Immune cells are increased in normal breast tissues of BRCA1/2 mutation carriers

CD105+ fibroblasts support an immunosuppressive niche in women at high risk of breast cancer initiation

BACKGROUND

Aging is the greatest risk factor for breast cancer, and although epithelial cells are the source of carcinomas, epithelial changes alone do not fully explain cancer susceptibility. Fibroblasts and macrophages are key stromal constituents around the cells of origin for cancer in breast tissue. With age, macrophages surrounding terminal ductal lobular units (TDLUs) become increasingly immunosuppressive. CD105+ fibroblasts intercalate within TDLUs, drive luminal differentiation, and give rise to immunosuppressive cancer-associated fibroblasts in other tissues. We propose that differences in fibroblasts are a crucial component of the stroma that shapes cancer susceptibility.

METHODS

Primary peri-epithelial fibroblast cultures were established from prophylactic and reduction mammoplasties from 30 women ranging in age from 16 to 70 years and from BRCA1 mutation carriers. Growth characteristics, transcriptional profiles, differentiation potential, and secreted proteins were profiled for fibroblast subtypes from diverse donors. Co-cultures with fibroblasts, macrophages, and T cells were used to ascertain the functional role played by CD105+ fibroblasts in immune cell modulation.

RESULTS

We found that peri-epithelial CD105+ fibroblasts are enriched in older women as well as women who carry BRCA1 mutations. These CD105+ fibroblasts exhibit robust adipogenesis and secrete factors related to macrophage polarization. Macrophages cocultured with fibroblasts better maintain or enhance polarization states than media alone. CD105+ fibroblasts increased expression of immunosuppressive macrophage genes. CD105+ fibroblasts supported anti-inflammatory macrophage-mediated suppression of T cell proliferation, whereas CD105- fibroblasts significantly reduced the suppressive effect of anti-inflammatory macrophages on T cell proliferation.

CONCLUSIONS

Establishment of a coculture system to dissect the molecular circuits between CD105+ fibroblasts and macrophages that drive immunosuppressive macrophage polarization has broad utility in understanding mammary gland development and events that precede cancer initiation. CD105+ fibroblasts and macrophages may coordinate to suppress immunosurveillance and increase breast cancer susceptibility.

Unraveling the role of stromal disruption in aggressive breast cancer etiology and outcomes

BACKGROUND

Aggressive (typically high-grade) breast cancers (BCs) remain major contributors to BC-related mortality globally. The tissue changes underpinning their etiology and outcomes, however, remain poorly characterized.

METHODS

Spatially resolved machine-learning algorithms were used to characterize "stromal disruption" as a morphological metric of reduced/altered extracellular matrix and increased immune, inflammatory, and/or wound response-related processes in normal, benign breast disease (BBD), and invasive hematoxylin and eosin (H&E)-stained breast tissues. Associations of stromal disruption with BC etiologic factors were assessed among 4023 healthy breast tissue donors, its impact on BC incidence was assessed among 974 BBD patients in a nested case-control study, while its prognostic associations were assessed in 4 BC patient cohorts (n = 4223).

RESULTS

Epidemiologic risk factors for aggressive BC, including younger age, multiparity, Black race, obesity, and family history, demonstrated strong associations with increasing stromal disruption in H&E sections prior to tumor development. Substantial stromal disruption in BBD H&E was associated with ∼4-fold increased risk of aggressive (high-grade) BC and ∼3 years shorter latency from BBD to BC diagnosis, independently of BBD histology. Across BC cohorts, stromal disruption in H&E was associated with aggressive (mostly high-grade) tumor phenotypes and with markedly poor prognosis among ER-positive patients, irrespective of histology. The immunobiology of stromal disruption reflected heightened innate (CD68+), adaptive (CD3+CD4+, CD3+CD8+), immunoregulatory (CD3+CD4+FOXP3+), immune escape (PD1+PDL1+), endothelial (CD31+), and myofibroblast (α-SMA+) marker expression.

CONCLUSION

Our findings highlight the active stromal role in aggressive BC etiology and outcomes, opening possibilities for readily identifying high-risk women across the BC continuum that may benefit from stroma-centric preventative or therapeutic strategies.

