Epithelial Expressed B7-H4 Drives Differential Immunotherapy Response in Murine and Human Breast Cancer

Combinations of immune checkpoint inhibitors (ICI, including anti-PD-1/PD-L1) and chemotherapy have been FDA approved for metastatic and early-stage triple-negative breast cancer (TNBC), but most patients do not benefit. B7-H4 is a B7 family ligand with proposed immunosuppressive functions being explored as a cancer immunotherapy target and may be associated with anti-PD-L1 resistance. However, little is known about its regulation and effect on immune cell function in breast cancers. We assessed murine and human breast cancer cells to identify regulation mechanisms of B7-H4 in vitro. We used an immunocompetent anti-PD-L1-sensitive orthotopic mammary cancer model and induced ectopic expression of B7-H4. We assessed therapy response and transcriptional changes at baseline and under treatment with anti-PD-L1. We observed B7-H4 was highly associated with epithelial cell status and transcription factors and found to be regulated by PI3K activity. EMT6 tumors with cell-surface B7-H4 expression were more resistant to immunotherapy. In addition, tumor-infiltrating immune cells had reduced immune activation signaling based on transcriptomic analysis. Paradoxically, in human breast cancer, B7-H4 expression was associated with survival benefit for patients with metastatic TNBC treated with carboplatin plus anti-PD-L1 and was associated with no change in response or survival for patients with early breast cancer receiving chemotherapy plus anti-PD-1. While B7-H4 induces tumor resistance to anti-PD-L1 in murine models, there are alternative mechanisms of signaling and function in human cancers. In addition, the strong correlation of B7-H4 to epithelial cell markers suggests a potential regulatory mechanism of B7-H4 independent of PD-L1.

SIGNIFICANCE

This translational study confirms the association of B7-H4 expression with a cold immune microenvironment in breast cancer and offers preclinical studies demonstrating a potential role for B7-H4 in suppressing response to checkpoint therapy. However, analysis of two clinical trials with checkpoint inhibitors in the early and metastatic settings argue against B7-H4 as being a mechanism of clinical resistance to checkpoints, with clear implications for its candidacy as a therapeutic target.

NKG2A Is a Therapeutic Vulnerability in Immunotherapy Resistant MHC-I Heterogeneous Triple-Negative Breast Cancer

Despite the success of immune checkpoint inhibition (ICI) in treating cancer, patients with triple-negative breast cancer (TNBC) often develop resistance to therapy, and the underlying mechanisms are unclear. MHC-I expression is essential for antigen presentation and T-cell-directed immunotherapy responses. This study demonstrates that TNBC patients display intratumor heterogeneity in regional MHC-I expression. In murine models, loss of MHC-I negates antitumor immunity and ICI response, whereas intratumor MHC-I heterogeneity leads to increased infiltration of natural killer (NK) cells in an IFNγ-dependent manner. Using spatial technologies, MHC-I heterogeneity is associated with clinical resistance to anti-programmed death (PD) L1 therapy and increased NK:T-cell ratios in human breast tumors. MHC-I heterogeneous tumors require NKG2A to suppress NK-cell function. Combining anti-NKG2A and anti-PD-L1 therapies restores complete response in heterogeneous MHC-I murine models, dependent on the presence of activated, tumor-infiltrating NK and CD8+ T cells. These results suggest that similar strategies may enhance patient benefit in clinical trials.

SIGNIFICANCE

Clinical resistance to immunotherapy is common in breast cancer, and many patients will likely require combination therapy to maximize immunotherapeutic benefit. This study demonstrates that heterogeneous MHC-I expression drives resistance to anti-PD-L1 therapy and exposes NKG2A on NK cells as a target to overcome resistance. This article is featured in Selected Articles from This Issue, p. 201.

[The role of surveillance bronchoscopy after lung transplantation]

The role of surveillance bronchoscopy after lung transplantation. Lung transplantation is currently accepted as a potential treatment for end-stage respiratory diseases. That said, airway complications and the onset of chronic lung allograft dysfunction remain major causes of morbidity and mortality subsequent to lung transplantation and a significant obstacle to long-term survival. In this article, we discuss the advantages and limitations of bronchial endoscopy in post-lung transplant monitoring.

STING-activating nanoparticles normalize the vascular-immune interface to potentiate cancer immunotherapy

The tumor-associated vasculature imposes major structural and biochemical barriers to the infiltration of effector T cells and effective tumor control. Correlations between stimulator of interferon genes (STING) pathway activation and spontaneous T cell infiltration in human cancers led us to evaluate the effect of STING-activating nanoparticles (STANs), which are a polymersome-based platform for the delivery of a cyclic dinucleotide STING agonist, on the tumor vasculature and attendant effects on T cell infiltration and antitumor function. In multiple mouse tumor models, intravenous administration of STANs promoted vascular normalization, evidenced by improved vascular integrity, reduced tumor hypoxia, and increased endothelial cell expression of T cell adhesion molecules. STAN-mediated vascular reprogramming enhanced the infiltration, proliferation, and function of antitumor T cells and potentiated the response to immune checkpoint inhibitors and adoptive T cell therapy. We present STANs as a multimodal platform that activates and normalizes the tumor microenvironment to enhance T cell infiltration and function and augments responses to immunotherapy.

Chronic intermittent ethanol exposure disrupts stress-related tripartite communication to impact affect-related behavioral selection in male rats

Alcohol use disorder (AUD) is characterized by loss of intake control, increased anxiety, and susceptibility to relapse inducing stressors. Both astrocytes and neurons contribute to behavioral and hormonal consequences of chronic intermittent ethanol (CIE) exposure in animal models. Details on how CIE disrupts hypothalamic neuro-glial communication, which mediates stress responses are lacking. We conducted a behavioral battery (grooming, open field, reactivity to a single, uncued foot-shock, intermittent-access two-bottle choice ethanol drinking) followed by Ca²⁺ imaging in ex-vivo slices of paraventricular nucleus of the hypothalamus (PVN) from male rats exposed to CIE vapor or air-exposed controls. Ca²⁺ signals were evaluated in response to norepinephrine (NE) with or without selective α-adrenergic receptor (αAR) or GluN2B-containing N-methyl-D-aspartate receptor (NMDAR) antagonists, followed by dexamethasone (DEX) to mock a pharmacological stress response. Expectedly, CIE rats had altered anxiety-like, rearing, grooming, and drinking behaviors. Importantly, NE-mediated reductions in Ca²⁺ event frequency were blunted in both CIE neurons and astrocytes. Administration of the selective α1AR antagonist, prazosin, reversed this CIE-induced dysfunction in both cell types. Additionally, the pharmacological stress protocol reversed the altered basal Ca²⁺ signaling profile of CIE astrocytes. Signaling changes in astrocytes in response to NE were correlated with anxiety-like behaviors, such as the grooming:rearing ratio, suggesting tripartite synaptic function plays a role in switching between exploratory and stress-coping behavior. These data show how CIE exposure causes persistent changes to PVN neuro-glial function and provides the groundwork for how these physiological changes manifest in behavioral selection.

Abstract 4152: Longitudinal local and peripheral immunologic changes associated with PD-L1 response in a murine breast cancer model

Immune checkpoint inhibitors (ICI) have significantly enhanced patient survival in many cancers but yield limited success in breast cancer. ICIs activate anti-tumor immunity by overriding the inhibition of tumor infiltrating lymphocytes (TILs). Clinical trials in triple negative breast cancer (TNBC) patients, who harbor TILs within tumor stroma, have demonstrated increased survival (IMpassion130) and pathologic complete response (KEYNOTE-522) to ICI leading to FDA-approval of ICI and chemotherapy combinations in metastatic TNBC. However, ICI benefit is heterogeneous among patients. We sought to model ICI response in vivo to evaluate therapeutic resistance and response heterogeneity and to ascertain predictive biomarkers for favorable ICI outcomes. An immunocompetent EMT6 orthotopic mammary tumor model was used to investigate the efficacy of anti-PD-L1. Matched longitudinal samples of the tumor microenvironment (TME) (collected by fine-needle aspiration) and peripheral blood (PBMC) from mice were profiled by bulk RNA and T-cell receptor sequencing.

