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.

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.

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.

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 4086: Histone deacetylase 6 (HDAC6) as a new target modulating the proliferation and immune-related pathways in melanoma

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. This includes the deacetylation of multiple non-histone targets, such as proteins involved in cell cycle/apoptosis and immune regulation. Specifically, HDACs have garnered significant interest due to the availability of drugs that selectively inhibits HDACs. We recently identified that the pharmacological or genetic abrogation of a single HDAC, HDAC6, modifies the immunogenicity and proliferation of melanoma in both in vitro and in vivo models.

Using specific HDAC6 inhibitors (HDAC6i) we observed decreased proliferation and G1 cell cycle arrest in all melanoma cell lines measured by MTS assay and flow cytometry. These results were also observed in stable HDAC6 knockdown melanoma cell lines (HDAC6KD) generated by specific lentiviral shRNA for HDAC6. In addition to the effects observed in proliferation and apoptosis after inhibiting HDAC6, we found important changes in the expression of immune-related pathways, including increased expression of MHC, co-stimulatory molecules, and specific melanoma tumor associated antigens such as gp100, MART-1, Tyrp1 and Tyrp2.

Our in vitro results were further supported by in vivo tumor growth studies. We observed a delayed tumor growth of inoculated B16 melanoma cells in C57BL/6 mice treated with selective HDAC6i. A similar outcome was identified after inoculation of HDAC6KD B16 melanoma cells in C57BL/6 mice. Such an effect was reverted partially in CD4+ and CD8+ depleted C57BL/6 mice challenged with HDAC6KD cells, suggesting that the disruption of HDAC6 enhances immune system recognition of melanoma cells. This delay in tumor growth could be a reflection of their diminished proliferation and an increase in their immunogenicity leading to improved immune recognition and clearance. These studies provide critical insights into the molecular pathways that are involved in the regulatory role of HDAC6 in cell proliferation, survival, and cytokine signaling of human melanoma cells. Collectively, our data has identified HDAC6 as an attractive therapeutic target in melanoma.

Citation Format: Patricio Perez-Villarroel, Maritza Lienlaf, Calvin Lee, Fengdong Cheng, David Woods, Kelly Barrios, Karrune Woan, Jorge Canales, Tessa Knox, Danay Marante, Hongwei Wang, Pedro Horna, Keiran Smalley, Esteban Celis, Ed Seto, Jeffrey S. Weber, Eduardo M. Sotomayor, Alejandro Villagra. Histone deacetylase 6 (HDAC6) as a new target modulating the proliferation and immune-related pathways 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 4086. doi:10.1158/1538-7445.AM2014-4086

A novel role for histone deacetylase 6 in the regulation of the tolerogenic STAT3/IL-10 pathway in APCs

APCs are critical in T cell activation and in the induction of T cell tolerance. Epigenetic modifications of specific genes in the APC play a key role in this process, and among them histone deacetylases (HDACs) have emerged as key participants. HDAC6, one of the members of this family of enzymes, has been shown to be involved in regulation of inflammatory and immune responses. In this study, to our knowledge we show for the first time that genetic or pharmacologic disruption of HDAC6 in macrophages and dendritic cells results in diminished production of the immunosuppressive cytokine IL-10 and induction of inflammatory APCs that effectively activate Ag-specific naive T cells and restore the responsiveness of anergic CD4(+) T cells. Mechanistically, we have found that HDAC6 forms a previously unknown molecular complex with STAT3, association that was detected in both the cytoplasmic and nuclear compartments of the APC. By using HDAC6 recombinant mutants we identified the domain comprising amino acids 503-840 as being required for HDAC6 interaction with STAT3. Furthermore, by re-chromatin immunoprecipitation we confirmed that HDAC6 and STAT3 are both recruited to the same DNA sequence within the Il10 gene promoter. Of note, disruption of this complex by knocking down HDAC6 resulted in decreased STAT3 phosphorylation--but no changes in STAT3 acetylation--as well as diminished recruitment of STAT3 to the Il10 gene promoter region. The additional demonstration that a selective HDAC6 inhibitor disrupts this STAT3/IL-10 tolerogenic axis points to HDAC6 as a novel molecular target in APCs to overcome immune tolerance and tips the balance toward T cell immunity.

Divergent roles of histone deacetylase 6 (HDAC6) and histone deacetylase 11 (HDAC11) on the transcriptional regulation of IL10 in antigen presenting cells

The anti-inflammatory cytokine IL-10 is a key modulator of immune responses. A better understanding of the regulation of this cytokine offers the possibility of tipping the balance of the immune response toward either tolerance, or enhanced immune responses. Histone deacetylases (HDACs) have been widely described as negative regulators of transcriptional regulation, and in this context, the primarily nuclear protein HDAC11 was shown to repress il-10 gene transcriptional activity in antigen-presenting cells (APCs). Here we report that another HDAC, HDAC6, primarily a cytoplasmic protein, associates with HDAC11 and modulates the expression of IL-10 as a transcriptional activator. To our knowledge, this is the first demonstration of two different HDACs being recruited to the same gene promoter to dictate divergent transcriptional responses. This dynamic interaction results in dynamic changes in the expression of IL-10 and might help to explain the intrinsic plasticity of the APC to determine T-cell activation versus T-cell tolerance.

