Cell-intrinsic Signaling Research Articles

Hippo pathway in cancer cells induces NCAM1+αSMA+ fibroblasts to modulate tumor microenvironment

Cancer cells adeptly manipulate the tumor microenvironment (TME) to evade host antitumor immunity. However, the role of cancer cell-intrinsic signaling in shaping the immunosuppressive TME remains unclear. Here, we found that the Hippo pathway in cancer cells orchestrates the TME by influencing the composition of cancer-associated fibroblasts (CAFs). In a 4T1 mouse breast cancer model, Hippo pathway kinases, large tumor suppressor 1 and 2 (LATS1/2), promoted the formation of neural cell adhesion molecule 1 (NCAM1)+alpha-smooth muscle actin (αSMA)+ CAFs expressing the transforming growth factor-β, which is associated with T cell inactivation and dysfunction. Depletion of LATS1/2 in cancer cells resulted in a less immunosuppressive TME, indicated by the reduced proportions of NCAM1+αSMA+ CAFs and dysfunctional T cells. Notably, similar Hippo pathway-induced NCAM1+αSMA+ CAFs were observed in human breast cancer, highlighting the potential of TME-manipulating strategies to reduce immunosuppression in cancer immunotherapy.

High levels of tumor cell-intrinsic STING signaling are associated with increased infiltration of CD8+ T cells in dMMR/MSI-H gastric cancer

Mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) gastric cancer (GC) exhibits an immune-active tumor microenvironment (TME) compared to MMR proficient (pMMR)/microsatellite stable/Epstein-Barr virus-negative [EBV (−)] GC. The tumor cell-intrinsic cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathway has been considered a key regulator of immune cell activation in the TME. However, its significance in regulating the immune-active TME in dMMR/MSI-H GC remains unclear. Here, we demonstrated that tumor cell-intrinsic cGAS–STING was highly expressed in dMMR GC compared to pMMR/EBV (−) GC. The expression of tumor cell-intrinsic STING was significantly and positively associated with the number of CD8+ tumor-infiltrating lymphocytes in GC. Analysis of TCGA datasets revealed that the expression of interferon-stimulated genes and STING downstream T-cell attracting chemokines was significantly higher in MSI-H GC compared to other subtypes of GC with EBV (−). These results suggest that tumor cell-intrinsic STING signaling plays a key role in activating immune cells in the dMMR/MSI-H GC TME and might serve as a novel biomarker predicting the efficacy of immunotherapy for GC treatment.

Activation of Cell-Intrinsic Signaling in CAR-T Cells via a Chimeric IL7R Domain.

To improve the phenotype of tumor-directed T-cell therapy, we show that provision of cell-intrinsic IL7R-mediated signaling is preferable to activation of cells with exogenous IL7. We engineer this signaling via independent receptor engineering and incorporation into a CAR and validate maintained antigen-specific cytotoxic activity.

Cell autonomous functions of CD47 in regulating cellular plasticity and metabolic plasticity.

CD47 is a ubiquitously expressed cell surface receptor, which is widely known for preventing macrophage-mediated phagocytosis by interacting with signal regulatory protein α (SIRPα) on the surface of macrophages. In addition to its role in phagocytosis, emerging studies have reported numerous noncanonical functions of CD47 that include regulation of various cellular processes such as proliferation, migration, apoptosis, differentiation, stress responses, and metabolism. Despite lacking an extensive cytoplasmic signaling domain, CD47 binds to several cytoplasmic proteins, particularly upon engaging with its secreted matricellular ligand, thrombospondin 1. Indeed, the regulatory functions of CD47 are greatly influenced by its interacting partners. These interactions are often cell- and context-specific, adding a further level of complexity. This review addresses the downstream cell-intrinsic signaling pathways regulated by CD47 in various cell types and environments. Some of the key pathways modulated by this receptor include the PI3K/AKT, MAPK/ERK, and nitric oxide signaling pathways, as well as those implicated in glucose, lipid, and mitochondrial metabolism. These pathways play vital roles in maintaining tissue homeostasis, highlighting the importance of understanding the phagocytosis-independent functions of CD47. Given that CD47 expression is dysregulated in a variety of cancers, improving our understanding of the cell-intrinsic signals regulated by this molecule will help advance the development of CD47-targeted therapies.

