The expression of B7-H4, a co-inhibitory molecule highly detected in cancer cells, serves as an important prognostic marker and therapeutic target in breast cancer. B7-H4 has been shown to modulate the malignancy of breast cancer cells through affecting cell stemness and the epithelial-mesenchymal transition (EMT). However, whether B7-H4 influences the expression of other immunoregulatory molecules, and how this crosstalk contributes to the clinicopathological features of breast cancer remain controversial. Although the majority of the tumors are positive for B7-H4 and negative for PD-L1, we noticed a portion of breast tumor cells (4.3–18.8%) showing co-expression of two molecules. Besides, there is an overall positive correlation in the expression of B7-H4 and PD-L1 in breast cancer. Mechanistically, B7-H4 promotes the transcription of PD-L1 via downregulating the DNA methyltransferase 1 (DNMT1)-mediated methylation in cg19724470 and cg15837913 CpG loci in the promoter of PD-L1. Moreover, the expression of B7-H4 is negatively associated with the methylation levels of these two loci in a breast cancer cohort in the TCGA database, and is necessary for interferon-γ (IFN-γ)-induced PD-L1 expression in breast cancer cells. Pharmacological inhibition of DNMT1 improves IFN-γ responsiveness in breast cancer cells. Functionally, individuals with co-expression of B7-H4 and PD-L1 present higher abundance of CD8A, granzyme B (GZMB) and perforin 1 (PRF1) than those without co-expression in tumor tissues, indicating increased T cell infiltration in these patients. Consistently, the co-expression of these two molecules is also associated with improved disease-free survival in breast cancer patients. Overall, our study unveils a mechanistic link between B7-H4 and PD-L1 expression through DNA methylation-mediated epigenetic regulation in breast cancer, and indicates that epigenetic therapy holds potential in remodeling the immune landscape and overcoming treatment resistance in breast cancer.
Acquired therapy resistance, particularly endocrine resistance in estrogen receptor-positive (ER +) breast cancer, remains a major clinical challenge. Proteolysis-targeting chimeras (PROTACs) have emerged as a novel therapeutic paradigm with the potential to overcome resistance by degrading target proteins. This study provides a comprehensive landscape analysis of PROTACs in breast cancer, synthesizing research trends and clinical trial progress to map the path from discovery to application. We conducted a dual-perspective analysis. Bibliometric data from 350 publications (Web of Science Core Collection) were analyzed to delineate the research evolution, collaboration networks, and target focus. Concurrently, 30 clinical trials registered on ClinicalTrials.gov were systematically reviewed to evaluate the clinical translational stage, target distribution, and safety profiles of PROTACs in breast cancer. Research output has grown exponentially since 2016, led by China and the United States. The estrogen receptor (ER) is the predominant target in both basic and clinical research. Clinical development is advancing rapidly, with the ER degrader ARV-471 reaching phase III trials. In patients with ER + /HER2 - advanced breast cancer and ESR1 mutations, ARV-471 demonstrated a median progression-free survival of 5.0 months, doubling that achieved with fulvestrant (2.1 months). While fatigue and nausea are common adverse events, the overall safety profile appears manageable. However, clinical exploration remains highly concentrated on ER + disease, with limited progress in other subtypes such as HER2 + and triple-negative breast cancer. PROTACs, especially ER degraders, suggest a potential strategy for addressing endocrine resistance in advanced ER + breast cancer, as reflected in encouraging preliminary clinical data. This integrated analysis highlights the rapid translation of this technology while underscoring the critical need to expand target scope, address inherent resistance mechanisms, and broaden applications to other breast cancer subtypes. Our article synthesizes current knowledge and trial landscape, thereby providing a consolidated foundation to inform future research and clinical development of PROTACs in breast cancer.
