Mouse Model Of Triple-negative Breast Cancer Research Articles

Tumor necrosis factor receptor 2 promotes endothelial cell-mediated suppression of CD8+ T cells through tuning glycolysis in chemoresistance of breast cancer

BackgroundT cells play a pivotal role in chemotherapy-triggered anti-tumor effects. Emerging evidence underscores the link between impaired anti-tumor immune responses and resistance to paclitaxel therapy in triple-negative breast cancer (TNBC). Tumor-related endothelial cells (ECs) have potential immunoregulatory activity. However, how ECs regulate T cell activity during TNBC chemotherapy remains poorly understood.MethodsSingle-cell analysis of ECs in patients with TNBC receiving paclitaxel therapy was performed using an accessible single-cell RNA sequencing (scRNA-seq) dataset to identify key EC subtypes and their immune characteristics. An integrated analysis of a tumor-bearing mouse model, immunofluorescence, and a spatial transcriptome dataset revealed the spatial relationship between ECs, especially Tumor necrosis factor receptor (TNFR) 2+ ECs, and CD8+ T cells. RNA sequencing, CD8+ T cell proliferation assays, flow cytometry, and bioinformatic analyses were performed to explore the immunosuppressive function of TNFR2 in ECs. The downstream metabolic mechanism of TNFR2 was further investigated using RNA sequencing, cellular glycolysis assays, and western blotting.ResultsIn this study, we identified an immunoregulatory EC subtype, characterized by enhanced TNFR2 expression in non-responders. By a mouse model of TNBC, we revealed a dynamic reduction in the proportion of the CD8+ T cell-contacting tumor vessels that could co-localize spatially with CD8+ T cells during chemotherapy and an increased expression of TNFR2 by ECs. TNFR2 suppresses glycolytic activity in ECs by activating NF-κB signaling in vitro. Tuning endothelial glycolysis enhances programmed death-ligand (PD-L) 1-dependent inhibitory capacity, thereby inducing CD8+ T cell suppression. In addition, TNFR2+ ECs showed a greater spatial affinity for exhausted CD8+ T cells than for non-exhausted CD8+ T cells. TNFR2 blockade restores impaired anti-tumor immunity in vivo, leading to the loss of PD-L1 expression by ECs and enhancement of CD8+ T cell infiltration into the tumors.ConclusionsThese findings reveal the suppression of CD8+ T cells by ECs in chemoresistance and indicate the critical role of TNFR2 in driving the immunosuppressive capacity of ECs via tuning glycolysis. Targeting endothelial TNFR2 may serve as a potent strategy for treating TNBC with paclitaxel.

High-motility pro-tumorigenic monocytes drive macrophage enrichment in the tumor microenvironment.

Enrichment of tumor-associated macrophages (TAMΦs) in the tumor microenvironment correlates with worse clinical outcomes in triple-negative breast cancer (TNBC) patients, prompting the development of therapies to inhibit TAMΦ infiltration. However, the lackluster efficacy of CCL2-based chemotaxis blockade in clinical trials suggests that a new understanding of monocyte/macrophage infiltration may be necessary. Here we demonstrate that random migration, and not only chemotaxis, drives macrophage tumor infiltration. We identified tumor- associated monocytes (TAMos) that display a dramatically enhanced migration capability, induced rapidly by the tumor microenvironment, that drives effective tumor infiltration, in contrast to low-motility differentiated macrophages. TAMo, not TAMΦ, promotes cancer cell proliferation through activation of the MAPK pathway. IL-6 secreted both by cancer cells and TAMo themselves enhances TAMo migration by increasing dendritic protrusion dynamics and myosin- based contractility via the JAK2/STAT3 signaling pathway. Independent from CCL2 mediated chemotaxis, IL-6 driven enhanced migration and pro-proliferative effect of TAMo were validated in a syngeneic TNBC mouse model. Depletion of IL-6 in cancer cells significantly attenuated monocyte infiltration and reversed TAMo-induced cancer cell proliferation. This work reveals the critical role random migration plays in monocyte driven TAMΦ enrichment in a tumor and pinpoints IL-6 as a potential therapeutic target in combination with CCL2 to ameliorate current strategies against TAMΦ infiltration.

Celecoxib Augments Paclitaxel-Induced Immunogenic Cell Death in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive malignancy that lacks effective targeted therapies. Inducing immunogenic cell death (ICD) in tumor cells represents a promising strategy to enhance therapeutic efficacy by promoting antitumor immunity. Paclitaxel (PTX), a commonly used chemotherapy drug for TNBC, can induce ICD; however, the resulting immunogenicity is limited. Thus, there is an urgent need to explore strategies that improve the effectiveness of ICD in TNBC by incorporating immunoregulatory agents. This study investigated the potential of celecoxib (CXB) to enhance PTX-induced ICD by blocking the biosynthesis of PGE2 in the tumor cells. We observed that the combination of CXB and PTX promoted the maturation of dendritic cells and primed a T cell-dependent immune response, leading to enhanced tumor rejection in a vaccination assay. To further optimize drug delivery in vivo, we developed cRGD-modified liposomes for the targeted codelivery of CXB and PTX. This delivery system significantly improved drug accumulation and triggered robust antitumor immunity in an orthotopic mouse model of TNBC. Moreover, it served as an in situ vaccine to inhibit tumor recurrence and lung metastasis. Overall, our findings provide in-depth insights into the therapeutic mechanism underlying the combination of CXB and PTX, highlighting their potential as effective immune-based therapies for TNBC.