Intrinsic signaling pathways modulate targeted protein degradation

Targeted protein degradation is a groundbreaking modality in drug discovery; however, the regulatory mechanisms are still not fully understood. Here, we identify cellular signaling pathways that modulate the targeted degradation of the anticancer target BRD4 and related neosubstrates BRD2/3 and CDK9 induced by CRL2VHL- or CRL4CRBN -based PROTACs. The chemicals identified as degradation enhancers include inhibitors of cellular signaling pathways such as poly-ADP ribosylation (PARG inhibitor PDD00017273), unfolded protein response (PERK inhibitor GSK2606414), and protein stabilization (HSP90 inhibitor luminespib). Mechanistically, PARG inhibition promotes TRIP12-mediated K29/K48-linked branched ubiquitylation of BRD4 by facilitating chromatin dissociation of BRD4 and formation of the BRD4–PROTAC–CRL2VHL ternary complex; by contrast, HSP90 inhibition promotes BRD4 degradation after the ubiquitylation step. Consequently, these signal inhibitors sensitize cells to the PROTAC-induced apoptosis. These results suggest that various cell-intrinsic signaling pathways spontaneously counteract chemically induced target degradation at multiple steps, which could be liberated by specific inhibitors.

Leucine Suppresses α-Cell cAMP and Glucagon Secretion via a Combination of Cell-Intrinsic and Islet Paracrine Signaling.

Glucagon is critical for the maintenance of blood glucose, however nutrient regulation of pancreatic α-cells remains poorly understood. Here, we identified a role for leucine, a well-known β-cell fuel, in the α-cell intrinsic regulation of glucagon release. In islet perifusion assays, physiological concentrations of leucine strongly inhibited alanine and arginine-stimulated glucagon secretion from human and mouse islets under hypoglycemic conditions. Mechanistically, leucine dose-dependently reduced α-cell cAMP, independently of Ca2+, ATP/ADP, or fatty acid oxidation. Leucine also reduced α-cell cAMP in islets treated with Sstr2 antagonists or diazoxide, compounds that limit paracrine signaling from β/δ-cells. Studies in dispersed mouse islets confirmed an α-cell intrinsic effect. The inhibitory effect of leucine on cAMP was mimicked by glucose, α-ketoisocaproate, succinate, and the glutamate dehydrogenase activator BCH, and blocked by cyanide, indicating a mechanism dependent on mitochondrial metabolism. Glucose dose-dependently reduced the impact of leucine on α-cell cAMP, indicating an overlap in function, however leucine was still effective at suppressing glucagon secretion in the presence of elevated glucose, amino acids, and the incretin GIP. Taken together, these findings show that leucine plays an intrinsic role in limiting α-cell secretory tone across the physiological range of glucose levels, complementing the inhibitory paracrine actions of β/δ-cells.

Fully equipped CARs to address tumor heterogeneity, enhance safety, and improve the functionality of cellular immunotherapies.

Although adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells has achieved unprecedented response rates in patients with certain hematological malignancies, this therapeutic modality is still far from fulfilling its remarkable potential, especially in the context of solid cancers. Antigen escape variants, off-tumor destruction of healthy tissues expressing tumor-associated antigens (TAAs), poor CAR-T cell persistence, and the occurrence of functional exhaustion represent some of the most prominent hurdles that limit CAR-T cell ability to induce long-lasting remissions with a tolerable adverse effect profile. In this review, we summarize the main approaches that have been developed to face such bottlenecks, including the adapter CAR (AdCAR) system, Boolean-logic gating, epitope editing, the modulation of cell-intrinsic signaling pathways, and the incorporation of safety switches to precisely control CAR-T cell activation. We also discuss the most pressing issues pertaining to the selection of co-stimulatory domains, with a focus on strategies aimed at promoting CAR-T cell persistence and optimal antitumor functionality.