CD105+ fibroblasts support an immunosuppressive niche in women at high risk of breast cancer initiation

BACKGROUND

Aging is the greatest risk factor for breast cancer, and although epithelial cells are the source of carcinomas, epithelial changes alone do not fully explain cancer susceptibility. Fibroblasts and macrophages are key stromal constituents around the cells of origin for cancer in breast tissue. With age, macrophages surrounding terminal ductal lobular units (TDLUs) become increasingly immunosuppressive. CD105 + fibroblasts intercalate within TDLUs, drive luminal differentiation, and give rise to immunosuppressive cancer-associated fibroblasts in other tissues. We propose that differences in fibroblasts are a crucial component of the stroma that shapes cancer susceptibility.

METHODS

Primary fibroblast cultures were established from prophylactic and reduction mammoplasties from women ranging in age from 16 to 70 years and breast cancer risk ( BRCA1 mutation carriers). Growth characteristics, transcriptional profiles, differentiation potential, and secreted proteins were profiled for fibroblast subtypes from diverse donors. Co-cultures with fibroblasts, monocytes, macrophages, and T cells were used to ascertain the functional role played by CD105 + fibroblasts in immune cell modulation.

RESULTS

We found that peri-epithelial CD105 + fibroblasts are enriched in older women as well as women who carry BRCA1 mutations. These CD105 + fibroblasts exhibit robust adipogenesis and secrete factors related to macrophage polarization. Macrophages cocultured with fibroblasts better maintain or enhance polarization states than media alone. CD105 + fibroblasts increased expression of immunosuppressive macrophage genes. CD105 + fibroblasts supported anti-inflammatory macrophage-mediated suppression of T cell proliferation, whereas CD105 - fibroblasts significantly reduced the suppressive effect of anti-inflammatory macrophages on T cell proliferation.

CONCLUSIONS

Establishment of a coculture system to dissect the molecular circuits between CD105 + fibroblasts and macrophages that drive immunosuppressive macrophage polarization has broad utility in understanding mammary gland development and events that precede cancer initiation. CD105 + fibroblasts and macrophages may coordinate to suppress immunosurveillance and increase breast cancer susceptibility.

Peripheral immunophenotyping reveals lymphocyte stimulation in healthy women living with hereditary breast and ovarian cancer syndrome

Germline pathogenic variants in BRCA1 and BRCA2 (gpath(BRCA1/2)) represent genetic susceptibility for hereditary breast and ovarian cancer syndrome. Tumor-immune interactions are key contributors to breast cancer pathogenesis. Although earlier studies confirmed pro-tumorigenic immunological alterations in breast cancer patients, data are lacking in healthy carriers of gpath(BRCA1/2). Peripheral blood mononuclear cells of 66 women with or without germline predisposition or breast cancer were studied with a mass cytometry panel that identified 4 immune subpopulations of altered frequencies between healthy controls and healthy gpath(BRCA1) carriers, while no difference was observed in healthy gpath(BRCA2) carriers compared to controls. Moreover, 3 (one IgD-CD27+CD95+ B cell subpopulation and two CD45RA-CCR7+CD38+ CD4+ T cell subpopulations) out of these 4 subpopulations were also elevated in triple-negative breast cancer patients compared to controls. Our results reveal an activated peripheral immune phenotype in healthy carriers of gpath(BRCA1) that needs to be further elucidated to be leveraged in risk-reducing strategies.

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.

The Tumor Immune Microenvironment in Breast Cancer Progression

BACKGROUND

The tumor microenvironment significantly influences breast cancer development, progression, and metastasis. Various immune cell populations, including T cells, B cells, NK cells, and myeloid cells exhibit diverse functions in different breast cancer subtypes, contributing to both anti-tumor and pro-tumor activities.

PURPOSE

This review provides an overview of the predominant immune cell populations in breast cancer subtypes, elucidating their suppressive and prognostic effects. We aim to outline the role of the immune microenvironment from normal breast tissue to invasive cancer and distant metastasis.

METHODS

A comprehensive literature review was conducted to analyze the involvement of immune cells throughout breast cancer progression.

RESULTS

In breast cancer, tumors exhibit increased immune cell infiltration compared to normal tissue. Variations exist across subtypes, with higher levels observed in triple-negative and HER2+ tumors are linked to better survival. In contrast,  ER+ tumors display lower immune infiltration, associated with poorer outcomes. Furthermore, metastatic sites commonly exhibit a more immunosuppressive microenvironment.