Repurposing hemostatic drug desmopressin in AVPR2-expressing triple-negative breast cancer: Target expression analysis and preclinical antineoplastic effects on tumor growth and metastatic progression.

e15087 Background: Desmopressin (dDAVP) is a hemostatic drug that acts as an agonist of the arginine vasopressin receptor 2 (AVPR2) that is present in vascular and malignant cells. Preclinical data show that dDAVP triggers cytostatic mechanisms, blocking angiogenesis and reducing metastases by limiting the survival of circulating tumor cells. Triple-negative breast cancer (TNBC) is associated with poor prognosis due to limited response to therapy and frequent early metastatic recurrence. Considering the unsatisfied clinical need for novel therapeutic options in TNBC, we evaluated the antitumoral activity of dDAVP on experimental models of TNBC, alone or in addition to chemotherapy. We also assessed the expression and clinical impact of AVPR2 in breast cancer samples. Methods: Human and murine TNBC cell lines were used for in vitro experiments. Target expression was assessed by qPCR and immunohistochemistry (IHC), in experimental or clinical tumors (NCT01606072). Effects of dDAVP were evaluated by proliferation, clonogenic, 3D growth and chemotaxis assays, qPCR arrays, and confocal microscopy. Local and distant tumor progression were assessed in vivo in nude or BALB/c mice. TIMER2.0 and UCSC Xena platforms (BRCA TCGA /n = 1260) were used for bioinformatic studies. Results: dDAVP significantly reduced growth and chemotaxis of AVPR2-expressing TNBC cells. Cytostatic effects of dDAVP were associated with altered actin cytoskeleton dynamics and differential expression of angiogenesis and metastasis-related genes. Cooperative effects were observed in vitro and in vivo after combining dDAVP with taxane or alkylating therapy. Tumor-bearing mice were treated with intravenous injections of dDAVP (0.3 µg/kg, thrice weekly) in combination with weekly cycles of paclitaxel (10 mg/kg i.p.) or carmustine (25 mg/kg i.p.). Combination regimens resulted in greater survival and tumor growth and metastasis inhibition. Bioinformatic analysis of the TCGA database showed that AVPR2 had a positive prognostic impact on overall survival in breast cancer patients, especially in the basal-like molecular subtype. AVPR2 also correlated with different immune cell infiltrates such as NK and dendritic cells, and CD4+ and CD8+ T cells. Moreover, AVPR2 expression was detected by IHC in 6/18 breast cancer clinical samples using a small cohort of surgical specimens. Conclusions: AVPR2 expression is associated with improved outcomes in patients with TNBC. Agonist activation of AVPR2 using dDAVP leads to cancer cell growth inhibition in TNBC cell lines and mouse models. We propose dDAVP as a potential novel therapeutic option for treating TNBC either as monotherapy or in combination with chemotherapy. The therapeutic impact of its addition to immune checkpoint inhibitors remains to be explored.

Neoantigen-augmented iPSC cancer vaccine combined with radiotherapy promotes antitumor immunity in poorly immunogenic cancers

Although irradiated induced-pluripotent stem cells (iPSCs) as a prophylactic cancer vaccine elicit an antitumor immune response, the therapeutic efficacy of iPSC-based cancer vaccines is not promising due to their insufficient antigenicity and the immunosuppressive tumor microenvironment. Here, we found that neoantigen-engineered iPSC cancer vaccines can trigger neoantigen-specific T cell responses to eradicate cancer cells and increase the therapeutic efficacy of RT in poorly immunogenic colorectal cancer (CRC) and triple-negative breast cancer (TNBC). We generated neoantigen-augmented iPSCs (NA-iPSCs) by engineering AAV2 vector carrying murine neoantigens and evaluated their therapeutic efficacy in combination with radiotherapy. After administration of NA-iPSC cancer vaccine and radiotherapy, we found that ~60% of tumor-bearing mice achieved a complete response in microsatellite-stable CRC model. Furthermore, splenocytes from mice treated with NA-iPSC plus RT produced high levels of IFNγ secretion in response to neoantigens and had a greater cytotoxicity to cancer cells, suggesting that the NA-iPSC vaccine combined with radiotherapy elicited a superior neoantigen-specific T-cell response to eradicate cancer cells. The superior therapeutic efficacy of NA-iPSCs engineered by mouse TNBC neoantigens was also observed in the syngeneic immunocompetent TNBC mouse model. We found that the risk of spontaneous lung and liver metastasis was dramatically decreased by NA-iPSCs plus RT in the TNBC animal model. Altogether, these results indicated that autologous iPSC cancer vaccines engineered by neoantigens can elicit a high neoantigen-specific T-cell response, promote tumor regression, and reduce the risk of distant metastasis in combination with local radiotherapy.

Abstract PO1-26-06: The effect of localized radiotherapy in combination with chemoimmunotherapy in a humanized triple-negative breast cancer mouse model

