Triple-negative Breast Cancer Microenvironment Research Articles

Phenanthroindolizidine Alkaloids Isolated from Tylophora ovata as Potent Inhibitors of Inflammation, Spheroid Growth, and Invasion of Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC), representing the most aggressive form of breast cancer with currently no targeted therapy available, is characterized by an inflammatory and hypoxic tumor microenvironment. To date, a broad spectrum of anti-tumor activities has been reported for phenanthroindolizidine alkaloids (PAs), however, their mode of action in TNBC remains elusive. Thus, we investigated six naturally occurring PAs extracted from the plant Tylophora ovata: O-methyltylophorinidine (1) and its five derivatives tylophorinidine (2), tylophoridicine E (3), 2-demethoxytylophorine (4), tylophoridicine D (5), and anhydrodehydrotylophorinidine (6). In comparison to natural (1) and for more-in depth studies, we also utilized a sample of synthetic O-methyltylophorinidine (1s). Our results indicate a remarkably effective blockade of nuclear factor kappa B (NFκB) within 2 h for compounds (1) and (1s) (IC50 = 17.1 ± 2.0 nM and 3.3 ± 0.2 nM) that is different from its effect on cell viability within 24 h (IC50 = 13.6 ± 0.4 nM and 4.2 ± 1 nM). Furthermore, NFκB inhibition data for the additional five analogues indicate a structure–activity relationship (SAR). Mechanistically, NFκB is significantly blocked through the stabilization of its inhibitor protein kappa B alpha (IκBα) under normoxic as well as hypoxic conditions. To better mimic the TNBC microenvironment in vitro, we established a 3D co-culture by combining the human TNBC cell line MDA-MB-231 with primary murine cancer-associated fibroblasts (CAF) and type I collagen. Compound (1) demonstrates superiority against the therapeutic gold standard paclitaxel by diminishing spheroid growth by 40% at 100 nM. The anti-proliferative effect of (1s) is distinct from paclitaxel in that it arrests the cell cycle at the G0/G1 state, thereby mediating a time-dependent delay in cell cycle progression. Furthermore, (1s) inhibited invasion of TNBC monoculture spheroids into a matrigel®-based environment at 10 nM. In conclusion, PAs serve as promising agents with presumably multiple target sites to combat inflammatory and hypoxia-driven cancer, such as TNBC, with a different mode of action than the currently applied chemotherapeutic drugs.

Identification of m6A modification patterns and development of m6A-hypoxia prognostic signature to characterize tumor microenvironment in triple-negative breast cancer.

BackgroundN6-methylation (m6A) modification of RNA has been found to have essential effects on aspects of the tumor microenvironment (TME) including hypoxia status and mobilization of immune cells. However, there are no studies to explore the combined effect of m6A modification and hypoxia on molecular heterogeneity and TME of triple-negative breast cancer (TNBC).MethodsWe collected The Cancer Genome Atlas (TCGA-TNBC, N=139), the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC-TNBC, N=297), the GSE103091, GSE21653, and GSE135565 series from the Gene Expression Omnibus (GEO-TNBC, N=247), and FUSCCTNBC (N=245) for our study. The non-negative matrix factorization algorithm was used to cluster TNBC samples. Immune cell infiltration was analyzed by the CIBERSORT algorithm. The enrichment scores were calculated by single-sample gene set enrichment analysis(ssGSEA) to characterize TME in TNBC samples. Immunohistochemistry (IHC) and qRT-PCR were performed to detect the gene expression.ResultsBased on the expression of m6A-related genes, we identified three distinct m6A clusters (denoted A, B, and C) in TNBC samples. Comparing the TME characteristics among the three clusters, we observed that cluster C was strongly related to hypoxia status and immune suppression, whereas clusters A and B displayed more immune cell infiltration. Therefore, we combine m6A and hypoxia related genes to classify two m6A-hypoxia clusters of TNBC and screened six prognostic genes by LASSO-Cox regression to construct a m6A-hypoxia signature(MHPS), which divided TNBC samples into high- and low-risk groups. We identified different TME features, immune cell infiltration between the two groups, and a better immunotherapy response was observed in the low-risk group. A nomogram was constructed with tumor size, lymph node, and risk score to improve clinical application of MHPS.ConclusionWe identified distinct TME characteristics of TNBC based on three different m6A modification patterns. Then, we constructed a specific m6A–hypoxia signature for TNBC to evaluate risk and predict immunotherapy response of patients, to enable more accurate treatment in the future.

Integrating Immunotherapy Into the Treatment Landscape for Patients With Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is the most aggressive histologic subtype of breast cancer for which, until recently, treatment options have been limited to chemotherapy. In recent years, an improved understanding of the importance of tumor-infiltrating lymphocytes and the tumor microenvironment in TNBC has led to investigation of immune checkpoint inhibitors for treatment. There is now evidence from several randomized controlled trials that supports the addition of immune checkpoint inhibitors to first-line treatment of advanced TNBC and to neoadjuvant chemotherapy for stage II-III TNBC. In parallel, the PARP inhibitors have emerged as a targeted therapy option for patients with HER2-negative breast cancer harboring mutations in BRCA1, BRCA2, and PALB2. Here, we review the recent clinical trials that inform the integration of immune checkpoint inhibitors into treatments for TNBC and discuss ongoing challenges-including patient selection, management of resistance to post-checkpoint inhibitor therapy, and combining immunotherapy with targeted therapies, including PARP inhibitors.

