Targeting HDAC6 improves anti-CD47 immunotherapy

BACKGROUND

Cancer cells can overexpress CD47, an innate immune checkpoint that prevents phagocytosis upon interaction with signal regulatory protein alpha (SIRPα) expressed in macrophages and other myeloid cells. Several clinical trials have reported that CD47 blockade reduces tumor growth in hematological malignancies. However, CD47 blockade has shown modest results in solid tumors, including melanoma. Our group has demonstrated that histone deacetylase 6 inhibitors (HDAC6is) have immunomodulatory properties, such as controlling macrophage phenotype and inflammatory properties. However, the molecular and cellular mechanisms controlling these processes are not fully understood. In this study, we evaluated the role of HDAC6 in regulating the CD47/SIRPα axis and phagocytosis in macrophages.

METHODS

We tested the role of HDAC6is, especially Nexturastat A, in regulating macrophage phenotype and phagocytic function using bone marrow-derived macrophages and macrophage cell lines. The modulation of the CD47/SIRPα axis and phagocytosis by HDAC6is was investigated using murine and human melanoma cell lines and macrophages. Phagocytosis was evaluated via coculture assays of macrophages and melanoma cells by flow cytometry and immunofluorescence. Lastly, to evaluate the antitumor activity of Nexturastat A in combination with anti-CD47 or anti-SIRPα antibodies, we performed in vivo studies using the SM1 and/or B16F10 melanoma mouse models.

RESULTS

We observed that HDAC6is enhanced the phenotype of antitumoral M1 macrophages while decreasing the protumoral M2 phenotype. In addition, HDAC6 inhibition diminished the expression of SIRPα, increased the expression of other pro-phagocytic signals in macrophages, and downregulated CD47 expression in mouse and human melanoma cells. This regulatory role on the CD47/SIRPα axis translated into enhanced antitumoral phagocytic capacity of macrophages treated with Nexturastat A and anti-CD47. We also observed that the systemic administration of HDAC6i enhanced the in vivo antitumor activity of anti-CD47 blockade in melanoma by modulating macrophage and natural killer cells in the tumor microenvironment. However, Nexturastat A did not enhance the antitumor activity of anti-SIRPα despite its modulation of macrophage populations in the SM1 tumor microenvironment.

CONCLUSIONS

Our results demonstrate the critical regulatory role of HDAC6 in phagocytosis and innate immunity for the first time, further underscoring the use of these inhibitors to potentiate CD47 immune checkpoint blockade therapeutic strategies.

Role of HDAC6-STAT3 in immunomodulatory pathways in Colorectal cancer cells

Colorectal cancer (CRC) is one of the most common malignant neoplasms and the second leading cause of death from tumors worldwide. Therefore, there is a great need to study new therapeutical strategies, such as effective immunotherapies against these malignancies. Unfortunately, many CRC patients do not respond to current standard immunotherapies, making it necessary to search for adjuvant treatments. Histone deacetylase 6 (HDAC6) is involved in several processes, including immune response and tumor progression. Specifically, it has been observed that HDAC6 is required to activate the Signal Transducer and Activator of Transcription 3 (STAT3), a transcription factor involved in immunogenicity, by activating different genes in these pathways, such as PD-L1. Over-expression of immunosuppressive pathways in cancer cells deregulates T-cell activation. Therefore, we focused on the pharmacological inhibition of HDAC6 in CRC cells because of its potential as an adjuvant to avoid immunotolerance in immunotherapy. We investigated whether HDAC6 inhibitors (HDAC6is), such as Nexturastat A (NextA), affected STAT3 activation in CRC cells. First, we found that NextA is less cytotoxic than the non-selective HDACis panobinostat. Then, NextA modified STAT3 and decreased the mRNA and protein expression levels of PD-L1. Importantly, transcriptomic analysis showed that NextA treatment affected the expression of critical genes involved in immunomodulatory pathways in CRC malignancies. These results suggest that treatments with NextA reduce the functionality of STAT3 in CRC cells, impacting the expression of immunomodulatory genes involved in the inflammatory and immune responses. Therefore, targeting HDAC6 may represent an interesting adjuvant strategy in combination with immunotherapy.

Radiotherapy-induced Immune Response Enhanced by Selective HDAC6 Inhibition

Radiotherapy is a curative cancer treatment modality that imparts damage to cellular DNA, induces immunogenic cell death, and activates antitumor immunity. Despite the radiotherapy-induced direct antitumor effect seen within the treated volume, accumulating evidence indicates activation of innate antitumor immunity. Acute proinflammatory responses mediated by anticancer M1 macrophages are observed in the immediate aftermath following radiotherapy. However, after a few days, these M1 macrophages are converted to anti-inflammatory and pro-cancer M2 phenotype, leading to cancer resistance and underlying potential tumor relapse. Histone deacetylase 6 (HDAC6) plays a crucial role in regulating macrophage polarization and innate immune responses. Here, we report targeting HDAC6 function with a novel selective inhibitor (SP-2-225) as a potential therapeutic candidate for combination therapy with radiotherapy. This resulted in decreased tumor growth and enhanced M1/M2 ratio of infiltrating macrophages within tumors. These observations support the use of selective HDAC6 inhibitors to improve antitumor immune responses and prevent tumor relapse after radiotherapy.

Abstract 666: Targeting the CD47/SIRPα “Do not eat me” phagocytic pathway in macrophages to improve anti-CD47 immune therapy

The cluster of differentiation 47(CD47) is a ubiquitously expressed innate immune checkpoint transmembrane protein but is often overexpressed in cancer cells. CD47 interacts with signal regulatory protein alpha (SIRPα) on macrophages leading to tyrosine phosphatase activation and preventing myosin accumulation at the phagocytic synapse. SIRPa activation triggers the “Do not eat me” signal, negatively regulating phagocytosis in macrophages. Blockade of CD47-SIRPα is a novel immunotherapeutic approach to enhance innate antitumor responses in cancer patients, and clinical data from melanoma patients also showed promising outcomes when CD47 blockade combined with other therapeutic approaches, such as anti-PD-L1. Publications from our lab have provided compelling evidence that histone deacetylase 6 (HDAC6) inhibitors with PD1 blockade delayed tumor progression, enhanced survival, and modulated macrophage phenotype both in vitro and in vivo. The present study aimed to explore the role of HDAC 6 in the CD47/SIRPα axis in phagocytosis and innate antitumor immunity. HDAC inhibition in primary mouse bone marrow-derived macrophages and human THP1 cells enhanced the pro-inflammatory M1 macrophages while downregulating the anti-inflammatory M2 phenotype. In the subsequent studies, we found that HDAC6 inhibition diminished the expression of SIRPα and enhanced the expression of other pro-phagocytic signals, such as Lrp1, CD36, and Mfge8 in macrophages. HDAC6 inhibition also downregulated the CD47 expression in mouse and human melanoma cells. Furthermore, modulation of CD47/SIRPα by HDAC6 inhibitors leads to an increase in phagocytosis in NextA-treated macrophages, further enhanced in CD47-blocking antibodies. We also demonstrated that the combination of systemic administration of the HDAC6 inhibitor Nexturastat A and intertumoral delivery of anti-CD47 reduced SM1 melanoma growth in vivo by increasing immune cell infiltration in the tumor microenvironment. Collectively our results suggest that HDAC6 inhibitors synergize with CD47 blockade to reduce tumor growth and enhance innate antitumor immunity.

Citation Format: Nithya Gajendran, Maria Gracia Hernandez, Ashutosh Yende, Zubaydah Alahmad, Xintang Li, Zuleima Munoz, Manasa Suresh, David Quiceno, Karen Tan, Maho Shibata, Satish Noonepalle, Alejandro Villagra. Targeting the CD47/SIRPα “Do not eat me” phagocytic pathway in macrophages to improve anti-CD47 immune therapy [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 666.

Abstract 2880: Inhibition of HDAC6 and HDAC11 has opposite effects on inflammation and the modulation of the functional phenotype of macrophages in the tumor microenvironment

Introduction: Pan-histone deacetylase (HDAC) inhibitors have been used as anti-cancer agents due to their cytotoxicity. However, studies from our group have reported that intervention of class-specific HDAC inhibitors can differentially affect immune-related pathways in macrophages and influence their pro- or anti-inflammatory phenotype and function. For example, specific HDAC6 inhibitors demonstrated promising anti-tumor effects by suppressing tumor-promoting M2 macrophages in the tumor microenvironment (TME). In contrast, inhibition of HDAC11 promoted the anti-inflammatory phenotype of macrophages. Besides the divergent roles and distinct signaling pathways, a comprehensive study on the effect of HDCA6 and HDAC11 inhibition on macrophage phenotype and the implications on TME and inflammation is warranted.

Objective: To determine the effect of HDAC6 and HDAC11 inhibition on the phenotype and function of macrophages in the context of the TME.

Methods: Bone marrow-derived macrophages (BMDMs) isolated from C57BL/6 mice were pre-treated with HDAC6 (NexturastatA) or HDAC11 (FT895) inhibitors prior to polarizing them to M1 and M2 phenotypes. Similarly, BMDMs were isolated from total knockouts (KO) of HDAC6 and HDAC11 mice. The changes in gene expression were identified by RNA-seq analysis. Furthermore, single-cell secretome analysis on Isoplexis platform was performed from human and mice BMDMs on a panel of cytokines and chemokines.

Results: Transcriptomic analysis revealed that HDAC6 inhibition in M1 polarized BMDMs sustained inflammatory gene signature while suppressing the tumor-promoting and anti-inflammatory genes in M2 macrophages. This supported our previous reports where HDAC6i increased M1/M2 ratio in murine melanoma models. In contrast, HDAC11 inhibition in M2 macrophages upregulated classical M2 markers, whereas M1-associated gene signature was minimally affected. These results were recapitulated in HDAC6KO and HDAC11KO macrophages, suggesting a high specificity of the inhibitors. Further validation at protein level by single-cell secretome analysis indicated that HDAC11 inhibition in M2 polarized BMDMs increased secretion of growth factors such as Egf and Pdgf and of anti-inflammatory cytokines such as Il10 and Il13. On the contrary, HDAC6 inhibition upregulated inflammatory cytokines such as Ifng and Tnf and T-cell recruiting chemokine Cxcl10 in the M1 phenotype.

Conclusions:Transcriptomics and single-cell secretome analyses of macrophages indicate that HDAC6 and HDAC11 affects macrophage function in diametrically opposite directions. Therefore, our study underscores the importance of class-selective inhibition of HDACs over pan-HDAC inhibitors and the potential use of selective HDAC inhibitors as a therapeutic option to control macrophage phenotype in cancer and other conditions.

Citation Format: Manasa Suresh, Hawa Coulibaly, Xintang Li, David Quiceno-Torres, Nithya Gajendran, Karen Tan, Matias Hepp, Karthik Musunuri, Satish Noonepalle, Alejandro Villagra. Inhibition of HDAC6 and HDAC11 has opposite effects on inflammation and the modulation of the functional phenotype of macrophages in the tumor microenvironment [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 2880.

Radiotherapy Induces Innate Immune Responses in Patients Treated for Prostate Cancers

PURPOSE

Radiotherapy is a curative therapeutic modality used to treat cancers as a single agent or in combination with surgery and chemotherapy. Advanced radiotherapy technologies enable treatment with large fractions and highly conformal radiation doses to effect free-radical damage to cellular DNA leading to cell-cycle arrest, cell death, and innate immune response (IIR) stimulation.