Multiregional transcriptomics identifies congruent consensus subtypes with prognostic value beyond tumor heterogeneity of colorectal cancer

Intra-tumor heterogeneity compromises the clinical value of transcriptomic classifications of colorectal cancer. We investigated the prognostic effect of transcriptomic heterogeneity and the potential for classifications less vulnerable to heterogeneity in a single-hospital series of 1093 tumor samples from 692 patients, including multiregional samples from 98 primary tumors and 35 primary-metastasis sets. We show that intra-tumor heterogeneity of the consensus molecular subtypes (CMS) is frequent and has poor-prognostic associations independently of tumor microenvironment markers. Multiregional transcriptomics uncover cancer cell-intrinsic and low-heterogeneity signals that recapitulate the intrinsic CMSs proposed by single-cell sequencing. Further subclassification identifies congruent CMSs that explain a larger proportion of variation in patient survival than intra-tumor heterogeneity. Plasticity is indicated by discordant intrinsic phenotypes of matched primary and metastatic tumors. We conclude that multiregional sampling reconciles the prognostic power of tumor classifications from single-cell and bulk transcriptomics in the context of intra-tumor heterogeneity, and phenotypic plasticity challenges the reconciliation of primary and metastatic subtypes.

N-MYC impairs innate immune signaling in high-grade serous ovarian carcinoma.

High-grade serous ovarian cancer (HGSC) is a challenging disease, especially for patients with immunologically "cold" tumors devoid of tumor-infiltrating lymphocytes (TILs). We found that HGSC exhibits among the highest levels of MYCN expression and transcriptional signature across human cancers, which is strongly linked to diminished features of antitumor immunity. N-MYC repressed basal and induced IFN type I signaling in HGSC cell lines, leading to decreased chemokine expression and T cell chemoattraction. N-MYC inhibited the induction of IFN type I by suppressing tumor cell-intrinsic STING signaling via reduced STING oligomerization, and by blunting RIG-I-like receptor signaling through inhibition of MAVS aggregation and localization in the mitochondria. Single-cell RNA sequencing of human clinical HGSC samples revealed a strong negative association between cancer cell-intrinsic MYCN transcriptional program and type I IFN signaling. Thus, N-MYC inhibits tumor cell-intrinsic innate immune signaling in HGSC, making it a compelling target for immunotherapy of cold tumors.

Epithelial−mesenchymal transition induced by tumor cell-intrinsic PD-L1 signaling predicts a poor response to immune checkpoint inhibitors in PD-L1-high lung cancer

BackgroundWe investigated the role of tumor cell-intrinsic PD-L1 signaling in the epithelial−mesenchymal transition (EMT) in non-small-cell lung cancer (NSCLC) and the role of EMT as a predictive biomarker for immune checkpoint inhibitor (ICI) therapy.MethodsPD-L1-overexpressing or PD-L1-knockdown NSCLC cells underwent RNA-seq and EMT phenotype assessment. Mouse lung cancer LLC cells were injected into nude mice. Two cohorts of patients with NSCLC undergoing ICI therapy were analyzed.ResultsRNA-seq showed that EMT pathways were enriched in PD-L1-high NSCLC cells. EMT was enhanced by PD-L1 in NSCLC cells, which was mediated by transforming growth factor-β (TGFβ). PD-L1 promoted the activation of p38-MAPK by binding to and inhibiting the protein phosphatase PPM1B, thereby increasing the TGFβ production. Tumor growth and metastasis increased in nude mice injected with PD-L1-overexpressing LLC cells. In the ICI cohort, EMT signature was higher in patients with progressive disease than in those with responses, and EMT was significantly associated with poor survival in PD-L1-high NSCLC. In PD-L1-high NSCLC, EMT was associated with increased M2-macrophage and regulatory T-cell infiltrations and decreased cytotoxic T-cell infiltration.ConclusionsTumor cell-intrinsic PD-L1 function contributes to NSCLC progression by promoting EMT. EMT may predict an unfavorable outcome after ICI therapy in PD-L1-high NSCLC.