In vivo multidimensional CRISPR screens identify Lgals2 as an immunotherapy target in triple-negative breast cancer.

Immune checkpoint inhibitors exhibit limited response rates in patients with triple-negative breast cancer (TNBC), suggesting that additional immune escape mechanisms may exist. Here, we performed two-step customized in vivo CRISPR screens targeting disease-related immune genes using different mouse models with multidimensional immune-deficiency characteristics. In vivo screens characterized gene functions in the different tumor microenvironments and recovered canonical immunotherapy targets such as Ido1. In addition, functional screening and transcriptomic analysis identified Lgals2 as a candidate regulator in TNBC involving immune escape. Mechanistic studies demonstrated that tumor cell–intrinsic Lgals2 induced the increased number of tumor-associated macrophages, as well as the M2-like polarization and proliferation of macrophages through the CSF1/CSF1R axis, which resulted in the immunosuppressive nature of the TNBC microenvironment. Blockade of LGALS2 using an inhibitory antibody successfully arrested tumor growth and reversed the immune suppression. Collectively, our results provide a theoretical basis for LGALS2 as a potential immunotherapy target in TNBC.

Mapping the Tumor Microenvironment in TNBC and Deep Exploration for M1 Macrophages-Associated Prognostic Genes.

Triple negative breast cancer (TNBC) remains the worst molecular subtype due to high heterogeneity and lack of effective therapeutic targets. Here we investigated the tumor and immune microenvironment heterogeneity of TNBC using scRNA-seq and bulk RNA-seq data from public databases and our cohort. Macrophage subpopulations accounted for a high proportion of tumor immune microenvironment (TIME), and M1 macrophages were associated with better clinical outcomes. Furthermore, three maker genes including IFI35, PSMB9, and SAMD9L showed a close connection with M1 macrophages. Specifically, IFI35 was positively associated with macrophage activation, chemotaxis, and migration. Also, patients with high IFI35 expression had a better prognosis. In vitro studies subsequently demonstrated that IFI35 was upregulated during the M1 subtype differentiation of macrophages. In summary, our data suggested that IFI35 maybe a promising novel target that helps to reshape macrophage polarization towards the M1 subtype for anti-tumor effects.

Abstract 6000: A millifluidic culture platform for quantifying premetastatic niche cultivation in quiescent organ stroma induced by real-time transport of tumor-derived factors

Abstract Progression to metastasis contributes to the poor overall survival of patients diagnosed with aggressive cancers such as triple negative breast cancer (TNBC). Tumor-derived factors (TDF) induce pathological changes in distant organ niches that render these organs more receptive to colonization by disseminated tumor cells. This process, termed premetastatic niche (PMN) cultivation, is characterized in part by pathological activation of stromal cells and induction acute extracellular matrix (ECM) deposition. There is an urgent and unmet need for models of PMN cultivation in human cancers to accelerate the discovery of mechanisms and develop PMN-targeting therapies. We engineered 3D culture models of aggressive carcinoma and quiescent organ interstitium and integrated them in a millifluidic device that enables interconnected coculture. Our devices are engineered for ease of adoption by labs with experience culturing cells and organoids in 3D hydrogels. Cultures can be performed in static, with continuous gravity-driven flow, or with a rocker for recirculating flow. Here we present a form of the model in which a patient-derived triple negative breast cancer microenvironment is linked with a quiescent lung interstitium. Fibroblast activation and ECM synthesis indicative of PMN cultivation are quantified relative to a physiological resting state. All device cultures were maintained with fibroblast growth medium containing 0.1% FBS and 1% ITS which maintains the lung compartment in a quiescent state in the absence of endogenous activating factors in the system. The TME compartment in our devices exhibited features of aggressive cancers after 7 days of culture including widespread 3D invasion of tumor cells and formation of a dense stroma comprised of myofibroblast-like CAF with prominent smooth muscle actin (SMA) cytoskeleton and nuclear translocation of activated Yes-associated protein 1 (aYAP1). These cellular features of the engineered tumor microenvironment were accompanied by a dense anisotropic matrix of newly-synthesized fibronectin. TNBC-derived factors transported in the system induced PMN cultivation in the lung compartment by 7 days, as evidenced by quantitative increases in focal deposition of fibronectin and a spectrum of activated phenotypes defined by SMA and aYAP1 expression patterns in previously quiescent fibroblasts. Thus, we have captured cancer-induced changes in the density and architecture of newly-synthesized ECM in a distant tissue that would support tumor cell adhesion. Citation Format: Elisabet A. Olsen, Omar M. Ahmad, Bradley Sweeney, Caroline C. Culp, Yasmin V. Maurice, Matthew R. Burow, Mark Mondrinos. A millifluidic culture platform for quantifying premetastatic niche cultivation in quiescent organ stroma induced by real-time transport of tumor-derived factors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6000.