EXPERIMENTAL DESIGN

To understand systemic clinical responses after radiation exposure, proteomic and metabolomic analyses were performed on plasma obtained from patients with cancer at intervals after prostate stereotactic body radiotherapy. Pathway and multivariate analyses were used to delineate molecular alterations following radiotherapy and its correlation with clinical outcomes.

RESULTS

DNA damage response increased within the first hour after treatment and returned to baseline by 1 month. IIR signaling also increased within 1 hour of treatment but persisted for up to 3 months thereafter. Furthermore, robust IIR and metabolite elevations, consistent with an early proinflammatory M1-mediated innate immune activation, were observed in patients in remission, whereas patients experiencing prostate serum antigen-determined disease progression demonstrated less robust immune responses and M2-mediated metabolite elevations.

CONCLUSIONS

To our knowledge, these data are the first report of longitudinal proteomic and metabolomic molecular responses in patients after radiotherapy for cancers. The data supports innate immune activation as a critical clinical response of patients receiving radiotherapy for prostate cancer. Furthermore, we propose that the observed IIR may be generalized to the treatment of other cancer types, potentially informing multidisciplinary therapeutic strategies for cancer treatment.

Inhibiting DNA methylation and RNA editing upregulates immunogenic RNA to transform the tumor microenvironment and prolong survival in ovarian cancer

BACKGROUND

Novel therapies are urgently needed for ovarian cancer (OC), the fifth deadliest cancer in women. Preclinical work has shown that DNA methyltransferase inhibitors (DNMTis) can reverse the immunosuppressive tumor microenvironment in OC. Inhibiting DNA methyltransferases activate transcription of double-stranded (ds)RNA, including transposable elements. These dsRNAs activate sensors in the cytoplasm and trigger type I interferon (IFN) signaling, recruiting host immune cells to kill the tumor cells. Adenosine deaminase 1 (ADAR1) is induced by IFN signaling and edits mammalian dsRNA with an A-to-I nucleotide change, which is read as an A-to-G change in sequencing data. These edited dsRNAs cannot be sensed by dsRNA sensors, and thus ADAR1 inhibits the type I IFN response in a negative feedback loop. We hypothesized that decreasing ADAR1 editing would enhance the DNMTi-induced immune response.

METHODS

Human OC cell lines were treated in vitro with DNMTi and then RNA-sequenced to measure RNA editing. Adar1 was stably knocked down in ID8 Trp53^-/- mouse OC cells. Control cells (shGFP) or shAdar1 cells were tested with mock or DNMTi treatment. Tumor-infiltrating immune cells were immunophenotyped using flow cytometry and cell culture supernatants were analyzed for secreted chemokines/cytokines. Mice were injected with syngeneic shAdar1 ID8 Trp53^-/- cells and treated with tetrahydrouridine/DNMTi while given anti-interferon alpha and beta receptor 1, anti-CD8, or anti-NK1.1 antibodies every 3 days.

RESULTS

We show that ADAR1 edits transposable elements in human OC cell lines after DNMTi treatment in vitro. Combining ADAR1 knockdown with DNMTi significantly increases pro-inflammatory cytokine/chemokine production and sensitivity to IFN-β compared with either perturbation alone. Furthermore, DNMTi treatment and Adar1 loss reduces tumor burden and prolongs survival in an immunocompetent mouse model of OC. Combining Adar1 loss and DNMTi elicited the most robust antitumor response and transformed the immune microenvironment with increased recruitment and activation of CD8+ T cells.

CONCLUSION

In summary, we showed that the survival benefit from DNMTi plus ADAR1 inhibition is dependent on type I IFN signaling. Thus, epigenetically inducing transposable element transcription combined with inhibition of RNA editing is a novel therapeutic strategy to reverse immune evasion in OC, a disease that does not respond to current immunotherapies.

CD137 agonist potentiates the abscopal efficacy of nanoparticle-based photothermal therapy for melanoma

Despite the promise of immunotherapy such as the immune checkpoint inhibitors (ICIs) anti-PD-1 and anti-CTLA-4 for advanced melanoma, only 26%-52% of patients respond, and many experience grade III/IV immune-related adverse events. Motivated by the need for an effective therapy for patients non-responsive to clinically approved ICIs, we have developed a novel nanoimmunotherapy that combines locally administered Prussian blue nanoparticle-based photothermal therapy (PBNP-PTT) with systemically administered agonistic anti-CD137 monoclonal antibody therapy (aCD137). PBNP-PTT was administered at various thermal doses to melanoma cells in vitro, and was combined with aCD137 in vivo to test treatment effects on melanoma tumor progression, animal survival, immunological protection against tumor rechallenge, and hepatotoxicity. When administered at a melanoma-specific thermal dose, PBNP-PTT elicits immunogenic cell death (ICD) in melanoma cells and upregulates markers associated with antigen presentation and immune cell co-stimulation in vitro. Consequently, PBNP-PTT eliminates primary melanoma tumors in vivo, yielding long-term tumor-free survival. However, the antitumor immune effects generated by PBNP-PTT cannot eliminate secondary tumors, despite significantly slowing their growth. The addition of aCD137 enables significant abscopal efficacy and improvement of survival, functioning through activated dendritic cells and tumor-infiltrating CD8⁺ T cells, and generates CD4⁺ and CD8⁺ T cell memory that manifests in the rejection of tumor rechallenge, with no long-term hepatotoxicity. This study describes for the first time a novel and effective nanoimmunotherapy combination of PBNP-PTT with aCD137 mAb therapy for melanoma.

Phase I Study of Entinostat in Combination with Enzalutamide for Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer

LESSONS LEARNED

Entinostat at the selected dose levels in combination with a standard dose of enzalutamide showed a promising safety profile in this small phase I study BACKGROUND: Entinostat inhibits prostate cancer (PCa) growth and suppresses Treg cell function in vitro and in vivo.

METHODS

This was a phase I study to explore the safety and preliminary efficacy of entinostat (3 and 5 mg orally per week) in combination with enzalutamide in castration resistant PCa (CRPC). The study was carried out in an open-label two-cohort design. Patients who had developed disease progression on or were eligible for enzalutamide were enrolled in the study. The safety profile of the combination therapy, Prostate specific antigen (PSA) levels, the pharmacokinetics of enzalutamide after entinostat administration, peripheral T-cell subtype (including Treg quantitation), and mononuclear cell (PBMC) histone H3 acetylation were analyzed.

RESULTS

Six patients with metastatic CRPC were enrolled. There was no noticeable increment of fatigue related to entinostat. Toxicities possibly or probably related to entinostat or the combination therapy included grade 3 anemia 1/6 (17%), grade 2 white blood cell (WBC) decrease 1/6 (17%), and other self-limiting grade 1 adverse events (AEs). Median duration of treatment with entinostat was 18 weeks. Entinostat did not affect the steady plasma concentration of enzalutamide. Increased PBMC histone H3 acetylation was observed in blood samples. No evident T-cell subtype changes were detected, including in Treg quantitation.

CONCLUSION

Entinostat 5 mg weekly in combination with enzalutamide showed an acceptable safety profile in this small phase I study. A planned phase II part of the trial was terminated because of sponsor withdrawal.

Abstract 1268: A novel treatment approach for melanoma by dually targeting MCT1 and MCT4 lactate transporters

Cancer cells are metabolically rewired to activate glycolysis, which results in the generation and excretion of lactate as a byproduct. Although lactate was previously thought to be a waste product of anaerobic respiration, increasing evidence has revealed that distinct cell populations within tumors use lactate as a source of energy through TCA cycle. This metabolic symbiosis between distinct cell populations, hypoxic lactate consumers, and oxidative glycolytic lactate exporters within the tumor is regulated by differential expression of lactate transporters, mainly MCT1 and MCT4. Therefore, dual targeting of MCT1 and MCT4 is a novel approach to treat cancer. We have developed a compound, NGY-B, which binds and inhibits both MCT1 and MCT4 transporters. This compound has shown to significantly increase intracellular lactate levels in melanoma models and thereby decreasing in vitro cell proliferation. When cultured in the media with exogenous lactate to mimic the tumor microenvironment, NGY-B greatly reduced lactate uptake by cancer cells. Mechanistically, NGY-B deactivated glycolytic pathway by reducing hexokinase 2 (HK2), phosphoglycerate dehydrogenase (PHGDH), and pyruvate dehydrogenase kinase 1 (PDK1) expression. Additionally, NGY-B treatment strongly decreased STAT3 and mTOR signaling pathways. Furthermore, the in vivo therapeutic efficacy of NGY-B was validated in xenograft and syngeneic mouse models of melanoma. While a significant reduction in tumor size was observed in A375 xenograft model treated with NGY-B, a robust tumor growth reduction was evident in SM1 immunocompetent syngeneic melanoma mouse model, suggesting the involvement of immune cells for higher response in this model. Supporting this premise, we also found that NGY-B treated cells showed a decrease in PD-L1, B7-H3, and B7-H4 expression. Overall, our results indicate that NGY-B inhibits melanoma by targeting metabolic symbiosis and activating antitumor immune response mechanisms.

Citation Format: Sambad Sharma, Gregory Goreczny, Satish Kumar Noonepalle, Erica Palmer, Maria Garcia-Hernandez, Daliya Banerjee, Jaime Escobedo, Alejandro Villagra, Vincent Sandanayaka. A novel treatment approach for melanoma by dually targeting MCT1 and MCT4 lactate transporters [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1268.

Phase I study of entinostat in combination with enzalutamide for treatment of patients with castration-resistant prostate cancer

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Background: Entinostat (SNDX-275, MS-275) is an oral histone deacetylase (HDAC) inhibitor with selectivity towards class I and IV HDACs. Entinostat inhibits prostate cancer (PCa) growth and suppresses Treg cell function in vitro and in vivo. The primary objective of this study was to determine the safe dose of Entinostat in combination with Enzalutamide in prostate cancer patients (PCa). Methods: Phase I, 2 cohorts "3+3", dose-escalation study to explore the safety and preliminary efficacy of Entinostat in combination with Enzalutamide in castration-resistant PCa (CRPC). The planned dose level of Entinostat was 3 and 5 mg orally per week. CRPC Patients progressed on Enzalutamide or eligible for Enzalutamide, able to tolerate 160 mg daily dose (in the initial run-in phase if Enzalutamide naïve), ECOG 0-1, and acceptable organ functions were enrolled in the study. The safety profile of the combination therapy, PSA, pharmacokinetics of Enzalutamide post-Entinostat administration, and peripheral T cell subtype (including Treg), mononuclear cell (PBMC) histone 3 acetylation were analyzed. Results: Total 6 mCRPC patients were enrolled. There was no dose limiting toxicity related to Entinostat in these patients. No obvious increased fatigue related to Entinostat. Toxicities possibly or probably related to Entinostat or the combination therapy included G3 anemia 1/6 (17%), G2 WBC decrease 1/6 (17%), All other toxicities were grade 1 only (Nausea 2/6, anorexia 1/6, emesis 1/6, constipation 1/6, headache 1/6, platelet count decrease 1/6, hypokalemia 1/6, hypoalbuminemia 1/6, hypermagnesemia 1/6). The median duration of treatment with Entinostat was 18 weeks. For patients already progressed on Enzalutamide there was no PSA response after Entinostat was added. Entinostat did not affect the steady plasma concentration of Enzalutamide. Increased PBMC H3 acetylation was observed (up to 3.6 fold from baseline) in the tested samples. No evident T cell subtype, including Treg, changes from these sample analysis. Phase II part of the trial was terminated because of sponsor withdrawal. Conclusions: Entinostat at the selected dose levels in combination with standard dose of enzalutamide showed promising safety profile in this small phase I study. Clinical trial information: NCT03829930.

