Triple-negative Breast Cancer Brain Metastases Research Articles

Breast Cancer Brain Metastasis: A Comprehensive Review.

The mechanisms underlying breast cancer brain metastasis (BCBM) development are complex, and its clinical presentation varies depending on the number, location, and size of brain metastases. Common symptoms include headache, neurologic deficits, and seizures. Diagnosis of BCBM typically relies on neuroimaging techniques, such as magnetic resonance imaging and computed tomography scans. Local therapies, such as surgery and stereotactic radiosurgery, can be used to control tumor growth and relieve symptoms. Whole-brain radiotherapy has been a mainstay of treatment for BCBM, but its use has been associated with cognitive decline. Systemic therapy with chemotherapy and targeted agents plays an increasingly important role in the management of BCBM. Novel agents, such as human epidermal growth factor receptor 2 (HER2)-targeted therapies and tyrosine kinase inhibitors, have shown promising results in improving survival for patients with HER2-positive and triple-negative BCBM. This comprehensive review synthesizes current knowledge, clinical insights, and evolving paradigms to provide a robust understanding and roadmap for optimizing the diagnosis and management of BCBM.

Abstract PO2-20-10: Exceptional long-term disease control on pembrolizumab monotherapy in a patient with TMB-high PMS2-mutated MMR-deficient triple negative breast cancer brain metastasis

Abstract Introduction The brain is among the most common sites of breast cancer (BC) spread. Prognosis of BC brain metastasis (BCBM) differs by receptor subtype, with poorest median overall survival (OS) for triple-negative (TN) BCBM at under 5 months. Though treatment guidelines have evolved in recent years, most strategies have focused on local therapies including surgery and stereotactic radiotherapy (SRT), rather than on systemic agents. The 2020 FDA approval of pembrolizumab (pembro) for patients (pts) with metastatic high-tumor mutational burden (TMB-h, ≥ 10 mutations/megabase) solid tumors, agnostic of primary site, combined with clinical trials in melanoma reporting efficacy of immune checkpoint inhibitors (ICI) against BM, suggest a potential use of ICI for pts with TMB-h BCBM. Results of the TAPUR study supported modest therapeutic benefit of pembro for 28 pts with metastatic BC selected for TMB-h, with median OS of 30.6 weeks, but did not include pts with active BCBM. TMB-h is uncommon in BC, and further genomic signatures remain to be elucidated to identify pts with BCBM responsive to ICI. We present a remarkable case of a pt with Lynch Syndrome (LS) due to a germline PMS2 mutation, who developed TMB-h, mismatch repair (MMR)-deficient TN BCBM, and has maintained stable disease for over 6 years on pembro monotherapy. Case description A 62-y.o. woman underwent screening mammography that identified a right breast mass. Pt has a family history of a mother with uterine and pancreatic cancer, and father with bladder cancer. Biopsy confirmed invasive ductal carcinoma (IDC), grade 1 (G1), ER/PR-positive, HER2 score 0. She underwent partial mastectomy, axillary dissection, radiation, and received adjuvant anastrozole. Three years later, while still on anastrozole, she presented with a 6 cm right breast mass. Mastectomy disclosed G3, ER/PR-negative, HER2-positive (3+, Her2:CEP17 ratio 5.6) IDC. She received adjuvant chemotherapy (AC-T) and 1 year of trastuzumab. Seven years later, pt presented with headaches and word finding difficulties. MRI identified a 3.6 cm frontal mass, which biopsy revealed as TN BCBM. Systemic imaging ruled out distant metastases. Pt proceeded with SRT and exemestane (despite receptor staining ER- in case of a possible false negative result). Despite radiotherapy, pt had BCBM progression within the same year with the largest mass diameter grown to 4.8 cm. Resection (followed by SRT) identified the dominant histology as G3 TNBC. Following transition of care to our institution, germline testing revealed a pathogenic mutation in PMS2 (c943C >T). Tumor sequencing of the resected brain metastasis showed TMB of 48 and MMR deficiency. Therefore, systemic therapy with pembro monotherapy was initiated and maintained with good tolerability. Two years later, concern for progression from rising tumor markers led to addition of concurrent carboplatin/gemcitabine for 5 cycles. Imaging and tumor markers stabilized, and pt returned to pembro monotherapy. Today, 3 years later, and over 6.5 years after initial TN BCBM diagnosis, pt continues to have stable disease on pembro with an excellent performance status (ECOG 0) and no evidence of intracranial or extracranial progression. Discussion We document an exceptional case of prolonged benefit to pembro in a pt with TMB-h PMS2-mutated MMR-deficient TN BCBM. This case highlights two major pragmatic points to clinical practice; (i) the significance of germline testing in all pts with metastatic BC, and (ii) the impact of molecular testing of tumor tissue to identify rare alterations which may have dramatic effects on pt outcomes. Altogether, this case is a remarkable addition to growing evidence that TMB could be a biomarker for predicting response to ICI therapy and provides an example of ICI efficacy in the setting of BCBM. Further research on additional genomic, clinical, and pathologic features associated with ICI responsiveness is warranted for greater precision in BCBM management. Citation Format: Jaeyoon Cha, Albert Grinshpun, Lauren Buckley, Brian Alexander, Sara Tolaney, Nancy Lin. Exceptional long-term disease control on pembrolizumab monotherapy in a patient with TMB-high PMS2-mutated MMR-deficient triple negative breast cancer brain metastasis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-20-10.