Liver Kinase B1 Regulates Remodeling of the Tumor Microenvironment in Triple-Negative Breast Cancer.

Liver kinase B1 (LKB1) is a potent tumor suppressor that regulates cellular energy balance and metabolism as an upstream kinase of the AMP-activated protein kinase (AMPK) pathway. LKB1 regulates cancer cell invasion and metastasis in multiple cancer types, including breast cancer. In this study, we evaluated LKB1’s role as a regulator of the tumor microenvironment (TME). This was achieved by seeding the MDA-MB-231-LKB1 overexpressing cell line onto adipose and tumor scaffolds, followed by the evaluation of tumor matrix-induced tumorigenesis and metastasis. Results demonstrated that the presence of tumor matrix enhanced tumorigenesis in both MDA-MB-231 and MDA-MB-231-LKB1 cell lines. Metastasis was increased in both MDA-MB-231 and -LKB1 cells seeded on the tumor scaffold. Endpoint analysis of tumor and adipose scaffolds revealed LKB1-mediated tumor microenvironment remodeling as evident through altered matrix protein production. The proteomic analysis determined that LKB1 overexpression preferentially decreased all major and minor fibril collagens (collagens I, III, V, and XI). In addition, proteins observed to be absent in tumor scaffolds in the LKB1 overexpressing cell line included those associated with the adipose matrix (COL6A2) and regulators of adipogenesis (IL17RB and IGFBP4), suggesting a role for LKB1 in tumor-mediated adipogenesis. Histological analysis of MDA-MB-231-LKB1-seeded tumors demonstrated decreased total fibril collagen and indicated decreased stromal cell presence. In accordance with this, in vitro condition medium studies demonstrated that the MDA-MB-231-LKB1 secretome inhibited adipogenesis of adipose-derived stem cells. Taken together, these data demonstrate a role for LKB1 in regulating the tumor microenvironment through fibril matrix remodeling and suppression of adipogenesis.

Pilot study with [18F]DPA-714 PET-CT to explore tumor-associated-macrophages in triple negative breast cancer.

e12557 Background: Triple-negative breast cancer (TNBC) tends to exhibit aggressive behavior lacking from targeted therapies. Tumor-associated-macrophages (TAMs as M2 and M1 macrophages) are interest targets in TNBC to approach the tumor patient immunity. The mitochondrial translocator protein (TSPO), a sensitive marker for macrophages, could be interesting for TNBC micro-environment stratification. We performed a multicenter imaging pilot study (NCT04320030) using non-invasive [18F]DPA-714 (DPA), a TSPO PET radioligand, aiming at assessing immunity to define the immunotherapy possibilities in TNBC patients. Methods: All patients underwent TSPO genotyping (LAB: Low Affinity Binder, MAB: Mixed and HAB: High), [18F]FDG (FDG) and DPA PET-CT, macrophages immunochemistry and in vitro TSPO autoradiography using both tritiated PK11195 (PK) and DPA. Thorax PET-CT was acquired just after injection (DPA1) to 30 min, then from 45 min (DPA2) to 60 min, followed by a whole body PET-CT. Groups of interest (Macrophages immunochemistry and Genotype) were compared using Kruskal-Wallis test. Correlation between continuous parameters were determined using Spearman’s Rho. Results: A total of 13 TNBC patients were included. No adverse events occurred after DPA injection. For TSPO genotyping, 2/13 (15.5%) patients were LAB, 6/13 (46%) MAB and 5/13 (38.5%) HAB. All of them showed FDG and DPA uptake regardless of the patient's genotype without significant difference between the 3 groups. The DPA kinetics showed a tracer accumulation between DPA1 and DPA2, whatever patient genotypes, observed on SUVmax (p = 0.0015), SUVmean (p = 0.0015) and TL-DPA (p = 0.0024). A correlation between FDG and DPA1 either DPA2 tumor volume was shown, respectively (p = 0.0252 and 0.0067) as well as between the TLG (FDG) and the TL-DPA1 (p = 0.0346) regardless of the patient's genotype. Macrophages immunochemistry showed a tendency difference for M2 percentage (p = 0.09) between the 3 genotypes groups. In vitro binding ratio (PK/DPA), measured for both radioligands, on adjacent tumor slices, was 1.77 (1.35-2.21). A difference in this binding ratio was observed between MAB and HAB (Mean 1.68±0.36) compared to LAB 3.04±0.23 (p = 0.0367), suggesting that DPA binding is sensitive to TSPO genotype, unlike PK binding. Conclusions: Despite the limited population, all TNBC tumor patients were DPA positive with an accumulation over time. The total glycolysis and total DPA uptake in the tumor were correlated, which may link tumor aggressiveness and DPA uptake. These data were confirmed by a better sensitivity for HAB and MAB vs LAB. DPA seemed to be a promising tracer to explore non-invasively TNBC patient’s immunity. Clinical trial information: NCT04320030.