Abstract PO023: Immune-mediated tumor growth inhibition by selective HDAC6 inhibitor SP-2-225

In addition to their canonical role in transcriptional regulation, Histone deacetylases (HDACs) regulate other cellular functions by maintaining a balance of lysine acetylation on key cellular proteins. HDAC inhibitors are under development for use in treating cancers, neurological, and immunological diseases. A barrier to the development of HDAC inhibitors has been the toxicity associated with non-selective pan-HDAC inhibitors, which simultaneously inhibit multiple HDAC isoforms. Isoform selective HDAC inhibitors offer disease targeting with an improved toxicity profile. HDAC6 presents an important target due to its role in immune regulatory processes involved in antitumor immune responses. We have shown that selective inhibition of HDAC6 regulates macrophages to recognize, phagocyte, and present antigens to the adaptive immune system. Treatment with our selective HDAC6 inhibitor, SP-2-225, was shown to enhance the production of cancer-associated antigens and macrophage antigen cross-presentation to T cells. Through a non-cytotoxic mechanism, SP-2-225 significantly reduced the tumor volume in a syngeneic SM1 melanoma model. Analysis of the tumors from treated animals showed a significant shift in the M1/M2 ratio of the infiltrating macrophages as compared to control, indicating that SP-2-225 caused a pro-inflammatory, antitumor shift in the macrophage equilibrium surrounding the tumor. This was identified as the putative mechanism through adoptive cell therapy where macrophages from naive animals were harvested and treated ex-vivo with SP-2-225. Reimplantation of these SP-2-225 ex-vivo treated macrophages resulted in reduced tumor volumes when compared to both vehicle and untreated macrophage animal cohorts. We propose that this selective inhibitor of HDAC6 offers potential as a stand-alone cancer therapy and in combination with other immunotherapies and radiation treatments.

Citation Format: Scott Grindrod, Satish Noonepalle, Nima Aghdam, Alfredo Velena, Maria Gracia-Hernandez, Christian Zevallos-Delgado, Mira Jung, Anatoly Dritschilo, Alejandro Villagra. Immune-mediated tumor growth inhibition by selective HDAC6 inhibitor SP-2-225 [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO023.

[Cancer immunotherapy: an update]

Cancer is one of the leading causes of death worldwide. The success rate of conventional anticancer therapeutic approaches such as chemotherapy is limited by the non-specific toxicity and low specificity towards specific tumors, which are highly dependent on the mutational burden present on each patient. Similarly, targeted therapies have proven to induce resistance in numerous malignancies. Therefore, immunotherapy has emerged as a better approach to discriminate between "the own" and "the non-own", which occurs through two types of mechanisms, innate and acquired immunity. Acquired immunity is one of the targets for new immunotherapeutic treatments, unleashing the power of antigen-specific T cells as a potential therapeutic weapon for cancer treatment. Thus, immunotherapy modifies the own immune system to increase the recognition and elimination of cancer cells by identifying these cancer antigens. One of the advantages of immunotherapy, when compared to conventional anticancer approaches, is the generation of long-term immunity (immunological memory). Currently, there are different potential types of immunotherapy in cancer to promote the modulation of the immune response. Among them, the use of cytokines, vaccines, viruses, monoclonal antibodies, and the generation of adaptive immune response cells have achieved successful results in some types of cancer.

Targeting Macrophages as a Therapeutic Option in Coronavirus Disease 2019

Immune cells of the monocyte/macrophage lineage are characterized by their diversity, plasticity, and variety of functions. Among them, macrophages play a central role in antiviral responses, tissue repair, and fibrosis. Macrophages can be reprogrammed by environmental cues, thus changing their phenotype during an antiviral immune response as the viral infection progresses. While M1-like macrophages are essential for the initial inflammatory responses, M2-like macrophages are critical for tissue repair after pathogen clearance. Numerous reports have evaluated the detrimental effects that coronaviruses, e.g., HCoV-229E, SARS-CoV, MERS-CoV, and SARS-CoV-2, have on the antiviral immune response and macrophage functions. In this review, we have addressed the breadth of macrophage phenotypes during the antiviral response and provided an overview of macrophage-coronavirus interactions. We also discussed therapeutic approaches to target macrophage-induced complications, currently under evaluation in clinical trials for coronavirus disease 2019 patients. Additionally, we have proposed alternative approaches that target macrophage recruitment, interferon signaling, cytokine storm, pulmonary fibrosis, and hypercoagulability.

CpG-coated prussian blue nanoparticles-based photothermal therapy combined with anti-CTLA-4 immune checkpoint blockade triggers a robust abscopal effect against neuroblastoma

High-risk neuroblastoma, which is associated with regional and systemic metastasis, is a leading cause of cancer-related mortality in children. Responding to this need for novel therapies for high-risk patients, we have developed a "nanoimmunotherapy," which combines photothermal therapy (PTT) using CpG oligodeoxynucleotide-coated Prussian blue nanoparticles (CpG-PBNPs) combined with anti-CTLA-4 (aCTLA-4) immunotherapy. Our in vitro studies demonstrate that in addition to causing ablative tumor cell death, our nanoimmunotherapy alters the surface levels of co-stimulatory, antigen-presenting, and co-inhibitory molecules on neuroblastoma tumor cells. When administered in a syngeneic, murine model of neuroblastoma bearing synchronous Neuro2a tumors, the CpG-PBNP-PTT plus aCTLA-4 nanoimmunotherapy elicits complete tumor regression in both primary (CpG-PBNP-PTT-treated) and secondary tumors, and long-term survival in a significantly higher proportion (55.5%) of treated-mice compared with the controls. Furthermore, the surviving, nanoimmunotherapy-treated animals reject Neuro2a rechallenge, suggesting that the therapy generates immunological memory. Additionally, the depletion of CD4+, CD8+, and NK+ populations abrogate the observed therapeutic responses of the nanoimmunotherapy. These findings demonstrate the importance of concurrent PTT-based cytotoxicity and the antitumor immune effects of PTT, CpG, and aCTLA-4 in generating a robust abscopal effect against neuroblastoma.

Rational Design of Suprastat: A Novel Selective Histone Deacetylase 6 Inhibitor with the Ability to Potentiate Immunotherapy in Melanoma Models

Selective inhibition of histone deacetylase 6 (HDAC6) is being recognized as a therapeutic approach for cancers. In this study, we designed a new HDAC6 inhibitor, named Suprastat, using in silico simulations. X-ray crystallography and molecular dynamics simulations provide strong evidence to support the notion that the aminomethyl and hydroxyl groups in the capping group of Suprastat establish significant hydrogen bond interactions, either direct or water-mediated, with residues D460, N530, and S531, which play a vital role in regulating the deacetylase function of the enzyme and which are absent in other isoforms. In vitro characterization of Suprastat demonstrates subnanomolar HDAC6 inhibitory potency and a hundred- to a thousand-fold HDAC6 selectivity over the other HDAC isoforms. In vivo studies reveal that a combination of Suprastat and anti-PD1 immunotherapy enhances antitumor immune response, mediated by a decrease of protumoral M2 macrophages and increased infiltration of antitumor CD8+ effector and memory T-cells.

HDAC6 Plays a Noncanonical Role in the Regulation of Antitumor Immune Responses, Dissemination, and Invasiveness of Breast Cancer

Despite the outstanding clinical results of immune checkpoint blockade (ICB) in melanoma and other cancers, clinical trials in breast cancer have reported low responses to these therapies. Current efforts are now focused on improving the treatment efficacy of ICB in breast cancer using new combination designs such as molecularly targeted agents, including histone deacetylase inhibitors (HDACi). These epigenetic drugs have been widely described as potent cytotoxic agents for cancer cells. In this work, we report new noncanonical regulatory properties of ultra-selective HDAC6i over the expression and function of epithelial-mesenchymal transition pathways and the invasiveness potential of breast cancer. These unexplored roles position HDAC6i as attractive options to potentiate ongoing immunotherapeutic approaches. These new functional activities of HDAC6i involved regulation of the E-cadherin/STAT3 axis. Pretreatment of tumors with HDAC6i induced critical changes in the tumor microenvironment, resulting in improved effectiveness of ICB and preventing dissemination of cancer cells to secondary niches. Our results demonstrate for the first time that HDAC6i can both improve ICB antitumor immune responses and diminish the invasiveness of breast cancer with minimal cytotoxic effects, thus departing from the cytotoxicity-centric paradigm previously assigned to HDACi. SIGNIFICANCE: Ultraselective HDAC6 inhibitors can reduce tumor growth and invasiveness of breast cancer by noncanonical mechanisms unrelated to the previously cytotoxic properties attributed to HDAC inhibitors.

Testing repeatability, measurement error and species differentiation when using geometric morphometrics on complex shapes: a case study of Patagonian lizards of the genus Liolaemus (Squamata: Liolaemini)

The repeatability of findings is the key factor behind scientific reliability, and the failure to reproduce scientific findings has been termed the ‘replication crisis’. Geometric morphometrics is an established tool in evolutionary biology. However, different operators (and/or different methods) could act as large sources of variation in the data obtained. Here, we investigated inter-operator error in geometric morphometric protocols on complex shapes of Liolaemus lizards, as well as measurement error in three taxa varying in their difficulty of digitalization. We also examined the potential for these protocols to discriminate among complex shapes in closely related species. We found a wide range of inter-operator error, contributing between 19.5% and 60% to the total variation. Moreover, measurement error increased with the complexity of the quantified shape. All protocols were able to discriminate between species, but the use of more landmarks did not imply better performance. We present evidence that complex shapes reduce repeatability, highlighting the need to explore different sources of variation that could lead to such low repeatability. Lastly, we suggest some recommendations to improve the repeatability and reliability of geometric morphometrics results.

Combining DNMT and HDAC6 inhibitors increases anti-tumor immune signaling and decreases tumor burden in ovarian cancer

Novel therapies are urgently needed for ovarian cancer, the deadliest gynecologic malignancy. Ovarian cancer has thus far been refractory to immunotherapies that stimulate the host immune system to recognize and kill cancer cells. This may be because of a suppressive tumor immune microenvironment and lack of recruitment and activation of immune cells that kill cancer cells. Our previous work showed that epigenetic drugs including DNA methyltransferase inhibitors and histone deacetylase 6 inhibitors (DNMTis and HDAC6is) individually increase immune signaling in cancer cells. We find that combining DNMTi and HDAC6i results in an amplified type I interferon response, leading to increased cytokine and chemokine expression and higher expression of the MHC I antigen presentation complex in human and mouse ovarian cancer cell lines. Treating mice bearing ID8 Trp53-/- ovarian cancer with HDAC6i/DNMTi led to an increase in tumor-killing cells such as IFNg+ CD8, NK, and NKT cells and a reversal of the immunosuppressive tumor microenvironment with a decrease in MDSCs and PD-1hi CD4 T cells, corresponding with an increase in survival. Thus combining the epigenetic modulators DNMTi and HDAC6i increases anti-tumor immune signaling from cancer cells and has beneficial effects on the ovarian tumor immune microenvironment.