Black women in the United States experience disproportionately high breast cancer mortality and have high rates of comorbid hypertension; however, the associations of hypertension and antihypertensive medication use with breast cancer survival are unclear. We examined these associations among 2474 Black Women's Health Study participants with invasive breast cancer. Hypertension and antihypertensive medication use were assessed biennially, and breast cancer diagnoses were confirmed through medical records and cancer registries. We used Cox proportional hazards models, adjusted for clinical and lifestyle factors and cancer treatment, to estimate hazard ratios (HR) for breast cancer-specific death. In the full study population, the HR for untreated hypertension compared to no hypertension was 1.17 (95% CI = 0.75-1.82), while the HR for treated hypertension compared to no hypertension was 0.81 (95% CI = 0.60-1.10). For ER+ cases, there was no association between untreated hypertension and breast cancer specific-death (HR = 0.96, 95% CI = 0.50-1.82), but a strong inverse association between treated hypertension and breast cancer-specific death (HR = 0.53, 95% CI = 0.34-0.83). In contrast, for ER- cases, we observed an increased risk of breast cancer specific death among those with untreated hypertension (HR = 2.19, 95% CI = 1.09-4.39), but there was little evidence of an association with treated hypertension (HR = 1.32, 95% CI = 0.80-2.19). Overall, our findings indicate that Black breast cancer patients with hypertension have better survival when their hypertension is treated, possibly due to regular healthcare engagement or the tumor suppressing actions of antihypertensive medications. Randomized trials are needed to establish causality and inform optimal cardiovascular management in oncology.
Tamoxifen (TAM) resistance remains a challenge in estrogen receptor-positive breast cancer treatment. Current research suggested that mesenchymal stem cells (MSCs) derived exosomes may mediate chemoresistance, but the underlying mechanisms are unclear. This study investigates how exosomes from tamoxifen-pretreated MSCs (Tt-MSC-exos) promote tamoxifen resistance through the miR-137/SERPINA3 axis. We isolated exosomes using ultracentrifugation. To investigate the effect of Tt-MSC-exos on TAM resistance, we co-cultured Tt-MSC-exos with ER-positive breast cancer cells and evaluated the cellular functional changes and apoptosis levels. Second-generation transcriptome sequencing was used to analyze the key genes for TAM resistance, and a dual luciferase reporter assay was used to detect the upstream factors of the key genes. The results were further validated by cellular function assays, xenograft modeling studies, and database analysis. We demonstrated that Tt-MSC-exos promote TAM resistance in ER-positive breast cancer cells. Next-generation sequencing revealed that the key gene for Tt-MSC-exos promoting resistance was SERPINA3. Downregulation of SERPINA3 expression enhances TAM resistance in breast cancer cells. In addition, we found that miR-137, which was highly expressed in Tt-MSC-exos, could bind to the 3' UTR region of SERPINA3 in breast cancer cells and thus inhibit the expression of SERPINA3. In this study, we clarified that Tt-MSC-exos inhibit the expression level of SERPINA3 in cancer cells by delivering miR-137 to ER-positive breast cancer cells, which in turn leads to TAM resistance in breast cancer. This study provides a new idea to overcome endocrine therapy resistance in ER-positive breast cancer.
Obesity and high-fat diet (HFD) are established risk factors for breast cancer, but the mechanisms by which dietary-induced gut microbiota alterations influence cancer progression are not fully understood. The interplay between microbial composition, metabolites, and cancer progression warrants further exploration. We employed Mendelian randomization (MR) and Bayesian colocalization analyses based on genome-wide association studies (GWAS) to identify gut microbial genera causally linked to breast cancer risk. Multi-omics, including 16S rRNA sequencing, fecal metabolomics and RNA-seq, were performed to depict HFD-induced microbial and metabolic shifts in breast cancer-bearing mice. In vitro co-culture systems and in vivo murine models examined interactions between Roseburia intestinalis (R. intestinalis) and Streptococcus mutans (S. mutans) under HFD conditions. Functional assays, including immunofluorescence, qRT-PCR, probe-based assays and fluorescent in situ hybridization, and flow cytometry, evaluated cancer stemness, bacterial colonization, and the impact of leucine metabolism. MR analysis revealed Roseburia as a potential causal microbial risk factor for breast cancer, with colocalized genes enriched in fatty acid metabolism. HFD feeding promoted the co-occurrence of R. intestinalis and S. mutans, facilitating S. mutans intratumoral colonization and consequent leucine accumulation in the tumor microenvironment (TME). S. mutans-derived leucine robustly enhanced breast cancer cell proliferation and stemness, as evidenced by increased tumor sphere formation and upregulation of CD44, CD133, and SOX2. Functional blockade of leucine transport with BCH attenuated S. mutans-mediated tumor growth and limited tumor-associated macrophage activation in vivo. This study reveals that HFD-induced reshaping of microbial interactions, particularly a commensal-like interaction between S. mutans and R. intestinalis, is associated with leucine accumulation in the TME, thereby supporting breast cancer stemness and progression. Targeting S. mutans-mediated leucine accumulation represents a promising strategy for therapeutic intervention in obesity-related breast cancer. Our findings highlight the pivotal role of dietary-microbiota crosstalk in modulating the TME and cancer stemness.