The immunoglobulin superfamily ligand B7H6 subjects T cell responses to NK cell surveillance.

Understanding the mechanisms that regulate T cell immunity is critical for the development of effective therapies for diseases associated with T cell dysfunction, including autoimmune diseases, chronic infections, and cancer. Co-inhibitory "checkpoint molecules," such as programmed cell death protein-1, balance excessive or prolonged immune activation by T cell-intrinsic signaling. Here, by screening for mediators of natural killer (NK) cell recognition on T cells, we identified the immunoglobulin superfamily ligand B7H6 to be highly expressed by activated T cells, including patient-infused CD19-targeting chimeric antigen receptor (CAR) T cells. Unlike other checkpoint molecules, B7H6 mediated NKp30-dependent recognition and subsequent cytolysis of activated T cells by NK cells. B7H6+ T cells were prevalent in the tissue and blood of several diseases, and their abundance in tumor tissue positively correlated with clinical response in a cohort of patients with immune checkpoint inhibitor-treated esophageal cancer. In humanized mouse models, NK cell surveillance via B7H6 limited the persistence and antitumor activity of CAR T cells, and its genetic deletion enhanced T cell proliferation and persistence. Together, we provide evidence of B7H6 protein expression by activated T cells and suggest the B7H6-NKp30 axis as a therapeutically actionable NK cell-dependent immune checkpoint that regulates human T cell function.

Abstract P53: Inhibition of STING/Galectin-9 Axis Sensitize Anthracyclines Treatment And Induce Anti-tumor Immunity

Abstract Anthracyclines, are a class of conventional and routinely used firstline chemotherapy drugs to treat breast cancer. Immunogenic cell death (ICD) is characterized by the exposure of danger signals that promote dendritic cell maturation and antigen presentation and is often associated with the induction of cancer cell-intrinsic IFN-I signaling pathway. In addition, among multiple chemotherapeutic drugs such as doxorubicin (Dox) is well-known to promote tumor immunogenicity by interfering with DNA synthesis. Galectin-9 (Gal-9), as a member of β-galactoside-binding protein family, has been demonstrated to induce T cell death and promote immunosuppression in the tumor microenvironment. In addition, it has been shown that some interferon (IFN) and interleukin (IL) factors can induce Gal-9 expression. However, the mechanism cross-talk between anthracyclines and Gal-9 immunecheckpoint inhibitor remains unknown. Here we show that doxorubicin induces PD-L1 expression in human breast cancer cell lines and animal models. Mechanistically, doxorubicin promoted IFNβ expression, which in turn enhanced doxorubicin-induced Gal-9. Furthermore, we discovered that doxorubicin induces tumor Gal-9 via STING upregulation. The combination of doxorubicin and anti-Gal-9 therapy compared with each agent alone significantly increased the therapeutic efficacy in vivo. Clinically, a higher Gal-9 and p-STING level in the tumor region of after-treatment anthracyclines as compared to before treatment is indicated in breast cancer tumor tissue. Taken together, our study demonstrates crosstalk between anthracyclines-induced ICD and tumor-associated immunosuppression and provides a novel therapeutic strategy by combining anthracyclines and Gal-9 antibody in breast cancer. Citation Format: Xian Sun, Wei-Jan Wang, Jilu Lang, Riyao Yang, Wan-Jou Shen, Linlin Sun, Mien-Chie Hung. Inhibition of STING/Galectin-9 Axis Sensitize Anthracyclines Treatment And Induce Anti-tumor Immunity [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P53.