Abstract Background: Metastatic triple-negative breast cancer (TNBC) is an aggressive sub-type of breast cancer that is challenging to treat. While the addition of immunotherapy (IT) with pembrolizumab (pembro) to chemotherapy prolongs overall survival in patients with programmed death-ligand 1 positive (PD-L1+) TNBC, few patients obtain long-term benefit. Radiotherapy (RT) can stimulate cellular damage, release of tumor antigens and promote the T cell anti-tumor response including at distant sites (abscopal response) when used with IT. The purpose of this study was to investigate the combination of RT with pembro and paclitaxel (pac) in a TNBC humanized mouse model. Methods: Human Immune System BRGS (BALB/c, Rag2-/-, IL2RγC-/-, NODSIRPa ) mice were engrafted with TNBC MDA-MB-231 cells in bilateral flanks. Treatments included: vehicle, pac 10 mg/kg intra-peritoneal (IP) weekly, pembro 15 mg/kg IP weekly, and RT 8 Gy x 3 fractions every other day the first week of treatment to one-sided tumors (contralateral tumors received no RT). Mice were treated and analyzed in the following groups: vehicle, pac + pembro, RT + pac, and RT + pac + pembro. Treatments began when tumors reached 100-300 mm3 and tumors were measured twice weekly. At the end of study, sera, lymph nodes (LNs), spleen, and tumor tissue were collected for immunohistochemistry, single cell suspensions, and flow cytometry analysis for immune cell populations. Results: All treatment arms resulted in a decrease in tumor volume when compared to vehicle with the greatest reduction in the RT + pac and RT + pac + pembro arms. Combination therapy with RT + paclitaxel (p=0.0002) and RT + pac + pembro (p=0.008) resulted in a statistically significant decrease in specific growth rate (SGR) when compared to vehicle. An abscopal effect was not observed in the non-RT tumors compared to RT-tumors in either group. RT + pembro was associated with an increase in hCD45 T cells in LNs and spleens but not in tumors. In mice that received RT, a decrease was noted in HLA-ABC class I and Intermediate Class II major histocompatibility complex (MHC). In addition, RT-tumors had reduced expression of PD-L1 and polio virus receptor (PVR) and increased expression of PD-1. The percentage of interferon gamma (IFNg+), tumor necrosis factor alpha (TNFa+) CD8+ T cells increased with radiation. This percentage was the highest in the triplet therapy with RT+ pembro + pac. Conclusion: Combination treatment with RT + immunochemotherapy resulted in a significant increase in anti-tumor activity when compared to immunochemotherapy alone, however, an abscopal effect was not observed in contralateral non-RT tumors. RT resulted in down-regulation of immune inhibitory receptors and tumor MHC. Citation Format: Anna Schreiber, Stacey Bagby, Stephen Smoots, Adrian Dominguez, Christine Fisher, Julie Lang, Todd Pitts, Jennifer Diamond. The effect of localized radiotherapy in combination with chemoimmunotherapy in a humanized triple-negative breast cancer mouse model [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 PO1-26-06.

Abstract PS07-06: A novel citrullinated-ENO1 peptide-based vaccine for triple-negative breast cancer prevention

Abstract Purpose: To evaluate the merits of a novel citrullinated-enolase 1 (ENO1) peptide-based vaccine for inducing an effective response against triple negative breast cancer (TNBC). Background: Targets for cancer vaccines have included mutated proteins and peptides, as well as proteins that are overexpressed in cancer but otherwise ubiquitous in their structure. However, protein modifications other than mutation may also induce an immune response. Several lines of evidence have demonstrated a role for the posttranslational modification (PTM) citrullination as inducing immunogenicity. Dysregulated protein citrullination by peptidyl arginine deiminases (PADI) has been associated with autoimmune diseases and is currently being explored for its relevance to cancer. Previously, our group established PADI2, which catalyzes the PTM from arginine to citrulline, to be highly expressed in TNBC compared to normal mammary and other tissues. We observed that PADI2-associated protein citrullination promotes antigenicity. Importantly, we demonstrated that protein citrullination, non-occurring in DNA and RNA-based vaccines, is highly cancer specific. On the basis of these findings, we developed a novel vaccine based on cancer-selective citrullinated-enolase 1 peptides (cit-ENO1) that were identified from mass spectrometry surfaceome and immunopeptidome data from breast cancer cells. We assessed the extent to which a citENO1 peptide based vaccine elicits a potent host response and attenuates tumor development in a syngeneic mouse model of TNBC. Design: To confirm that the cit-ENO1 peptide vaccine elicited an immune response, we immunized female B6129SF1/J mice with 10nmol cit-ENO1 peptides or 10nmol of corresponding unmodified peptides as the antigen, plus the TLR3 agonist poly I:C as an adjuvant (10mg), subcutaneously once a week, for three weeks. Saline or the adjuvant alone were used as controls. One week post the last round of immunization, draining lymph nodes (LNs) and immunized skin were harvested, and T cell phenotypes evaluated using flow-cytometry. To assess anti-cancer efficacy, female B6129SF1/J mice were immunized with cit-ENO1 peptides or unmodified peptides with poly I:C as an adjuvant followed by orthotopic implantation with murine BRCA1co/co; MMTV-Cre; p53+/- TNBC cells (1.5 x 106) and tumor growth as well as overall survival were assessed. Results: We observed that the cit-ENO1 peptide vaccination induced a statistically significantly greater percentage of activated CD8+ PD-1+ effector T cells as well as CD8+ CD44+ CD62L- effector memory T cells in the LNs compared with either the control groups or the unmodified ENO1 peptide. CD8+ PD-1+ T-cells were also found to be significantly elevated in immunized skin of cit-ENO1 vaccinated mice. Both cit-ENO1 and unmodified ENO1 vaccine increased CD4+ PD-1+ T cells from the LNs and immunized skin. Remarkably, the cit-ENO1 vaccine but not the unmodified-ENO1 vaccine significantly delayed tumor growth and markedly improved overall survival compared to respective controls (Logrank test for trend 2-sided p< 0.05). Conclusion: We have developed a novel vaccine based on cancer-selective cit-ENO1 peptides that stimulates a potent anti-cancer immune response and significantly delays tumor initiation and progression in a preclinical, immune competent mouse model of TNBC. Importantly, the anti-cancer effects were not observed with corresponding unmodified ENO1 peptides. Citation Format: Ricardo Leon Letelier, Hiroyuki Katayama, Yihui Chen, Yinning Cai, Fuchung Hsiao, Banu Arun, Samir Hanash. A novel citrullinated-ENO1 peptide-based vaccine for triple-negative breast cancer prevention [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 PS07-06.