Tumor-associated macrophages of the M1/M2 phenotype are involved in the regulation of malignant biological behavior of breast cancer cells through the EMT pathway.

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. More and more studies have shown that the tumor immune microenvironment (TME) of TNBC is closely related to its poor prognosis and early metastasis. We try to explain how tumor-associate macrophages (TAMs), an important component of the TME, function in the matrix of TNBC. Therefore, we induced THP-1 cells to become M1-TAMs and M2-TAMs, investigated their influence on breast cancer cells. 82 TNBC paraffin samples were made into tissue microarrays. The expression of macrophages makers were measured by immunohistochemistry. Scratch assay, Transwell assay, CCK-8 cell proliferation assay were performed in the co-culture system of breast cancer cells lines and macrophages to observe the invasion and proliferation ability of breast cancer cell lines. Western Blot (WB) was performed to detect the expression of E-cadherin (CDH1) and N-cadherin (CDH2). M2-TAMs were more numerous than M1-TAMs in the matrix of TNBC cancer nests and associated with poor prognosis. M2-TAMs promoted the invasion, migration, and proliferation of TNBC cells. M1-TAMs had inhibitory effects. In MCF-7 cells, WB showed a decrease in CDH1 and an increase in CDH2. In MDA-MB-231 cells and BT549 cells, CDH2 expression was reduced and CDH1 expression was increased. All of the above results were statistically significant, p < 0.001. M2-TAMs were more numerous in TNBC and associated with poor prognosis. M2-TAMs promoted the invasion, migration, and proliferation of breast cancer cells. The mechanism may be related to the epithelial-mesenchymal transition.

Establishment of a Cell Necroptosis Index to Predict Prognosis and Drug Sensitivity for Patients With Triple-Negative Breast Cancer.

Background: Necroptosis has been an alternatively identified mechanism of programmed cancer cell death, which plays a significant role in cancer. However, research about necroptosis-related long noncoding RNAs (lncRNAs) in cancer are still few. Moreover, the potentially prognostic value of necroptosis-related lncRNAs and their correlation with the immune microenvironment remains unclear. The present study aimed to explore the potential prognostic value of necroptosis-related lncRNAs and their relationship to immune microenvironment in triple-negative breast cancer (TNBC). Methods: The RNA expression matrix of patients with TNBC was obtained from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases. Finally, 107 patients of GSE58812, 159 patients of TCGA, and 143 patients of GSE96058 were included. Necroptosis-related lncRNAs were screened by Cox regression and Pearson correlation analysis with necroptosis-related genes. By LASSO regression analysis, nine necroptosis-related lncRNAs were employed, and a cell necroptosis index (CNI) was established; then, we evaluated its prognostic value, clinical significance, pathways, immune infiltration, and chemotherapeutics efficacy. Results: Based on the CNI value, the TNBC patients were divided into high- and low-CNI groups, and the patients with high CNI had worse prognosis, more lymph node metastasis, and larger tumor (p < 0.05). The receiver operating characteristic (ROC) analysis showed that the signature performed well. The result of the infiltration proportion of different immune cell infiltration further explained that TNBC patients with high CNI had low immunogenicity, leading to poor therapeutic outcomes. Moreover, we found significant differences of the IC50 values of various chemotherapeutic drugs in the two CNI groups, which might provide a reference to make a personalized chemotherapy for them. Conclusion: The novel prognostic marker CNI could not only precisely predict the survival probability of patients with TNBC but also demonstrate a potential role in antitumor immunity and drug sensitivity.

Effector memory cytotoxic CD3+/CD8+/CD45RO+ T cells are predictive of good survival and a lower risk of recurrence in triple-negative breast cancer

Triple-negative breast cancer (TNBC) with high tumour-infiltrating lymphocytes (TILs) has been associated with a promising prognosis. To better understand the prognostic value of immune cell subtypes in TNBC, we characterised TILs and the interaction between tumour cells and immune cell subtypes. A total of 145 breast cancer tissues were stained by multiplex immunofluorescence (mIF), including panel 1 (PD-L1, PD-1, CD3, CD8, CD68 and CK) and panel 2 (Foxp3, Granzyme B, CD45RO, CD3, CD8 and CK). Phenotypes were analysed and quantified by pathologists using InForm software. We found that in the ER-negative (ER <1% and HER2-negative) group and the ER/PR-low positive (ER 1–9% and HER2-negative) group, 11.2% and 7.1% of patients were PD-L1+ by the tumour cell score, 29.0% and 28.6% were PD-L1+ by the modified immune cell score and 30.8% and 32.1% were PD-L1+ by the combined positive score. We combined ER-negative and ER/PR-low positive cases for the survival analysis since a 10% cut-off is often used in clinical practice for therapeutic purposes. The densities of PD-L1+ tumour cells (HR: 0.366, 95% CI: 0.138–0.970; p = 0.043) within the tumour compartment and CD3+ immune cells in the total area (tumour and stromal compartments combined) (HR: 0.213, 95% CI: 0.070–0.642; p = 0.006) were favourable prognostic biomarkers for overall survival (OS) in TNBC. The density of effector/memory cytotoxic T cells (CD3+CD8+CD45RO+) in the tumour compartment was an independent prognostic biomarker for OS (HR: 0.232, 95% CI: 0.086–0.628; p = 0.004) and DFS (HR: 0.183, 95% CI: 0.1301–0.744; p = 0.009) in TNBC. Interestingly, spatial data suggested that patients with a higher density of PD-L1+ tumour cells had shorter cell-cell distances from tumour cells to cytotoxic T cells (p < 0.01). In conclusion, we found that phenotyping tumour immune cells by mIF is highly informative in understanding the immune microenvironment in TNBC. PD-L1+ tumour cells, total T cells and effector/memory cytotoxic T cells are promising prognostic biomarkers in TNBC.