This annual report of the National Clinical Database-Breast Cancer Registry (NCD-BCR) by the Japanese Breast Cancer Society presents nationwide breast cancer statistics for patients registered in Japan in 2023. Among 107,372 patients with breast cancer at 1317 institutions, 99.3% were females with a median age of 62 years. The distribution of the clinical stages was as follows: stage 0 (15.5%); stage I (42.1%); stage II (31.1%); stage III (7.0%); and stage IV (2.1%). Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) positivity was observed in 78.9%, 70.0%, and 13.3% of patients, respectively. Among 102,717 patients without distant metastases, 41.2% underwent breast-conserving surgery, 76.5% underwent sentinel lymph node biopsy, and 6.0% underwent breast reconstruction. The distribution of radiotherapy was as follows: 75.2% received whole-breast irradiation, 15.7% chest-wall irradiation, and 20.7% regional irradiation. Among the 13,061 patients with pT1abN0M0 breast cancer, comprising 10,819 hormone receptor [HR]-positive/HER2-negative, 1479 HER2-positive and 763 HR-negative/HER2-negative individuals, 92.4% of HR-positive/HER2-negative patients received endocrine therapy, 46.9% of HER2-positive patients received chemotherapy and/or anti-HER2 therapy, and 31.2% of HR-negative/HER2-negative patients received chemotherapy. This annual report provides a nationwide overview of contemporary systemic therapy patterns in small breast cancer and highlights size‑dependent and subtype‑specific use of systemic therapy in Japan, reflecting a risk‑adapted treatment strategy.
BACKGROUND: Breast cancer risk prediction models aid identification of high-risk women for earlier or more frequent screening. The two most commonly used U.S. models appear to perform less well in Black women, possibly because Black women have a lower proportion of estrogen-receptor positive breast cancer. We recently developed and externally validated a model for use in Black women (BWHS model). Here, we compare performance metrics of that model with the other two models using data from a large cohort of Black women. RESULTS: We assessed the NCI Breast Cancer Risk Assessment Tool (BCRAT) using the option for Black women, the IBIS model, including clinical variables only, and the BWHS model in data from a cohort of 50,235 Black women followed over four sequential 5 year periods. Predictors were updated at the start of each 5 year period, and 2041 invasive breast cancers occurred. Calibration metrics, expected over observed number of cancers, were 0.99 (0.94–1.04), 0.97 (0.93–1.02), and 1.13 (1.08–1.18) from the BWHS, BCRAT, and IBIS models, respectively. The metrics for discriminatory accuracy, age-adjusted area under the curve (AUC), were 0.58 (0.56–0.59), 0.56 (0.55–0.57), and 0.56 (0.55–0.57), from the BWHS, BCRAT, and IBIS models, respectively. CONCLUSIONS: In this comparison, the BWHS model had better calibration and discrimination than BCRAT and IBIS, including among women age < 40, indicating a benefit to using the BWHS model for Black women. While models that incorporate mammographic features may have higher AUCs, models based on clinical factors are beneficial for young women and those without available mammography data.
Neoadjuvant chemotherapy (NACT) for early breast cancer is a systemic treatment administered before surgery to achieve regression of the primary lesion, perform breast-conserving surgery, if possible, and ensure long-term recurrence-free survival. The main aim of this study was to investigate the impact of NACT on the active DNA demethylation process and the relationship between the compounds involved in this path and disease-free survival (DFS) and overall survival (OS) during a six-year follow-up. This study included 71 patients with breast cancer who were eligible for NACT consisting of 4 cycles of doxorubicin and cyclophosphamide regimens at doses of 60 mg/m2 and 600 mg/m2, respectively, on the first day every 21 days, as well as paclitaxel administered at a dose of 80 mg/m2 weekly for 12 weeks. Peripheral blood and urine samples were collected from breast cancer patients at four time points. Additionally, tissue samples from a breast cancer tumor and regional metastatic lymph nodes were collected during surgery. The levels of 5-methylcytosine (5-mCyt) and its derivatives in DNA and urine were determined via two-dimensional ultra-performance liquid chromatography with tandem mass spectrometry (2D-UPLC-MS/MS). The qRT‒PCR technique was used to determine the transcript levels of the genes involved in active DNA demethylation. During chemotherapy, increases in the levels of 5-methyl-2'-deoxycytidine (5-mdC), 5-formyl-2'-deoxycytidine (5-fdC), and 5-carboxyl-2'-deoxycytidine (5-cadC) and decreases in the expression of genes encoding TET (ten-eleven translocation) proteins, TDG (thymine DNA glycosylase), and AID (activation-induced cytidine deaminase) were observed in peripheral blood leukocytes. The Kaplan‒Meier curves revealed that patients with a lower level of 5-mdC in leukocyte DNA and urine before NACT, higher levels of 5-cadC, and lower TDG expression in tumor cells after treatment had a more favorable prognosis. Furthermore, significant correlations were found between the levels of 5-fdC in the DNA of leukocytes, 5-cadC in DNA tumor cells, the expression of TET2, and decreased Ki-67 after NACT. Our results indicate that NACT can alter active DNA demethylation markers. Breast cancer patients with prolonged DFS had lower leukocyte 5-mdC and higher urinary 5-mdC levels before chemotherapy. Thus, assessing 5-mdC in these minimally invasive biospecimens may provide prognostic information for breast cancer patients undergoing NACT.