Discovery of a New Isoxazole-3-hydroxamate-Based Histone Deacetylase 6 Inhibitor SS-208 with Antitumor Activity in Syngeneic Melanoma Mouse Models

Isoxazole is a five-membered heterocycle that is widely used in drug discovery endeavors. Here, we report the design, synthesis, and structural and biological characterization of SS-208, a novel HDAC6-selective inhibitor containing the isoxazole-3-hydroxamate moiety as a zinc-binding group as well as a hydrophobic linker. A crystal structure of the Danio rerio HDAC6/SS-208 complex reveals a bidentate coordination of the active-site zinc ion that differs from the preferred monodentate coordination observed for HDAC6 complexes with phenylhydroxamate-based inhibitors. While SS-208 has minimal effects on the viability of murine SM1 melanoma cells in vitro, it significantly reduced in vivo tumor growth in a murine SM1 syngeneic melanoma mouse model. These findings suggest that the antitumor activity of SS-208 is mainly mediated by immune-related antitumor activity as evidenced by the increased infiltration of CD8+ and NK+ T cells and the enhanced ratio of M1 and M2 macrophages in the tumor microenvironment.

Abstract LB-074: Priming the tumor microenvironment with epigenetic modifiers to overcome resistance to immune checkpoint inhibitors

Histone deacetylases (HDACs) are involved in diverse cellular regulatory mechanisms including functions outside the chromatin environment. Several publications have demonstrated that selective HDAC inhibitors (HDACi) can influence tumor immunogenicity and the functional activity of specific immune cells. In particular, the selective inhibition of HDAC6 has been reported to decrease tumor growth in several malignancies. However, there is still no clarity about the cellular components mediating this effect. In this study, we evaluated the immunological modulation of the HDAC6i Nexturastat A in combination with anti-PD-1 checkpoint blockade therapy and the use of this HDAC6i as a priming agent to facilitate the transition of the tumor microenvironment from “cold” to “hot” in order to more specifically augment immune check-point blockade therapies. This combination of Nexturastat A and anti-PD-1 therapy demonstrated a significant reduction of tumor growth in syngeneic melanoma tumor animal models. Additionally, we observed a complete neutralization of the up-regulation of PD-L1 and other immunosuppressive pathways induced by the treatment with anti-PD-1 blockade. This combination also showed that the pre-treatment with selective HDAC6i induced major changes in the tumor microenvironment such as enhanced infiltration of immune cells, increased central and effector T cell memory, and a significant reduction of pro-tumorigenic M2 macrophages. The evaluation of the effect of HDAC6i on individual immune components suggest that the in vivo anti-tumor activity of HDAC6i is mediated by its effect on tumor cells and tumor associated macrophages, and not directly over T cells. Overall, our results indicate that selective HDAC6i could be used as immunological priming agents to sensitize immunologically “cold” tumors and subsequently improve ongoing immune check-point blockade therapies.

Note: This abstract was not presented at the meeting.

Citation Format: Tessa J. Knox, Eva Sahakian, Debarati Banik, Melissa Hadley, Erica Palmer, Jennifer Kim, Satish Noonepalle, John Powers, Maria Gracia-Hernandez, Vasco Oliveira, Fengdong Cheng, Jie Chen, Cyril Barinka, Javier Pinilla-Ibarz, Norman Lee, Alan Kozikowski, Alejandro Villagra. Priming the tumor microenvironment with epigenetic modifiers to overcome resistance to immune checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-074.

Abstract 2019: Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6

Histone deacetylases (HDAC) are recognized for diverse functions beyond remodeling of chromatin landscape. It may range from regulating the cellular-health to immune-diseases like cancer, positioning the HDAC inhibitors (HDACi) at a crucial junction of immunotherapy. The toxicity among pan-HDACi has led to the development of selective inhibitors, which helped to understand the roles of specific HDACs in immune responses. For example, HDAC6 is reported to promote the pro-tumorigenic STAT3 pathway. By using specific HDAC6i, the downstream immune-modulatory pathways of STAT3, such as PDL1, could be targeted. HDAC6 has been associated with numerous structural functions, including cellular motility, shape, antigen processing, and intracellular transport through the acetylation of tubulin and cortactin, among others. This function suggests that HDAC6 could also a regulator of cellular processes involved in metastasis. In this respect, we found that the selective HDAC6i NextA was able to reduce the primary tumor growth and the appearance of spontaneously metastatic nodules in the murine Triple Negative Breast Cancer (TNBC) tumor model 4T1. Additionally, the in vitro use of NextA in multiple murine and human breast cancer cell lines was found to reduce invasion and modulate multiple EMT-specific genes without exhibiting excessive cytotoxicity. PDL1 expression was also reduced, as described previously in melanoma models. Given that 4T1 is a TIL-infiltrated tumor, we tested the efficacy of αPD-1 immune checkpoint inhibitors (ICI) and found a lower dose of αPD-1 to be more effective than the higher doses to reduce primary and secondary tumor growth. However, the expression of IFNγ & PD-L1 were enhanced with the monotherapy. In an in vitro setting, we were able to nullify the upregulation of PD-L1 by αPD-1 with either NextA or IFNγ neutralization. To apply this insight in vivo, we tested the combination of NextA and αPD-1 to find a significant reduction in tumor growth, both in primary & secondary nodules. Analysis of the effector molecules revealed a reduction in intra-tumoral PD-L1 and IDO1 along with a moderate level of IFNγ, as well as a reduction in several key EMT signature genes, including cMYC, MMP9, vimentin, and twist. We also identified E-cadherin, a negative regulator of the metastatic process, as a novel target of NextA that was found to be upregulated in vivo. This was corroborated by the in vitro observations in several murine and human breast cancer cell lines, irrespective of hormonal receptor status. In conclusion, we propose that combining HDAC6i along with ICI such as αPD-1 may offer a novel avenue to enhance the efficacy of immunotherapy, as well as alter the tumor-intricate physiology, without incurring unnecessary toxicity.

Note: This abstract was not presented at the meeting.

Citation Format: Debarati Banik, Melissa Beaty, Erical Palmer, Maria Del Mar Gracia Hernandez, Satish K. Noonepalle, Prathima Vembu, Alan P. Kozikowski, Alejandro Villagra. Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2019.

Epigenetic therapy for ovarian cancer: promise and progress

Ovarian cancer is the deadliest gynecologic malignancy, with a 5-year survival rate of approximately 47%, a number that has remained constant over the past two decades. Early diagnosis improves survival, but unfortunately only 15% of ovarian cancers are diagnosed at an early or localized stage. Most ovarian cancers are epithelial in origin and treatment prioritizes surgery and cytoreduction followed by cytotoxic platinum and taxane chemotherapy. While most tumors will initially respond to this treatment, recurrence is likely to occur within a median of 16 months for patients who present with advanced stage disease. New treatment options separate from traditional chemotherapy that take advantage of advances in understanding of the pathophysiology of ovarian cancer are needed to improve outcomes. Recent work has shown that mutations in genes encoding epigenetic regulators are mutated in ovarian cancer, driving tumorigenesis and resistance to treatment. Several of these epigenetic modifiers have emerged as promising drug targets for ovarian cancer therapy. In this article, we delineate epigenetic abnormalities in ovarian cancer, discuss key scientific advances using epigenetic therapies in preclinical ovarian cancer models, and review ongoing clinical trials utilizing epigenetic therapies in ovarian cancer.

Functional Analysis of HDACs in Tumorigenesis

HDACs, originally described as histone modifiers, have recently been demonstrated to modify a variety of other proteins that are involved in diverse cellular processes unrelated to the chromatin environment. This includes deacetylation of nonhistone targets involved in multiple signaling pathways. In this regard, a considerable number of reports have analyzed the role of nonspecific inhibition of HDACs through pan-HDACi in cancer as well as processes of immune regulation. However, with pan-HDACi there is a lack of understanding about the exact contribution of inhibition of each individual HDAC, which makes the rational design of improved drug candidates extremely difficult. Additionally, current approaches using nonselective HDACi in the clinic have critical limitations, including pan-HDACi which elicit poor activity in solid tumors and cardiac toxicity, class I HDACi which activate multiple apoptotic pathways, limiting its use for longer periods of time, and class I-HDAC6i that evidenced a number of adverse effects in initial clinical trials. Therefore, there is a growing interest in the identification of more selective HDACi, and the subsequent development of accurate functional tests to identify the effectiveness and selectivity of these inhibitors. In this chapter, we are describing some selected methodologies to identify the individual activities of HDACs. In addition, we present specific methods to identify enzymatic and nonenzymatic molecular targets of HDACs.

Abstract 1395: HDAC6 and DNMT inhibition affect immunogenicity of ovarian cancer cells: A rationale for combining epigenetic and immune therapy in ovarian cancer

Background: Therapies that activate the immune system to fight cancer have shown robust responses in solid tumors. However, most patients, including those with ovarian cancer, do not respond to these therapies alone. Drugs that inhibit epigenetic modifiers increase immune signaling from cancer cells. Epigenetic modifiers DNA methyltransferase inhibitors (DNMTi) and selective histone deacetylase inhibitors (HDACi),in particular selective HDAC6i, modulate immune-related pathways involved in anti-tumor immune responses. HDAC6i downregulate immunosuppressive ligands PD-L1 and PD-L2 via dephosphorylating pSTAT3 and upregulate tumor associated antigens (TAA) and antigen presentation machinery. Similarly, DNMTi activate anti-viral signaling via expression of Endogenous Retroviruses (ERVs) to trigger the type I interferon response, upregulate tumor antigen processing and presentation, and stimulate pro-inflammatory cytokines. The aim of our study is to test if the combination of epigenetic modulators Nexturastat A (Next A), a selective HDAC6i, and 5-azacytidine (AZA), a DNMTi, can be safely used to increase an immune response in ovarian cancer. We hypothesize that these drugs will enhance tumor immunity alone and when combined with immune checkpoint blockades targeting PD-1. Results: HDAC enzymes are differentially expressed in A2780, HEY, OVCAR3, SKOV3, and TYKNu human ovarian cancer cell lines. HDAC1 and HDAC2 proteins were similarly expressed in HEY and SKOV3 whereas HDAC6 was expressed at lower levels in HEY and TYKNu but at higher levels in SKOV3, OVCAR3, and A2780. As previously reported we believe this may be due to the presence of the chromatin modifier ARID1A mutation in the SKOV3 and A2780 cell lines. The upregulation of HDAC6 also correlated with a higher IC50 for NextA treatment in those particular cell lines. Further immunoblots showed that PD-L1, a marker of poor prognosis in ovarian cancer, decreased after treatment with NextA and even more in combination with AZA. Additionally, DNMT1, the known target of AZA, was decreased after treatment with AZA and NextA, both independently and in combination, a finding that has not been previously reported. Conclusions: As shown previously, HDAC6 enzyme levels are higher in cell lines with ARID1A mutations. DNMT1 was decreased after treatment with AZA, as expected, but surprisingly also after treatment with NextA. PD-L1 decreased after treatment with NextA and even more so when combined with AZA. We thus believe that combining these two epigenetic modifiers will lead to an additive effect on immune signaling through stimulation of antiviral signaling (DNMTi), which can upregulate the immunosuppressive ligand PD-L1, which is then reduced by HDAC6 inhibition. We are currently testing the combination of both epigenetic modifiers with anti-PD-1 in an immunocompetent mouse model of ovarian cancer.