Abstract PO3-26-09: A novel class of RNR inhibitors that induces genomic instability and breast cancer cell death without inducing overt toxicities

Abstract Despite the development of screening techniques and therapies, nearly 30% of breast cancers progress to Stage IV metastatic disease. These advanced cancers are highly proliferative, engaging in ongoing DNA synthesis that requires ribonucleotide reductase (RNR), the rate-limiting enzyme for dNTP synthesis. RRM2, the small subunit of RNR, activates the enzyme, increases deoxynucleotide pools, and is overexpressed in many cancers, including breast cancer. Thus, RNR is an established therapeutic target in advanced breast cancer. Currently, gemcitabine is the only FDA-approved RNR inhibitor used to treat Stage IV disease. As a nucleoside analog, gemcitabine also causes severe dose-limiting toxicities (i.e. myelosuppression and hepatotoxicity) due to off-target DNA replication termination. We hypothesize that a novel, non-nucleoside, RNR inhibitor may overcome these limitations. To address this, we developed TMU27a, a derivative of naphthyl salicylic acyl hydrazone (NSAH), which was identified in an in silico screen for its high-affinity binding to the RNR catalytic site. To measure direct interactions between TMU27a and purified RNR protein, we used surface plasmon resonance, revealing on-target, tight binding (Kd = 150 nM). Unbiased docking and molecular dynamics simulations (using lowest energy calculations) predicted the binding sight of TMU27a to be the catalytic site of RNR, where it is stabilized through extensive interactions formed with conserved residues. Preliminary docking predictions also indicate multiple clash sites between TMU27a and the DNA polymerase lambda nucleotide pocket even in the lowest energy pose (unlike gemcitabine), suggesting that TMU27a inhibits RNR activity through a novel mechanism without significant off-target binding to other nucleotide binding proteins that contribute to toxicity. Demonstrating on-target inhibition, TMU27a reduces dATP levels and induces S and G2/M-phase stalling, leading to significant DNA damage and chromosomal instability. This excessive genomic damage causes growth repression, apoptosis, and senescence in several triple negative breast cancer (TNBC) cell lines. In xenograft mouse models of TNBC, TMU27a fully suppressed tumor growth without impacting mouse weight, suggesting strong drug efficacy in the absence of overt toxicity. Moreover, while short-term exposure to gemcitabine suppresses red and white blood cell populations, TMU27a does not. Together, these data indicate that TMU27a and its potential analogs are novel, non-toxic RNR inhibitors that overcome the limitations of gemcitabine for treating breast cancer. We are currently investigating how and where TMU27a binds human RNR using cryo-electron microscopy with the goal of generating a novel class of RNR inhibitors through structure-based drug design, improving binding affinity and selectivity. Citation Format: Taylor Baker, Kristen Weber-Bonk, Wei Huang, Derek Taylor, Ruth Keri. A novel class of RNR inhibitors that induces genomic instability and breast cancer cell death without inducing overt toxicities [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 PO3-26-09.

Small animal PET imaging with the 68Ga-labeled pH (low) insertion peptide-like peptide YJL-4 in a triple-negative breast cancer mouse model

BackgroundThe aim of this study was to prepare a novel 68Ga-labeled pH (low) insertion peptide (pHLIP)-like peptide, YJL-4, and determine its value for the early diagnosis of triple-negative breast cancer (TNBC) via in vivo imaging of tumor-bearing nude mice. The novel peptide YJL-4 was designed using a template-assisted method and synthesized by solid-phase peptide synthesis. After modification with the chelator 1,4,7‑triazacyclononane-N,N′,N″-triacetic acid (NOTA), the peptide was labeled with 68Ga. Then, the biodistribution of 68Ga-YJL-4 in tumor-bearing nude mice was investigated, and the mice were imaged by small animal positron emission tomography (PET).ResultsThe radiochemical yield and radiochemical purity of 68Ga-YJL-4 were 89.5 ± 0.16% and 97.95 ± 0.06%, respectively. The biodistribution of 68Ga-YJL-4 in tumors (5.94 ± 1.27% ID/g, 6.72 ± 1.69% ID/g and 4.54 ± 0.58% ID/g at 1, 2 and 4 h after injection, respectively) was significantly greater than that of the control peptide in tumors at the corresponding time points (P < 0.01). Of the measured off-target organs, 68Ga-YJL-4 was highly distributed in the liver and blood. The small animal PET imaging results were consistent with the biodistribution results. The tumors were visualized by PET at 2 and 4 h after the injection of 68Ga-YJL-4. No tumors were observed in the control group.ConclusionsThe novel pHLIP family peptide YJL-4 can adopt an α-helical structure for easy insertion into the cell membrane in an acidic environment. 68Ga-YJL-4 was produced in high radiochemical yield with good stability and can target TNBC tissue. Moreover, the strong concentration of radioactive 68Ga-YJL-4 in the abdomen does not hinder the imaging of early TNBC.

IL1R2 Blockade Alleviates Immunosuppression and Potentiates Anti-PD-1 Efficacy in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with limited therapeutic options. IL1 receptor type 2 (IL1R2) promotes breast tumor-initiating cell (BTIC) self-renewal and tumor growth in TNBC, indicating that targeting it could improve patient treatment. In this study, we observed that IL1R2 blockade strongly attenuated macrophage recruitment and the polarization of tumor-associated macrophages (TAM) to inhibit BTIC self-renewal and CD8+ T-cell exhaustion, which resulted in reduced tumor burden and prolonged survival in TNBC mouse models. IL1R2 activation by TAM-derived IL1β increased PD-L1 expression by interacting with the transcription factor Yin Yang 1 (YY1) and inducing YY1 ubiquitination and proteasomal degradation in both TAMs and TNBC cells. Loss of YY1 alleviated the transcriptional repression of c-Fos, which is a transcriptional activator of PDL-1. Combined treatment with an IL1R2-neutralizing antibodies and anti-PD-1 led to enhanced antitumor efficacy and reduced TAMs, BTICs, and exhausted CD8+ T cells. These results suggest that IL1R2 blockade might be a strategy to potentiate immune checkpoint blockade efficacy in TNBC to improve patient outcomes. Significance: IL1R2 in both macrophages and breast cancer cells orchestrates an immunosuppressive tumor microenvironment by upregulating PD-L1 expression and can be targeted to enhance the efficacy of anti-PD-1 in triple-negative breast cancer.