TP53 mutation is a critical driver of breast cancer, yet its relationship with treatment outcomes for breast cancer remains unclear. This study investigates the association between TP53 mutation and response to CDK4/6 inhibitors (CDK4/6i) and immune checkpoint inhibitors (ICI) in breast cancer using real-world data from the Center for Cancer Genomics and Advanced Therapeutics (C-CAT) cohort, focusing on age-related differences. METABRIC (n = 1355) was used for initial survival analysis, and gene set enrichment analysis (GSEA) was performed to identify pathways enriched in TP53-mutated ER-positive/HER2-negative breast cancers. Clinical and genomic data of metastatic breast cancer (mBC) patients in Japan were analyzed in the C-CAT (n = 1668) cohort. Treatment duration was used as a real-world surrogate endpoint reflecting treatment exposure and potential clinical benefit. Patients were stratified by age into four groups: Adolescents and Young Adults (AYA; 15-39 years), perimenopausal (40-54 years), menopausal (55-64 years), and older (≥ 65 years). TP53 mutations were associated with poor prognosis in the METABRIC cohort. GSEA showed TP53-mutated tumors were enriched with gene sets related to cell proliferation and immune response, while TP53 wild-type tumors enriched for estrogen response pathways. In the C-CAT cohort, TP53 mutations were linked to shorter CDK4/6i treatment duration with similar trends observed for both abemaciclib and palbociclib. However, TP53 mutations were not associated with ICI treatment duration. Patients in the AYA group had the shortest treatment duration, with TP53 mutation prevalence decreasing with age. In age-stratified analyses, TP53 mutation was associated with shorter treatment duration in perimenopausal, menopausal, and older groups but not in the AYA group. However, formal interaction testing did not detect a significant interaction between TP53 mutation and age group. TP53 mutation is associated with shorter CDK4/6i treatment duration, highlighting the importance of considering both genomic and age-related clinical context when interpreting treatment duration in ER-positive/HER2-negative breast cancer.
Breast cancer is the leading cause of cancer-related death in women, with mortality increasing when tumor cells spread to nearby lymph nodes, particularly the axillary lymph nodes (ALNs). Although several studies predict patients with ALN metastasis at diagnosis (pdALN+), few examine the prognostic value of immune elements within ALNs. Given the impact of immune response on breast cancer, this study develops a machine learning model to identify the clinicopathological and immune features of the primary tumor and non-metastatic ALNs (ALN-) most frequently associated with pdALN+. Two datasets of luminal breast cancer patients diagnosed between 1995 and 2008 were used: Dataset 1 involved 83 women (42 pdALN- and 41 pdALN+), and Dataset 2 comprised 344 women (204 pdALN- and 140 pdALN+). Three machine learning models were developed using the Random Forest algorithm: Model 1 included clinicopathological data from Dataset 1; Model 2 used clinicopathological and immune response data from Dataset 1; and Model 3 used clinicopathological data from Dataset 2. All models followed the same machine learning pipeline, including data pre-processing, feature selection using recursive feature elimination with cross-validation, algorithm optimization using random search cross-validation, and results interpretability using Shapley additive explanations values. After selecting the best-performing model, Model 4 was developed using its dataset and features. The optimal feature set was determined at the point where adding more features led to a decline in model performance metrics. Model 2 outperformed Models 1 and 3, despite the larger cohort on which Model 3 was developed. This highlights the crucial role of the immune response in breast cancer progression. Model 4 achieved a median ROC AUC of 0.84, a median accuracy of 0.76, and a median recall of 0.75. Remarkably, nine of the ten predictive features were immune populations. The intratumoral follicular dendritic cell marker CD21+ was the most predictive feature, even surpassing tumor diameter, a well-established prognostic factor in breast cancer. Thus, it might stand as a novel biomarker candidate. This study not only identifies promising biomarker candidates but also highlights the importance of including mechanistic features, such as mediating inflammation, in breast cancer patient stratification.