256 (PB-072) Poster - Investigation of the metabolic switch in a triple-negative breast cancer brain metastasis mouse model

256 (PB-072) Poster - Investigation of the metabolic switch in a triple-negative breast cancer brain metastasis mouse model

A novel axis of circKIF4A-miR-637-STAT3 promotes brain metastasis in triple-negative breast cancer

Among patients with triple-negative breast cancer (TNBC), distant metastasis is the leading cause of death. Our previous studies have shown that TNBC progression is greatly facilitated by circKIF4A, but uncertainty remains regarding its role in TNBC brain metastasis and the molecular mechanism. In this study, we found notable upregulation of circKIF4A in TNBC cell lines and brain metastases. Inhibition of circKIF4A impaired the ability of TNBC to proliferate, migrate, and cause brain metastasis. Luciferase reporter assays confirmed that circKIF4A competed for binding to miR-637 with STAT3 3’ UTR. Western blot analysis revealed that inhibition of circKIF4A decreased STAT3 and p62 expression, while increased the LC3B-II/LC3B–I ratio and the expression of Beclin, indicating that downregulation of circKIF4A induced autophagy by competing with STAT3 for binding to miR-637. By employing a competitive endogenous RNA (ceRNA) mechanism, the circKIF4A-miR-637-STAT3 axis coordinates brain metastasis in TNBC. circKIF4A can therefore be used as a prognostic biomarker for brain metastasis in TNBC and as a therapeutic target.

2279P Glucocorticoid receptor antagonism and beta adrenergic receptor inhibition: Implications in triple-negative breast cancer brain metastasis

2279P Glucocorticoid receptor antagonism and beta adrenergic receptor inhibition: Implications in triple-negative breast cancer brain metastasis

MEF2C and miR-194-5p: New Players in Triple Negative Breast Cancer Tumorigenesis.

Among breast cancer (BC) subtypes, the most aggressive is triple negative BC (TNBC), which is prone to metastasis. We previously found that microRNA (miR)-194-5p is downregulated at the early stages of TNBC brain metastasis development. Additionally, the transcription factor myocyte enhancer factor 2 (MEF2)C, a bioinformatically predicted miR-194-5p target, was increasingly expressed throughout TNBC brain metastasis formation and disease severity. However, the contributions of these two players to malignant cells' features remain undetermined. This study aimed at disclosing the role of miR-194-5p and MEF2C in TNBC tumorigenesis. The transfection of 4T1 cells with a silencer for MEF2C or with a pre-miRNA for miR-194-5p was employed to study TNBC cells' phenotypic alterations regarding epithelial and mesenchymal markers, as well as migratory capability alterations. MEF2C-silenced cells presented a decline in both vimentin and cytokeratin expression, whereas the overexpression of miR-194-5p promoted an increase in cytokeratin and a reduction in vimentin, reflecting the acquisition of an epithelial phenotype. Both treatments reduced TNBC cells' migration. These results suggest that MEF2C may determine TNBC cells' invasive properties by partially determining the occurrence of epithelial-mesenchymal transition, while the overexpression of miR-194-5p promotes a decline in TNBC cells' aggressive behavior and reinforces this miRNA's role as a tumor suppressor in TNBC.