Anti-PD-L1 robustly suppressed primary tumor growth and extended survival beyond the control group. The addition of chemotherapy demonstrated moderate therapeutic efficacy but failed to enhance ICI benefit. Phenotypic profiling of the TME revealed increased T cells, DCs, and NK cells in anti-PD-L1 only and chemotherapy combination groups. Despite using a genetically identical tumor model and host, PD-L1 blockade induced heterogeneous responses, like clinical outcomes in TNBC patients, ranging from complete response (CR) to intrinsic resistance (IR). The primary TME showed upregulated signatures of cytotoxic T cell response and activation, specifically inflammatory interferon signaling (both prior to and post ICI administration) that corresponded to favorable outcomes to anti-PD-L1 in individual mice. Longitudinal analysis of the peripheral blood identified modest changes among mice at baseline that progressively deviated by response type (IR-vs-CR). Mice harbored enriched myeloid signatures and clonal T cell expansion during therapy corresponding to ICI resistance and response, respectively. Further investigations of matched peripheral blood and the primary TME signatures may identify systemic biomarkers and tumor antigen-specific T cell clones to accurately predict ICI response in patients and uncover mechanisms for sensitizing tumors refractory to ICI.

Thus, we identify an in vivo model that emulates TNBC patient heterogeneous outcomes to ICI combinatorial approaches. We describe host-specific signatures, specifically from myeloid cells, that correlate with differential responses to ICI, which may serve as a basis for peripheral blood tracking of breast cancer patient responses.

Citation Format: Ann Hanna, Xiaopeng Sun, Emily Tran, Quanhu Sheng, Brandie C. Taylor, Susan R. Opalenik, Justin M. Balko. Longitudinal local and peripheral immunologic changes associated with PD-L1 response in a murine breast cancer model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4152.

No rest for the wicked: Tumor cell senescence reshapes the immune microenvironment

Senescence induces key phenotypic changes that can modulate immune responses. Four recent publications in Cancer Discovery, Nature, and Nature Cancer highlight how senescent cells (aged normal or chemotherapy-treated cells) express antigen presentation machinery, present antigens, and interact with T cells and dendritic cells to robustly activate the immune system and promote anti-tumor immunity.

Abstract PD2-02: Longitudinal local and peripheral immunologic changes associated with checkpoint inhibition response in murine models of breast cancer

Immune checkpoint inhibitors (ICI) have significantly enhanced patient survival in some cancer types but yield limited success in breast cancer. ICIs activate anti-tumor immunity by overriding the inhibition of tumor infiltrating lymphocytes (TILs). Clinical trials in triple negative breast cancer (TNBC) patients, who are more likely to harbor TILs within tumor stroma, have demonstrated increased progression-free survival (IMpassion130) and pathologic complete response (KEYNOTE-522) to ICI. Consequently, combinations of ICI and chemotherapy have been FDA-approved for metastatic TNBC. However, the therapeutic benefit of ICIs is highly heterogeneous among breast cancer patients; as such, we sought to model ICI response in vivo to evaluate therapeutic resistance and response heterogeneity, as well as ascertain predictive biomarkers for favorable outcomes to ICI in breast cancer. We used an immunocompetent EMT6 orthotopic mammary tumor model to investigate the efficacy of ICI (anti-PD-L1). Analysis of the primary tumor immune landscape was performed by flow cytometry and single-cell RNA sequencing. Matched longitudinal samples of the tumor microenvironment (collected by fine-needle aspiration) and peripheral blood (PBMC) from mice were profiled by bulk RNA and T-cell receptor (TCR) sequencing to identify systemic genomic alterations and T-cell expansion, respectively. Single-agent ICI robustly suppressed primary tumor growth (p =0.0046) and extended survival (p< 0.0001) beyond the control group in the EMT6 model. The addition of chemotherapy (paclitaxel and/or doxorubicin) demonstrated moderate therapeutic efficacy but failed to enhance ICI benefit. Phenotypic profiling of the tumor microenvironment (TME) revealed increased T cells, dendritic cells, and NK cells in anti-PD-L1 only and chemotherapy combination groups. Despite using a genetically identical tumor model and murine host, we found that PD-L1 blockade induced heterogeneous responses, similar to clinical outcomes in breast cancer patients, ranging from complete response to intrinsic resistance. Analysis of the primary tumor microenvironment showed upregulated signatures of cytotoxic T cell response and activation, specifically inflammatory interferon signaling (both prior to and post ICI administration) that corresponded to favorable response to anti-PD-L1 in individual mice. Longitudinal analysis of the peripheral blood identified modest changes among mice at baseline that progressively deviated by response type (non responders-vs-responder mice). Moreover, mice harbored enriched myeloid signatures and clonal T cell expansion during therapy corresponding to ICI resistance and response, respectively. Further investigations of matched peripheral blood and the primary tumor microenvironment signatures may identify systemic biomarkers and tumor antigen-specific T cell clones to accurately predict ICI response in patients and uncover mechanisms for sensitizing tumors refractory to ICI. In conclusion, we identify a heterogeneously ICI-responsive in vivo model that emulates TNBC patient response to combinatorial ICI approaches. We describe host-specific signatures, specifically myeloid cell responses, that correlate with differential responses to immunotherapy, which may serve as a basis for tracking immunotherapy response in peripheral blood from breast cancer patients.

Citation Format: Ann Hanna, Xiaopeng Sun, Quanhu Sheng, Melinda Sanders, Justin Balko. Longitudinal local and peripheral immunologic changes associated with checkpoint inhibition response in murine models of breast cancer [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 PD2-02.

Hedgehog blockade remodels the gut microbiota and the intestinal effector CD8+ T cells in a mouse model of mammary carcinoma

Given the gut microbiome's rise as a potential frontier in cancer pathogenesis and therapy, leveraging microbial analyses in the study of breast tumor progression and treatment could unveil novel interactions between commensal bacteria and disease outcomes. In breast cancer, the Hedgehog (Hh) signaling pathway is a potential target for treatment due to its aberrant activation leading to poorer prognoses and drug resistance. There are limited studies that have investigated the influences of orally administered cancer therapeutics, such as Vismodegib (a pharmacological, clinically used Hh inhibitor) on the gut microbiota. Using a 4T1 mammary carcinoma mouse model and 16 S rRNA sequencing, we longitudinally mapped alterations in immunomodulating gut microbes during mammary tumor development. Next, we identified changes in the abundance of commensal microbiota in response to Vismodegib treatment of 4T1 mammary tumor-bearing mice. In addition to remodeling gut microbiota, Vismodegib treatment elicited an increase in proliferative CD8⁺ T cells in the colonic immune network, without any remarkable gastrointestinal-associated side effects. To our knowledge, this is the first study to assess longitudinal changes in the gut microbiome during mammary tumor development and progression. Our study also pioneers an investigation of the dynamic effects of an orally delivered Hh inhibitor on the gut microbiome and the gut-associated immune-regulatory adaptive effector CD8⁺ T cells. These findings inform future comprehensive studies on the consortium of altered microbes that can impact potential systemic immunomodulatory roles of Vismodegib.

T cells specific for α-myosin drive immunotherapy-related myocarditis

Immune-related adverse events, particularly severe toxicities such as myocarditis, are major challenges to the utility of immune checkpoint inhibitors (ICIs) in anticancer therapy1. The pathogenesis of ICI-associated myocarditis (ICI-MC) is poorly understood. Pdcd1-/-Ctla4+/- mice recapitulate clinicopathological features of ICI-MC, including myocardial T cell infiltration2. Here, using single-cell RNA and T cell receptor (TCR) sequencing of cardiac immune infiltrates from Pdcd1-/-Ctla4+/- mice, we identify clonal effector CD8+ T cells as the dominant cell population. Treatment with anti-CD8-depleting, but not anti-CD4-depleting, antibodies improved the survival of Pdcd1-/-Ctla4+/- mice. Adoptive transfer of immune cells from mice with myocarditis induced fatal myocarditis in recipients, which required CD8+ T cells. The cardiac-specific protein α-myosin, which is absent from the thymus3,4, was identified as the cognate antigen source for three major histocompatibility complex class I-restricted TCRs derived from mice with fulminant myocarditis. Peripheral blood T cells from three patients with ICI-MC were expanded by α-myosin peptides. Moreover, these α-myosin-expanded T cells shared TCR clonotypes with diseased heart and skeletal muscle, which indicates that α-myosin may be a clinically important autoantigen in ICI-MC. These studies underscore the crucial role for cytotoxic CD8+ T cells, identify a candidate autoantigen in ICI-MC and yield new insights into the pathogenesis of ICI toxicity.