477 Evaluating the therapeutic efficacy of combination IL-12 and trabectedin for the treatment of triple negative breast cancer

OBJECTIVES/GOALS: IL-12 has potent immune effects but the presence of myeloid-derived suppressor cells (MDSC) can inhibit IL-12-induced NK cell cytotoxicity. Thus, we hypothesized that combining IL-12 with trabectedin, an immunosuppressive myeloid cell depleting agent, would improve its therapeutic efficacy in triple negative breast cancer (TNBC). METHODS/STUDY POPULATION: Combination IL-12 and trabectedin was tested in the 4T1 mouse model of TNBC. 4T1 cells were injected into the mammary fat pad of female BALB/cj mice. When tumors reached 50 mm3, mice were randomly divided into 4 groups and treated with PBS, IL-12 (0.5 μg/mouse 3x/wk), 0.15 mg/kg trabectedin weekly or the combination. Tumor volumes were measured by calipers. Mass cytometry was performed on spleens and tumors using a 35-antibody panel. Plasma IFN-γ levels were measured by ELISA. The role of NK cells was evaluated via depletion with anti-asialo-GM1. The Luminex Discovery Assay was used to measure plasma cytokines and immunohistochemistry was performed for CD4 and CD8a. Linear/nonlinear mixed effects modeling was used for in vivo data analysis and applicable t- or ANOVA tests were used for in vitrodata analysis. RESULTS/ANTICIPATED RESULTS: Combination IL-12 and trabectedin led to a significant reduction in tumor burden compared to single-agent IL-12, trabectedin and control treatments (all p&lt;0.001), as well as higher levels of IFN-γ (all p&lt;0.04). One combination treated mouse had complete tumor regression. Splenic MDSC were significantly decreased in combination treated mice. NK depletion abrogated the effects of combination therapy. Compared to mice receiving a control antibody, NK depletion of combination treated mice led to lower levels of CCL5 (p&lt;0.01) and CXCL10 (p&lt;0.001) and significantly higher tumor burden (p=0.001). CD8+T cell levels were significantly higher in combination treated mice compared to those receiving IL-12 (p&lt;0.01), and these levels were decreased when mice were depleted of NK cells (p=0.01). DISCUSSION/SIGNIFICANCE: TNBC represents 15% of all breast cancer diagnoses and is associated with a worse prognosis compared to other subtypes. Black women are twice as likely to be diagnosed with TNBC and more likely to die from disease than White women. Thus, there is an increasing need to develop additional therapeutic options for this disease.

Targeting CD73 with flavonoids inhibits cancer stem cells and increases lymphocyte infiltration in a triple-negative breast cancer mouse model.

Chemotherapy remains the mainstay treatment for triple-negative breast cancer (TNBC) due to the lack of specific targets. Given a modest response of immune checkpoint inhibitors in TNBC patients, improving immunotherapy is an urgent and crucial task in this field. CD73 has emerged as a novel immunotherapeutic target, given its elevated expression on tumor, stromal, and specific immune cells, and its established role in inhibiting anti-cancer immunity. CD73-generated adenosine suppresses immunity by attenuating tumor-infiltrating T- and NK-cell activation, while amplifying regulatory T cell activation. Chemotherapy often leads to increased CD73 expression and activity, further suppressing anti-tumor immunity. While debulking the tumor mass, chemotherapy also enriches heterogenous cancer stem cells (CSC), potentially leading to tumor relapse. Therefore, drugs targeting both CD73, and CSCs hold promise for enhancing chemotherapy efficacy, overcoming treatment resistance, and improving clinical outcomes. However, safe and effective inhibitors of CD73 have not been developed as of now. We used in silico docking to screen compounds that may be repurposed for inhibiting CD73. The efficacy of these compounds was investigated through flow cytometry, RT-qPCR, CD73 activity, cell viability, tumorsphere formation, and other in vitro functional assays. For assessment of clinical translatability, TNBC patient-derived xenograft organotypic cultures were utilized. We also employed the ovalbumin-expressing AT3 TNBC mouse model to evaluate tumor-specific lymphocyte responses. We identified quercetin and luteolin, currently used as over-the-counter supplements, to have high in silico complementarity with CD73. When quercetin and luteolin were combined with the chemotherapeutic paclitaxel in a triple-drug regimen, we found an effective downregulation in paclitaxel-enhanced CD73 and CSC-promoting pathways YAP and Wnt. We found that CD73 expression was required for the maintenance of CD44highCD24low CSCs, and co-targeting CD73, YAP, and Wnt effectively suppressed the growth of human TNBC cell lines and patient-derived xenograft organotypic cultures. Furthermore, triple-drug combination inhibited paclitaxel-enriched CSCs and simultaneously improved lymphocyte infiltration in syngeneic TNBC mouse tumors. Conclusively, our findings elucidate the significance of CSCs in impairing anti-tumor immunity. The high efficacy of our triple-drug regimen in clinically relevant platforms not only underscores the importance for further mechanistic investigations but also paves the way for potential development of new, safe, and cost-effective therapeutic strategies for TNBC.