Upregulation of Matrix Metalloproteinases in the Metastatic Cascade of Breast Cancer to the Brain.

In patients with triple-negative breast cancer (TNBC), brain metastasis is a fatal consequence. Matrix metalloproteinases (MMPs), especially MMP-2 and MMP-9 as the major members of the MMP family, are involved in many different facets of breast cancer metastasis. In this study, we sought the MMPs expression in the metastatic cascade of TNBC. Primary breast cancer cells known as 4T1T were extracted from the tumor mass following the creation of an animal model of TNBC. The brain metastasis lesions of malignant mice were used to extract highly brain metastatic tumor cells known as 4T1B. Gelatinase zymography and real-time polymerase chain reaction (RT-PCR) were used to examine the expression of MMPs at the proteomic and transcriptomic levels in 4T1T and 4T1B. Our results indicated; brain metastatic tumor cells greatly increased their expression of MMPs. In 4T1B, MMP-2 and MMP-9 gene expression were upregulated by 4 and 3.4 folds respectively. Zymographic analysis found MMP activity only in 4T1B. These results offer significant information about the massive alteration of MMPs expression in the brain metastasis of TNBC. By analyzing the molecular characteristics of brain metastatic tumor cells, we can understand the molecular and genetic features of brain metastasis and develop tailored therapeutic strategies to combat TNBC brain metastasis.

Available Systemic Treatments and Emerging Therapies for Breast Cancer Brain Metastases

In 2023, breast cancer brain metastases (BCBrM) remain a major clinical challenge gaining well-deserved attention. Historically managed with local therapies alone, systemic therapies including small molecule inhibitors and antibody-drug conjugates (ADCs) have shown unprecedented activity in recent trials including patients with brain metastases. These advancements stem from efforts to include patients with stable and active BCBrM in early- and late-phase trial design. Tucatinib added to trastuzumab and capecitabine improves intracranial and extracranial progression-free survival and overall survival in stable and active human epidermal growth factor receptor 2 (HER2+)-positive brain metastases. Trastuzumab deruxtecan (T-DXd) has both shown impressive intracranial activity in stable and active HER2+ BCBrMs challenging historical thinking of ADCs' inability to penetrate the central nervous system (CNS). T-DXd has shown potent activity in HER2-low (immunohistochemistry scores of 1+ or 2+, non-amplified by fluorescence in situ hybridization) metastatic breast cancer and will be studied in HER2-low BCBrM as well. Novel endocrine therapies including oral selective estrogen downregulators (SERDs) and complete estrogen receptor antagonists (CERANs) are being studied in hormone receptor-positive BCBrM clinical trials due to robust intracranial activity in preclinical models. Triple-negative breast cancer (TNBC) brain metastases continue to portend the worst prognosis of all subtypes. Clinical trials leading to the approval of immune checkpoint inhibitors have enrolled few BCBrM patients leading to a lack of understanding of immunotherapies contribution in this subgroup. Data surrounding the use of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors in patients with germline BRCA mutation carriers with CNS disease is hopeful. ADCs including those targeting low-level HER2 expression and TROP2 are under active investigation in triple-negative BCBrMs.

Frequent Overexpression of HER3 in Brain Metastases from Breast and Lung Cancer.

HER3 belongs to a family of receptor tyrosine kinases with oncogenic properties and is targeted by a variety of novel anticancer agents. There is a huge unmet medical need for systemic treatment options in patients with brain metastases (BM). Therefore, we aimed to investigate HER3 expression in BM of breast (BCa) and non-small cell lung cancer (NSCLC) as the basis for future clinical trial design. We analyzed 180 BM samples of breast cancer or NSCLC and 47 corresponding NSCLC extracranial tissue. IHC was performed to evaluate protein expression of HER3, and immune cells based on CD3, CD8, and CD68. To identify dysregulated pathways based on differential DNA methylation patterns, we used Infinium MethylationEPIC microarrays. A total of 99/132 (75.0%) of BCa-BM and 35/48 (72.9%) of NSCLC-BM presented with HER3 expression. Among breast cancer, HER2-positive and HER2-low BM showed significantly higher rates of HER3 coexpression than HER2-negative BM (87.1%/85.7% vs. 61.0%, P = 0.004). Among NSCLC, HER3 was more abundantly expressed in BM than in matched extracranial samples (72.9% vs. 41.3%, P = 0.003). No correlation of HER3 expression and intratumoral immune cell density was observed. HER3 expression did not correlate with overall survival from BM diagnosis. Methylation signatures differed according to HER3 status in BCa-BM samples. Pathway analysis revealed subtype-specific differences, such as TrkB and Wnt signaling pathways dysregulated in HER2-positive and triple-negative breast cancer BM, respectively. HER3 is highly abundant in BM of breast cancer and NSCLC. Given the promising results of antibody-drug conjugates in extracranial disease, BM-specific trials that target HER3 are warranted. See related commentary by Kabraji and Lin, p. 2961.