Abstract 2726: Host myeloid response drives anti-PD-L1 resistance in murine models of triple negative breast cancer

Immune checkpoint inhibitors (ICI) have improved patient overall and progression-free survival in some cancer types with limited success in breast cancer. Clinical trials in triple negative breast cancer (TNBC) patients, who harbor extensive tumor-infiltrating lymphocytes within tumor stroma, have demonstrated increased progression-free survival (IMpassion130) and pathologic complete response (KEYNOTE-522). Thus, combinations of ICI and chemotherapy have been FDA-approved for metastatic TNBC. However, the therapeutic benefit of ICI alone is poorly characterized. We sought to model ICI response in vivo to ascertain the immune repertoire responsible for ICI efficacy in breast cancer and identify the therapeutic benefit of ICI alone or in combination with approved chemotherapeutics.

We used an immunocompetent EMT6 orthotopic mammary tumor model to investigate the efficacy of single-agent ICI (anti-PD-L1) or in combination with standard-of-care chemotherapy (paclitaxel or doxorubicin). Analysis of the primary tumor immune landscape was performed by flow cytometry and single-cell RNA sequencing. Peripheral blood from mice was serially sampled by bulk and T-cell receptor (TCR) sequencing to identify systemic genomic alterations and T-cell expansion, respectively.

Single-agent ICI robustly suppressed primary tumor growth (p =0.0046) and extended survival (p<0.0001) beyond the control group. While chemotherapy demonstrated moderate therapeutic efficacy, it did not enhance ICI benefit. Transcriptomic and phenotypic profiling of the tumor microenvironment (TME) revealed increased T cells, dendritic cells, and NK cells in the combination groups versus chemotherapy alone, but this did not translate into improved benefit. Interestingly, despite using a genetically identical tumor model and murine host, ICI induced heterogeneous responses, ranging from complete response to intrinsic resistance. The longitudinal analysis of peripheral blood from heterogeneously responding mice uncovered enriched myeloid signatures and clonal T cell expansion corresponding to ICI resistance and response, respectively.

In conclusion, we identify a heterogeneously ICI-responsive in vivo model that emulates TNBC patient response to combinatorial ICI approaches. We report the efficacy of single-agent ICI in upregulating cytotoxic immune cell infiltration and expansion within the primary tumor, thereby diminishing tumor growth and enhancing survival. We describe host-specific signatures, specifically myeloid cells, that correlate with differential responses to immunotherapy, which models heterogeneous patient response to ICI. Ongoing characterization of matched peripheral blood and TME samples may identify systemic biomarkers and tumor antigen-specific T cell clones to accurately predict ICI response in patients and uncover mechanisms for sensitizing tumors refractory to ICI.

Citation Format: Ann Hanna, Xiaopeng Sun, Paula I. Gonzalez-Ericsson, Violeta Sanchez, Justin M. Balko. Host myeloid response drives anti-PD-L1 resistance in murine models of triple negative breast cancer [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 2726.

Abstract 2103: Hedgehog signaling regulates metabolism and polarization of mammary tumor-associated macrophages

In the United States, a woman has a 12% chance of developing breast cancer, and current treatments offer little relief to patients diagnosed with metastatic disease. Tumorigenesis and successful establishment of metastases depend upon tumor cell interactions with the surrounding immune microenvironment. Elevated tumor infiltration of immunosuppressive (M2) macrophages correlates with poor prognosis of breast cancer patients. The tumor microenvironment remarkably orchestrates molecular mechanisms that program these macrophages toward the M2 phenotype. Also, metabolic programming is instrumental in orchestrating the polarization of macrophages to assume an M1 (tumor-eradicating) or an M2 (tumor-promoting) phenotype. Aberrant activation of Hedgehog (Hh) signaling in breast cancer cells enables them to survive, proliferate, and metastasize, thus making it a promising target for breast cancer treatment. Hh signaling also enables a crosstalk between breast cancer cells and cells in their milieu, thus contributing to M2 macrophage polarization. We used two immunocompetent orthotopic mouse models of mammary tumors to test the effect of inhibiting Hh signaling on tumor-associated macrophages, and discovered that treatment with the pharmacologic Hh inhibitor, Vismodegib, induced a significant shift in the profile of tumor-infiltrating macrophages. We hypothesized that Hh activity calibrates the metabolism in macrophages, leading to enhanced M2 phenotype and function within the tumor microenvironment. Using a mass spectrometry-enabled untargeted metabolomics approach, we identified that inhibiting Hh signaling reduces flux through the hexosamine biosynthetic pathway, resulting in reduced cellular O-GlcNAcylation in M2 macrophages. This impinges upon diminished STAT6 O-GlcNAcylation, which consequently decreases fatty acid oxidation and ultimately enacts a metabolic cascade including lipid utilization, cellular bioenergetics, and mitochondrial dynamics. As such, inhibiting Hh activity mitigates the metabolomic and bioenergetic underpinnings of the immunosuppressive program of M2 macrophages, resulting in macrophages that are functionally and phenotypically reminiscent of inflammatory, anti-tumor macrophages. In conclusion, we discovered a novel role for Hh signaling in promoting polarization of tumor-associated macrophages to the M2 type through recalibrating their metabolic circuitries, ultimately leading to diminished M2 phenotype and function within the tumor microenvironment. This is the first evidence highlighting the relevance of Hh signaling in controlling a complex metabolic network in immune cells. This knowledge will help us to better understand how to target and diminish the pro-tumorigenic functions of tumor-infiltrating macrophages.

Citation Format: Dominique C. Hinshaw, Ann Hanna, Tshering Lama-Sherpa, Brandon Metge, Sarah C. Kammerud, Gloria A. Benavides, Atul Kumar, Heba A. Alsheikh, Mateus Mota, Dongquan Chen, Scott Ballinger, Jeffrey C. Rathmell, Selvarangan Ponnazhagan, Victor Darley-Usmar, Rajeev S. Samant, Lalita A. Shevde. Hedgehog signaling regulates metabolism and polarization of mammary tumor-associated macrophages [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 2103.

Abstract P1-04-03: Host myeloid response to tumor and immunotherapy is associated with heterogeneity in outcomes to anti-PDL1