Abstract 3902: The Nanoprimer: A significant opportunity to boost the efficacy of cancer therapies

Abstract Nanomedicines are among the most promising novel delivery systems and are highly promising as therapeutic agents in oncology. However, their use is still limited by nanoparticle hepatic clearance which is responsible for low delivery to the target site. Moreover, the unintended liver distribution could cause harmful side effects. Curadigm’s innovative Nanoprimer technology aims to shift the balance of therapeutics bioavailability and toxicity. The platform is designed to decrease nanomedicines' liver trapping and increase their systemic bioavailability for optimal accumulation in target tissues. This technology can redefine the benefit/risk ratio of therapeutics, improving their clinical outcomes and treatment value. The Nanoprimer is an engineered, biocompatible liposome that transiently and specifically occupies the cells of the mononuclear phagocytic system responsible for sub-optimal therapeutics bioavailability. The Nanoprimer is administered just before the therapeutic, temporarily reducing drug clearance and elimination. Proofs-of-concept were realized by combining the Nanoprimer with different therapeutic agents such as irinotecan-loaded liposomes and nucleic acid-loaded lipid nanoparticles (LNP). One example is a study conducted in collaboration with the Langer Lab at MIT that shows that the Nanoprimer increases mRNA- and siRNA-based therapeutics efficiency by 32% and 49% respectively. Efficacy studies in a triple-negative breast cancer mouse model reveal that the Nanoprimer increases by 2-fold the anti-tumor efficacy of siRNA LNP therapy. Data demonstrate the safety of the Nanoprimer, along with its ability to maximize the inhibition of primary tumor growth and pulmonary metastasis by systemic siRNA LNP treatment. In a collaborative study with the NCL*, the Nanoprimer was shown to stimulate the immune response in a systemic vaccine model using ovalbumin-coated gold nanoparticles (GNP-OVA). Administration of the Nanoprimer before immunization of mice by intravenous injection of GNP-OVA, results in a dramatic increase in anti-OVA antibody levels with IgGs detected as early as 7 days. Furthermore, IgG and IgM antibodies remain elevated at day 28 showing a robust and sustainable immune response. Nanoprimer ability to enhance immune response shows its great potential in immunotherapy, especially for cancer vaccines. Altogether, these data demonstrate that the ubiquitous nature of the Nanoprimer mode of action allows its application to a broad spectrum of therapeutics, from nucleic acid-loaded LNP to immunotherapy. Efficacy studies conducted in mouse models highlight the potential for the Nanoprimer to empower nanotechnology for oncology treatments. *We acknowledge NCL, Frederick National Laboratory for Cancer Research sponsored by the NCI for the help with conducting these experiments. Citation Format: Julie Devallière, Laurence Poul, Maxime Bergère, Francis Mpambani, Audrey Darmon, Océane Jibault, Matthieu Germain. The Nanoprimer: A significant opportunity to boost the efficacy of cancer therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3902.

Abstract 4098: A citrullinated-ENO1 peptide vaccine delayed tumor growth and markedly improved overall survival in a mouse model of triple-negative breast cancer

Abstract Purpose: To evaluate the impact of a novel citrullinated-enolase 1 (cit-ENO1) peptide-based vaccine on the immune response, tumor growth and overall survival in a mouse model of triple-negative breast cancer (TNBC). Background: Cancer vaccines have consisted primarily of mutated or overexpressed proteins in cancer. We have uncovered dysregulated protein citrullination by peptidyl arginine deiminases (PADI) as a feature of triple negative breast cancer inducing immunogenicity to citrullinated proteins. On the basis of these findings, we investigated a novel vaccine based on cancer-selective cit-ENO1 peptides that we identified from mass spectrometry analysis of the surfaceome and immunopeptidome in TNBC. We assessed the extent to which the vaccine elicited an immune response and delayed tumor growth and improved overall survival in a syngeneic mouse model of TNBC. Experimental Design: We immunized female B6129SF1/J mice with cit-ENO1 peptides or corresponding unmodified ENO1 (unm-ENO1) peptides as antigens, together with the TLR3 agonist poly I:C as an adjuvant, once a week, for three weeks. PBS or poly I:C alone were used as controls. One week post the last round of immunization, draining lymph nodes (LN) and immunized skin were harvested, and T cell phenotypes evaluated using flow cytometry. To assess anti-cancer efficacy, mice were immunized with cit-ENO1 or unm-ENO1 peptides, followed by orthotopic implantation with murine BRCA1co/co; MMTV-Cre; p53+/- TNBC cells. Tumor growth and overall survival were assessed. Results: Cit-ENO1 peptide vaccination induced a statistically significantly greater percentage of activated CD8+ PD-1+ effector T cells as well as CD8+ CD44+ CD62L- effector memory T cells in the LNs compared with either the control groups or the unm-ENO1 peptide. CD8+ PD-1+ T-cells were also significantly elevated in immunized skin of cit-ENO1 vaccinated mice. Both cit-ENO1 and unm-ENO1 vaccine increased CD4+ PD-1+ T cells from the LNs and immunized skin. Remarkably, the cit-ENO1 vaccine but not the um-ENO1 vaccine significantly delayed tumor growth and markedly improved overall survival compared to respective controls. Conclusion: Cancer-selective cit-ENO1 peptides induced a potent anti-cancer immune response and significantly delayed tumor initiation and progression in a preclinical, immune competent mouse model of TNBC. Citation Format: Ricardo A. Leon Letelier, Hiroyuki Katayama, Yihui Chen, Yinning Cai, Fuchung Hsiao, Banu Arun, Samir Hanash. A citrullinated-ENO1 peptide vaccine delayed tumor growth and markedly improved overall survival in a mouse model of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4098.