Abstract GS5-07: Estradiol represses anti-tumoral immune response to promote progression of triple-negative breast cancer brain metastases

Abstract Background: Younger women with breast cancer have increased risk of development of brain metastases irrespective of the tumor subtype. We have shown that pre-menopausal levels of 17-β-Estradiol (E2) contributes to the promotion of brain metastases by influencing the tumor microenvironment. E2 promotes brain metastasis (BM) of estrogen receptor negative (ER¯) BC cells by inducing neuroinflammatory ER+ astrocytes in the brain niche to secrete pro-metastatic factors critical for early brain colonization. Ovarieoctomy (OVX) in combination with the aromatase inhibitor (Letrozole) prevented brain colonization of triple negative (TNBC) (ER-PR-HER2-) human xenografts (MDA231BR/NSG) and murine models (E0711/C57Bl6, 4T1/BALBc) through paracrine activation of EGFR and TRKB, pathways involved in increased invasion and early tumor initiation. Yet, the extent to which E2-depletion therapies can decrease progression of established BM in combination with current standard of care for brain metastasis remains unknown. Goal: Current standard of care (SOC) for patients with TNBC brain metastasis includes irradiation (SRS, whole brain) and immunotherapy (PD-1/PDL-1 inhibitors). The goal of this study was to assess how E2-depletion therapies affects brain immune function in the context of SOC for brain metastatic progression of TNBC. Results: To assess whether E2-depletion could decrease BM progression in a model that mimics standard of care for BM, TNBC E0771-GFP-luc cells were injected intracardially in syngeneic ovariectomized (OVX)-female C57Bl6 mice supplemented with pre-menopausal levels of E2. Seven days after injection (when cancer cells have colonized), mice received a single 15Gy dose brain irradiation and were randomized to continue receiving E2, E2 withdrawal (E2WD) or E2WD plus the aromatase-inhibitor letrozole (E2WD+LET). Brain metastatic burden significantly decreased in E2WD and E2WD+Letrozole treated mice as compared to E2-treated mice. Injection of E0711 cells in immunocompromised NSG mice or in the absence of brain irradiation abolished this effect, suggesting that E2-depletion therapies decrease BM progression through boosting radiation-induced anti-tumor immunity. Accordingly, there were no differences in BM progression in E2, E2WD or E2WD+let treated mice in a xenograft model (F2-7 TNBC cells) in NSG mice, even in the presence of brain irradiation. Immune-profiling of brains from OVX+E2, OVX and OVX+Let C57BL6 mice carrying BMs showed dynamic changes in immune populations at early and late stages of brain metastatic colonization. At early stages post brain colonization (3 days post ic injection) E2-treated mice showed a decreased fraction of CD11b+CD45Int CD206+ microglia/CNS macrophages as compared to OVX+LET-treated mice, without significant changes in the fraction of infiltrated lymphocytes, suggesting E2 represses early immunosurveillance through repression of microglia/CNS macrophage activation. At later stages of brain colonization (7 days post ic injection), E2-treated mice showed an increased fraction of proinflammatory microglia and decreased fraction of T and B cells as compared to OVX or OVX+let treated mice. While E2-depletion increased the recruitment of T cells to the brain niche, the fraction of CD279 (PD1+) brain T cells was similar among groups. Ongoing studies assess the efficacy of E2-depletion therapies in combination with brain radiation and PD-1 inhibitors to decrease metastatic burden and improve survival in preclinical models. Conclusion: Our results support the hypothesis that estradiol promotes brain metastatic progression by stimulating an immunosuppressive brain microenvironment. As such, FDA-approved E2-depletion therapies (aromatase inhibitors and selective-estrogen modulators) could be used in combination with brain irradiation and PD-1 inhibitors to promote a more effective anti-tumoral immune response. Citation Format: Diana Cittelly, Maria J. Contreras-Zarate, Karen ALvarez-Eraso, Vesna Tesic, Nicole Tsuji, Leanna Chafee, Sana Karam, D. Ryan Ormond, Peter Kabos. Estradiol represses anti-tumoral immune response to promote progression of triple-negative breast cancer brain metastases [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS5-07.