Background: Immune checkpoint inhibitors (ICI) have improved patient overall and progression-free survival in some cancer types but yielded limited success in breast cancer. Phase-III clinical trials in triple negative breast cancer (TNBC) patients, who harbor extensive tumor-infiltrating lymphocytes within tumor stroma, have demonstrated increased progression-free survival (IMpassion130) and pathologic complete response (KEYNOTE-522). Consequently, combinations of ICI and chemotherapy have been FDA-approved for metastatic TNBC patients, and potentially in the early breast cancer setting. Despite FDA-approval, the therapeutic benefit of ICI alone and the most efficacious chemotherapy combinations are poorly characterized. Objective: We sought to model ICI response in vivo to elucidate the mechanisms responsible for immunotherapy efficacy in breast cancer and ascertain the therapeutic benefits of different chemotherapeutic combinations with ICI. Methods: In this study, we used an immunocompetent EMT6 orthotopic mammary tumor model to investigate the efficacy of single-agent immunotherapy and in combination with standard-of-care chemotherapy (paclitaxel [PAC] or doxorubicin [DOX]). We used single-cell RNA sequencing to analyze the cellular landscape of the primary tumor in response to combinatorial therapeutic strategies. Additionally, we serially sampled and analyzed peripheral blood from mice with differential responses by bulk and T-cell receptor (TCR) sequencing to identify systemic genetic alterations and T-cell expansion. Results: Single-agent anti-PD-L1 robustly suppressed primary tumor growth (p =0.0046) and extended survival (p<0.0001) beyond the isotype control group. While either PAC or DOX demonstrated moderate therapeutic efficacy, neither agent potentiated single-agent anti-PD-L1 benefit. Interestingly, despite using a genetically identical tumor model and murine host, anti-PD-L1 induced heterogeneous responses, ranging from complete response to complete intrinsic resistance. The longitudinal analysis of peripheral blood from heterogeneously responding mice uncovered signatures of myeloid cell recruitment corresponding to transient responses ultimately converting to resistance. We also identified specific clonal T cell expansion present only in responders. Single-cell transcriptomic profiling of the tumor microenvironment revealed an increase of T cells and natural killer cells and reduction of regulatory T cells in the combination groups versus chemotherapy alone, although this did not translate into improved benefit. Finally, we performed gene-set enrichment analysis on infiltrating T cells and identified a robust signature of cytotoxic T cell activation characterized by a significant enrichment in inflammatory pathways in both single-agent anti-PD-L1 and in combination with chemotherapy. Conclusions: This study identifies a heterogeneously ICI-responsive in vivo model that emulates TNBC patient response to combinatorial ICI approaches. We describe the efficacy of single-agent ICI in upregulating cytotoxic immune cell infiltration and expansion within the primary tumor, thereby diminishing tumor growth and enhancing survival. Moreover, this study describes differential responses in a genetically similar host, which reflects heterogeneous patient response to ICI. Further characterization may identify systemic biomarkers and tumor antigen-specific T cell clones to accurately predict immunotherapy response in patients and uncover mechanisms for sensitizing tumors refractory to ICI. This study also has potentially significant clinical implications for re-evaluating the benefits of chemotherapy in combination with ICI in TNBC patients.

Citation Format: Ann Hanna, Xiaopeng Sun, Paula I. Gonzalez-Ericsson, Violeta M. Sanchez, Melinda E. Sanders, Justin M. Balko. Host myeloid response to tumor and immunotherapy is associated with heterogeneity in outcomes to anti-PDL1 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-04-03.

Réponse vaccinale contre la Covid en transplantation pulmonaire

Introduction

La vaccination contre la Covid a été recommandée chez les patients transplantés d’organes solides en début d’année 2021, selon un schéma comprenant 3 doses chez les patients n’ayant pas présenté d’infection par la Covid 19 et selon un schéma comprenant 2 injections chez les patients ayant été infectés par la Covid.

Méthodes

Nous avons étudié la réponse vaccinale après un schéma complet dans une cohorte de patients transplantés pulmonaires et cardiopulmonaires à l’hôpital Marie Lannelongue. Selon les recommandations de l’OMS, l’absence de réponse vaccinale est définie par une sérologie dont le taux est < 30 BAU/ml. Le taux d’Anticorps considéré comme protecteur est un taux > 260 BAU/ml. Les patients dont le taux est compris entre 30 et 260 BAU/ml sont considérés comme faiblement répondeurs. La sérologie a été effectuée entre 1 et 3 mois après la dernière injection.

Résultats

Dans notre cohorte comprenant 373 patients, une sérologie Covid a pu être obtenue chez 75% des patients. Une absence complète de séroconversion a été constatée chez 75% des patients. Une séroconversion avec un taux d’anticorps considéré comme protecteur n’a été obtenu que chez 14% des patients, dont la moitié a présenté une infection par la Covid. Par ailleurs, 11% des patients ont été faiblement répondeurs.

Conclusion

Notre étude mono-centrique suggère une très faible réponse vaccinale chez les patients transplantés pulmonaires et cardiopulmonaires, suggérant la réalisation d’une 4^e dose chez les patients partiellement répondeurs et/ou un traitement par anticorps monoclonaux spécifiques chez les patients non répondeurs.

Pharmacological Activation of cGAS for Cancer Immunotherapy

When compartmentally mislocalized within cells, nucleic acids can be exceptionally immunostimulatory and can even trigger the immune-mediated elimination of cancer. Specifically, the accumulation of double-stranded DNA in the cytosol can efficiently promote antitumor immunity by activating the cGAMP synthase (cGAS) / stimulator of interferon genes (STING) cellular signaling pathway. Targeting this cytosolic DNA sensing pathway with interferon stimulatory DNA (ISD) is therefore an attractive immunotherapeutic strategy for the treatment of cancer. However, the therapeutic activity of ISD is limited by several drug delivery barriers, including susceptibility to deoxyribonuclease degradation, poor cellular uptake, and inefficient cytosolic delivery. Here, we describe the development of a nucleic acid immunotherapeutic, NanoISD, which overcomes critical delivery barriers that limit the activity of ISD and thereby promotes antitumor immunity through the pharmacological activation of cGAS at the forefront of the STING pathway. NanoISD is a nanoparticle formulation that has been engineered to confer deoxyribonuclease resistance, enhance cellular uptake, and promote endosomal escape of ISD into the cytosol, resulting in potent activation of the STING pathway via cGAS. NanoISD mediates the local production of proinflammatory cytokines via STING signaling. Accordingly, the intratumoral administration of NanoISD induces the infiltration of natural killer cells and T lymphocytes into murine tumors. The therapeutic efficacy of NanoISD is demonstrated in preclinical tumor models by attenuated tumor growth, prolonged survival, and an improved response to immune checkpoint blockade therapy.

245 Host myeloid response to tumor and immunotherapy is associated with heterogeneity in outcomes to anti-PDL1

Background

Immune checkpoint inhibitors (ICI) improve patient survival in some cancer types but yield limited success in breast cancer. Phase-III clinical trials in triple-negative breast cancer (TNBC) patients, who harbor extensive tumor-infiltrating lymphocytes, demonstrate increased progression-free survival (IMpassion130) and pathologic complete response (KEYNOTE-522). Consequently, combinations of ICI and chemotherapy have been FDA-approved for metastatic TNBC patients. However, the therapeutic benefit of ICI alone and the most efficacious chemotherapy combinations are poorly characterized. We sought to model ICI response in vivo to elucidate the mechanisms of immunotherapy efficacy in breast cancer and ascertain the therapeutic benefits of different chemotherapeutic combinations with ICI.

Methods

Using an immunocompetent EMT6 orthotopic mammary tumor model, we investigated the efficacy of single-agent immunotherapy and in combination with standard-of-care chemotherapy (paclitaxel [PAC] or doxorubicin [DOX]). We used single-cell RNA sequencing and bulk RNA and T-cell receptor (TCR) sequencingto assess the cellular landscape of the primary tumor in response to combinatorial therapeutic strategies and identify systemic genetic alterations and T-cell expansion, respectively.

Results

Single-agent anti-PD-L1 robustly suppressed primary tumor growth (p =0.0046) and extended survival (p<0.0001) beyond the isotype control. Chemotherapy demonstrated moderate therapeutic efficacy without potentiating the benefit of single-agent anti-PD-L1. Interestingly, despite using a genetically identical murine tumor model/host, anti-PD-L1 induced heterogeneous responses, from complete response to intrinsic resistance. Longitudinal analysis of peripheral blood from heterogeneously responding mice uncovered myeloid cell recruitment signatures corresponding to transient responses ultimately converting to resistance. We identified specific clonal T cell expansion present only in responders. Single-cell transcriptomic profiling of the tumor microenvironment revealed increased T cells and natural killer cells and reduced regulatory T cells in the combination groups versus chemotherapy alone, although this did not translate into improved benefit. Gene-set enrichment analysis on infiltrating T cells identified a robust signature of cytotoxic T cell activation characterized by a significant enrichment in inflammatory pathways in both single-agent anti-PD-L1 and in combination with chemotherapy.