The antimelanoma activity of the histone deacetylase inhibitor panobinostat (LBH589) is mediated by direct tumor cytotoxicity and increased tumor immunogenicity

Melanoma is the deadliest skin cancer, and its incidence has been increasing faster than any other cancer. Although immunogenic, melanoma is not effectively cleared by host immunity. In this study, we investigate the therapeutic, antimelanoma potential of the histone deacetylase inhibitor (HDACi) panobinostat (LBH589) by assessing both its cytotoxic effects on melanoma cells as well as enhancement of immune recognition of melanoma. Utilizing murine and human melanoma cell lines, we analyzed the effects of LBH589 on proliferation and survival. In addition, we analyzed the expression of several immunologically relevant surface markers and melanoma differentiation antigens, and the ability of LBH589-treated melanoma to activate antigen-specific T cells. Finally, we assessed the in-vivo effects of LBH589 in a mouse melanoma model. Low nanomolar concentrations of LBH589 inhibit the growth of all melanoma cell lines tested, but not normal melanocytes. This inhibition is characterized by increased apoptosis as well as a G1 cell cycle arrest. In addition, LBH589 augments the expression of major histocompatibility complex and costimulatory molecules on melanoma cells leading to an increased ability to activate antigen-specific T cells. Treatment also increases expression of melanoma differentiation antigens. In vivo, LBH589 treatment of melanoma-bearing mice results in a significant increase in survival. However, in immunodeficient mice, the therapeutic effect of LBH589 is lost. Taken together, LBH589 exerts a dual effect upon melanoma cells by affecting not only growth/survival but also by increasing melanoma immunogenicity. These effects provide the framework for future evaluation of this HDAC inhibitor in melanoma treatment.

Abstract 3554: The histone deacetylase inhibitor LBH589 augments anti-tumor immunity through direct effects on tumor and immune cells leading to impaired tumor progression in vivo

Overcoming immune tolerance is critical for the development of effective immunotherapy against cancer. Tumor cells induce tolerance through a variety of modalities including the secretion of IL-10 and TGF-β, the expression of inhibitory ligands, and the generation of cells with regulatory properties. Epigenetic modifiers have gained special attention due to their ability to modify immune regulatory pathways. In this context, a group of chemical compound collectively named histone deacetylase inhibitors (HDACi) have recently been shown to modulate tumor cell immunogenicity, adding a new property to their already well-documented cytotoxic effect against transformed cells. LBH589 is a potent, pan-HDACi that has been used in clinical trials for the treatment of several hematological malignancies. Here, we provide evidence of the anti-melanoma effect of LBH589 through its direct effects upon tumor cells as well as its modulatory effects upon immune cells. Indeed, treatment of human and murine melanoma cells in vitro with LBH589 resulted in inhibition of melanoma proliferation, characterized by cell cycle arrest in G1. Moreover, we found that LBH589 enhances the expression of MHC class I and II molecules on melanoma cells, which is critical for immune recognition. In addition, LBH589 treatment inhibits the production of IL-10, while enhancing the secretion of pro-inflammatory cytokines such as IL-12 and the expression of the costimulatory molecule B7.2 on antigen-presenting cells (APCs). LBH-treated APCs also displayed an enhanced capability to activate naïve antigen-specific T-cells as evidenced by their increased production of IL-2 and IFN-γ. More importantly, LBH589-treated APCs also restored the function of anergic T-cells isolated from tumor bearing mice. Finally, in vivo treatment of B16 melanoma bearing mice with LBH589 resulted in a substantial decrease in tumor growth when compared to vehicle-control treated mice (mean 602mm3 vs. 1316mm3, respectively). In conclusion, the dual ability of the pan-HDACi LBH589 to target both melanoma cells and to enhance anti-tumor immune responses provides the rationale for evaluating this compound either alone or in combination with immune enhancing therapeutic approaches (eg, CTLA4 blockade) for melanoma treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3554. doi:1538-7445.AM2012-3554

Abstract 3555: Histone deacetylase 6 as a novel regulator of the immunogenicity and aggressiveness of melanoma