Characterisation of the immune microenvironment of primary breast cancer and brain metastasis reveals depleted T-cell response associated to ARG2 expression

Immune checkpoint inhibition is an established treatment in programmed death-ligand 1 (PD-L1)-positive metastatic triple-negative (TN) breast cancer (BC). However, the immune landscape of breast cancer brain metastasis (BCBM) remains poorly defined. The tumour-infiltrating lymphocytes (TILs) and the messenger RNA (mRNA) levels of 770 immune-related genes (NanoString™, nCounter™ Immuno-oncology IO360) were assessed in primary BCs and BCBMs. The prognostic role of ARG2 transcripts and protein expression in primary BCs and its association with outcome was determined. There was a significant reduction of TILs in the BCBMs in comparison to primary BCs. 11.5% of BCs presented a high immune infiltrate (hot), 46.2% were altered (immunosuppressed/excluded) and 34.6% were cold (no/low immune infiltrate). 3.8% of BCBMs were hot, 23.1% altered and 73.1% cold. One hundred and twelve immune-related genes including PD-L1 and CTLA4 were decreased in BCBM compared to the primary BCs (false discovery rate <0.01, log2 fold-change >1.5). These genes are involved in matrix remodelling and metastasis, cytokine-chemokine signalling, lymphoid compartment, antigen presentation and immune cell adhesion and migration. Immuno-modulators such as PD-L1 (CD274), CTLA4, TIGIT and CD276 (B7H3) were decreased in BCBMs. However, PD-L1 and CTLA4 expression was significantly higher in TN BCBMs (P= 0.01), with CTLA4 expression also high in human epidermal growth factor receptor 2-positive (P < 0.01) compared to estrogen receptor-positive BCBMs. ARG2 was one of four genes up-regulated in BCBMs. High ARG2 mRNA expression in primary BCs was associated with worse distant metastasis-free survival (P= 0.038), while ARG2 protein expression was associated with worse breast-brain metastasis-free (P= 0.027) and overall survival (P= 0.019). High transcript levels of ARG2 correlated to low levels of cytotoxic and T cells in both BC and BCBM (P < 0.01). This study highlights the immunological differences between primary BCs and BCBMs and the potential importance of ARG2 expression in T-cell depletion and clinical outcome.

Fn14-Directed DART Nanoparticles Selectively Target Neoplastic Cells in Preclinical Models of Triple-Negative Breast Cancer Brain Metastasis.

Triple-negative breast cancer (TNBC) patients with brain metastasis (BM) face dismal prognosis due to the limited therapeutic efficacy of the currently available treatment options. We previously demonstrated that paclitaxel-loaded PLGA-PEG nanoparticles (NPs) directed to the Fn14 receptor, termed "DARTs", are more efficacious than Abraxane─an FDA-approved paclitaxel nanoformulation─following intravenous delivery in a mouse model of TNBC BM. However, the precise basis for this difference was not investigated. Here, we further examine the utility of the DART drug delivery platform in complementary xenograft and syngeneic TNBC BM models. First, we demonstrated that, in comparison to nontargeted NPs, DART NPs exhibit preferential association with Fn14-positive human and murine TNBC cell lines cultured in vitro. We next identified tumor cells as the predominant source of Fn14 expression in the TNBC BM-immune microenvironment with minimal expression by microglia, infiltrating macrophages, monocytes, or lymphocytes. We then show that despite similar accumulation in brains harboring TNBC tumors, Fn14-targeted DARTs exhibit significant and specific association with Fn14-positive TNBC cells compared to nontargeted NPs or Abraxane. Together, these results indicate that Fn14 expression primarily by tumor cells in TNBC BMs enables selective DART NP delivery to these cells, likely driving the significantly improved therapeutic efficacy observed in our prior work.