Conclusions

We identify a heterogeneously ICI-responsive in vivo model that emulates TNBC patient response to combinatorial ICI approaches. We describe single-agent ICI efficacy in upregulating cytotoxic immune cell infiltration and expansion within the primary tumor that diminishes tumor growth and enhances survival. Moreover, this study describes differential responses in a genetically similar host, which reflects heterogeneous patient response to ICI. Further characterization may identify systemic biomarkers and tumor antigen-specific T cell clones to accurately predict immunotherapy response in patients and uncover mechanisms for sensitizing refractory tumors to ICI

Breast cancer resistance mechanisms: challenges to immunotherapy

PURPOSE

The clinical implementation of immunotherapy has profoundly transformed cancer treatment. Targeting the immune system to mount anti-tumor responses can elicit a systemically durable response. Employing immune checkpoint blockade (ICB) has suppressed tumor growth and vastly improved patient overall and progression-free survival in several cancer types, most notably melanoma and non-small cell lung carcinoma. Despite widescale clinical success, ICB response is heterogeneously efficacious across tumor types. Many cancers, including breast cancer, are frequently refractory to ICB. In this review, we will discuss the challenges facing immunotherapy success and address the underlying mechanisms responsible for primary and acquired breast cancer resistance to immunotherapy.

FINDINGS

Even in initially ICB-responsive tumors, many acquire resistance due to tumor-specific alterations, loss of tumor-specific antigens, and extrinsic mechanisms that reshape the immune landscape within the tumor microenvironment (TME). The tumor immune interaction circumvents the benefits of immunotherapy; tumors rewire the tumor-suppressive functions of activated immune cells within their stroma to propagate tumor growth and progression.

CONCLUSIONS

The breast cancer immune TME is complex and the mechanisms driving resistance to ICB are multifaceted. Continued study in both preclinical models and clinical trials should help elucidate these mechanisms so they can be targeted to benefit more breast cancer patients.

Hedgehog signaling regulates metabolism and polarization of mammary tumor-associated macrophages

Elevated infiltration of immunosuppressive alternatively polarized (M2) macrophages is associated with poor prognosis in cancer patients. The tumor microenvironment remarkably orchestrates molecular mechanisms that program these macrophages. Here we identify a novel role for oncogenic Hedgehog (Hh) signaling in programming signature metabolic circuitries that regulate alternative polarization of tumor-associated macrophages. Two immunocompetent orthotopic mouse models of mammary tumors were used to test the effect of inhibiting Hh signaling on tumor-associated macrophages. Treatment with the pharmacological Hh inhibitor Vismodegib induced a significant shift in the profile of tumor-infiltrating macrophages. Mass spectrometry-based metabolomic analysis showed Hh inhibition induced significant alterations in metabolic processes, including metabolic sensing, mitochondrial adaptations, and lipid metabolism. In particular, inhibition of Hh in M2 macrophages reduced flux through the UDP-GlcNAc biosynthesis pathway. Consequently, O-GlcNAc-modification of STAT6 decreased, mitigating the immune suppressive program of M2 macrophages, and the metabolically demanding M2 macrophages shifted their metabolism and bioenergetics from fatty acid oxidation to glycolysis. M2 macrophages enriched from Vismodegib-treated mammary tumors showed characteristically decreased O-GlcNAcylation and altered mitochondrial dynamics. These Hh-inhibited macrophages are reminiscent of inflammatory (M1) macrophages, phenotypically characterized by fragmented mitochondria. This is the first report highlighting the relevance of Hh signaling in controlling a complex metabolic network in immune cells. These data describe a novel immunometabolic function of Hh signaling that can be clinically exploited.

Hedgehog signaling interfaces with the Hexoseamine Biosynthetic Pathway to promote M2 polarization of mammary tumor associated macrophages

The Hedgehog (Hh) signaling pathway is aberrantly activated in breast cancer, and contributes to tumor cell survival, proliferation, and migration. The success of these events is heavily influenced by the surrounding immune microenvironment. One such cell type, macrophages (MΦ) can make up to 50% of the tumor mass. MΦs can be polarized to M1 (tumor-eradicating) or M2 (tumor-promoting), and a high M2/M1 ratio within the tumor microenvironment (TME) is correlated with worse prognosis.

We have uncovered a novel role for Hh signaling in promoting M2 polarization. We propose that the mechanism underlying this phenomenon is due to changes in the Hexoseamine Biosynthetic Pathway and consequently cellular O-GlcNAcylation. M2 MΦs have considerably higher levels of UDP-GlcNAc, the substrate for O-GlcNAcylation, compared to M1s, but the consequences of this are unknown. We hypothesize that O-GlcNAc modifications on key M2-specific proteins contribute to enhanced M2 phenotype and function within the TME, and that this phenomenon can be reversed with Hh blockade.

Methodology: mouse model of mammary carcinoma, flow cytometry, RNA-seq, metabolomics, IP.

This study is the first to elucidate Hh signaling’s role in recalibrating the metabolism of tumor-supporting MΦs. Inhibition of Hh signaling reduces MΦ O-GlcNAcylation resulting in weakened suppressive properties of M2 MΦs through the reduced activity of STAT6. Moreover, mitigating O-GlcNAcylation through Hh blockade pivots M2 MΦs to resemble M1s.

Our work provides evidence for modulating Hh activity, and consequently MΦ metabolism, to sculpt the plasticity of MΦs. This knowledge will help us to better understand how to target and diminish the pro-tumorigenic phenotypes of MΦs in the TME.

Abstract PS17-14: Evaluating the efficacy of immunotherapy in triple negative breast cancer

The breast cancer microenvironment comprises a complex stroma including tumor-infiltrating lymphocytes (TILs), which can either stimulate tumor progression or promote anti-tumor immunity in response to tumor-derived cues. In general, of all clinical subtypes, triple-negative breast cancer (TNBC) is characterized by the most extensive infiltration of TILs within tumor stroma, which is consistent with the observation that TNBC seems to clinically respond to immunotherapies at the highest rates. Immune checkpoint blockade (ICB), an immunotherapy that promotes prolonged activation of cytotoxic immune cells to mount robust anti-tumorigenic responses, has yielded limited success in treating breast cancer. IMpassion130 was the first clinical trial to indicate that combining anti-PD-L1 with standard-of-care chemotherapy (nab-paclitaxel) to treat TNBC increases progression-free survival in patients exclusively those with PD-L1 positive tumors. Furthermore, the KEYSTONE-522 trial showed that administering anti-PD-1 in addition to various neoadjuvant chemotherapies increased the pathologic complete response in early stage TNBC patients. Despite promising evidence for immunotherapy success, both clinical trials lacked an experimental ICB-only group, and thus cannot address the therapeutic benefit of ICB alone, or which chemotherapy combination would maximize this benefit. Finally, mechanisms of resistance to ICB in breast cancer remain unexplored. We sought to model ICB response in vivo to elucidate the mechanisms responsible for immunotherapy efficacy in breast cancer, explore the synergistic effects of ICB with chemotherapies, and model ICB resistance.In this study, we investigated the efficacy of anti-PD-L1 as single-agent or in combination with paclitaxel or doxorubicin in the EMT6 (Balb/c) orthotopic mammary tumor model. In this model, single-agent immunotherapy was efficacious in reducing primary tumor growth compared to combination treatment, with a small proportion of complete responses, whereas modest benefit was observed with either chemotherapy alone. Following two rounds of treatment, we analyzed the tumor-immune microenvironment by flow cytometry and gene expression analysis. Anti-PD-L1 alone or in combination with either chemotherapy enhanced infiltration of cytotoxic and effector T cell as well as natural killer cells into the tumor microenvironment. Using gene expression analysis, we observed elevated expression of myeloid recruitment and activation markers in combination-treated tumors, supporting a known role of chemotherapy-induced cell death in myeloid recruitment; however as chemotherapy did not add benefit to tumor response or survival, it is unclear if this effect is detrimental or supportive. Interestingly, completely responsive anti-PD-L1 treated tumors that eventually recurred retained resistance to ICB upon re-implantation in naïve recipient mice, suggesting that tumor-intrinsic factors may contribute to resistance.Herein, we explore an in vivo model that corroborates clinical response to combinatorial immunotherapy approaches in breast cancer patients. We report the immunogenic efficacy of single-agent ICB that upregulates tumoricidal immune cell infiltration into the primary tumor, thereby controlling tumor growth, albeit without achieving complete response in all mice. Additionally, post-therapy recurrent tumors retain resistance upon transplantation, indicating tumor-specific adaptive resistance. This study has potentially significant clinical implications for re-evaluating the contributions of chemotherapy in combination with ICB in TNBC patients.