Development of an immune-related prognostic biomarker for triple-negative breast cancer

Purpose: Oncology studies employing digital dissection methodologies have provided some insight on the biological features of tumor microenvironment of Triple-negative breast cancer (TNBC), but molecular diagnostics rarely have therapeutic impact. We aimed to identify a novel prognostic biomarker to investigate immune characteristics of TNBC using transcriptomic features. Patients and Methods: We extracted whole transcriptome from breast cancer tissue of 30 TNBC patients and then used bioinformatics approaches to characterize the different immune cell contents in tumor tissue and para-cancerous tissue. We extract 2 indicators to describe the major differences in immune infiltration in the microenvironment between tumor tissue and para-cancerous tissue. We then combined the 2 indicators that represent the levels of increased and decreased infiltration in each sample to obtain the Immune Infiltration Score (IIS). Then we compared the tumor-infiltrating immune cell contents and immune infiltrating status in TNBC samples with CIBERSORT and ESTIMATE score to validate the IIS. Finally, 132 TNBC patients from the Cancer Genome Atlas program (TCGA) dataset was used to validate the predictive power of IIS. Results: 4 types of upregulated and 4 types of downregulated immune cells were identified in the tumor tissue samples of the TNBC patients. Then we developed a novel biomarker, IIS. Results showed that IIS score can clearly separate cancer and para-cancerous tissue. Using the same cutoff value of 0 in the TNBC-TCGA cohort, we show that those patients with a higher IIS had significantly higher PD-L1 expression and shorter progression-free survival time than those with a lower IIS value, indicating IIS score can be generalized to other TNBC datasets. Conclusion: we explored the immune infiltration landscape in 30 TNBC patients and provided IIS as a novel and reliable biomarker to evaluate the progression-free survival and prognosis of the TNBC patients.

Identification of Cancer-Associated Fibroblast Subtype of Triple-Negative Breast Cancer

Background There is limited knowledge about the role of cancer-associated fibroblasts (CAF) in the tumor microenvironment of triple-negative breast cancer (TNBC). Methods Three hundred and thirty-five TNBC samples from four datasets were retrieved and analyzed. In order to determine the CAF subtype by combining gene expression profiles, an unsupervised clustering analysis was adopted. The prognosis, enriched pathways, immune cells, immune scores, and tumor purity were compared between CAF subtypes. The genes with the highest importance were selected by bioinformatics analysis. The machine learning model was built to predict the TNBC CAF subtype by these selected genes. Results TNBC samples were classified into two CAF subtypes (CAF+ and CAF-). The CAF- subtype of TNBC was linked to the longer overall survival and more immune cells than the CAF+ subtype. CAF- and CAF+ were enriched in immune-related pathways and extracellular matrix pathways, respectively. Bioinformatics analysis identified 9 CAF subtype-related markers (ADAMTS12, AEBP1, COL10A1, COL11A1, CXCL11, CXCR6, EDNRA, EPPK1, and WNT7B). We constructed a robust random forest model using these 9 genes, and the area under the curve (AUC) value of the model was 0.921. Conclusion The current study identified CAF subtypes based on gene expression profiles and found that CAF subtypes have significantly different overall survival, immune cells, and immunotherapy response rates.

Integrated multi-cohorts for characterizing the immunogenomic landscape and predicting drug response in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the breast cancer subtype with the highest fatality rate, and it seriously threatens women's health. Recent studies found that the level of immune cell infiltration in TNBC was associated with tumor progression and prognosis. However, due to practical constraints, most of these TNBC immune infiltration studies only used a small number of patient samples and a few immune cell types. Therefore, it is necessary to integrate more TNBC patient samples and immune cell types to comprehensively study immune infiltration in TNBC to contribute to the prognosis and treatment of patients. In this study, 12 TNBC datasets were integrated and an extensive collection of 182 gene sets with immune-related signatures were included to comprehensively investigate tumor immune microenvironment of TNBC. A single sample gene set enrichment analysis was performed to calculate the infiltration score of each immune-related signature in each patient, and an immune-related risk scoring model for TNBC was constructed to accurately assess patient prognosis. Significant differences were found in immunogenomic landscape between different immune risk subtypes. In addition, the immunotherapy response and chemotherapy drug sensitivity of patients with different immune risk subtypes were also analyzed. The results showed that there were significant differences in these characteristics. Finally, a prediction model for immune risk subtypes of TNBC patients was constructed to accurately predict patients with unknown subtypes. Based on the aforementioned findings, we believed that the immune-related risk score constructed in this study can assist in providing personalized medicine to TNBC patients.