EGFR as a potent CAR T target in triple negative breast cancer brain metastases.

There is currently no curative treatment for patients diagnosed with triple-negative breast cancer brain metastases (TNBC-BM). CAR T cells hold potential for curative treatment given they retain the cytolytic activity of a T cell combined with the specificity of an antibody. In this proposal we evaluated the potential of EGFR re-directed CAR T cells as a therapeutic treatment against TNBC cells in vitro and in vivo. We leveraged a TNBC-BM tissue microarray and a large panel of TNBC cell lines and identified elevated epidermal growth factor receptor (EGFR) expression. Next, we designed a second-generation anti-EGFR CAR T construct incorporating a clinically relevant mAb806 tumor specific single-chain variable fragment (scFv) and intracellular 4-1BB costimulatory domain and CD3ζ using a lentivirus system and evaluated in vitro and in vivo anti-tumor activity. We demonstrate EGFR is enriched in TNBC-BM patient tissue after neurosurgical resection, with six of 13 brain metastases demonstrating both membranous and cytoplasmic EGFR. Eleven of 13 TNBC cell lines have EGFR surface expression ≥ 85% by flow cytometry. EGFR806 CAR T treated mice effectively eradicated TNBC-BM and enhanced mouse survival (log rank p < 0.004). Our results demonstrates anti-tumor activity of EGFR806 CAR T cells against TNBC cells in vitro and in vivo. Given EGFR806 CAR T cells are currently undergoing clinical trials in primary brain tumor patients without obvious toxicity, our results are immediately actionable against the TNBC-BM patient population.

SYST-13 PHASE II STUDY OF THE COMBINATION OF LIPOSOMAL IRINOTECAN AND PEMBROLIZUMAB FOR TRIPLE-NEGATIVE BREAST CANCER (TNBC) WITH BRAIN METASTASES (BM)

Abstract BACKGROUND Breast cancer is one of the most common cancers associated with brain metastases (BM). Up to 50% of patients with metastatic triple-negative breast cancer (TNBC) develop BM which portends a poor prognosis, with a median survival of 4.4-7.3 months. There is a lack of effective systemic therapy. Irinotecan is a topoisomerase-1 inhibitor with a response rate of 5-23% in advanced breast cancer. Nal-IRI is an intravenous liposomal formulation of irinotecan, with greater efficacy in tumor growth inhibition and the ability to cross the blood brain barrier (BBB) than irinotecan, resulting in a prolonged survival in preclinical TNBC BM models. Additionally, Nal-IRI has demonstrated promising anti-tumor activity in patients with TNBC- BM in a phase-I trial (NCT01770353). Pembrolizumab is a humanized anti-PD-1 monoclonal antibody which has shown efficacy in TNBC. The purpose of this study is to evaluate whether the combination of Nal-IRI and pembrolizumab can provide a synergic effect to control the CNS disease and prolong survival in TNBC with progressive BM. METHODS This is a phase II, single arm trial with a safety lead-in to evaluate the efficacy of nal-IRI (50-70mg/m2 IV Q2W) in combination with pembrolizumab (400mg IV Q6W). Simon’s 2-stage design is used, with 18 patients in the 1st stage and additional 24 at 2nd stage for a total of 42. The first 6 patients will serve as a safety lead-in. Key eligibilities include: histologically/cytologically confirmed TNBC with new or progressive BM; prior immunotherapy is allowed but not prior nal-IRI/irinotecan; prior sacituzumab-govitecan is permitted if disease stable for ≥16-week while on therapy and ≥24-week washout prior to starting trial; measurable disease; and ≤4 prior lines of therapy in the metastatic setting. The primary endpoint is CNS disease control rate (DCR) at 6 months using RANO-BM criteria. Secondary endpoints include CNS and non-CNS ORR, PFS and OS. (ClinicalTrials.gov: NCT05255666)

Comprehensive Analysis of the Immunogenomics of Triple-Negative Breast Cancer Brain Metastases From LCCC1419.

