRCA) is a highly heterogeneous systemic disease. It is ranked first globally in the incidence of new cancer cases and has emerged as the primary cause of cancer-related death among females. Among the distinct subtypes of BRCA, triple-positive breast cancer (TPBC) has been associated with increased metastasis and invasiveness, exhibiting greater resistance to endocrine therapy involving trastuzumab. It is now understood that invasion, metastasis, and treatment resistance associated with BRCA progression are not exclusively due to breast tumor cells but are from the intricate interplay between BRCA and its tumor microenvironment (TME). Accordingly, understanding the pathogenesis and evolution of the TPBC microenvironment demands a comprehensive approach. Moreover, addressing BRCA treatment necessitates a holistic consideration of the TME, bearing significant implications for identifying novel targets for anticancer interventions. This review expounds on the relationship between critical cellular components and factors in the TPBC microenvironment and the inception, advancement, and therapeutic resistance of breast cancer to provide perspectives on the latest research on TPBC.

Recent progress on the effect of extracellular matrix on occurrence and progression of breast cancer

Breast cancer (BC) metastasis is an enormous challenge targeting BC therapy. The extracellular matrix (ECM), the principal component of the BC metastasis niche, is the pivotal driver of breast tumor development, whose biochemical and biophysical characteristics have attracted widespread attention. Here, we review the biological effects of ECM constituents and the influence of ECM stiffness on BC metastasis and drug resistance. We provide an overview of the relative signal transduction mechanisms, existing metastasis models, and targeted drug strategies centered around ECM stiffness. It will shed light on exploring more underlying targets and developing specific drugs aimed at ECM utilizing biomimetic platforms, which are promising for breast cancer treatment.

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development.

Breast cancers as ecosystems: a metabolic perspective

Breast cancer (BC) is the most frequently diagnosed cancer and one of the major causes of cancer death. Despite enormous progress in its management, both from the therapeutic and early diagnosis viewpoints, still around 700,000 patients succumb to the disease each year, worldwide. Late recurrency is the major problem in BC, with many patients developing distant metastases several years after the successful eradication of the primary tumor. This is linked to the phenomenon of metastatic dormancy, a still mysterious trait of the natural history of BC, and of several other types of cancer, by which metastatic cells remain dormant for long periods of time before becoming reactivated to initiate the clinical metastatic disease. In recent years, it has become clear that cancers are best understood if studied as ecosystems in which the impact of non-cancer-cell-autonomous events-dependent on complex interaction between the cancer and its environment, both local and systemic-plays a paramount role, probably as significant as the cell-autonomous alterations occurring in the cancer cell. In adopting this perspective, a metabolic vision of the cancer ecosystem is bound to improve our understanding of the natural history of cancer, across space and time. In BC, many metabolic pathways are coopted into the cancer ecosystem, to serve the anabolic and energy demands of the cancer. Their study is shedding new light on the most critical aspect of BC management, of metastatic dissemination, and that of the related phenomenon of dormancy and fostering the application of the knowledge to the development of metabolic therapies.

Macrophages maintain mammary stem cell activity and mammary homeostasis via TNF-α-PI3K-Cdk1/Cyclin B1 axis

Adult stem cell niche is a special environment composed of a variety stromal cells and signals, which cooperatively regulate tissue development and homeostasis. It is of great interest to study the role of immune cells in niche. Here, we show that mammary resident macrophages regulate mammary epithelium cell division and mammary development through TNF-α-Cdk1/Cyclin B1 axis. In vivo, depletion of macrophages reduces the number of mammary basal cells and mammary stem cells (MaSCs), while increases mammary luminal cells. In vitro, we establish a three-dimensional culture system in which mammary basal cells are co-cultured with macrophages, and interestingly, macrophage co-culture promotes the formation of branched functional mammary organoids. Moreover, TNF-α produced by macrophages activates the intracellular PI3K/Cdk1/Cyclin B1 signaling in mammary cells, thereby maintaining the activity of MaSCs and the formation of mammary organoids. Together, these findings reveal the functional significance of macrophageal niche and intracellular PI3K/Cdk1/Cyclin B1 axis for maintaining MaSC activity and mammary homeostasis.

PMN-MDSCs modulated by CCL20 from cancer cells promoted breast cancer cell stemness through CXCL2-CXCR2 pathway

Our previous studies have showed that C-C motif chemokine ligand 20 (CCL20) advanced tumor progression and enhanced the chemoresistance of cancer cells by positively regulating breast cancer stem cell (BCSC) self-renewal. However, it is unclear whether CCL20 affects breast cancer progression by remodeling the tumor microenvironment (TME). Here, we observed that polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) were remarkably enriched in TME of CCL20-overexpressing cancer cell orthotopic allograft tumors. Mechanistically, CCL20 activated the differentiation of granulocyte-monocyte progenitors (GMPs) via its receptor C-C motif chemokine receptor 6 (CCR6) leading to the PMN-MDSC expansion. PMN-MDSCs from CCL20-overexpressing cell orthotopic allograft tumors (CCL20-modulated PMN-MDSCs) secreted amounts of C-X-C motif chemokine ligand 2 (CXCL2) and increased ALDH+ BCSCs via activating CXCR2/NOTCH1/HEY1 signaling pathway. Furthermore, C-X-C motif chemokine receptor 2 (CXCR2) antagonist SB225002 enhanced the docetaxel (DTX) effects on tumor growth by decreasing BCSCs in CCL20high-expressing tumors. These findings elucidated how CCL20 modulated the TME to promote cancer development, indicating a new therapeutic strategy by interfering with the interaction between PMN-MDSCs and BCSCs in breast cancer, especially in CCL20high-expressing breast cancer.