We evaluated whether Apolipoprotein E (APOE) ε2 homozygosity, a germline variant associated with lower LDL cholesterol, is linked to reduced risk of breast cancer. We analyzed data from 234,857 cancer-free and dementia-free women in the UK Biobank. APOE genotypes were classified as ε2 homozygotes, ε2 heterozygotes, and non-ε2 carriers. Incident breast cancer was assessed via national registry linkage. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs). Subgroup analyses were conducted by lifestyle, metabolic, and female-specific factors. Over a median follow-up of 12.3 years, 7,961 first primary breast cancers occurred. Compared to non-ε2 carriers, ε2 homozygotes had significantly lower breast cancer risk (HR, 0.64; 95% CI 0.45-0.90). The protective association of ε2/ε2 was stronger in participants with smoking history. APOE ε2 homozygosity was associated with reduced risk of breast cancer, particularly under inflammatory stress. These findings suggest that genetically determined lipid and inflammatory regulation may influence breast cancer susceptibility.
Benign breast disease (BBD) is common and confers heterogeneous increases in breast cancer risk; however, risk prediction relies mainly on histopathology and clinical factors. Sclerosing adenosis (SA) is a proliferative BBD lesion associated with an approximately two-fold increase in risk, yet most women with SA never develop breast cancer. We hypothesize that the immune-stromal microenvironment of SA and its surrounding lobular field relates to subsequent invasive breast cancer. In a nested case-control study within a BBD cohort, we profiled 24 sclerosing adenosis (SA) biopsies (9 developing invasive breast cancer within 15 years, cases; 15 cancer-free at ≥ 15 years, controls). We integrated whole-tissue NanoString gene-expression profiling with multiplex immunofluorescence (MxIF) imaging of SA lesions and surrounding morphologically normal lobules. We measured immune and stromal biomarkers in SA lesions and adjacent lobules, with image analysis masked to case-control status, integrated these data with whole-tissue gene expression, and summarized both microenvironment patterns and the proximity of immune cells to proliferating epithelium. SA biopsies from women who later developed cancer showed a low-immune, high-stromal gene-expression program, whereas controls were enriched for immune signatures. Stromal densities of CD8⁺, CD68⁺ and RUNX3⁺ cells in both lobular stroma and SA lesions mirrored this axis and were markedly lower in cases than controls. Unsupervised clustering identified immune-cold and immune-hot lobule types and four SA lesion field archetypes; immune-hot lobules and immune-hot/epithelium-proliferative lesion fields were enriched in controls. Spatial analyses further showed that immune-hot lobules have stromal immune cells positioned closer to proliferating epithelium and enriched CD27-CD8 microclusters, whereas SA lesions from cases exhibit greater immune-to-Ki67 distances, fewer boundary-proximal CD8⁺ sentinels, and depletion of CD27-RUNX3 and RUNX3-CD8 microclusters. These findings support an association of an immune-cold SA lesion embedded within an immune-cold lobular field phenotype with subsequent invasive breast cancer risk in women with SA, and suggest that spatially organized, RUNX3-rich immune microenvironments may contribute to epithelial surveillance. Validation in larger cohorts will be needed to confirm generalizability and clarify lesion-specific versus field-wide contributions.