Citation Format: Ann Hanna, Paula I. Gonzalez-Ericsson, Violeta Sanchez, Melinda E. Sanders, Justin M. Balko. Evaluating the efficacy of immunotherapy in triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-14.

Older age and comorbidity are independent mortality predictors in a large cohort of 1305 COVID-19 patients in Michigan, United States

INTRODUCTION

Higher comorbidity and older age have been reported as correlates of poor outcomes in COVID-19 patients worldwide; however, US data are scarce. We evaluated mortality predictors of COVID-19 in a large cohort of hospitalized patients in the United States.

DESIGN

Retrospective, multicenter cohort of inpatients diagnosed with COVID-19 by RT-PCR from 1 March to 17 April 2020 was performed, and outcome data evaluated from 1 March to 17 April 2020. Measures included demographics, comorbidities, clinical presentation, laboratory values and imaging on admission. Primary outcome was mortality. Secondary outcomes included length of stay, time to death and development of acute kidney injury in the first 48-h.

RESULTS

The 1305 patients were hospitalized during the evaluation period. Mean age was 61.0 ± 16.3, 53.8% were male and 66.1% African American. Mean BMI was 33.2 ± 8.8 kg m^-2 . Median Charlson Comorbidity Index (CCI) was 2 (1-4), and 72.6% of patients had at least one comorbidity, with hypertension (56.2%) and diabetes mellitus (30.1%) being the most prevalent. ACE-I/ARB use and NSAIDs use were widely prevalent (43.3% and 35.7%, respectively). Mortality occurred in 200 (15.3%) of patients with median time of 10 (6-14) days. Age > 60 (aOR: 1.93, 95% CI: 1.26-2.94) and CCI > 3 (aOR: 2.71, 95% CI: 1.85-3.97) were independently associated with mortality by multivariate analyses. NSAIDs and ACE-I/ARB use had no significant effects on renal failure in the first 48 h.

CONCLUSION

Advanced age and an increasing number of comorbidities are independent predictors of in-hospital mortality for COVID-19 patients. NSAIDs and ACE-I/ARB use prior to admission is not associated with renal failure or increased mortality.

Hedgehog signaling induced metabolic reprogramming is essential for M2 polarization of macrophages in breast cancer

Current treatments for breast cancer offer little relief to patients with metastatic disease. The aberrant activation of Hedgehog (Hh) signaling enables cancer cells to survive, proliferate, and metastasize. Effective metastasis depends upon the surrounding immune microenvironment. Macrophages (MΦ) can be polarized to M1 (inflammatory) or M2 (suppressive), and increased populations of M2 tumor infiltrating MΦs are correlated with worse prognosis. We have discovered that Hh signaling contributes to M2 polarization. M1 and M2 MΦs have inherently different metabolic profiles, so we hypothesize that Hh signaling alters M2 MΦ metabolism to reflect M1 MΦ metabolism, leading to diminished M2 phenotype and function within the tumor microenvironment (TME).

Methodology includes a mouse model of mammary carcinoma, RNA-seq, mass spectrometry-based metabolomics, confocal imaging, and flow cytometry.

We elucidated the impact of Hh signaling blockade on the metabolism of MΦs diminishing their M2 polarization. Inhibition of Hh signaling reduces MΦ O-GlcNAcylation which directly correlates with the diminished suppressive attributes of M2 MΦs through the reduced activity of STAT6. Since STAT6 plays a dual role in governing the M2 phenotype and fatty acid oxidation, this ultimately enacts a metabolic cascade, including lipid utilization, cellular bioenergetics and mitochondrial morphology and function, that metabolically alters M2 MΦs to resemble M1 MΦs.

We have discovered that blockade of Hh signaling initiates a metabolic cascade diminishing the M2 phenotype and function. This knowledge will help us to better understand how to target and diminish the pro-tumorigenic phenotypes of MΦs in the TME and at the metastatic site.

Abstract P3-01-25: Hedgehog signaling-mediated adaptation to hypoxic microenvironment promotes osteoclastogenesis in advanced breast cancer

Primary tumors often experience hypoxic microenvironment due to increased demand for oxygen in the proliferating cells. Moreover, the proportions of hypoxic tumor cells in the primary tumor strongly correlate to the incidence of metastasis, with bone presenting as the preferred site for breast cancer metastasis. Hence, studying how breast cancer adapts to its hypoxic microenvironment is crucial to understanding the process of breast cancer metastasis to bones. Previous studies in our lab have shown that the developmental signaling pathway, Hh pathway promotes osteopontin (OPN) and parathyroid hormone-related (PTHrP) expression in breast cancer. Additionally, activation of the Hh signaling in breast cancer enables an increase in osteoclastic activity facilitating osteolysis invivo. Hence, we hypothesized that inhibition of Hh signaling diminishes the ability of breast cancer cells to adapt to hypoxia and consequently their metastatic potential. Hh signaling can be canonically activated through smoothened (SMO) dependent activation of the transcriptional regulator GLI. Hence, we inhibited Hh signaling using small molecule inhibitor GANT61 (GLI inhibitor) and pharmacological inhibitor BMS833923 (SMO inhibitor).

Since hypoxic microenvironment is prevalent in the bone, we investigated the effect of conditioned medium from breast cancer cells in hypoxic condition on bone marrow-derived macrophages (BMDMs). We found that hypoxia increases osteoclastogenesis and osteoclastic activity, whereas abrogating GLI1 and GLI2 dampens this effect as evidenced by TRAP and toluidine blue staining. Hypoxia-dependent increase in glucose consumption and lactate production were also dampened in Hh inhibited breast cancer cells. Additionally, we found increased nuclear localization of GLI1 and activation of Hh signaling in breast cancer cells in hypoxic condition compared to the control indicating hypoxia-dependent Hh signaling upregulation. To understand the importance of the Hh activation in hypoxic condition, we inhibited Hh signaling pathway with BMS and GANT61. Interestingly, our results indicate that cellular adaptation to hypoxia is dependent on Hh signaling-mediated stabilization of hypoxia-inducible factors (HIF-1α) and its transcriptional activity. This crosstalk suggests a feed-forward mechanism between Hh signaling and HIF-1α. In the future, we will further investigate the mechanistic role of Hh signaling-mediated modulation of HIF-1α. This study will possibly yield new therapeutic targets in controlling hypoxia-mediated cancer metabolism and tumorigenesis of breast cancer.

This work is supported by NIH grant R01CA169202

Citation Format: Tshering Dolma Lama-Sherpa, Shamik Das, Ann Hanna, Sarah Kammerud, Lalita A Shevde. Hedgehog signaling-mediated adaptation to hypoxic microenvironment promotes osteoclastogenesis in advanced breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-25.

O-GlcNAcylation of GLI transcription factors in hyperglycemic conditions augments Hedgehog activity

Modification of proteins by O-linked β-N-acetylglucosamine (O-GlcNAc) promotes tumor cell survival, proliferation, epigenetic changes, angiogenesis, invasion, and metastasis. Here we demonstrate that in conditions of elevated glucose, there is increased expression of key drug resistance proteins (ABCB1, ABCG2, ERCC1, and XRCC1), all of which are regulated by the Hedgehog pathway. In elevated glucose conditions, we determined that the Hedgehog pathway transcription factors, GLI1 and GLI2, are modified by O-GlcNAcylation. This modification functionally enhanced their transcriptional activity. The activity of GLI was enhanced when O-GlcNAcase was inhibited, while inhibiting O-GlcNAc transferase caused a decrease in GLI activity. The metabolic impact of hyperglycemic conditions impinges on maintaining PKM2 in the less active state that facilitates the availability of glycolytic intermediates for biosynthetic pathways. Interestingly, under elevated glucose conditions, PKM2 directly influenced GLI activity. Specifically, abrogating PKM2 expression caused a significant decline in GLI activity and expression of drug resistance proteins. Cumulatively, our results suggest that elevated glucose conditions upregulate chemoresistance through elevated transcriptional activity of the Hedgehog/GLI pathway. Interfering in O-GlcNAcylation of the GLI transcription factors may be a novel target in controlling cancer progression and drug resistance of breast cancer.