Abstract 2458: Targeting the CXCR3 axis in HER2+ breast cancer to enhance anti-tumor immunity

Abstract Breast cancer (BC) is the most frequently diagnosed cancer in women worldwide with more than 2 million new cases in 2020. The efficacy of immunotherapies for BC is limited, with response rates of &amp;lt;10% for anti-PD-1/PDL1 monotherapy in pre-treated triple-negative breast cancer (TNBC) patients and even lower in subtypes that express human epidermal growth factor receptor 2 (HER2+) and/or hormone receptors. Hence, there is an urgent need to improve immune based strategies for BC. One possible approach to enhance response is the application of intratumoral (IT) immunotherapy utilizing IL-12; a potent pro-inflammatory cytokine that is critical in producing an anti-tumor response. However, systemic delivery of IL-12 has substantial toxicity and localized delivery of protein has insufficient residence time. To circumvent these issues, we have previously reported the efficacy of intratumorally injected plasmid IL-12 (pIL-12-EP) followed by electroporation in a TNBC mouse model and in clinical trials. Following pIL-12-EP, treated tumor expressed genes that were associated with increased CD8+ T cell infiltration, activation, trafficking, antigen presentation, and exhaustion. Single-cell RNA sequencing (scRNAseq) of tumor infiltrating immune cells from treated tumors revealed a striking enrichment of the CXCL9/10/11/CXCR3 family. This CXCR3 axis is upregulated in response to IFNγ production and has been studied extensively in melanoma and NSCLC patients as a potential predictive biomarker for responses to immune checkpoint inhibitors but has not been well characterized in BC. We hypothesized that this axis may be the critical component downstream of pIL-12-EP treatment that is responsible for anti-tumor responses and that targeting it will be effective in other molecular subtypes of BC beyond TNBC. We first evaluated the expression of CXCR3 by tumor infiltrating lymphocytes (TILs) in biopsies of human HER2+ BC. Using a single cell resolution spatial transcriptomic Xenium instrument we find not only expression of CXCR3 by TILs, but can also track the distance and gradients of the chemokine ligands CXCL9 and CXCL10 in this tumor microenvironment. Having confirmed the activity of this axis in human HER2+ BC, we used our well-established spontaneous HER2-driven mouse model to compare treatment of HER2+ tumors with pIL-12-EP or pCXCL9-EP intratumorally. We observed tumor growth inhibition in both treatment groups as compared to control treated tumors. Interestingly, the abscopal effect previously seen with pIL-12-EP was not evident for distant tumors in mice treated with pCXCL9-EP. These data suggest that IT CXCL9 therapies may benefit from combination with a systemic immune activator like a vaccine or immunogenic chemotherapy. Ongoing studies will continue to evaluate ways to better target this axis therapeutically and define clinically active combination therapies. Citation Format: Anchit Bhagat, Jesuchristopher Joseph, Joshua D. Ginzel, Christopher Rabiola, Amy C. Hobeika, Joshua C. Snyder, Herbert K. Lyerly, Erika J. Crosby. Targeting the CXCR3 axis in HER2+ breast cancer to enhance anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2458.

Abstract 4726: Identification of efficacy biomarkers for therapies targeting miR-10b

Abstract Breast cancer stemness is one of the drivers of metastatic spread and presents a key target in the battle against metastatic disease, especially in triple-negative breast cancer (TNBC). Existing treatment options for TNBC are limited due to recurrence and resistance, representing a major unmet clinical need. MicroRNA-10b (miR-10b) is one of the major drivers of breast cancer cell migration and invasion. In our earlier studies, we discovered that miR-10b is also responsible for metastatic cell viability. With the goal of translation of this finding to the clinic, we developed a novel therapeutic, or “nanodrug,” that targets miR-10b, consisting of antisense anti-miR-10b oligonucleotides conjugated to magnetic nanoparticles (MN) that serve as delivery vehicles. Administration of the nanodrug in mice bearing metastatic MDA-MB-231 TNBC tumors prevents the development of metastases and stops the growth of pre-existing metastases. Additionally, combination treatment with adjuvant doxorubicin induced a stable regression of metastases in immunocompromised and immunocompetent mouse models of metastatic TNBC. A limitation of our previous studies is the lack of understanding of the molecular basis for the therapeutic effect of MN-anti-miR10b. To address this gap in knowledge, we performed RNA sequencing on MDA-MB-231 cells treated with the nanodrug or controls. Functional enrichment analysis of differentially expressed genes (DEGs) between cells treated with the nanodrug versus controls (PBS or bare MN) identified a significant overrepresentation of genes associated with cell differentiation. It has been suggested that miR-10b confers stem cell-like properties such as self-renewal and drug resistance onto cancer cells. Our RNA sequencing findings led us to hypothesize that MN-anti-miR10b functions by inhibiting these stem-like cancer cell (CSC) features that are critical to cancer survival. Here, we present preliminary data showing that miR-10b is overexpressed in MDA-MB-231 cells expressing a CSC-associated surface marker phenotype (CD44+/CD24-, compared to CD44-/CD24- cells) and that this trend is not universal among other miRNAs. Furthermore, we found that the nanodrug interferes with the ability of cells to assemble as spheroids, a property associated with CSCs. With our recent observation that the nanodrug inhibits miR-10b in metastases in vivo in as little as one dose after 72 hours, our next steps are to determine whether the cell differentiation-associated DEGs identified in RNA sequencing results can be used as biomarkers of nanodrug efficacy in vivo. Understanding the changes in gene expression induced by MN-anti-miR10b as a function of time will be critical for guiding treatment regimens in future preclinical and clinical trials. Citation Format: Alan Halim, Nasreen Al-Qadi, Sujan K. Mondal, Elizabeth Kenyon, N. Anna Savan, Hussein Mackie, Anna Moore. Identification of efficacy biomarkers for therapies targeting miR-10b [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4726.