 Mammographic density (MD) is a known predictor of breast cancer risk and may be influenced by modifiable lifestyle factors. This study aimed to assess the association between adherence to the 2018 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) cancer prevention recommendations prior to diagnosis and MD in women diagnosed with breast cancer.  We analyzed data from 759 breast cancer patients recruited from eight Spanish hospitals enrolled in the case-case Breast Cancer & Density Association Study. Participants completed an epidemiological and a food frequency questionnaire. A standardized score was constructed to assess adherence to six WCRF/AICR recommendations. MD percentage was measured using the validated DM-Scan software on the digital mammogram of the contralateral, tumor-free, breast obtained prior to any treatment. Standardized prevalences and standardized prevalence ratios (SPRs) for four MD categories and for MD ≥ 50% across categories of adherence to the WCRF/AICR recommendations were estimated based on multinomial and binary multivariable logistic regression models.  Overall, adherence to the WCRF/AICR recommendations was not consistently associated with MD. However, the standardized prevalence of MD ≥ 50% was higher among women with high adherence compared to those with low adherence (SPR high vs. low = 1.73; 95% CI = 1.03-2.91). This positive association was particularly evident with the physical activity recommendation (SPR fully met vs. no/partially met = 1.51; 95% CI = 1.02-2.25).  Breast cancer participants with greater adherence to the WCRF/AICR recommendations prior to diagnosis, particularly to physical activity guidelines, showed higher percent MD at diagnosis. This association likely reflects lower absolute breast adiposity rather than a greater amount of fibroglandular tissue, and would therefore not imply an increased carcinogenic risk. These findings highlight the complex relationship between lifestyle behaviors and breast tissue composition.
While the majority of breast cancers arising in women with germline BRCA1 pathogenic variants (gBRCA1) are triple-negative (TNBC), these women also have a moderately increased risk of ER+ breast cancers. The contribution of BRCA1 deficiency to the development of ER+ breast cancers in gBRCA1 carriers is incompletely understood. BRCA1 epimutations (promoter hypermethylation) have emerged as a major factor in TNBC. About 25–30% of all TNBCs harbor clonal BRCA1 epimutations. In the majority of these patients, the tumor seems to arise from small subclones of normal cells harboring constitutional BRCA1 epimutations. Mirroring findings for gBRCA1 carriers, a minor fraction of ER+ breast cancers seems to arise from BRCA1 epimutated subclones as well. An important difference between normal cells in individuals harboring gBRCA1 pathogenic variants and BRCA1 constitutional epimutations is that constitutional epimutations are mosaic, most often affecting < 1% of an individual’s cells. Considering cancers arising in gBRCA1 carriers, where all cells of the individual are affected, in some cases BRCA1 deficiency may be of limited importance to the tumorigenesis; the BRCA1 variants could be passenger events only. In contrast, the fact that women harboring constitutional epimutations in a small fraction of normal cells have increased risk of developing a TNBC harboring fully clonal BRCA1 epimutations strongly suggest BRCA1 deficiency to be an underlying cause in the tumor evolution. Most likely, the same argument applies to ER+ tumors harboring clonal BRCA1 epimutations, making these cancers valuable tools exploring the role of BRCA1 deficiency in development of ER+ breast cancers.
Polygenic risk scores (PRSes) have emerged as promising tools for stratifying breast cancer risk on the basis of genomic data. However, PRSes developed in one ancestral population may vary in predictive performance when applied to a different population. This study aimed to evaluate the utility of six breast cancer PRSes developed via European and East Asian genome-wide association studies (GWASes) in a Japanese prospective cohort. We analysed data from 7,965 women enrolled in the Japan Multi-Institutional Collaborative Cohort (J-MICC) study, with a mean follow-up of 11.3 years. Six published PRSes were calculated via genome-wide genotype data, and their associations with breast cancer incidence were assessed via Cox proportional hazards models adjusted for age, survey area, and population structure. Hazard ratios (HRs), 95% confidence intervals (CIs), and Harrell’s C statistics are reported. Five of the six PRSes were significantly associated with breast cancer risk. The European-derived PRS313_BC demonstrated the highest predictive performance (HR per standard deviation (SD) = 1.64; C statistic = 0.69; P < 0.001), particularly among women diagnosed with breast cancer before 50 years of age. Despite cross-ancestry differences, a European-derived PRS demonstrated strong predictive value for breast cancer risk in a Japanese population, likely reflecting the scale and optimization of the original GWAS. These findings indicate that GWAS scale and statistical power may currently outweigh ancestry matching in PRS performance. However, large-scale ancestry-specific GWASes remain essential to improve prediction accuracy in East Asian populations. The online version contains supplementary material available at 10.1186/s13058-026-02256-1.