Abstract ES5-2: Optimizing the management of early stage TNBC

Abstract The recent approvals of the immunotherapeutic agent pembrolizumab, the antibody-drug conjugate sacituzumab govitecan and the PARP inhibitors olaparib and talazoparib for select patients with metastatic triple negative breast cancer (TNBC) have spurred interest in evaluating these and other novel agents in patients with earlier stage disease. For the last several decades, a standard approach to treating early stage TNBC was to administer neoadjuvant chemotherapy, most often an anthracycline/taxane-based regimen. Pathologic complete response (pCR) rates generally ranged 30-40%. Trials such as CALGB 40603, GeparSixto and BrighTNess demonstrated that the addition of carboplatin to an anthracycline and taxane based chemotherapy could increase the pCR rates (53-58%). At the most recent ESMO conference, the BrighTNess investigators reported that the addition of carboplatin improved event free survival (EFS) after a median follow-up of 4.5 years. For patients not experiencing a pCR, the Create-X trial showed benefit of capecitabine in the adjuvant setting.As of August 2021, there is a new standard for treating early stage TNBC. Specifically, based on the KEYNOTE-522 trial, pembrolizumab, in combination with chemotherapy, is FDA approved for this indication. KEYNOTE-522 enrolled over 1170 stage 2-3 TNBC patients and randomized them to chemotherapy +/- pembrolizumab. The most recent report showed the trial met it’s co-primary endpoints of improved pCR (63% vs 56%) and EFS (84.5% vs 76.8%) after a median follow-up of 39 months. Importantly, the benefit was regardless of the PD-L1 status of the patient’s tumor. With the approval of pembrolizumab comes a number of questions: 1) which patients should receive this regimen which is associated with immune-related toxicities, some of which are lifelong, 2) what is the optimal chemotherapy backbone, 3) is a full year of pembrolizumab required and 4) are there other biomarkers to be explored that may predict response to therapy or the development of toxicity? Other studies either have or are evaluating other targeted agents in the preoperative setting for early stage TNBC. In a small study of 20 BRCA mutation carriers treated preoperatively with single agent talazoparib, investigators reported a pCR rate of 53%. A study looking at sacituzumab monotherapy in the preoperative setting has completed accrual and the results are awaited. These two trials begin to address the question of whether we can identify an “achilles” heel in TNBC and if so, will targeting it improve patient outcomes. Good correlative studies that provide improved understanding of the impact of these therapies on the TNBC microenvironment will help inform the next generation of trials; likely combination therapies.There is also the question of adjuvant therapy, particularly for those that do not experience a pCR with preoperative therapy. As stated above, the CREATE-X trial supports the use of capecitabine in patients with residual disease, however EA1131 demonstrated that outcomes are still poor for this population. More recently, for patients with BRCA-mutated cancers, the OlympiA trial showed benefit to a year of adjuvant olaparib. There is also growing interest in whether patients with residual disease who are at highest risk for recurrence can be identified using technologies looking for cell-free DNA to find those with minimal residual disease. Historically we’ve thought about TNBC for what it’s not – it is not ER, PR or HER2 positive. With multiple studies now showing benefit of specific agents in TNBC, the next several years will provide an opportunity to more extensively dissect triple negative tumors and their. microenvironment. This will allow us to learn what TNBC “is”, and which of likely multiple different therapeutic strategies will be best applied to which patients. Citation Format: E Mittendorf. Optimizing the management of early stage TNBC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES5-2.

Abstract P5-08-04: LMP7-specific inhibitor M3258 modulates the tumor microenvironment of aggressive breast cancer