Abstract 5568: Understanding the role of immune exclusion in mammary tumor growth

Abstract Multiple solid tumor types, including triple-negative breast cancer (TNBC), respond poorly to immunotherapy due to low infiltration of CD8+ T cells into the tumor core. The extracellular matrix (ECM) and its components such as collagen have been found to contribute to immune cell exclusion. Discoidin domain receptor 1 (DDR1) is a collagen receptor known to be aberrantly expressed in TNBC among multiple solid tumor types. We have uncovered a previously unappreciated function of DDR1 in immune exclusion through shaping a collagen fiber-based tumor defense against anti-tumor immunity (Sun et al, Nature 599, 673-678 (2021)). Our study showed that deletion of DDR1 in mouse mammary carcinoma cell lines such as E0771 and M-Wnt (syngeneic with C57BL/6 strain background) promotes infiltration of CD8+ T cells and reduces tumor growth in an immunocompetent mouse model. Extending the published study to other immunocompetent mouse strain backgrounds, we observed that deletion of DDR1 in EMT6 cells, another immune excluded TNBC mouse model in the BALB/c strain, increased the infiltration of CD8+ T cells to the tumor core and reduced tumor growth. Data concerning the DDR1-dependent spatial architecture of the mammary tumor microenvironment will be presented. Identifying specific immune and stromal cell populations and proteins spatially modified in the presence or absence of DDR1 may aid in development of new stand-alone or combination anti-cancer treatments with anti DDR1 antibody. Citation Format: Payal Mitra, Jorge Azpurua, Huai-Chin Chiang, Rong Li. Understanding the role of immune exclusion in mammary tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5568.

Evaluating immunotherapeutic outcomes in triple-negative breast cancer with a cholesterol radiotracer in mice.

Evaluating the response to immune checkpoint inhibitors (ICIs) remains an unmet challenge in triple-negative breast cancer (TNBC). The requirement for cholesterol in the activation and function of T cells led us to hypothesize that quantifying cellular accumulation of this molecule could distinguish successful from ineffective checkpoint immunotherapy. To analyze accumulation of cholesterol by T cells in the immune microenvironment of breast cancer, we leveraged the PET radiotracer, eFNP-59. eFNP-59 is an analog of cholesterol that our group validated as an imaging biomarker for cholesterol uptake in preclinical models and initial human studies. In immunocompetent mouse models of TNBC, we found that elevated uptake of exogenous labeled cholesterol analogs functions as a marker for T cell activation. When comparing ICI-responsive and -nonresponsive tumors directly, uptake of fluorescent cholesterol and eFNP-59 increased in T cells from ICI-responsive tumors. We discovered that accumulation of cholesterol by T cells increased in ICI-responding tumors that received anti-PD-1 checkpoint immunotherapy. In patients with TNBC, tumors containing cycling T cells had features of cholesterol uptake and trafficking within those populations. These results suggest that uptake of exogenous cholesterol analogs by tumor-infiltrating T cells allows detection of T cell activation and has potential to assess the success of ICI therapy.

The deubiquitinase BRCC3 increases the stability of ZEB1 and promotes the proliferation and metastasis of triple-negative breast cancer cells.

Triple negative breast cancer (TNBC) has a high recurrence rate, metastasis rate and mortality rate. The aim of this study is to identify new targets for the treatment of TNBC. Clinical samples are used for screening deubiquitinating enzymes (DUBs). MDA-MB-231 cells and a TNBC mouse model are used for in vitro and in vivo experiments, respectively. Western blot analysis is used to detect the protein expressions of DUBs, zinc finger E-box binding homeobox 1 (ZEB1), and epithelial-mesenchymal transition (EMT)-related markers. Colony formation and transwell assays are used to detect the proliferation, migration and invasion of TNBC cells. Wound healing assay is used to detect the mobility of TNBC cells. Immunoprecipitation assay is used to detect the interaction between breast cancer susceptibility gene 1/2-containing complex subunit 3 (BRCC3) and ZEB1. ZEB1 ubiquitination levels, protein stability, and protein degradation are also examined. Pathological changes in the lung tissues are detected via HE staining. Our results show a significant positive correlation between the expressions of BRCC3 and ZEB1 in clinical TNBC tissues. Interference with BRCC3 inhibits TNBC cell proliferation, migration, invasion and EMT. BRCC3 interacts with ZEB1 and interferes with BRCC3 to inhibit ZEB1 expression by increasing ZEB1 ubiquitination. Interference with BRCC3 inhibits TNBC cell tumorigenesis and lung metastasis in vivo. In all, this study demonstrates that BRCC3 can increase the stability of ZEB1, upregulate ZEB1 expression, and promote the proliferation, migration, invasion, EMT, and metastasis of TNBC cells, providing a new direction for cancer therapy.

S100A8/A9 predicts response to PIM kinase and PD-1/PD-L1 inhibition in triple-negative breast cancer mouse models

BackgroundUnderstanding why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well remains a challenge. This study aims to understand the potential underlying mechanisms distinguishing early-stage TNBC tumors that respond to clinical intervention from non-responders, as well as to identify clinically viable therapeutic strategies, specifically for TNBC patients who may not benefit from existing therapies.MethodsWe conducted retrospective bioinformatics analysis of historical gene expression datasets to identify a group of genes whose expression levels in early-stage tumors predict poor clinical outcomes in TNBC. In vitro small-molecule screening, genetic manipulation, and drug treatment in syngeneic mouse models of TNBC were utilized to investigate potential therapeutic strategies and elucidate mechanisms of drug action.ResultsOur bioinformatics analysis reveals a robust association between increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors and subsequent disease progression in TNBC. A targeted small-molecule screen identifies PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Notably, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC.ConclusionsOur data propose S100A8/A9 as a potential predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC. This work encourages the development of S100A8/A9-based liquid biopsy tests for treatment guidance.