Citation Format: Aneil P. Srivastava, Sara M. Moufarrij, Melissa Hadley, Sarah Chisholm, Micael Lopez-Acevedo, Alejandro Villagra, Katherine B. Chiappinelli. HDAC6 and DNMT inhibition affect immunogenicity of ovarian cancer cells: A rationale for combining epigenetic and immune therapy in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1395.

Abstract 4967: HDAC11 function as a transcriptional regulator in immature myeloid cells to myeloid-derived suppressor cells transition

In normal myelopoiesis, immature myeloid cells (IMCs) differentiate into macrophages, neutrophils or dendritic cells, a process that is tightly controlled by transcription factors and epigenetic regulators. However, under tumor burden, IMCs differentiate into myeloid derived suppressor cells (MDSCs) and with subsequent up-regulation of immune suppressive factors and a pro-tumor effect. In prior studies, we found that MDSCs from HDAC11 KO mice displayed an increased T-cell suppressive activity that was associated with a more aggressive tumor growth as compared to MDSCs from wild type control mice. Unlike MDSC's in which absence of HDAC11 is associated with a suppressive phenotype, T-cell lacking HDAC11 are hyper-reactive and endowed with strong antitumor activity. To assess which phenotype will be the dominant one in vivo, we performed adoptive immune cell transfer experiments of MDSC and/or T-cells from HDAC11 KO mice into C57BL/6 tumor-bearing mice. The transfer of HDAC11KO MDSCs was able to eliminate, at least partially, the anti-tumor effect elicited by the adoptive transfer of HDAC11KO T cells.

Mechanistically we have found that MDSCs lacking HDAC11 displayed up-regulation of expression and enzymatic activity of arginase 1 and Nos2, two enzymes that are crucial in regulating MDSCs suppressive function. The aberrant enzymatic activities of Arg1 and Nos2 in HDAC11KO MDSCs correlate with over-expression of the lineage-specific transcription factor C/EBPβ, which has been shown to be essential for the differentiation of functional MDSCs. Furthermore, ChIP analysis confirmed that HDAC11 is recruited to the C/EBPβ gene promoter where exerts a negative regulatory effect upon gene transcription.

Taken together, we have uncovered a previously unknown role for HDAC11 as a transcriptional regulator of MDSCs function. A better understanding of this novel role of HDAC11 in myeloid biology will lead to targeted epigenetic therapies to manipulate the suppressive effect of these immunoregulatory cells.

Citation Format: Jie Chen, Fengdong Cheng, Eva Sahakian, John Powers, Zi Wang, Alejandro Villagra, Javier Pinilla-Ibarz, Eduardo M. Sotomayor. HDAC11 function as a transcriptional regulator in immature myeloid cells to myeloid-derived suppressor cells transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4967.

Abstract 5126: Modulation of lactate in the tumor microenvironment with lactate transporter inhibitor in a melanoma syngeneic mouse model

Solid tumors often have altered metabolism that depend on aerobic glycolysis for energy and macromolecules for cell survival thereby generating lactate as a metabolic byproduct. Lactate is transported across the cell membrane into tumor microenvironment (TME) using monocarboxylate transporters, MCT1 and MCT4. MCTs facilitate proton linked transport of monocarboxylate molecules such as lactate, pyruvate, and ketone bodies across the plasma membrane. Lactate released by glycolytic cells into the TME results in a metabolic symbiosis when other tumor cells utilize lactate as an energy source that undergo oxidative metabolism which is referred to as “lactate shuttle”. Moreover, lactate induces inhibitory pathways on immune cells, especially on cytotoxic CD8+ T-cells resulting in local immunosuppression in the TME. Additionally, acidosis of TME through lactate results in local inflammation and angiogenesis by activation of VEGFR signaling. The net result of an increased lactate in TME is that it generates a conducive milieu for tumor growth and metastasis. Although studies show that MCT inhibitors mitigate the effects of lactate and promote immune function, its effect on immune cells in the context of tumor infiltration is yet to be explored. In this study, we used a MCT inhibitor NGY-A to determine the effect of suppressing lactate levels in the TME and restoring the anti-tumor immunity. In our preliminary studies to determine the cytotoxicity, NGY-A showed significant cancer cell killing in multiple cell lines in vitro. To determine the in vivo effect of NGY-A, syngeneic mouse model of SM1 melanoma cells harboring BRAF mutation in C57BL/6 mice was studied. When treated with NGY-A (10 mg/kg, i.p injection) (n=15), a significant decrease in tumor volumes was observed compared to controls (n=15). Gene expression analysis of total RNA isolated from SM1 tumors by quantitative RT-PCR indicated that expression of immunosuppressive molecules such as Cd274 (PD-L1), Cd276 (B7-H3) and Lgals9 (Galactin-9) was down regulated in NGY-A (n=5) treated tumors compared to the control tumors (n=5). An increase in IFN-γ (IFNG) gene expression in NGY-A treated samples indicated an increase in CD8+ T-cell tumor infiltration. Future studies would include analysis of phenotype of tumor infiltrating immune cells and cytokine profiles after treatment with NGY-A in combination with immune checkpoint blockade inhibitors which could potentially be an effective strategy to treat melanoma.

Citation Format: Satish Kumar Reddy Noonepalle, Jennifer Kim, Melissa Hadley, Erica Palmer, Debarati Banik, Tessa Knox, Sophiya Ephrame, Prathima Vembu, Summer Rudish, Sara Moufarrij, Jaime Escobedo, Vincent Sandanayaka, Alejandro Villagra. Modulation of lactate in the tumor microenvironment with lactate transporter inhibitor in a melanoma syngeneic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5126.

Tet-Mediated DNA Demethylation Is Required for SWI/SNF-Dependent Chromatin Remodeling and Histone-Modifying Activities That Trigger Expression of the Sp7 Osteoblast Master Gene during Mesenchymal Lineage Commitment

Here we assess histone modification, chromatin remodeling, and DNA methylation processes that coordinately control the expression of the bone master transcription factor Sp7 (osterix) during mesenchymal lineage commitment in mammalian cells. We find that Sp7 gene silencing is mediated by DNA methyltransferase1/3 (DNMT1/3)-, histone deacetylase 1/2/4 (HDAC1/2/4)-, Setdb1/Suv39h1-, and Ezh1/2-containing complexes. In contrast, Sp7 gene activation involves changes in histone modifications, accompanied by decreased nucleosome enrichment and DNA demethylation mediated by SWI/SNF- and Tet1/Tet2-containing complexes, respectively. Inhibition of DNA methylation triggers changes in the histone modification profile and chromatin-remodeling events leading to Sp7 gene expression. Tet1/Tet2 silencing prevents Sp7 expression during osteoblast differentiation as it impairs DNA demethylation and alters the recruitment of histone methylase (COMPASS)-, histone demethylase (Jmjd2a/Jmjd3)-, and SWI/SNF-containing complexes to the Sp7 promoter. The dissection of these interconnected epigenetic mechanisms that govern Sp7 gene activation reveals a hierarchical process where regulatory components mediating DNA demethylation play a leading role.

Synthesis and Pharmacological Evaluation of Selective Histone Deacetylase 6 Inhibitors in Melanoma Models

Only a handful of therapies offer significant improvement in the overall survival in cases of melanoma, a cancer whose incidence has continued to rise in the past 30 years. In our effort to identify potent and isoform-selective histone deacetylase (HDAC) inhibitors as a therapeutic approach to melanoma, a series of new HDAC6 inhibitors based on the nexturastat A scaffold were prepared. The new analogues 4d, 4e, and 7b bearing added hydrophilic substituents, so as to establish additional hydrogen bonding on the rim of the HDAC6 catalytic pocket, exhibit improved potency against HDAC6 and retain selectivity over HDAC1. Compound 4d exhibits antiproliferative effects on several types of melanoma and lymphoma cells. Further studies indicates that 4d selectively increases acetylated tubulin levels in vitro and elicits an immune response through down-regulating cytokine IL-10. A preliminary in vivo efficacy study indicates that 4d possesses improved capability to inhibit melanoma tumor growth and that this effect is based on the regulation of inflammatory and immune responses.

Abstract LB-295: A novel regulatory role of HDAC6 in the functional inflammatory phenotype of glia cells

Background: Histone Deacetylases (HDACs) have been demonstrated to modify a variety of non-histone proteins involved in oncogenic- and immune-related pathways. Recent studies in macrophages and tumor cells have implicated HDAC6 in the regulation of the immunomodulatory cytokines IL10 and IL6, and the immunosuppressive proteins PD-L1 and PD-L2. Additionally, specific inhibitors for this HDAC have shown promising results when used alone or in combination with other anticancer agents. Despite this newly characterized role of HDAC6 in immunobiology, its role in the regulation of immune-related pathways in the brain parenchymal environment is still unclear. Glia cells play a key role in a number of physiological processes in the brain, including the productions of inflammatory mediators and antigen presentation. Here, we report the first evidence of the functional effects of selective HDAC6inh in the modulation of the cytokine homeostasis and immune-related pathways in antigen presenting cells in the brain.

Methods: Thioglycolate elicited peritoneal macrophages (PEM), primary murine cortical astrocytes, macrophage cell lines RAW264.7 and microglial cell line BV.2 were treated with the HDAC6 inhibitors Nexturastat and Tubastatin A, and the pan-HDACinh LBH589. Cytokine production was measured by qRT-PCR and ELISA. Viability, apoptosis, cell cycle, and HDAC activity was evaluated in parallel for all tested conditions.

Results: In our comparative studies, the HDAC6 inhibition significantly lowered levels of cytokines IL6, IL10, IL1β, TNFα and IL12p70 levels in macrophages, and primary murine PEMs, indicating that both, anti- and pro-inflammatory cytokines are affected by this particular HDAC. Similar results were found in the expression of the pro-inflammatory cytokines IL1β, TNFα and IL12p70b in parallel studies using BV.2 microglia cells. In contrast, we observed an increase in the expression of IL6 and only slight variations in IL10 expression in BV.2, suggesting that HDAC6 might be controlling preferentially pro-inflammatory cytokines in glia cells. Additional control studies using the non-specific pan-HDACinh LBH589 showed similar outcomes in all analyzed cytokines in macrophages and glia cells. To further investigate the functional consequences of HDAC6inh in microglia cells, we evaluated the polarization phenotype of primary astrocytes and BV.2 cells under HDAC6inh treatment. While macrophages treated with Nexturastat and Tubastatin A were equally distributed between M1 and M2, we observed an important transition from M1 to M2 in brain cells, indicating a reduction in the pro-inflammatory phenotype of these cells when treated with HDAC6inh.

Conclusion: Taken collectively, our studies demonstrate that HDAC6 plays a major role in the modulation of the functional phenotype and production of pro-inflammatory mediators in brain glia cells. These findings open the possibility for further evaluation of selective HDAC6inh as adjuvants in antitumor brain therapies.