Abstract Background: LMP7 (beta5i/PSMB8) is a proteolytic subunit of the immunoproteasome that is predominantly expressed in leukocytes and inflamed tissues. The immunoproteasome degrades ubiquitinated proteins for maintenance of cell homeostasis and generation of peptides for MHC class I presentation. LMP7 has been implicated in multiple myeloma, autoimmune and inflammatory diseases, and inflammation-related cancers. Here, we evaluated the effect of M3258, an orally bioavailable, highly-selective, and reversible inhibitor of LMP7, on the tumor microenvironment (TME) using in vitro and in vivo models of triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC). Methods: The proteolytic activity of M3258 was determined using the fluorogenic LMP7-specific peptidic substrate (Ac-ANW)2R110. Its anti-proliferation activity was determined using the CellTiter-Blue cell viability and sulforhodamine B staining assays. Expression of immunoproteasome subunits under different conditions was examined by Western blotting. All in vitro assessments were done with or without IFNγ, which is known to increase immunoproteasome expression. The in vivo anti-tumor efficacy of M3258 was evaluated using a SUM-149 PT TN-IBC xenograft mouse model implanted in humanized mice. Single-cell RNA sequencing (scRNA-seq) was used in this same study to examine the impact of M3258 on the TME. Results: M3258 inhibited LMP7 activity (IC50 = 6.5-212.8 nM) and had no effects on LMP7 protein expression in a panel of TNBC cells (DU4475, HCC1187), IBC cells (SUM190, IBC3, KPL4), and TN-IBC cells (SUM-149 PT, BCX-010, FC-IBC02). M3258 inhibited proliferation of TNBC and IBC cell lines in vitro (IC50 = 1-20 µM). In keeping with previous reports, IFNγ treatment strongly induced LMP7 expression and enhanced its proteolytic activity in these cell lines in vitro and increased M3258 sensitivity (2- to 5-fold). In the humanized SUM-149 PT xenograft mouse model, M3258 orally administered at 10 mg/kg significantly inhibited tumor growth versus vehicle (31.4%, P &amp;lt; 0.01) and was tolerated. ScRNA-seq analysis of the terminal tumor samples from this study revealed that M3258 reduced the abundance of CD4+ and CD8+ T cells, Tregs, M1 and M2 macrophages, and dendritic cells. Gene expression profiling indicated a particularly pronounced inhibitory effect of M3258 on M1 and M2 macrophages. Furthermore, M3258 treatment activated CD8+ T cells and suppressed expression of genes involved in inflammatory response, IFNα signaling, IFNγ signaling, and TNFα signaling in immune cells. In light of the scRNA-seq findings, we assessed the impact of M1 and M2 macrophages on the invasiveness of TN-IBC cells in vitro. Co-cultures with M1 or M2 macrophages enhanced invasiveness of SUM-149 PT cells (4.6-fold by M1, P &amp;lt; 0.001; 6.3-fold by M2, P &amp;lt; 0.01) and BCX-010 cells (2.1-fold by M1, P &amp;lt; 0.05; 4.0-fold by M2, P &amp;lt; 0.01). Since M2 macrophages showed a superior effect than M1 macrophages on TN-IBC cell invasiveness, we further assessed M3258’s ability to inhibit such activity. M3258 at 500 nM significantly inhibited M2 macrophage-induced invasion of SUM-149 PT cells (29.6%, P &amp;lt; 0.05) and BCX-010 (49.5%, P &amp;lt; 0.01). Conclusion: Using the exquisitely selective LMP7 inhibitor M3258, we were able to demonstrate for the first time that LMP7 plays an important role in the inflammatory microenvironment, proliferation and invasiveness of TNBC and IBC cells, in particular by modulating the pathogenic role of M2 macrophages. These data warrant future in vivo studies into the antitumor efficacy of M3258 when used with immunotherapy agents. Citation Format: Xuemei Xie, Jangsoon Lee, Ganiraju C Manyam, Troy Pearson, Gina Walter-Bausch, Manja Friese-Hamim, Samantha M Goodstal, Debu Tripathy, Wang Jing, Michael Sanderson, Naoto T Ueno. LMP7-specific inhibitor M3258 modulates the tumor microenvironment of aggressive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-08-04.

Abstract PD3-08: Novel cancer stem cell inhibitor 108600 modulates tumor immunomicroenvironment of triple negative breast cancer (TNBC)