Meeting report: Metastasis Research Society (MRS) 17th Biennial conference and associated Young Investigator Satellite Meeting (YISM) on cancer metastasis

The Metastasis Research Society (MRS) 17th Biennial conference on metastasis was held on the 1st to the 5th of August 2018 at Princeton University, NJ, USA. The meeting was held around themes addressing notable aspects of the understanding and treatment of metastasis and metastatic disease covering basic, translational, and clinical research. Importantly, the meeting was largely supported by our patient advocate partners including Susan G. Komen for the Cure, Theresa's Research Foundation and METAvivor. There were a total of 85 presentations from invited and selected speakers spread across the main congress and presentations from the preceding Young Investigator Satellite Meeting. Presentations are summarized in this report by session topic.

Inhibition of Hedgehog signaling reprograms the dysfunctional immune microenvironment in breast cancer

Host responses to tumor cells include tumor suppressing or promoting mechanisms. We sought to detail the effect of Hedgehog (Hh) pathway inhibition on the composition of the mammary tumor immune portfolio. We hypothesized that Hh signaling mediates a crosstalk between breast cancer cells and macrophages that dictates alternative polarization of macrophages and consequently supports a tumor-promoting microenvironment. We used an immunocompetent, syngeneic mouse mammary cancer model to inhibit Hh signaling with the pharmacological inhibitor, Vismodegib. Using molecular and functional assays, we identified that Hedgehog (Hh) signaling mediates a molecular crosstalk between mammary cancer cells and macrophages that culminates in alternative polarization of macrophages. We carried out an unbiased kinomics and genomics assessment to unravel changes in global kinomic and gene signatures impacted by Hh signaling. Our investigations reveal that in an immunocompetent mammary cancer model, the administration of Vismodegib led to changes in the portfolio of tumor-infiltrating immune cells. This was characterized by a marked reduction in immune-suppressive innate and adaptive cells concomitant with an enrichment of cytotoxic immune cells. Breast cancer cells induce M2 polarization of macrophages via a crosstalk mediated by Hh ligands that alters critical kinomic and genomic signatures. Macrophage depletion improved the benefit of Hedgehog inhibition on eliciting an immunogenic, pro-inflammatory profile. We define a novel role for Hh signaling in disabling anti-tumor immunity. Inhibition of Hh signaling presents with dual advantages of tumor cell-targeting as well as re-educating a dysfunctional tumor microenvironment.

Abstract 2954: The role of hedgehog signaling in breast cancer progression through macrophage polarization

The tumor microenvironment is comprised of stromal cells that constantly crosstalk with the cancer cells. Stromal cells, specifically tumor infiltrating immune cells, secrete cytokines and chemokines that regulate host responses to cancer through tumor-suppressing or tumor-promoting mechanisms. Macrophages within the tumor microenvironment are very plastic and can modulate different functions that promote tumor growth or tumor suppression, depending on their phenotype. Classically activated macrophages (M1) suppress tumor growth by mounting a pro-inflammatory immune response; while alternatively activated macrophages (M2) promote tumor progression by inducing an anti-inflammatory response which suppresses immune system function.

Hedgehog (Hh) signaling is essential for normal mammalian embryonic development by modulating vital functions such as cell proliferation, differentiation, and angiogenesis. Although the Hh signaling pathway is tightly controlled, it often is deregulated, thus promoting tumorigenesis and tumor progression. Aberrant Hh signaling has particularly been implicated in breast cancer progression and metastasis.

In this project, we investigate the role of Hh signaling in polarizing cancer associated macrophages toward the tumor-promoting M2 phenotype in a breast cancer model. We have discovered that using small molecule inhibitors to inhibit Hh signaling attenuates the cytokine profile associated with M2 macrophages, while adding recombinant Hh ligand potentiates it. Our data thus far supports a role for Hh signaling in alternatively polarizing macrophages. We hypothesize that Hh inhibitors will reduce the abundance of M2 macrophages and prevent metastasis.

Citation Format: Ann Hanna, Lalita A. Shevde. The role of hedgehog signaling in breast cancer progression through macrophage polarization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2954. doi:10.1158/1538-7445.AM2017-2954

Salba-chia (Salvia hispanica L.) in the treatment of overweight and obese patients with type 2 diabetes: A double-blind randomized controlled trial

BACKGROUND AND AIM

Preliminary findings indicate that consumption of Salba-chia (Salvia hispanica L.), an ancient seed, improves management of type 2 diabetes and suppresses appetite. The aim of this study was to assesse the effect of Salba-chia on body weight, visceral obesity and obesity-related risk factors in overweight and obese adults with type 2 diabetes.

METHODS

A double-blind, randomized, controlled trial with two parallel groups involved 77 overweight or obese patients with type 2 diabetes (HbA_1c: 6.5-8.0%; BMI: 25-40 kg/m²). Both groups followed a 6-month calorie-restricted diet; one group received 30 g/1000 kcal/day of Salba-chia, the other 36 g/1000 kcal/day of an oat bran-based control. Primary endpoint was change in body weight over 6-months. Secondary endpoints included changes in waist circumference, body composition, glycemic control, C-reactive protein, and obesity-related satiety hormones.

RESULTS

At 6-months, participants on Salba-chia had lost more weight than those on control (1.9 ± 0.5 kg and 0.3 ± 0.4 kg, respectively; P = 0.020), accompanied by a greater reduction in waist circumference (3.5 ± 0.7 cm and 1.1 ± 0.7 cm, respectively; P = 0.027). C-reactive protein was reduced by 1.1 ± 0.5 mg/L (39 ± 17%) on Salba-chia, compared to 0.2 ± 0.4 mg/L (7 ± 20%) on control (P = 0.045). Plasma adiponectin on the test intervention increased by 6.5 ± 0.7%, with no change observed on control (P = 0.022).

CONCLUSIONS

The results of this study, support the beneficial role of Salba-chia seeds in promoting weight loss and improvements of obesity related risk factors, while maintaining good glycemic control. Supplementation of Salba-chia may be a useful dietary addition to conventional therapy in the management of obesity in diabetes. REGISTRATION: clinicaltrials.gov identifier: NCT01403571.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

Analysis of pathological complete response rates with paclitaxel-based regimens in trimodality therapy for esophageal cancer

The study aimed to examine whether omission of 5-fluorouracil (5-FU)-containing chemotherapy alters pathological complete response rates in patients receiving trimodality therapy for locally advanced esophageal cancer. A total of 159 patients were identified. One hundred twenty-nine patients received platinum/5-FU concurrently with radiotherapy, and 30 received taxane/platinum-containing chemoradiotherapy prior to esophagectomy. Patients were staged using the 2002 American Joint Committee on Cancer staging system. Patients were matched between chemotherapeutic groups, with no significant demographic or clinical differences other than T stage (14% T2 in the 5-FU group; no T2 in the platinum/taxane group) and radiotherapy technique (8.5% received intensity-modulated radiotherapy in the 5-FU group; 60% in the platinum/taxane group). Pathological complete response rates for 5-FU and platinum/taxane-based groups were not significantly different (45% and 30%, respectively; P = 0.1548). Five-year overall survival and progression-free survival were not statistically different between the two groups. Significant predictors of pathological complete response included N stage (56% N0 and 33% N1; P = 0.0083), histology (37% adenocarcinoma and 59% squamous cell; P = 0.0123), tumor location (39% distal and 59% proximal/mid; P = 0.048), gastroesophageal junction involvement (33% involved and 55% uninvolved; P = 0.005), and radiotherapy end-to-surgery interval (50% < 55 days and 34% ≥ 55 days; P = 0.04). Grades 3-4 hematological toxicity was higher in the 5-FU group (36%) than in the paclitaxel-containing therapy group (17%; P = 0.0484). Use of paclitaxel-containing chemoradiotherapy did not result in inferior pathological complete response, overall survival, or progression-free survival rates, and resulted in less hematological toxicity than 5-FU treatment.