CD81, a member of the tetraspanin family, is implicated in tumor progression, and its elevated expression in tumor cells has been associated with poor prognosis across multiple cancers. However, the functional significance of CD81 within the stromal compartments of the tumor microenvironment (TME) remains unclear. This study investigated the clinical relevance and mechanistic role of stromal CD81 (sCD81) in invasive breast cancer. A total of 462 human primary invasive breast cancer samples, along with 13 normal breast tissues and 10 ductal carcinoma in situ samples collected between 2000 and 2013, were analyzed. Immunohistochemistry and spatial analyses were used to evaluate sCD81 expression, and its association with cancer-associated fibroblast (CAF) subsets and immune components in the TME, as well as correlation with clinicopathological correlations and survival outcome. sCD81 expression was significantly higher in invasive breast cancer than in normal breast stromal tissue but did not differ across clinical subtypes. High sCD81 expression was associated with significantly longer disease-free survival, and multivariate analysis identified sCD81 as an independent prognostic factor alongside nuclear grade, estrogen receptor status, and lymph node metastasis. Co-expression analyses demonstrated that sCD81-high stromal cells exhibited a CD34-positive, FAP-low, and PDGFRα-low phenotype, indicating that they are distinct from established CAF subtypes. Both sCD81 and podoplanin (PDPN) expression correlated with increased immune cell infiltration. However, PDPN-positive CAFs promoted an immunosuppressive TME characterized by enrichment of regulatory T cells and M2-like macrophages, whereas CD81-high stromal cells did not exert such effects. Spatial analyses revealed that CD81-high stromal cells were preferentially localized near tumor vasculature and CCL19-expressing cells, suggesting a potential association with T-cell recruitment into the TME through CCL19-mediated mechanisms. These findings identify stromal CD81 expression as a novel prognostic marker in invasive breast cancer and highlight its association with a tumor-suppressive immune microenvironment, distinct from the immunosuppressive phenotype typically associated with PDPN-positive CAFs.
BACKGROUND: Despite established guidelines, women with breast cancer often experience complex care pathways. This study explored the lived experiences of treatment and service utilisation pathways for women living with and beyond breast cancer in Australia. We mapped real-world treatment journeys against optimal care pathway guidelines to identify specific gaps and improvement opportunities for healthcare delivery. METHODS: Women at least two years post initial diagnosis participated in semi-structured focus groups organised by cancer typology: non-metastatic, de novo metastatic, recurrent non-metastatic, and recurrent metastatic. Participants (n = 32) described their complete cancer care trajectories, including treatments received and services accessed. Framework analysis identified distinct care phases, compared experiences to guideline recommendations, and revealed nuanced experiences. RESULTS: Analysis revealed five critical phases in breast cancer care: initial diagnosis and treatment planning, initial treatment, post-treatment care management and recovery, managing recurrent and progressive disease, and end-of-life care. Within these phases, 13 sub-phases showed consistent gaps between guidelines and patient experiences. Key challenges included poor care coordination and access, delayed diagnoses and navigation challenges in metastatic cases, poor tolerance of ongoing systemic therapy, and unmet end-of-life planning needs. CONCLUSIONS: This study reveals complex longitudinal pathways in breast cancer care and highlights the distinct challenges women face at different phases. Findings demonstrate differences across non-metastatic and metastatic patients, and between primary and recurrent cases. Many participants experienced fragmented care, despite established guidelines. Continuity gaps across care phases suggest survivors may benefit from more tailored phase-specific support services. To improve care delivery, healthcare providers should develop targeted resources for each care phase, implement structured care transition protocols, and create specialised support programs that address the unique challenges within different survivor groups. These findings provide specific targets for healthcare systems to enhance cancer care continuity and reduce fragmentation in real-world practice.
BACKGROUND: Mechanical memory has recently emerged as an important concept in tumor mechanobiology, reflecting the ability of cancer cells to retain and integrate past mechanical cues to guide future behaviors. However, a systematic definition of mechanical memory–related genes and their functional implications across cancers remains lacking. METHODS: We curated literature-supported mechanotransduction and mechanical memory pathways to construct a 79-gene Mechanical Memory Signature (MMS). MMS expression patterns and prognostic relevance were evaluated across 32 cancer types using TCGA datasets, followed by focused analyses in breast cancer. Single-cell RNA sequencing datasets containing primary and liver metastatic hormone receptor–positive (HR+) breast cancer cells were used to assess MMS activity at single-cell resolution. Pseudotime and transcriptional regulatory analyses were performed to define MMS-associated cellular states. A three-dimensional stiffness-tuned collagen mechanical memory model was employed for experimental validation. RESULTS: MMS expression was broadly elevated in aggressive tumors and predicted unfavorable survival outcomes, with the strongest association observed in breast cancer. Single-cell integration revealed MMS-high tumor cell clusters exhibiting a progressive rise in MMS activity along pseudotime, suggesting acquisition and persistence of mechanical memory during metastatic evolution. Within these clusters, RELA was identified as a central transcriptional node strongly correlated with MMS activity and linked to cytoskeletal remodeling and ECM-regulatory genes, including PFN1, CFL1, RHOA, TIMP1, and MMP14. In 3D collagen cultures, matrix stiffening markedly increased RELA and MMP14 expression, while pharmacological activation of the RELA–RhoA axis further amplified this effect even under soft matrix conditions. CONCLUSION: Our study revealed RELA as a key mediator of mechanical memory–driven metastatic behavior in ER+ breast cancer, providing a mechanistic framework and actionable targets for understanding and potentially disrupting mechanically informed tumor progression.