Abstract 108600, a novel CK2/DYRK1/TNIK inhibitor, targets and inhibits cancer stem cells (CSC) in triple negative breast cancer (TNBC), inhibiting tumor growth and metastases in patient-derived xenograft models. CSC’s have been shown to promote immune evasion of several types of cancer. Specifically, over-expression of CK2 has been shown to promote intratumoral recruitment of myeloid derived suppressor cells. We investigated the effects of 108600 treatment on the immune microenvironment of triple negative breast cancer since targeting CSC’s could promote favorable anti-tumor immune responses and mechanistically contribute to tumor growth inhibition. Methods:C57BL/6 mice bearing murine triple negative E0771 tumors were generated by orthotopic injection and treated either with vehicle control or 108600 for 5 days. Tumor growth was assessed by daily caliper measurement All tumors were recovered at endpoint, and processed for RNA sequencing, flow cytometry or Western blot analysis. Results:108600 treatment significantly inhibited growth of E0771 tumors in vivo, demonstrating for the first time efficacy of 108600 against TNBC in immunocompetent models. 108600 treatment decreased intratumoral phosphorylation and expression of 108600 targets AKT1 (Ser 129) and Cyclin D1, which are substrates of CK2α and Dyrk1, respectively. To further explore nature of transcriptional and signaling pathways affected by 108600 treatment in vivo, RNA sequencing was performed. DGE and subsequent annotation analysis showed that various immune (GO:0006955, GO) and inflammatory (GO:0006954, GO) signaling pathways associated with Stat1 (mmu04062, KEGG) and IFNγ (mmu04060, KEGG) were down-regulated in 108600-treated E0771 tumors. GSEA (Gene set enrichment analysis) indicated that the regulatory T cell (Treg) population (GSE42021, GSE40685) was suppressed by 108600 treatment. To validate these findings, tumor infiltrating leukocytes (TIL) were isolated from vehicle or 108600-treated tumors and analyzed by flow cytometry. CD4, CD25, and FOXP3 expression was used to gate the Treg population. The Treg population was significantly suppressed by 108600 treatment, confirming the RNA sequencing results. 108600 also likely regulates expression of immunomodulatory molecules in TNBC tumor cells since 108600 treatment increased PD-L1 surface expression on E0771 cells in vitro. Conclusions:Our study supports 108600, an inhibitor that targets breast cancer stem cells, as a modulator of the immune microenvironment of TNBC. 108600 suppresses the Treg population among the TIL population and increases tumoral expression of PD-L1. Tregs have been associated with disease progression and metastases of TNBC. Further studies are ongoing to clarify the functional consequences of these changes in the setting of tumor growth inhibition. Synergies between 108600 and checkpoint inhibition are also under investigation and could lead to novel combination therapies for TNBC. Citation Format: Katsutoshi Sato, Stacey J. Baker, E. P. Reddy, Hanna Y. Irie. Novel cancer stem cell inhibitor 108600 modulates tumor immunomicroenvironment of triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD3-08.

Triple-Negative Breast Cancer: A Brief Review About Epidemiology, Risk Factors, Signaling Pathways, Treatment and Role of Artificial Intelligence.

Triple-negative breast cancer (TNBC) is a kind of breast cancer that lacks estrogen, progesterone, and human epidermal growth factor receptor 2. This cancer is responsible for more than 15–20% of all breast cancers and is of particular research interest as it is therapeutically challenging mainly because of its low response to therapeutics and highly invasive nature. The non-availability of specific treatment options for TNBC is usually managed by conventional therapy, which often leads to relapse. The focus of this review is to provide up-to-date information related to TNBC epidemiology, risk factors, metastasis, different signaling pathways, and the pathways that can be blocked, immune suppressive cells of the TNBC microenvironment, current and investigation therapies, prognosis, and the role of artificial intelligence in TNBC diagnosis. The data presented in this paper may be helpful for researchers working in the field to obtain general and particular information to advance the understanding of TNBC and provide suitable disease management in the future.

The Characteristics of Tumor Microenvironment in Triple Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a special subtype of breast cancer, accounting for 10–20% of breast cancers with high intrinsic heterogeneity. Its unique immune microenvironment, including high expression of vascular endothelial growth factors, tumor infiltrating lymphocytes (TILs), tumor-associated macrophages (TAMs), and other molecules that promote the growth and migration of tumor cells, has been shown to play a dual role in the occurrence, growth, and metastasis of TNBC. Understanding the TNBC microenvironment is of great significance for the prognosis and treatment of TNBC. In this article, we describe the composition and function of immune cells in the TNBC microenvironment and summarize the major cytokine growth factors and chemokines in the TNBC microenvironment. Finally, we discuss the progress of TNBC, cytokine-induced killer cell therapy, and immune checkpoint therapy.

Assessment of programmed death-ligand 1 receptor immunohistochemical expression and its association with tumor-infiltrating lymphocytes and p53 status in triple-negative breast cancer.

Breast cancer (BC) is the second most frequent type of cancer for both sexes combined, after lung cancer. Triple-negative BC (TNBC) molecular subtype is characterized by lack of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) immunoexpression or amplification and represent 10–20% of all BC cases. The issue of the present study was to analyze the associations between programmed death-ligand 1 (PD-L1) immunoexpression and distribution of stromal tumor-infiltrating lymphocytes (stTILs) combined with clinico-morphological features of patients with TNBC. Secondly, our research evaluated PD-L1 immunoexpression as a prognostic factor and its correlation with p53 immunoexpression. Thirty cases with primary TNBC without prior neoadjuvant therapy were included in this research. stTILs were identified in all cases, most of them with low distribution (66.7%). A positive immunoreaction for PD-L1 was observed in 40% of cases. The PD-L1 immunoexpression was statistically significant associated with age, pathological tumor size, lymphovascular invasion, stTILs level, the presence of cluster of differentiation 8-positive (CD8+) TILs and p53 immunoexpression. In the present study, a positive PD-L1 immunoexpression was associated with a worse distant metastasis free survival (DMFS). We also found not only that high stTILs level were associated with a better DMFS but also that there was a statistically significant association between stTILs level and PD-L1 immunoexpression. Our results bring new insights to the fine connections between tumor microenvironment and molecular changes of TNBC. It helps us to better understand these aggressive tumors to identify the more useful biomarkers for predicting the response to adjuvant therapy and can represent a method for selecting the most suitable patients for immunotherapy.