Abstract NG04: Targeting DHX9 to trigger viral mimicry and immunotherapy responsiveness in small cell lung cancer

Abstract NG04: Targeting DHX9 to trigger viral mimicry and immunotherapy responsiveness in small cell lung cancer

Abstract 3355: Unraveling the molecular mechanisms of glioma migration: Exploring the role of cell intrinsic and stromal ephrin receptor-ligand signaling

Abstract Diffuse invasion, a hallmark of malignant gliomas, makes these tumors surgically incurable and is the ultimate cause of death. While glioma cells can migrate along blood vessels and in neuron-rich regions, their preferred route of migration is along white matter (WM) tracts, which allows tumor cells to spread to the contralateral hemisphere with devastating neurocognitive consequences. The underlying mechanisms of in vivo glioma cell migration are poorly understood. There is emerging evidence that glioblastoma multiforme (GBM) cells may hijack migration mechanisms used during brain development. Accordingly, we used a neonatal plasmid electroporation GBM model (CRISPR-Cas9, -Cre,gRNAs targeting NF1, p53, PTEN, and piggyBac-glast) to generate a highly penetrant diffusely invasive glioma models with preference for migration along myelinated fiber tracts including the corpus callosum (CC). To test the in vivo role of integrin-mediated migration, tumors were generated using conditional integrin β1f/f (ITGB1) or focal adhesion kinase (FAKf/f) mice. Both ITGB1 and FAK null GBM cells (confirmed by western blot analysis) showed diffuse infiltration similar to WT mice, suggesting that integrin signaling is not essential for in vivo GBM cell migration. Next, we tested the role ephrin-signaling using a series of transgenic neonatal mice, including EPH-B1-/-, -B2-/-, -B1/2-/-, -kinase-dead (KD) and a gain-of-function mutant). EPH1/2-/- GBM, but not the other genetic models, consistently formed tumors which showed no diffuse single-cell infiltration, but rather grew as a solid expanding mass. An extensive panel of in vitro studies comparing WT and EPHB1/2-/- GBM patterns of growth and migration, including time-lapse random walk, neurosphere radial migration, migration along patterned surfaces, and laminin-coated confined 3D channels, showed similar patterns of migration, despite the marked differences in vivo. These contrasting in vivo and in vitro results raise the possibility that EPH-B1/2 receptors may require their cognate ephrin ligands to facilitate migration through the WM tracts. To test this hypothesis, we are using Ephrin-B1f/f, B2f/f mice for in vivo cell-type specific deletion in WM tract stroma cells and primary astrocytes derived from these mice for ex vivo co-culture studies. Our preliminary data suggest that EPH/EPHRIN interactions may regulate GBM cell migration. Citation Format: Jesung Moon, Xiaofei Gao, Peiguo Ding, Fnu Bilal, Smita Rindhe, Ning Gao, Digant P. Dave, Mark Henkemeyer, Elizabeth A. Maher, Robert M. Bachoo. Unraveling the molecular mechanisms of glioma migration: Exploring the role of cell intrinsic and stromal ephrin receptor-ligand signaling [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 3355.

Abstract 6535: Targeting estrogen receptor signaling in tumor associated myeloid cells to enhance anti-tumor immunity

Abstract Immune checkpoint inhibitors (ICB) have significantly improved outcomes across the spectrum of cancers, especially in patients with metastatic melanoma or non-small cell lung cancer (NSCLC). Despite encouraging efficacy in some patients, the development of primary and acquired resistance and severe toxicity associated with these treatment regimens, together with the overall low response rates, have limited their widespread use. Mining publicly available transcriptomic datasets, we have demonstrated that the response to ICB in patients with melanoma is influenced by the functionality of tumor associated macrophages (TAMs). Thus, it is of significance that we have demonstrated that 17-β estradiol (E2), working through myeloid cell intrinsic estrogen receptor alpha (ERα), promotes tumor growth in preclinical mouse models by polarizing tumor associated macrophages towards an immune-suppressive state in a manner that suppresses CD8+T cell functionality and limits ICB efficacy independent of gender. Transcriptomic analysis of tumor infiltrating myeloid cells isolated from E2-treated syngeneic tumors revealed that the type I interferon (IFN) signaling pathway was suppressed and that this activity could be reversed by the addition of fulvestrant a Selective Estrogen Receptor Downregulator. The importance of type I IFN signaling in E2-regulated tumor growth was confirmed in syngeneic mouse tumor models (B16F10-melanoma and LLC1-NSCLC cells) by showing that inhibiting type I interferon receptor (IFNAR) activity using blocking antibodies reversed the protective effects of E2 deprivation (ovariectomy) on tumor growth. Further, using in vitro cultures of macrophages from mouse bone marrow or peripheral blood mononuclear cells from deidentified human donors, we demonstrated that E2-dependent inhibition of type I IFN signaling could be attributed to increased efferocytosis by myeloid cells. These findings were recapitulated in vivo using an IFN reporter mouse (Mx1-egfp) implanted with labelled tumor cells (mCherry-Spectrin labelled LLC1), where we demonstrated that E2 mediated-suppression of myeloid cell intrinsic interferon signaling within the tumor microenvironment is contingent upon their engulfment of apoptotic cancer cells. Mechanistically, this enhanced efferocytosis was attributed to increased expression of the fractalkine receptor (CX3CR1) in E2-treated myeloid cells- as either genetic or pharmacological depletion of CX3CR1 in mouse reversed E2-mediated tumor growth (B16F10 and LLC1), myeloid cell polarization (from immunosuppressive to proinflammatory), myeloid cell intrinsic type I IFN signaling and reinvigorated CD8+T cell function. Taken together, our results highlight the potential clinical utility of targeting the E2/ER-CX3CR1 pathway as a means to enhance response to ICBs. Citation Format: Binita Chakraborty, Michael Brown, Prabuddha Chakraborty, Aditi Goyal, Ching Yi Chang, Donald McDonnell. Targeting estrogen receptor signaling in tumor associated myeloid cells 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 6535.