Lymph node metastasis marks a clinically and biologically important transition in breast cancer, reflecting more aggressive disease and increased risk of recurrence. Expression of the Notch ligand JAG1 is linked to poor breast cancer outcomes, but its role in lymphatic dissemination is unclear. Tumor microarray analysis with multiplex staining was performed on synchronous breast and lymph node metastases from node-positive patients to quantify JAG1 expression and correlate findings with clinical outcomes. Orthotopic implantation of human and murine breast cancer cells was used to assess the impact of JAG1 expression on lymphovascular invasion and lymph node metastasis in vivo. The contribution of VEGFR3 signaling to JAG1-mediated lymphatic dissemination was evaluated using a soluble VEGFR3 antagonist. The cell-specific response of lymphatic endothelial cells to JAG1 was assessed by transendothelial migration assays, barrier examination, and sequencing. Mammary tumor cells expressing JAG1 demonstrated increased lymphovascular and lymph node metastasis in mouse models. Inhibition with a soluble VEGFR3 antagonist attenuated JAG1-dependent lymph node metastasis. Exposure to JAG1 disrupted lymphatic endothelial barrier integrity, promoted tumor cell migration across cultured endothelium, and induced pro-inflammatory and pro-adhesion changes in lymphatic endothelial cells. Tumor microarray analyses revealed enrichment of JAG1 in metastatic tumor cells within lymph nodes relative to matched primary tumors. High JAG1 expression in lymph node metastases was significantly associated with increased risk of recurrence. These findings support a role for tumor cell JAG1 promoting lymphatic dissemination and lymph node metastasis in breast cancer through effects on lymphatic endothelial signaling and barrier function. Enrichment of JAG1 in lymph node metastases and its association with recurrence further support its potential utility as a prognostic biomarker and therapeutic target in node-positive breast cancer.
Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype that presents therapeutic challenges due to the lack of expression of biomarkers required for conventional targeted treatments. Although a subset of TNBC tumors respond to androgen receptor (AR) inhibitors, the majority exhibit low AR expression and poor outcomes. These AR-negative tumors have been subclassified as quadruple-negative breast cancer (QNBC). Notably, women of African ancestry (WAA) experience a disproportionate burden of TNBC and higher mortality compared to white women, a disparity not fully explained by socio-economic factors, thus suggesting a genetic susceptibility. The transcription factor Kaiso, previously implicated in TNBC progression and poor survival in WAA patients, may play a key role in QNBC biology. Expression profiling of TNBC tumors from WAA and white women was performed using publicly available datasets and tissue microarrays. To examine the role of Kaiso in AR regulation, we generated CRISPR-Cas9 Kaiso knockout TNBC cell lines and assessed AR expression using chromatin immunoprecipitation, immunoblotting, RT-qPCR and promoter-reporter assays. Cell viability, migration and invasion assays were used to evaluate the effect of Kaiso knockout on sensitivity to the AR inhibitor enzalutamide. High Kaiso expression combined with low AR expression correlated with poorer survival across breast cancer subtypes, including TNBC. WAA expressed significantly lower AR expression and a higher prevalence of the QNBC subtype. Kaiso associated with the endogenous AR promoter, and Kaiso knockout in TNBC cells increased AR expression while reducing ACSL4, an AR target gene that promotes metastasis through phospholipid remodeling. Notably, Kaiso knockout cells were more sensitive to enzalutamide compared to parental cells and reduced migration and invasion. Collectively, our findings implicate Kaiso as a key player in TNBC and QNBC, highlighting its potential as a druggable target for improving outcomes in these aggressive breast cancer subtypes.