Modelling the species jump: towards assessing the risk of human infection from novel avian influenzas

The scientific understanding of the driving factors behind zoonotic and pandemic influenzas is hampered by complex interactions between viruses, animal hosts and humans. This complexity makes identifying influenza viruses of high zoonotic or pandemic risk, before they emerge from animal populations, extremely difficult and uncertain. As a first step towards assessing zoonotic risk of influenza, we demonstrate a risk assessment framework to assess the relative likelihood of influenza A viruses, circulating in animal populations, making the species jump into humans. The intention is that such a risk assessment framework could assist decision-makers to compare multiple influenza viruses for zoonotic potential and hence to develop appropriate strain-specific control measures. It also provides a first step towards showing proof of principle for an eventual pandemic risk model. We show that the spatial and temporal epidemiology is as important in assessing the risk of an influenza A species jump as understanding the innate molecular capability of the virus. We also demonstrate data deficiencies that need to be addressed in order to consistently combine both epidemiological and molecular virology data into a risk assessment framework.

Evaluation of Neoadjuvant Radiochemotherapy Response (RCT) in Squamous Esophageal Cancer (ESC) and Implications in Therapeutic Conduct

The multidisciplinary approach in ESC emerged as a result of efforts to maximize the treatment outcome of this disease.Surgical approach as the only therapeutic option is not always followed by a good distance survival. A concomitant neoadjuvant radiochemotherapy in ESC may result in a favourable outcome for responding patients, reducing the size of the tumor and the degree of lymph node damage increasing resectability and the R0 resection rate, improving prognosis. For non-responding patients or if the disease continues to progress under RCT therapy, the surgical time is delayed, adverse effects of radiochemotherapy are added and postoperative morbidity and mortality are increased. The imaging methods for the assessment of response have only limited value and metabolic response; only FDG-PET manages to come close to pathological response. Determining the response degree is very important for the establishment of the surgical conduct: planned or necessity surgery, or non-surgical palliative therapy.

Balancing cationic and hydrophobic content of PEGylated siRNA polyplexes enhances endosome escape, stability, blood circulation time, and bioactivity in vivo

A family of pH-responsive diblock polymers composed of poly[(ethylene glycol)-b-[(2-(dimethylamino)ethyl methacrylate)-co-(butyl methacrylate)], PEG-(DMAEMA-co-BMA), was reversible addition-fragmentation chain transfer (RAFT) synthesized with 0-75 mol % BMA in the second polymer block. The relative mole % of DMAEMA and BMA was varied in order to identify a polymer that can be used to formulate PEGylated, siRNA-loaded polyplex nanoparticles (NPs) with an optimized balance of cationic and hydrophobic content in the NP core based on siRNA packaging, cytocompatibility, blood circulation half-life, endosomal escape, and in vivo bioactivity. The polymer with 50:50 mol % of DMAEMA:BMA (polymer "50 B") in the RAFT-polymerized block efficiently condensed siRNA into 100 nm NPs that displayed pH-dependent membrane disruptive behavior finely tuned for endosomal escape. In vitro delivery of siRNA with polymer 50 B produced up to 94% protein-level knockdown of the model gene luciferase. The PEG corona of the NPs blocked nonspecific interactions with constituents of human whole blood, and the relative hydrophobicity of polymer 50 B increased NP stability in the presence of human serum or the polyanion heparin. When injected intravenously, 50 B NPs enhanced blood circulation half-life 3-fold relative to more standard PEG-DMAEMA (0 B) NPs (p < 0.05), due to improved stability and a reduced rate of renal clearance. The 50 B NPs enhanced siRNA biodistribution to the liver and other organs and significantly increased gene silencing in the liver, kidneys, and spleen relative to the benchmark polymer 0 B (p < 0.05). These collective findings validate the functional significance of tuning the balance of cationic and hydrophobic content of polyplex NPs utilized for systemic siRNA delivery in vivo.

Experimental liver transplantation on pigs -- technical considerations

The purpose was to improve and refine our technique for orthotopic liver transplantation.

MATERIAL AND METHOD

Experimental interventions were performed on pigs, 26 pairs. Orthotopic transplantation was performed after lavage of the donor pig liver by pressure gradient and transplantation was performed using portocavo- jugular shunt and veno-venous, arterio-arterial and choledocho-choledochal sutures in end-to-end manner.

RESULTS

Immediate survival was 88.46%.

CONCLUSIONS

Experimental transplant activity on pigs is of real value, contributing to a faster learning curve and at the same time improving handling, increasing the efficiency of sutures, as well as anesthetic and surgical team building.

Phylogenetic and molecular characteristics of Eurasian H9 avian influenza viruses and their detection by two different H9-specific RealTime reverse transcriptase polymerase chain reaction tests

Avian influenza viruses (AIVs) of the H9 haemagglutinin subtype are endemic in many Asian and Middle-East countries, causing mortality and morbidity in poultry. Consequently there is a need for accurate and sensitive detection of Eurasian H9 subtype viruses. Two H9 RealTime reverse transcriptase polymerase chain reaction (RRT-PCR) tests, developed by Monne et al. (2008) and Ben Shabat et al. (2010), were originally validated with a limited number of H9 specimens. In the present study, the two tests have been assessed using 66 diverse H9 isolates and 139 clinical specimens from six H9 poultry outbreaks in four geographically disparate Eurasian countries. The Monne et al. (2008) test was modified and successfully detected all H9 viruses from all three Eurasian H9 lineages. Bayesian analysis of the clinical specimens' results revealed this test to be more sensitive (97%) than the Ben Shabat et al. (2010) test (31%). The latter test detected most H9 isolates of the G1 lineage, but no isolates from other H9 lineages. Mismatches in the primer/probe binding sequences accounted for sensitivity differences between the two H9 RRT-PCRs. Genetic analysis of 34 sequenced H9 haemagglutinin genes showed the South Asian and Middle-East H9 isolates to belong to the H9 G1 lineage, and possessed residues that appear to preferably bind alpha 2,6-linked sialic acid receptors which indicate a potential for human infection. European H9s clustered phylogenetically in a broader geographical group that includes recent North American H9 wild bird isolates and contemporary Asian viruses in the Y439 H9 lineage.

First reported detection of a low pathogenicity avian influenza virus subtype H9 infection in domestic fowl in England

In December 2010, infection with a H9N1 low pathogenicity avian influenza (LPAI) virus was detected in a broiler breeder flock in East Anglia. Disease suspicion was based on acute drops in egg production in two of four sheds on the premises, poor egg shell quality and evidence of diarrhoea. H9N1 LPAI virus infection was confirmed by real-time reverse transcription PCR. Sequencing revealed high nucleotide identity of 93.6 per cent and 97.9 per cent with contemporary North American H9 and Eurasian N1 genes, respectively. Attempted virus isolation in embryonated specific pathogen free (SPF) fowls' eggs was unsuccessful. Epidemiological investigations were conducted to identify the source of infection and any onward spread. These concluded that infection was restricted to the affected premises, and no contacts or movements of poultry, people or fomites could be attributed as the source of infection. However, the infection followed a period of extremely cold weather and snow which impacted on the biosecurity protocols on site, and also led to increased wild bird activity locally, including waterfowl and game birds around the farm buildings. Analysis of the N1 gene sequence suggested direct introduction from wild birds. Although H9 infection in poultry is not notifiable, H9N2 LPAI viruses have been associated with production and mortality episodes in poultry in many parts of Asia and the Middle East. In the present H9N1 outbreak, clinical signs were relatively mild in the poultry with no mortality, transient impact on egg production and no indication of zoonotic spread. However, this first reported detection of H9 LPAI virus in chickens in England was also the first H9 UK poultry case for 40 years, and vindicates the need for continued vigilance and surveillance of avian influenza viruses in poultry populations.