BackgroundTriple negative breast cancer (TNBC) is an aggressive variant of breast cancer that lacks the expression of estrogen and progesterone receptors (ER and PR) and HER2. Nearly 50% of patients with advanced TNBC will develop brain metastases (BrM), commonly with progressive extracranial disease. Immunotherapy has shown promise in the treatment of advanced TNBC; however, the immune contexture of BrM remains largely unknown. We conducted a comprehensive analysis of TNBC BrM and matched primary tumors to characterize the genomic and immune landscape of TNBC BrM to inform the development of immunotherapy strategies in this aggressive disease.MethodsWhole-exome sequencing (WES) and RNA sequencing were conducted on formalin-fixed, paraffin-embedded samples of BrM and primary tumors of patients with clinical TNBC (n = 25, n = 9 matched pairs) from the LCCC1419 biobank at UNC—Chapel Hill. Matched blood was analyzed by DNA sequencing as a comparison for tumor WES for the identification of somatic variants. A comprehensive genomics assessment, including mutational and copy number alteration analyses, neoantigen prediction, and transcriptomic analysis of the tumor immune microenvironment were performed.ResultsPrimary and BrM tissues were confirmed as TNBC (23/25 primaries, 16/17 BrM) by immunohistochemistry and of the basal intrinsic subtype (13/15 primaries and 16/19 BrM) by PAM50. Compared to primary tumors, BrM demonstrated a higher tumor mutational burden. TP53 was the most frequently mutated gene and was altered in 50% of the samples. Neoantigen prediction showed elevated cancer testis antigen- and endogenous retrovirus-derived MHC class I-binding peptides in both primary tumors and BrM and predicted that single-nucleotide variant (SNV)-derived peptides were significantly higher in BrM. BrM demonstrated a reduced immune gene signature expression, although a signature associated with fibroblast-associated wound healing was elevated in BrM. Metrics of T and B cell receptor diversity were also reduced in BrM.ConclusionsBrM harbored higher mutational burden and SNV-derived neoantigen expression along with reduced immune gene signature expression relative to primary TNBC. Immune signatures correlated with improved survival, including T cell signatures. Further research will expand these findings to other breast cancer subtypes in the same biobank. Exploration of immunomodulatory approaches including vaccine applications and immune checkpoint inhibition to enhance anti-tumor immunity in TNBC BrM is warranted.

Abstract 2401: Investigating the role of type II IL4 receptor in breast cancer brain metastasis

Abstract Breast-to-brain metastasis is a devastating disease complication for which there are currently few treatment options. Among breast cancer subtypes, patients with triple-negative breast cancer (TNBC) and HER2+ breast cancer experience elevated rates of brain metastasis. The cytokines IL4 and IL13 are overexpressed by many human solid tumors. Both are associated with invasive and metastatic phenotypes; IL13 is additionally consequential in primary brain tumors. These cytokines signal through type I (IL4 only) and type II (IL4/IL13) IL4 receptors (IL4R). Importantly, expression of type II IL4R correlates with poor patient prognosis in basal-like (i.e., triple-negative) breast cancer, and HER2+ tumors display elevated type II IL4R expression. Our laboratory has shown that genetic loss of IL4R signaling in tumor cells attenuates lung and liver metastasis in mice. Additionally, we recently identified a role for IL4R signaling in modulating glycosylation in tumor cells. We hypothesize that IL4R signaling influences TNBC brain metastasis at least in part via modulating glycosylation. In a pilot mouse study, pharmacological blockade of IL4R after intracardiac injection of syngeneic TNBC cells resulted in attenuation of brain metastatic growth and circulating tumor cell burden. We have also observed significant changes in the expression of a sialyltransferase (ST8SIA1) that has been implicated in primary brain tumors, as well as in the abundance of several sialic acid-containing protein species in breast cancer cells following treatment with IL4 or IL13. Further, IL4 stimulation increases the overall glycosylation of several proteins of interest, including a glucose transporter and a glutamine transporter, without altering gene expression. Overall, our data suggest that type II IL4R signaling promotes metastasis, potentially through a mechanism involving protein glycosylation. Blockade of this receptor may be a useful therapeutic approach for patients with breast cancer brain metastases. Citation Format: Wendy Bindeman, Demond Williams, Ebony Hargrove-Wiley, Barbara Fingleton. Investigating the role of type II IL4 receptor in breast cancer brain metastasis [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 2401.