Abstract 3906: Ex vivo breast tumors for understanding the patient specific tumor microenvironment remodeling and drug responses

Abstract Breast cancer is a heterogeneous disease driven by cell-intrinsic and cell-extrinsic signaling cues. Many of these cues derive from the tumor microenvironment (TME), which is composed of adipocytes, vasculature, stem cells, immune cells, and the extracellular matrix (ECM). Through these diverse components, the TME modulates cellular proliferation, survival, and ultimately response to therapy. Despite this high-level understanding of tumor-TME crosstalk, no existing pre-clinical models accurately capture the TME in vitro. We overcame that hurdle by developing a method to maintain healthy human breast tissue (HBT) alive ex vivo for at least 8 weeks. By culturing breast cancer cells in that HBT, we created ex vivo breast tumors (EVBTs) that retained patient-specific features relevant to breast cancer including menopause status, obesity status, and response to therapy. Using these EVBTs, we demonstrate breast cancer subtype-specific alterations in lipid accumulation, ECM remodeling, and cytokine profiles. RNA sequencing showed that breast cancer cell line signatures were retained in the EVBTs system at 1 week and 2 weeks in vitro. We demonstrated donor-specific transcriptional changes to the core matrisome gene set. Finally, we demonstrate that our EVBTs retained patient-specific heterogeneity in response to standard of care endocrine therapy and neoadjuvant chemotherapies. Our novel tumor model allows for 1) real-time examination of breast cancer interactions with HBT and the TME and 2) the isolation of breast cancer-specific factors vs. patient-specific factors in the development and progression of breast cancer. Citation Format: Elizabeth Martin, Megan Benz, Katie Hebert, Ethan Byrne, Frank Lau. Ex vivo breast tumors for understanding the patient specific tumor microenvironment remodeling and drug responses [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 3906.

Abstract B022: Targeting epithelial-mesenchymal plasticity and CD73 to enhance responses of breast cancers to immune checkpoint blockade therapies