Melanoma is currently the fastest growing cancer in incidence according to the World Health Organization. Currently, few therapies provide significant prolongation of survival for metastatic melanoma. Immunotherapy is an attractive modality with potentially few side effects due to the antigen specificity of adaptive immunity. The latest therapy approved by the FDA for the treatment of melanoma was ipilimumab, an antibody against CTLA-4, a key regulator of T-cell activity; however, this therapy offers modest improvements in overall survival. Overcoming mechanisms of tumor-mediated immune suppression requires targeting multiple pathways. One strategy that has gained attention has been the use of histone deacetylase inhibitors (HDACi). Indeed, HDACi treatment has been shown to augment the expression of immunologically relevant genes such as MHC and costimulatory molecules. Furthermore, we have previously demonstrated inhibition of IL-10, a potent anti-inflammatory cytokine, upon treatment of macrophages with HDACi. However, most studies to date have used pan-HDACi, which inhibit all 11 zinc-dependent HDACs. Therefore, the use of more selective HDACi might be preferable in order to minimize side effects. Herein, we demonstrate that HDAC6 is a molecular target in melanoma. Both pharmacologic and genetic disruption of HDAC6 in B16 murine melanoma cells using HDAC6-selective inhibitors (HDAC6i) and targeted shRNA (HDAC6KD), respectively, led to inhibition of proliferation, characterized by G1 arrest measured by propidium iodine staining for DNA content. Furthermore, treatment with HDAC6i led to enhanced expression of immunologically relevant receptors including MHC I and MHC II. In vivo, subcutaneous injection in wild type mice of HDAC6KD B16 cells led to delayed tumor growth as compared with control cells. However, this effect was abrogated in experiments using SCID mice, which lack T- and B-cells, suggesting a critical immune component for tumor control in vivo. The mechanism(s) by which HDAC6 regulates tumor immunogenicity are yet to be defined. One possible mechanism arises from protein immunoprecipitation studies which demonstrate that HDAC6 interacts with, and potentially regulates of STAT3, an important survival and pathogenic factor in melanoma, which also has implications for immune tolerance. Finally, the expression HDAC6 was found to be upregulated in a majority of melanoma patient tumor biopsies by gene microarray analysis, as compared with normal skin. This observation was supported by immunohistochemically-stained patient melanoma tissue microarray. Taken together, HDAC6 presents as an attractive therapeutic target in melanoma by both delaying tumor growth and conferring a more attractive immune target, providing rationale for the development and use of selective HDAC6i. Moreover, the current availability of HDAC6i enhances the translational implications of this work.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3555. doi:1538-7445.AM2012-3555

RING domain mutations uncouple TRIM5α restriction of HIV-1 from inhibition of reverse transcription and acceleration of uncoating

Rhesus TRIM5α (TRIM5α(rh)) is a cytosolic protein that potently restricts HIV-1 at an early postentry stage, prior to reverse transcription. The ability of TRIM5α(rh) to block HIV-1 infection has been correlated with a decrease of pelletable HIV-1 capsid during infection. To genetically dissect the ability of TRIM5α to block reverse transcription, we studied a set of TRIM5α(rh) RING domain mutants that potently restrict HIV-1 but allow the occurrence of reverse transcription. These TRIM5α(rh) RING variants blocked HIV-1 infection after reverse transcription but prior to integration, as suggested by the routing of nuclear viral DNA to circularization in the form of 2-long terminal repeat (2-LTR) circles. The folding of RING domain variants was similar to that of the wild type, as evaluated by nuclear magnetic resonance. RING domain changes that allowed the occurrence of reverse transcription were impaired in their ability to decrease the amount of pelletable capsid compared with wild-type TRIM5α. Similar effects of this particular group of mutations were observed with human TRIM5α inhibition of N-tropic murine leukemia virus (N-MLV). Interestingly, TRIM5α(rh) RING domain variants also prevented the degradation of TRIM5α(rh) that occurs following cell entry of HIV-1. These data correlated the block of reverse transcription with the ability of TRIM5α to accelerate uncoating. Collectively, these results suggest that TRIM5α(rh) blocks HIV-1 reverse transcription by inducing premature viral uncoating in target cells.

Helicobacter pylori HopE and HopV porins present scarce expression among clinical isolates

AIM

To evaluate how widely Helicobacter pylori (H. pylori) HopE and HopV porins are expressed among Chilean isolates and how seroprevalent they are among infected patients in Chile.

METHODS

H. pylori hopE and hopV genes derived from strain CHCTX-1 were cloned by polymerase chain reaction (PCR), sequenced and expressed in Escherichia coli AD494 (DE3). Gel-purified porins were used to prepare polyclonal antibodies. The presence of both genes was tested by PCR in a collection of H. pylori clinical isolates and their expression was detected in lysates by immunoblotting. Immune responses against HopE, HopV and other H. pylori antigens in sera from infected and non-infected patients were tested by Western blotting using these sera as first antibody on recombinant H. pylori antigens.

RESULTS

PCR and Western blotting assays revealed that 60 and 82 out of 130 Chilean isolates carried hopE and hopV genes, respectively, but only 16 and 9, respectively, expressed these porins. IgG serum immunoreactivity evaluation of 69 H. pylori-infected patients revealed that HopE and HopV were infrequently recognized (8.7% and 10.1% respectively) compared to H. pylori VacA (68.1%) and CagA (59.5%) antigens. Similar values were detected for IgA serum immunoreactivity against HopE (11.6%) and HopV (10.5%) although lower values for VacA (42%) and CagA (17.4%) were obtained when compared to the IgG response.

CONCLUSION

A scarce expression of HopE and HopV among Chilean isolates was found, in agreement with the infrequent seroconversion against these antigens when tested in infected Chilean patients.