CONCLUSION

Understanding the complex interaction between tumor and immune cells during breast cancer progression is essential for future research and the development of immune-based strategies. This comprehensive understanding may pave the way for more effective treatment approaches and improved patients outcomes.

Non-sclerosing (T-cell) and sclerosing (B-cell) lymphocytic lobulitis in diagnostic breast biopsies: Clinical, imaging, and pathologic features

Lymphocytic lobulitis (LL) is characterized by prominent lymphocytic infiltrates centered on lobules. Sclerosing lymphocytic lobulitis (SCLL) associated with diabetes mellitus (DM) or autoimmune disease (AI) was the first type to be described. Subsequently, non-sclerosing LL (NSCLL) was reported as an incidental finding in prophylactic mastectomies due to high risk germline mutations or a family history of breast cancer. The two types of LL were distinguished by stromal features and a predominant population of B-cells in the former and T-cells in the latter. In this study, 8 cases of NSCLL detected clinically or by screening were compared to 44 cases of SCLL. One case of NSCLL presented as a palpable mass, 2 as masses on screening, and 5 as MRI enhancement. In contrast, 80% of SCLL cases presented as palpable masses. Half the cases of NSCLL were associated with a BRCA1 or 2 mutation compared to 1 case of SCLL (2%). Three additional cases of NSCLL were associated with a strong family and/or personal history of breast cancer. Almost half (52%) of SCLL cases were associated with DM or AI, but only 25% of NSCLL. Immunoperoxidase studies confirmed a predominance of T-cells in NSCLL and B-cells in SCLL associated with DM or AI. It is important for pathologists to be aware of this new observation that NSCLL can be detected as a palpable mass or an imaging finding in diagnostic biopsies, as its presence can be indicative of a significant risk for breast cancer.

Breast cancers arising in subjects with germline BRCA1 or BRCA2 mutations: Different biological and clinical entities with potentially diverse therapeutic opportunities

Breast cancers (BCs) arising in carriers of germline BRCA1 and BRCA2 pathogenic variants (PVs) have long been considered as indistinguishable biological and clinical entities. However, the loss of function of BRCA1 or BRCA2 proteins has different consequences in terms of tumor cell reliance on estrogen receptor signaling and tumor microenvironment composition. Here, we review accumulating preclinical and clinical data indicating that BRCA1 or BRCA2 inactivation may differentially affect BC sensitivity to standard systemic therapies. Based on a different crosstalk between BRCA1 or BRCA2 and the ER pathway, BRCA2-mutated Hormone Receptor-positive, HER2-negative advanced BC may be less sensitive to endocrine therapy (ET) plus CDK 4/6 inhibitors (CDK 4/6i), whereas BRCA2-mutated triple-negative breast cancer (TNBC) may be especially sensitive to immune checkpoint inhibitors. If validated in future prospective studies, these data may have relevant clinical implications, thus establishing different treatment paths in patients with BRCA1 or BRCA2 PVs.

Identification of BRCA1/2 mutation female carriers using circulating microRNA profiles

Identifying germline BRCA1/2 mutation carriers is vital for reducing their risk of breast and ovarian cancer. To derive a serum miRNA-based diagnostic test we used samples from 653 healthy women from six international cohorts, including 350 (53.6%) with BRCA1/2 mutations and 303 (46.4%) BRCA1/2 wild-type. All individuals were cancer-free before and at least 12 months after sampling. RNA-sequencing followed by differential expression analysis identified 19 miRNAs significantly associated with BRCA mutations, 10 of which were ultimately used for classification: hsa-miR-20b-5p, hsa-miR-19b-3p, hsa-let-7b-5p, hsa-miR-320b, hsa-miR-139-3p, hsa-miR-30d-5p, hsa-miR-17-5p, hsa-miR-182-5p, hsa-miR-421, hsa-miR-375-3p. The final logistic regression model achieved area under the receiver operating characteristic curve 0.89 (95% CI: 0.87-0.93), 93.88% sensitivity and 80.72% specificity in an independent validation cohort. Mutated gene, menopausal status or having preemptive oophorectomy did not affect classification performance. Circulating microRNAs may be used to identify BRCA1/2 mutations in patients of high risk of cancer, offering an opportunity to reduce screening costs.