Abstract Immune checkpoint blockade (ICB) therapy has generated dramatic responses in certain types of human tumors however, the response of breast cancers has been largely limited. Epithelial-mesenchymal plasticity (EMP) enables carcinoma cells to metastasize, gain tumor-initiating ability and mount resistance to chemotherapies. In addition, we have demonstrated that this plasticity program also contributes to the establishment of an immunosuppressive tumor microenvironment and confers resistance to ICB therapy (Dongre and Weinberg 2019). By establishing novel, preclinical models of more-epithelial or more-mesenchymal breast tumors, we observed that epithelial tumors recruit CD8+ T-cells to their microenvironment and are sensitive to anti-CTLA4 ICB. In contrast, mesenchymal tumors recruit Tregs and M2-like macrophages and are resistant to the same treatment (Dongre et al., 2017). Strikingly, abrogation of CD73 from more-mesenchymal cells completely sensitizes otherwise refractory tumors to anti-CTLA4 ICB (Dongre et al., 2021). These findings demonstrated for the first time that more-mesenchymal breast cancer cells can be completely sensitized to anti-tumor immunity by interrupting certain cell-intrinsic signaling channels. However, the underlying mechanisms of such sensitization remain elusive. Additionally, the regulatory networks that control the expression of CD73 itself in more-mesenchymal but not epithelial breast cancer cells are not well defined. To determine the subset of T-cells that is functionally important in sensitizing mesenchymal tumors lacking CD73, we depleted either conventional CD4+ T-cells or CD8+ cytotoxic T-cells in combinatoin with ICB. While responding mice recruited both T-cells to their tumors, only CD4+ T-cells (and not CD8+ T-cells) were functionally important in driving sensitization. Along these lines, more-mesenchymal cancer cells lacking CD73 failed to respond to anti-CTLA4 ICB when propagated in genetically engineered mice lacking CD4+ T-cells relative to wild type controls. Importantly, depletion of CD4+ T-cells also prevented the recruitment of peripheral CD8+ T-cells to responding tumors, thereby driving resistance to ICB. In addition, we observed that human triple negative breast cancer cell lines expressed the highest amount of CD73 relative to hormone receptor-positive cell lines. Most importantly, activating EMP in human breast cancer cells by doxycycline-controlled expression of various transcription factors, induced the expression of CD73. Taken together, our work demonstrates that (i) the phenotypic plasticity of breast cancer cells can predict responses to ICB (ii) targeting CD73 can completely sensitize more-mesenchymal tumors to anti-CTLA4 ICB in a CD4+ T-cell dependent fashion and; (iii) altering the cellular plasticity of cancer cells can regulate CD73 expression. Given the highly refractory nature of more-mesenchymal cancer cells, our findings hold tremendous potential in aiding translational efforts to target cancer plasticity to enhance responses of breast cancers to ICB therapy. Citation Format: Anushka Dongre. Targeting epithelial-mesenchymal plasticity and CD73 to enhance responses of breast cancers to immune checkpoint blockade therapies [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B022.

Tumor Cell-Intrinsic p38 MAPK Signaling Promotes IL1α-Mediated Stromal Inflammation and Therapeutic Resistance in Pancreatic Cancer.

Inhibition of p38 MAPK suppresses tumor cell-derived IL1α and attenuates the inflammatory stroma and immunosuppressive tumor microenvironment to overcome chemotherapeutic resistance in pancreatic cancer.

Blockade of tumor cell-intrinsic PD-L1 signaling enhances AURKA-targeted therapy in triple negative breast cancer.

Triple negative breast cancer (TNBC) accounts for 15-20% of all breast cancers and mainly affects pre-menopausal and minority women. Because of the lack of ER, PR or HER2 expression in TNBC, there are limited options for tailored therapies. While TNBCs respond initially to standard of care chemotherapy, tumor recurrence commonly occurs within 1 to 3 years post-chemotherapy and is associated with early organ metastasis and a high incidence of mortality. One of the major mechanisms responsible for drug resistance and emergence of organ metastasis is activation of epithelial to mesenchymal transition (EMT) reprogramming. EMT-mediated cancer cell plasticity also promotes the enrichment of cancer cells with a CD44high/CD24low and/or ALDHhigh cancer stem-like phenotype [cancer stem cells (CSCs)], characterized by an increased capacity for tumor self-renewal, intrinsic drug resistance, immune evasion and metastasis. In this study we demonstrate for the first time a positive feedback loop between AURKA and intra-tumoral PD-L1 oncogenic pathways in TNBC. Genetic targeting of intra-tumoral PD-L1 expression impairs the enrichment of ALDHhigh CSCs and enhances the therapeutic efficacy of AURKA-targeted therapy. Moreover, dual AURKA and PD-L1 pharmacological blockade resulted in the strongest inhibition of tumor growth and organ metastatic burden. Taken together, our findings provide a compelling preclinical rationale for the development of novel combinatorial therapeutic strategies aimed to inhibit cancer cell plasticity, immune evasion capacity and organ metastasis in patients with advanced TNBC.