Citation Format: Jennifer Kim, Jayakumar R. Nair, Melissa M. Hadley, Alan Kozikowski, Robert Miller, Alejandro Villagra. A novel regulatory role of HDAC6 in the functional inflammatory phenotype of glia cells [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 LB-295. doi:10.1158/1538-7445.AM2017-LB-295

Abstract 4055: Enhancing anti-PD-1 immune blockade in melanoma through selective inhibition of histone deacetylase 6

Histone deacetylases (HDACs), were originally described in a limited context as histone modifiers. New evidence has demonstrated that HDACs are also involved in a diverse range of cellular processes that are not restricted to the chromatin environment, such as the regulation of the cell cycle/apoptosis and, more recently, a modulator of immune response. However, much remains unknown about the mechanism of action of HDACs and their roles in the immune-biology of cancer. The non-specific nature of pan-HDAC inhibitors results in a narrow therapeutic window of use, limiting the dose and duration due to toxicity. Our group has focused in one specific HDAC, HDAC6, and shown that both the genetic abrogation and pharmacological inhibition of this HDAC modulates the expression of a variety of immune-regulatory proteins in the tumor microenvironment, including PD-L1, PD-L2, MHC class I, B7-H4 and TRAIL-R1. In particular, we have previously demonstrated that both pharmacological inhibition and/or genetic abrogation of HDAC6 plays a critical role in the immune check point blockade by down-regulating the expression of PD-L1 and other check-point modulators such as PD-L2, B7-H4, etc. Moreover, we have also observed that in vivo inhibition of HDAC6 reduces tumor growth in B16 and SM1 murine melanoma models within syngeneic immunocompetent hosts. Additionally, we have found that the combination of low doses of the HDAC6i Nexturastat A and checkpoint immune blockade, including anti-PD-1 and anti-CTLA4, results in an important improvement in anti-tumor immune responses as evidenced by the reduction of tumor growth when compared to treatment with individual stand-alone agents. In these studies we also evidenced an increased production of IFNγ and IL-2 in the stand-alone check-point inhibitor treatments, which leads to an upregulation of PD-L1 and PD-L2. Similar levels of IFNγ and IL-2 were found in the combination groups. However, the expression level of PD-L1 and PD-L2 were comparable to the non-treated group. Taking all together, we have found that HDAC6i could be used as a potential adjuvant in ongoing therapeutic options involving immune check-point blockade.

Citation Format: Tessa Knox, Eva Sahakian, Jayakumar Nair, Jennifer Kim, Debarati Banik, Melissa Hadley, John Powers, Fengdong Cheng, Sida Shen, Javier Pinilla, Jeffrey Weber, Alan Kozikowski, Eduardo Sotomayor, Alejandro Villagra. Enhancing anti-PD-1 immune blockade in melanoma through selective inhibition of histone deacetylase 6 [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 4055. doi:10.1158/1538-7445.AM2017-4055

Abstract LB-294: In vivo evaluation of Ames negative HDAC6 inhibitor in melanoma model

Histone deacetylases (HDAC), originally known for their ability to modify histones, have also been found to modulate a multitude of cellular processes unrelated to chromatin modification, including the regulation of cellular pathways involved in anti-tumor immune responses. Our group and others have shown that the selective inhibition of HDAC6 impairs in vitro and in vivo tumor growth in a number of cancer models. Selective HDAC6 inhibitors (HDAC6i) such as Tubastatin A have proven to be very useful in cellular models. However, due to their mutagenic characteristics (Ames positive), usage has been limited only to preclinical research and a few types of cancer. We report that the novel and selective HDAC6i SS-2-08 is negative in the Ames assay and shows promising in vivo anti-tumor activity. SS-2-08 was obtained via five synthetic steps in 20% overall yield and 99% purity. It was incubated with two strains of Salmonella typhimurium (TA98 and TA1537) in the presence and absence of mammalian microsomal enzymes (S9 mix) for Ames assessment. Murine SM1 melanoma cells were treated with SS-2-08 in vitro to evaluate the expression of HDAC6-target genes by qRT-PCR, immunoblot and flow cytometry. CellTox Green Cytotoxicity® and HDAC-Glo I/II® assays were used to evaluate viability and HDAC activity, respectively. Cellular pathway analysis was performed by Cignal™ Reporter. In vivo studies were performed with SM1 cells injected into C57/BL/6 mice. Tumors were grown until they reached 5-8 mm in diameter and then treated with vehicle control, 25 mg/kg, and 50 mg/kg of SS-2-08 three times a week. Tumor measurements were recorded twice a week. At the experimental endpoint, tissue samples were collected for analysis. SS-2-08 shows nanomolar level potency against HDAC6 and over 400-fold selectivity over HDAC1. In the Ames assay, no significant number of reverting colonies was found for either strain, thus supporting the lack of mutagenicity of SS-2-08. Preliminary in vitro work revealed that SS-2-08 has low cytotoxicity and selective HDAC inhibitory properties, an observation verified in multiple cancer cell types. The selectivity and potency of this novel compound was similar to or better than other conventional HDAC6i as demonstrated by comprehensive molecular profiling including previously characterized HDAC6 targets such as IL-10, STAT3 and PD-L1. Additionally, in vivo experiments using murine SM1 melanoma tumors showed an important reduction in tumor growth at a dose of 25 mg/kg. Acetylated tubulin was increased in the end-point tumor samples in the treatment group, indicating that SS-2-08 reached the tumor site in vivo. Finally, we observed a down regulation of PD-L1 and PD-L2 in tumor samples from the treated group previously reported for other HDAC6i. These results provide evidence for the effectiveness of this new Ames negative-HDAC6i in vivo. SS-2-08 and derivatives have potential for use as therapeutic agents to treat cancer and other diseases where the inhibition of HDAC6 could be used as a therapeutic option.

Citation Format: Melissa Hadley, Sida Shen, Debarati Banik, Jennifer Kim, Jayakumar Nair, Tessa Knox, Vincent Gallub, Shannon Kirkland, Katherine B. Chiappinelli, Eduardo Sotomayor, Alan Kozikowski, Alejandro Villagra. In vivo evaluation of Ames negative HDAC6 inhibitor in melanoma model [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 LB-294. doi:10.1158/1538-7445.AM2017-LB-294

Abstract 4854: Evaluating HDAC6 as a causal factor in metastatic breast cancer to develop immunotherapy

Histone deacetylases (HDACs), originally described as histone modifiers, have recently been demonstrated to modify a variety of other proteins involved in diverse cellular processes unrelated to the chromatin environment, including the modulation of proteins related to cell cycle/apoptosis and immune regulation. In contrast to the well-documented effects of HDAC inhibitors (HDACi) in the control of cell cycle and apoptosis, their role in immune-biology is incompletely understood. We have found that the pharmacological or genetic abrogation of a single HDAC, i.e. HDAC6, inactivates the STAT3 pathway and modulates the expression of immuno-regulatory proteins, including the down-regulation of PD-L1, PD-L2 and B7-H4, important negative regulators of immune function, often over-expressed in cancer cells; including breast cancer. HDAC6 has been also involved in a number of structural functions related to cellular motility, shape and intracellular transport through the regulation of the acetylation of numerous targets, including tubulin and cortactin. This function is strongly suggestive of HDAC6 being a key player in metastatic cancer progression. In our initial studies we observed that the selective HDAC6 inhibitor Nexturastat A is capable of reducing the tumor growth in a highly aggressive murine mammary carcinoma that mimics human triple negative breast cancer (TNBC), under both orthotopic and subcutaneous conditions of implantation. Additionally, we observed that the size and number of secondary tumor nodules in lungs were significantly diminished after the HDAC6i treatment. In order to boost the anti-tumor T-cell response, we also tested check-point inhibitors against the tumor (such as anti PD-1 and CTLA4 antibodies). While each of the standalone treatments showed a certain degree of success in reducing tumor growth and enhancing intra-tumoral IFNγ, we demonstrated that HDAC6i improves anti-tumor immune responses when combined with immune check-point blockade.

Citation Format: Debarati Banik, Melissa Hadley, Jennifer Kim, Tessa Knox, Jayakumar Nair, Alan Kozikowski, Sida Shen, Charu Vyas, Ashleyn Donohue, Eduardo Sotomayor, Alejandro Villagra. Evaluating HDAC6 as a causal factor in metastatic breast cancer to develop immunotherapy [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 4854. doi:10.1158/1538-7445.AM2017-4854

Abstract 4976: Ricolinostat, a selective HDAC6 inhibitor with immunomodulatory properties, has significant antimelanoma activity in vitro and in vivo

Melanoma is a less common but the most aggressive type of skin cancer and the rates of melanoma have been rising for the last 30 years. Immunotherapy may represent a new treatment paradigm to benefit melanoma patients. Previous studies have identified HDAC6 playing a central role in the regulating melanoma immunogenicity. We have shown that genetic knockdown (KD) of HDAC6 in murine and human melanoma cells resulted in an increased the expression of MHCI and costimulatory molecules as well as melanoma associated antigens. In vivo studies demonstrated that the growth of melanoma cells lacking HDAC6 was significantly delayed as compared to wild-type cells. This growth was further delayed when HDAC6KD melanoma bearing mice were treated with anti-PD-1 antibodies.

Recently, we have shown that in vitro treatment of murine melanoma cells with Ricolinostat decreases PD-L1 expression and increases the expression of acetyl tubulin. Surprisingly, in vivo treatment of B16 melanoma bearing animals with increasing concentrations of ricolinostat resulted in a dose-dependent inhibition of melanoma growth (p<0.05). No toxicities were observed at the doses studied; however, the antitumor effect exerted by ricolinostat was not observed when melanoma bearing SCID mice were treated with this compound, indicating that an intact host immune system is required for the observed antitumor activity. In lieu of these previously unknown immunomodulatory properties of ricolinostat, we next assessed the effects of this compound upon T-cells and whether ricolinostat could augment the efficacy of checkpoint blockade in vivo. Murine T-cells were activated with anti-CD3 plus anti-CD28 in the presence or absence of ricolinostat. Then, those T-cells were adoptively transferred into B16 melanoma bearing mice. T-cell subpopulations from the lymph nodes were analyzed ex vivo. We show here that treatment of murine T-cells with ricolinostat resulted in a significant increase in central memory T-cells endowed with a strong anti-melanoma activity in vivo as compared to control group (p<0.05). Finally, the addition of ricolinostat treatment to either anti-CTLA4 or anti-PD1 treatment was associated with an enhanced inhibition of melanoma tumor growth.

In summary, our results have identified HDAC6 as a novel target for melanoma immunotherapy and point out ricolinostat as an attractive agent to add to the immuno-oncology armamentarium.