Immune Checkpoint Inhibitors in the Treatment of Breast Cancer Brain Metastases.

The management of breast cancer brain metastases (BCBM) has historically involved local therapies. However, as novel systemic treatments have become more effective in controlling visceral disease, BCBM have also been better controlled. Immune checkpoint inhibitors (ICIs) have demonstrated efficacy in brain metastases in patients with lung cancer and melanoma and represent a promising option for patients with triple-negative BCBM, a group with limited systemic therapy options. In this review we summarize current data about the role of ICIs in the treatment BCBM. We identified 15 clinical trials that evaluated ICIs ± chemotherapy in patients with breast cancer. The studies were mostly focused on triple-negative breast cancer (TNBC). Of these trials, 4 excluded patients with BCBM, while 11 allowed patients with stable, treated or asymptomatic BCBM. In total, 2692 patients were enrolled in the identified clinical trials, but only 91 trial patients (3.3%) had BCBM. Furthermore, only 2 of these clinical trials reported BCBM-specific outcomes and none of the clinical trials reported BCBM-specific adverse events. Up to 45% of patients with TNBC will develop BCBM; however, only 3.3% of the patients included in the clinical trials that led to the U.S. Food and Drug Administration approvals for ICIs in advanced breast cancer had brain metastases. This review reinforces that efficacy data are greatly needed for patients with BCBM—this is an area of unmet need in oncology. More inclusive clinical trials and real-world data that evaluate the safety and efficacy of ICIs in patients with BCBM are greatly needed.

Comprehensive Analysis of the Immunogenomics of Triple-Negative Breast Cancer Brain Metastases From LCCC1419

Comprehensive Analysis of the Immunogenomics of Triple-Negative Breast Cancer Brain Metastases From LCCC1419

281P Prognostic impact of immune interactions in HER2+ and triple-negative breast cancer brain metastases

Despite clinical implications, the complexity of immune microenvironment in breast cancer (BC) brain metastases (BM) is still poorly understood. Multiplex immunofluorescence (mIF) simultaneously visualizes several IF labeled proteins while maintaining spatial information and can be used to identify spatially interacting cells, potentially providing useful information to guide therapeutic approaches.

Abstract 7: Modeling cell-cell crosstalk in TNBC brain metastasis

Abstract Brain metastasis (BrM) is a difficult clinical problem in triple-negative breast cancer (TNBC) patients: it occurs in 25% to 40% of metastatic patients while two-year survival rate stubbornly remains a single digit. TNBC usually spreads to the brain rapidly at earlier stages or before the diagnosis of primary cancer. The shorter development time of BrM in TNBC and shorter survival time after BrM diagnosis may indicate a unique innate ability of TNBC tumor cells in adapting to the brain. Indeed, emerging data including ours indicates that TNBC tumor cells have intrinsic brain-like traits resulting in brain-tropism metastasis. Our preliminary studies identified enriched and diverse expressions of receptors and transporters of various neuro-active substances in brain metastatic TNBC cells, including neurotransmitters, gliotransmitters, neurotrophic factors and neural cytokines. By immunopanning astrocytes and microglia/macrophages from mouse brains bearing TNBC brain metastatic tumors at day 3 post tumor cell injection through left cardiac ventricle, and use the CCCExplorer software in modeling the interactions among tumor cells, astrocytes, and microglia/macrophage with cell-type specific RNAseq data, we identified several novel crosstalk signaling, including tumor autocrine TPH1-HTR2, astrocyte→tumor PCDH7-EGFR, IL6-IL6R, CCL5-CCR5 and VGF-C3AR1, and microglia/macrophage→tumor ARTN-GFAR3. Functional experiments demonstrated that cell type-specific depletion of the secreted neuro-active substances deactivated the activities of corresponding receptor and downstream signaling in co-cultured BrM tumor cells. Given that more complex paracrine/autocrine signaling network may dynamically evolve during BrM development, we are characterizing the spatiotemporal cell-cell crosstalk in the BrM metastatic niche that will have important implications for novel therapeutics development. Citation Format: Hong Zhao, Xin Wang, Nikola Liu, Jianting Sheng, Stephen Wong. Modeling cell-cell crosstalk in TNBC brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 7.