RCN3: a Ca2+ homeostasis regulator that promotes esophageal squamous cell carcinoma progression and cisplatin resistant

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent cancers worldwide. There is a critical need to identify new mechanisms that contribute to ESCC progression. Reticulocalbin3 (RCN3) is mainly located in the endoplasmic reticulum and Ca²⁺‐binding protein containing EF‐hands. The function of RCN3 in tumor progression has not been clarified. We observed that the expression level of RCN3 was higher in ESCC tissues than in paired normal tissues. Overexpression of RCN3 was positively associated with tumor size, lymph node metastasis, TNM stage, lymphatic vessel infiltration, and poor outcome in patients with ESCC. Increased malignant phenotypes were observed in RCN3 overexpressing ESCC cells, whereas the opposite effects were achieved in RCN3‐silenced cells. Reticulocalbin3 promoted the expression of MMP‐2 and MMP‐9 by regulating the inositol 1,4,5‐trisphosphate receptor 1 (IP3R1)–Ca²⁺–calcium/calmodulin‐dependent protein kinase II–c‐Jun signaling pathway. Reticulocalbin3 induced cisplatin resistance by regulating IP3R1/Ca²⁺ to maintain intracellular Ca²⁺ homeostasis and reduced reactive oxygen species in ESCC cells. Finally, the expression of RCN3 was regulated by hypoxia inducible factor‐1α. Collectively, these data strongly support that RCN3 regulates Ca²⁺ homeostasis by targeting IP3R1 to promote the progression and platinum resistance of ESCC. Our studies suggest that RCN3 could serve as predictive factor of poor prognosis and potential therapeutic target for ESCC patients.

Single-Cell Transcriptomics Identifies Heterogeneity of Mouse Mammary Gland Fibroblasts With Distinct Functions, Estrogen Responses, Differentiation Processes, and Crosstalks With Epithelium

Fibroblasts have been shown to be one of the essential players for mammary gland organization. Here, we identify two major types of mouse mammary gland fibroblasts through single-cell RNA sequencing analysis: Dpp4 ⁺ fibroblasts and Dpp4 ^- fibroblasts. Each population exhibits unique functional characteristics as well as discrete localization in normal mouse mammary glands. Remarkably, estrogen, a crucial mediator of mammary gland organization, alters the gene expression profiles of fibroblasts in a population-specific manner, without distinct activation of estrogen receptor signaling. Further integrative analysis with the inclusion of five other publicly available datasets reveals a directional differentiation among the mammary gland fibroblast populations. Moreover, the combination with the mouse mammary epithelium atlas allows us to infer multiple potential interactions between epithelial cells and fibroblasts in mammary glands. This study provides a comprehensive view of mouse mammary gland fibroblasts at the single-cell level.

Anti-Tumor Role of CAMK2B in Remodeling the Stromal Microenvironment and Inhibiting Proliferation in Papillary Renal Cell Carcinoma

The tumor microenvironment (TME) is variable across tumor types and has diverse effects on malignant progression, based on the type and number of infiltrating stromal cells. In particular, TME effector genes and their competitive endogenous RNA (ceRNA) networks play a critical role in regulating malignant tumor progression. However, the core effector molecules involved in TME modulation of kidney renal papillary cell carcinoma (KIRP) are poorly understood. To address this question, a cohort containing 233 KIRP patients was derived from The Cancer Genome Atlas (TCGA) database, and the data were processed using the ESTIMATE algorithm. We further evaluated the relationship between immune scores (ISs) and stromal scores (SSs) and disease progression and found that high SSs were associated with a poor prognosis in KIRP. Differentially expressed genes (DEGs) were therefore screened based on SS scores, resulting in 2509 DEGs, including 1668 mRNAs, 783 long noncoding (lnc)RNAs, and 58 micro (mi)RNAs. DEGs were then filtered using the random variance and subjected to hierarchical clustering using EPCLUST. Weighted gene co-expression network analysis (WGCNA) was used to assess the prognostic capacity of these DEGs and identify target ceRNA networks, and lncRNA GUSBP11/miR-432-5p/CAMK2B in the turquoise module was selected as a promising ceRNA network. From this analysis CAMK2B was selected as the core gene predicted to be involved in stromal TMA regulation. We therefore explored the expression and function of CAMK2B in vitro and in vivo and provide evidence that this protein promotes stromal TME remodulation and inhibits proliferation in KIRP. Lastly, we show that vascular endothelial growth factor (VEGF), transforming growth factor (TGF)β, and close homolog of L1 (CHL1) act as downstream effectors of CAMK2B in KIRP. Thus, in this study, we show that the TME determines prognosis of KIRP patients via the core effector molecule CAMK2B, which mediates both microenvironmental remodeling and tumor progression. Based on these findings, we propose that remodeling of the stromal microenvironment could represent an improved therapeutic approach relative to immunotherapy for KIRP.