Citation Format: Fengdong Cheng, Sodre Andressa, Jie Chen, Alejandro Villagra, David Woods, Jeffrey Weber, Steven Quayle, Jones Simon, Eduardo Sotomayor. Ricolinostat, a selective HDAC6 inhibitor with immunomodulatory properties, has significant antimelanoma activity in vitro and in vivo [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 4976. doi:10.1158/1538-7445.AM2017-4976

Essential role for histone deacetylase 11 (HDAC11) in neutrophil biology

Epigenetic changes in chromatin structure have been recently associated with the deregulated expression of critical genes in normal and malignant processes. HDAC11, the newest member of the HDAC family of enzymes, functions as a negative regulator of IL-10 expression in APCs, as previously described by our lab. However, at the present time, its role in other hematopoietic cells, specifically in neutrophils, has not been fully explored. In this report, for the first time, we present a novel physiologic role for HDAC11 as a multifaceted regulator of neutrophils. Thus far, we have been able to demonstrate a lineage-restricted overexpression of HDAC11 in neutrophils and committed neutrophil precursors (promyelocytes). Additionally, we show that HDAC11 appears to associate with the transcription machinery, possibly regulating the expression of inflammatory and migratory genes in neutrophils. Given the prevalence of neutrophils in the peripheral circulation and their central role in the first line of defense, our results highlight a unique and novel role for HDAC11. With the consideration of the emergence of new, selective HDAC11 inhibitors, we believe that our findings will have significant implications in a wide range of diseases spanning malignancies, autoimmunity, and inflammation.

Changes in objectively measured physical activity in adolescents with Down syndrome: the UP&DOWN longitudinal study

BACKGROUND

It is a priority to understand that physical activity behaviour over time is a priority in Down syndrome population in order to design and promote succesfull interventions to maintain or increase levels of physical activity. We aimed to study 1 and 2-year changes in objectively measured physical activity among a relatively large sample of adolescents with Down syndrome.

METHODS

This study comprised a total of 99 adolescents with Down syndrome (38 girls) aged from 11 to 20 years old at baseline. Participants with valid accelerometer data at baseline and at least one of the follow-up visits were included in the analysis.

RESULTS

Overall, levels of physical activity observed in adolescents with Down syndrome declined from baseline to follow-ups, but these changes were not significant (all P > 0.05). Moderate-to-moderately high tracking of physical activity was observed in adolescents with Down syndrome (all P < 0.001). Youths who met physical activity guidelines at baseline demonstrated a greater decline in physical activity in 1 and 2-year changes (P < 0.05), although they were also more likely to meet physical activity guidelines at 1 and 2-year follow-ups (P < 0.05).

CONCLUSIONS

Adolescents with Down syndrome do not change their levels of physical activity at 2-year follow-ups, but those who met physical activity guidelines presented stronger declines in physical activity over time.

Abstract 2331: HDAC6, new role as master regulator of PD-L1 and immune-related pathways

Histone deacetylases (HDACs), originally described as histone modifiers, have more recently been demonstrated to modify a variety of other proteins involved in diverse cellular processes unrelated to the chromatin environment, including the modulation of proteins related to cell cycle/apoptosis and immune regulation. In contrast to the well-documented effects of HDAC inhibitors (HDACi) in the control of cell cycle and apoptosis, their role in immunobiology is still not completely understood, and the reported immunological outcomes when using HDACi are heterogeneous. Our group recently reported that the pharmacological or genetic abrogation of a single HDAC, HDAC6, modulates the expression of immuno-regulatory proteins, including PD-L1, PD-L2, MHC class I, B7-H4 and TRAIL-R1. We primarily focused in PD-L1, which is an important negative regulator of T-cell function and often over-expressed in cancer cells. In a mechanistic point of view, we have found that the pharmacological inhibition and genetic abrogation of HDAC6 inactivates the STAT3 pathway, impairs the nuclear translocation and the recruitment of STAT3 to the PD-L1 promoter and subsequently down-regulates the expression of PD-L1. Moreover, the in vivo abrogation of HDAC6 reduces tumor growth in melanoma models, effect that is enhanced in the presence of the immune check-point blocking antibodies anti-PD-1 and anti-CTLA4. These results provide a key pre-clinical rationale and justification to further study isotype selective HDAC6 inhibitors as potential immunomodulatory agents in cancer.

Citation Format: Tessa Knox, Maritza Lienlaf, Patricio Perez, Mibel Pabon, Calvin Lee, Fengdong Cheng, Eva Sahakian, John Powers, Susan Deng, Smalley Keiran, Alan Kozikowski, Javier Pinilla, Amod Sarnaik, Ed Seto, Jeffrey Weber, Eduardo Sotomayor, Alejandro Villagra. HDAC6, new role as master regulator of PD-L1 and immune-related pathways. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2331.

Functional Analysis of Histone Deacetylase 11 (HDAC11)

The physiological role of histone deacetylase 11 (HDAC11), the newest member of the HDAC family, remained largely unknown until the discovery of its regulatory function in immune cells. Among them, the regulation of cytokine production by antigen-presenting cells and the modulation of the suppressive ability of myeloid-derived suppressor cells (MDSCs) (Sahakian et al. Mol Immunol 63: 579-585, 2015; Wang et al. J Immunol 186: 3986-3996, 2011; Villagra et al. Nat Immunol 10: 92-100, 2009). Our earlier data has demonstrated that HDAC11, by interacting at the chromatin level with the IL-10 promoter, downregulates il-10 transcription in both murine and human APCs in vitro and ex vivo models (Villagra et al. Nat Immunol 10: 92-100, 2009). However the role of HDAC11 in other cell types still remains unknown. Here we present several methods that can potentially be used to identify the functional role of HDAC11, assigning special attention to the evaluation of immunological parameters.

Expression and Function of Histone Deacetylase 10 (HDAC10) in B Cell Malignancies

Histone deacetylase 10 (HDAC10) belongs to the class IIb HDAC family and its biological role remains mostly unidentified. A decreased HDAC10 expression has been reported in patients with aggressive solid tumors (Osada et al. Int J Cancer 112: 26-32, 2004; Jin et al. Int J Clin Exp Pathol 7: 5872-5879, 2014), suggesting that loss of HDAC10 expression might confer a survival advantage to malignant cells. Consequently, results from our lab suggests that overexpression of HDAC10 in aggressive mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) Z138c and MEC1 cells, respectively, resulted in a rapid induction of cell death in vitro with only 5 % of cells being alive at 48 h, cell cycle arrest, and up-regulation of co-stimulatory molecules. Here we present several standard methods to study the function of HDAC10 in B cell malignancies.

Abstract A066: Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity

The efficacy of immunotherapy is dependent on the ability of antigen-specific T-cells to mount a proper anti-tumor response while avoiding a plethora of immunosuppressive mechanisms. Unfortunately, these immunosuppressive mechanisms often overwhelm the T-cell response, resulting in patients failing to respond. Histone deacetylases (HDACs) are a family of epigenetic modifiers named for their ability to remove acetyl groups from lysine residues of histone tails, thereby regulating the chromatin structure and gene expression. Here we report that HDAC11, the most recently discovered HDAC, is a regulator of T-cell pro-inflammatory function. Previous reports have shown HDAC11 expression to be tissue restricted. Consequently, we compared expression levels of HDAC11 using an eGFP reporter mouse, in various immune cells. It was found that T-cells expressed relatively high levels of HDAC11. However, while resting T-cells, both central memory and naïve, had high levels of HDAC11 expression, effector or effector memory T-cells displayed lower levels. Additionally, T-cells experienced rapid down-regulation of HDAC11 upon activation. To expand upon these observations, the function of T-cells from HDAC11KO mice were investigated. Initial experiments revealed no gross changes in the numbers or maturation of T-cells. However, HDAC11KO mice displayed an increased percentage of central memory CD8+ T-cells (p&lt;0.05). Additionally, upon activation these T-cells were more apt to acquire effector status (p&lt;0.001). Upon activation, HDAC11KO T-cells demonstrated a robust increase in IL-2, TNF and IFNγ production (p&lt;0.01), but showed no differences in Th2 or Th17 cytokine production. These T-cells also expressed higher levels of the effector molecules granzyme B and perforin (p&lt;0.01). Moreover, post-activation, CD8+ T-cells lacking HDAC11 also displayed a higher percentage of proliferating cells, and more divisions of proliferating cells (p&lt;0.01). HDAC11KO T-cells displayed higher resistance to proliferative suppression by Tregs and failed to succumb to anergy in a high dose antigen model. Indeed, while OTII T-cells from mice injected with high dose OVA peptide displayed reduced levels of IFNγ production compared to cells from non-injected mice after rechallenge, HDAC11KO/OTII T-cells had an increase in IFNγ production. Mechanistically, T-cells devoid of HDAC11 did not appear to have differences in TCR signaling, but did express higher levels of the transcription factors EOMES and T-bet. Chromatin immunoprecipitation (ChIP) revealed higher basal levels of acetylation of these genes in HDAC11KO mice. ChIP analysis also revealed interactions of HDAC11 at the promoters of both EOMES and T-bet. In a graft vs. host disease (GvHD) model, HDAC11KO T-cells produced a more rapid onset of GvHD, and were able to do so with transfers of cell numbers below that able to induce GvHD using WT T-cells (p&lt;0.01). This GvHD was characterized by greater levels of IFNγ and TNF as well as increased T-cell expansion (p&lt;0.05). In a B16 melanoma model, adoptive transfer of HDAC11KO T-cells resulted in delayed tumor progression (p&lt;0.05) compared to WT T-cells. To begin investigating the clinical potential of these data, the expression levels of HDAC11 were investigated in melanoma tumor sections utilized to grow tumor infiltrating lymphocytes (TIL) for clinical trials of adoptive cell therapy. A reduced level of HDAC11 was found in tumor sections from those patients responding to TIL therapy compared to progressing patients (p&lt;0.01). Collectively, beyond demonstrating HDAC11 as a novel epigenetic regulator of T-cell pro-inflammatory function, these results highlight HDAC11 as a novel target for enhancing the efficacy of immunotherapy.

Citation Format: David M. Woods, Andressa L. Sodre, Karrune Woan, Alejandro Villagra, Amod Sarnaik, Jeffrey Weber, Eduardo M. Sotomayor. Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A066.

HDAC Inhibition Upregulates PD-1 Ligands in Melanoma and Augments Immunotherapy with PD-1 Blockade

Expression of PD-1 ligands by tumors and interaction with PD-1-expressing T cells in the tumor microenvironment can result in tolerance. Therapies targeting this coinhibitory axis have proven clinically successful in the treatment of metastatic melanoma, non-small cell lung cancer, and other malignancies. Therapeutic agents targeting the epigenetic regulatory family of histone deacetylases (HDAC) have shown clinical success in the treatment of some hematologic malignancies. Beyond direct tumor cell cytotoxicity, HDAC inhibitors have also been shown to alter the immunogenicity and enhance antitumor immune responses. Here, we show that class I HDAC inhibitors upregulated the expression of PD-L1 and, to a lesser degree, PD-L2 in melanomas. Evaluation of human and murine cell lines and patient tumors treated with a variety of HDAC inhibitors in vitro displayed upregulation of these ligands. This upregulation was robust and durable, with enhanced expression lasting past 96 hours. These results were validated in vivo in a B16F10 syngeneic murine model. Mechanistically, HDAC inhibitor treatment resulted in rapid upregulation of histone acetylation of the PD-L1 gene leading to enhanced and durable gene expression. The efficacy of combining HDAC inhibition with PD-1 blockade for treatment of melanoma was also explored in a murine B16F10 model. Mice receiving combination therapy had a slower tumor progression and increased survival compared with control and single-agent treatments. These results highlight the ability of epigenetic modifiers to augment immunotherapies, providing a rationale for combining HDAC inhibitors with PD-1 blockade.