The Dual Inflammasome/Myddosome Inhibitor HT-6184 Restores Erythropoiesis in MDS/AML

Background: The NLRP3 inflammasome is one of the key biological drivers of ineffective hematopoiesis and inflammation in myelodysplastic syndrome (MDS). Inflammasome activation arises from both cell-extrinsic (e.g., Toll-like receptors) and cell-intrinsic signals (e.g., somatic mutations) that direct caspase-1 maturation leading to GATA-1 degradation, myeloid skewing, and pyroptotic cell death. HT-6184 is a potent allosteric inhibitor of the inflammasome scaffold protein NEK7 that blocks inflammasome assembly, promotes ASC speck dissolution, and inhibits myddosome activation of NFκβ. To investigate preclinical activity in MDS, we evaluated HT-6184 in MDS and acute myeloid leukemia (AML) models, including patient-derived sample cultures. Results: Expression of inflammasome pathway components was first assessed by gene expression profiling in a large cohort of MDS bone marrow CD34+-selected cells and healthy age-matched controls. Cellular expression of the inflammasome components, caspase-1, gasdermin D, IL-18 and Pycard was significantly upregulated in MDS specimens compared to healthy controls. Furthermore, cases with the highest expression of inflammasome effectors had significantly inferior overall survival (Log Rank P <0.05). The novel inflammasome inhibitor, HT-6184, was designed to prevent NEK7 from mediating the oligomerization of NLRP3 monomers following an activation signal, ultimately preventing inflammasome assembly. Thus, the structure of HT-6184 was tailored to maximize its interactions with NEK7, rigidifying the protein, and locking it in a conformation that prevents interaction with NLRP3. The allosteric activity of HT-6184 was examined using nano differential scanning fluorimetry and confirmed with limited proteolysis assays, which demonstrated that HT-6184 disrupts NEK7 conformations at single-digit nanomolar concentrations. This was confirmed in cell-based assays showing its ability to inhibit IL-1β release with a 50% inhibitory concentration (IC) of 46 nM in THP-1 cells. These data further correlate with HT-6184 blocking of ASC speck formation with an IC90 of 100 nM in THP-1 cells as well as speck dissolution. HT-6184 also affects the NF-κΒ pathway, by blocking myddosome function and resulting in a decreased expression of an NF-κΒ driven reporter gene, with an IC50 of 10.2 nM in transfected cells. HT-6184 exerts its pharmacological activity by inhibiting the priming and activation steps of the NLRP3 inflammasome. It is pharmacologically active in a human whole blood assay, strongly downregulating the production of pro-inflammatory cytokines. Anti-inflammatory efficacy was also observed in vivo in a murine inflammation model of inflammatory bowel disease. HT-6184 incubation with human monocytes abrogated production of IL-1β and IL-6, reverting human monocytes to a less inflamed state as demonstrated by single cell proteomic studies (isoplexis platform). It similarly decreased IL-1β production from monocytes derived from a TET2 -/+ mouse model that preferentially develops monocytic expansion. Finally, treatment initiation of primary MDS/AML bone marrow specimens (N=10) with HT-6184 in methylcellulose cultures markedly increased erythroid differentiation and reduced myelomonocytic colonies in the majority of samples. This was evidenced by the change in total number of colonies and by fluorescence activated cell sorting (FACS) assessment of differentiation markers (Glycophorin A, CD71, CD11b, CD14) after 14 days of incubation. Inflammasome-directed IL-1β secretion in primary MDS samples was also abrogated by HT-6184 treatment. Conclusions: These findings demonstrate that the novel dual inflammasome/myddosome inhibitor, HT-6184 effectively suppresses myeloid skewing, restores erythroid commitment in MDS/AML specimens, and provides a rationale for clinical development in myeloid malignancies.