Targeting histone deacetylase 6 mediates a dual anti-melanoma effect: Enhanced antitumor immunity and impaired cell proliferation

The median survival for metastatic melanoma is in the realm of 8-16 months and there are few therapies that offer significant improvement in overall survival. One of the recent advances in cancer treatment focuses on epigenetic modifiers to alter the survivability and immunogenicity of cancer cells. Our group and others have previously demonstrated that pan-HDAC inhibitors induce apoptosis, cell cycle arrest and changes in the immunogenicity of melanoma cells. Here we interrogated specific HDACs which may be responsible for this effect. We found that both genetic abrogation and pharmacologic inhibition of HDAC6 decreases in vitro proliferation and induces G1 arrest of melanoma cell lines without inducing apoptosis. Moreover, targeting this molecule led to an important upregulation in the expression of tumor associated antigens and MHC class I, suggesting a potential improvement in the immunogenicity of these cells. Of note, this anti-melanoma activity was operative regardless of mutational status of the cells. These effects translated into a pronounced delay of in vivo melanoma tumor growth which was, at least in part, dependent on intact immunity as evidenced by the restoration of tumor growth after CD4+ and CD8+ depletion. Given our findings, we provide the initial rationale for the further development of selective HDAC6 inhibitors as potential therapeutic anti-melanoma agents.

Ligand-independent EPHA2 signaling drives the adoption of a targeted therapy-mediated metastatic melanoma phenotype

Many patients with BRAF inhibitor resistance can develop disease at new sites, suggesting that drug-induced selection pressure drives metastasis. Here, we used mass spectrometry-based phosphoproteomic screening to uncover ligand-independent EPHA2 signaling as an adaptation to BRAF inhibitor therapy that led to the adoption of a metastatic phenotype. The EPHA2-mediated invasion was AKT-dependent and readily reversible upon removal of the drug as well as through PI3K and AKT inhibition. In xenograft models, BRAF inhibition led to the development of EPHA2-positive metastases. A retrospective analysis of patients with melanoma on BRAF inhibitor therapy showed that 68% of those failing therapy develop metastases at new disease sites, compared with 35% of patients on dacarbazine. Further IHC staining of melanoma specimens taken from patients on BRAF inhibitor therapy as well as metastatic samples taken from patients failing therapy showed increased EPHA2 staining. We suggest that inhibition of ligand-independent EPHA2 signaling may limit metastases associated with BRAF inhibitor therapy.

SIGNIFICANCE

This study provides evidence that BRAF inhibition promotes the adoption of a reversible, therapy-driven metastatic phenotype in melanoma. The cotargeting of ligand-independent EPHA2 signaling and BRAF may be one strategy to prevent the development of therapy-mediated disease at new sites.

Abstract 4089: Histone deacetylase 6 (HDAC6) as a regulator of PD-L1 expression through STAT3 modulation in melanoma

In spite of the progress made in the understanding of the cell biology, genetics and immunology of melanoma, the outcome for patients with advanced-stage disease has remained poor with a median survival ranging from 2-16 months. Some optimism was recently provided in metastatic melanoma by the improved clinical outcomes observed in patients receiving PD-L1 blocking antibodies. A better understanding of the environmental, genetic and epigenetic factors limiting the efficacy of melanoma immunotherapy will provide appropriate partner(s) for combination with Ipilimumab or PD1/PDL1 antibodies. Among the epigenetic factors, we have found that one member of the histone deacetylase family, HDAC6, plays a critical role not only in the regulation of survival/apoptosis of melanoma cells but also in limiting their immunogenicity and recognition by immune effector cells. Particularly, we found a major role of HDAC6 as a modulator of the immunosuppresive STAT3/IL-10 pathway and down-regulation of tolerogenic PD-L1 molecules in melanoma cells. By analyzing HDAC6 knock-down melanoma cell lines (HDAC6KD) we demonstrated the inactivation of the STAT3 pathway and the subsequent down-regulation of its target genes, including the expression of PD-L1. We also observed that the PD-L1 expression and phosphorylation of STAT3 was decreased in melanoma isolated from xenograph tumor growth models after in vivo treatment with specific HDAC6 inhibitors

Fortunately, there are multiple HDAC6-selective inhibitors available to mechanistically study the role of HDAC6 on these processes and provide a viable therapeutic avenue, which may minimize undesirable side effects that are characteristic of pan-HDACi such as SAHA. By building on our understanding of HDAC6 and applying these findings to novel experimental design, we hope to identify innovative therapeutic options to benefit cancer patients.

Citation Format: Maritza Lienlaf, Patricio Perez-Villarroel, Calvin Lee, Fengdong Cheng, Jorge Canales, Tessa Knox, Danay Marante, Amod Sarnaik, Pedro Horna, Ed. Seto, Keiran Smalley, Jeffrey S. Weber, Eduardo M. Sotomayor, Alejandro Villagra. Histone deacetylase 6 (HDAC6) as a regulator of PD-L1 expression through STAT3 modulation in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4089. doi:10.1158/1538-7445.AM2014-4089

Abstract 5537: Histone deacetylase 11 (HDAC11) regulates B cell lymphopoiesis and potentiates plasma cell survival in multiple myeloma

Initially studied mainly for its role as a regulator of neural cell differentiation and development, expression of HDAC11 was once thought to be restricted exclusively to brain, kidney and testes. Hence, our recent discovery that HDAC11 acts as an important modulator of antigen presentation and T cell activation, downregulating IL-10 transcription via interactions with the IL-10 promoter at the chromatin level, exposes a previously unknown capacity and tissue specificity for this enzyme. Transgenic mice harboring an eGFP reporter construct driven by the HDAC11 promoter (Tg-HDAC11-eGFP) (Heinz, N Nat. Rev. Neuroscience 2001) clearly illustrate the dynamic changes in HDAC11 gene expression in hematopoietic cell lineages, additionally unveiling an important role for HDAC11 in B cell lymphopoiesis and plasma cell biology. While common lymphoid progenitors appear to be devoid of HDAC11 transcriptional activation as indicated by minimal detectable eGFP expression, eGFP intensity markedly increases in the B-1 stage of differentiation in the periphery. Interestingly, examination of both the bone marrow (BM) and peripheral blood (PB) plasma cell compartment demonstrates an increase in expression of eGFP/HDAC11 mRNA at the steady-state, and these results are consistent with HDAC11 expression measured in PB from healthy human subjects. Furthermore, mice globally deficient in HDAC11 expression (HDAC11KO mice) exhibit a 50% decrease in plasma cells in both the bone marrow and peripheral blood plasma cell compartments relative to wild-type mice. The concordance of HDAC11 expression and plasma cell differentiation leads us to hypothesize that HDAC11 may also be critical to malignant plasma cell survival. A comparison of normal bone marrow and malignant plasma cells isolated from multiple myeloma patient samples reveals a significantly higher level of HDAC11 expression associated with malignancy. Similar results are observed in 8 of 12 myeloma cell lines suggesting that HDAC11 expression may provide a distinct survival advantage to malignant plasma cells. Further stratification of patients into “newly diagnosed” and “proteasome inhibitor resistant” categories defines a positive correlation between HDAC11 expression and refractory disease. Treatment of the myeloma cell lines with Quisinostat, a second-generation HDAC inhibitor with enhanced selectivity for HDAC 1, 2, 4, 10 and 11 induces growth retardation at low nanomolar concentrations. Future studies will entail direct targeting of HDAC11 in myeloma cell lines and patient specimens to determine the contribution of HDAC11 to Quinsinostat activity. Taken together, we have unveiled a previously unknown role for HDAC11 in plasma cell differentiation and survival. The demonstration of HDAC11 overexpression in primary human myeloma cells provides a framework for therapeutics targeting this HDAC in multiple myeloma.

Citation Format: Eva Sahakian, Jason Brayer, John Powers, Mark Meads, Susan Deng, Allison Distler, Melissa Alsina, Taiga Nishihori, Rachid Baz, Alejandro Villagra, Javier Pinilla-Ibarz, Eduardo Sotomayor, Kenneth Shain. Histone deacetylase 11 (HDAC11) regulates B cell lymphopoiesis and potentiates plasma cell survival in multiple myeloma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5537. doi:10.1158/1538-7445.AM2014-5537

Abstract 4090: Inhibition of class I histone deacetylases promotes robust and durable enhancement of PDL1 expression in melanoma: Rationale for combination therapy

Histone deacetylase inhibitors (HDACi) have shown remarkable anti-tumor activity, leading to FDA approval of two HDACi for the treatment of CTCL and several others currently at various stages of clinical development for the treatment of both solid and hematological malignancies. Previous work from our lab has shown that treatment with HDACi results in increased expression of pro-inflammatory promoting surface markers on melanoma cells, promoting enhanced T-cell activation. Recent clinical trial data has shown that blockade of the PD1/PDL1 interaction is effective in the treatment of melanoma, renal cell and non-small cell lung cancer. Importantly, responses to PD1 blocking antibodies were preferentially seen in patients with tumors expressing PDL1. Here we report that HDACi targeting class I HDACs, but not class II, augments expression of PDL1 in melanoma cells. Two murine and five human melanoma cell lines were treated for up to 72 hours with DMSO, LBH589 (pan-HDACi), MS275 (class I inhibitor), MGCD0103 (class I inhibitor), an HDAC6 specific inhibitor, or a class IIa inhibitor. Using flow cytometry, dose dependent, increases in PDL1 expression were found in the LBH589, MS275 and MGCD0103 treated groups, but not in those receiving HDAC6i or class IIa inhibitor, relative to DMSO. Increased expression was noted as early as 24 hours after treatment and peaked at 72 to 96 hours post-treatment. As IFN-γ is known to upregulate the expression of PDL1 in both normal and transformed cells, we evaluated whether these results were associated with induction of IFN-γ expression by the melanoma cells. However, no detectable levels of IFN-γ were seen in either non-treated, class I HDACi, or class II HDACi-treated cells. Melanoma cells treated with HDACi in addition to IFN-γ have enhanced expression of PDL1 relative to either treatment alone. To further gain insight into the specific HDAC regulating the expression of PDL1, preliminary experiments utilizing knockdowns (KD) of individual class I HDACs were performed. In all KD melanoma cells no increase in PDL1 expression was seen, suggesting that the increased expression of PDL1 is dependent on inhibition of multiple class I HDACs. Supporting this conclusion, treatment of class I HDAC-KDs with HDACi recapitulates the increased PDL1 expression seen with WT melanoma. Finally, in preliminary in vivo experiments combining treatment of melanoma bearing mice with anti-PDL1 antibodies, mice receiving the combination treatment had a survival advantage over those receiving PDL1 blocking antibodies or HDACi alone. These results provide a strong rationale for the evaluation of combination therapies utilizing PDL1 or PD1 blocking antibodies in combination with HDACi. Furthermore, these results support the need for further development and investigation of iso-specific HDACi in order to obtain more directed therapeutic efficacy.

Citation Format: David M. Woods, Andressa L. Sodre, Eva Sahakian, John Powers, Maritza Lienlaf-Moreno, Patricio Perez-Villarroel, Alejandro Villagra, Javier Pinilla-Ibarz, Eduardo Sotomayor. Inhibition of class I histone deacetylases promotes robust and durable enhancement of PDL1 expression in melanoma: Rationale for combination therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4090. doi:10.1158/1538-7445.AM2014-4090