Inhibition of Histone Deacetylase (HDAC) Enhances Checkpoint Blockade Efficacy by Rendering Bladder Cancer Cells Visible for T Cell-Mediated Destruction

Advances in targeting histone deacetylase for treatment of solid tumors

Histone deacetylase (HDAC) serves as a critical molecular regulator in the pathobiology of various malignancies and have garnered attention as a viable target for therapeutic intervention. A variety of HDAC inhibitors (HDACis) have been developed to target HDACs. Many preclinical studies have conclusively demonstrated the antitumor effects of HDACis, whether used as monotherapy or in combination treatments. On this basis, researchers have conducted various clinical studies to evaluate the potential of selective and pan-HDACis in clinical settings. In our work, we extensively summarized and organized current clinical trials, providing a comprehensive overview of the current clinical advancements in targeting HDAC therapy. Furthermore, we engaged in discussions about several clinical trials that did not yield positive outcomes, analyzing the factors that led to their lack of anticipated therapeutic effectiveness. Apart from the experimental design factors, issues such as toxicological side effects, tumor heterogeneity, and unexpected off-target effects also contributed to these less-than-expected results. These challenges have naturally become significant barriers to the application of HDACis. Despite these challenges, we believe that advancements in HDACi research and improvements in combination therapies will pave the way or lead to a broad and hopeful future in the treatment of solid tumors.

Epigenetic alterations and advancement of lymphoma treatment

Lymphomas, complex and heterogeneous malignant tumors, originate from the lymphopoietic system. These tumors are notorious for their high recurrence rates and resistance to treatment, which leads to poor prognoses. As ongoing research has shown, epigenetic modifications like DNA methylation, histone modifications, non-coding RNA regulation, and RNA modifications play crucial roles in lymphoma pathogenesis. Epigenetic modification-targeting drugs have exhibited therapeutic efficacy and tolerability in both monotherapy and combination lymphoma therapy. This review discusses pathogenic mechanisms and potential epigenetic therapeutic targets in common lymphomas, offering new avenues for lymphoma diagnosis and treatment. We also discuss the shortcomings of current lymphoma treatments, while suggesting potential areas for future research, in order to improve the prediction and prognosis of lymphoma.

A novel small molecule inhibitor of CD73 triggers immune-mediated multiple myeloma cell death

CD73 is the key ectoenzyme involved in the generation of AMP-derived adenosine, which contributes to immunosuppression in the MM BM milieu. Blocking CD73 activity with a potent, selective, orally bioavailable CD73 inhibitor ORIC-533 decreases adenosine generation, overcomes immune suppression, and restores immune cell-mediated MM cell lysis. Based on these preclinical studies, a multi-center clinical trial of ORIC-533 has been initiated in patients with relapsed refractory MM (NCT05227144).

Targeting histone modifiers in bladder cancer therapy - preclinical and clinical evidence

Bladder cancer in the most advanced, muscle-invasive stage is lethal, and very limited therapeutic advances have been reported for decades. To date, cisplatin-based chemotherapy remains the first-line therapy for advanced bladder cancer. Late-line options have historically been limited. In the past few years, next-generation sequencing technology has enabled chromatin remodelling gene mutations to be characterized, showing that these alterations are more frequent in urothelial bladder carcinoma than in other cancer types. Histone modifiers have functional roles in tumour progression by modulating the expression of tumour suppressors and oncogenes and, therefore, have been considered as novel drug targets for cancer therapy. The roles of epigenetic reprogramming through histone modifications have been increasingly studied in bladder cancer, and the therapeutic efficacy of targeting those histone modifiers genetically or chemically is being assessed in preclinical studies. Results from preclinical studies in bladder cancer encouraged the investigation of some of these drugs in clinical trials, which yield mixed results. Further understanding of how alterations of histone modification mechanistically contribute to bladder cancer progression, drug resistance and tumour microenvironment remodelling will be required to facilitate clinical application of epigenetic drugs in bladder cancer.

Modulation of tumor microenvironment by targeting histone acetylation in bladder cancer

Alterations in the epigenetic machinery in both tumor and immune cells contribute to bladder cancer (BC) development, constituting a promising target as an alternative therapeutic option. Here, we have explored the effects of a novel histone deacetylase (HDAC) inhibitor CM-1758, alone or in combination with immune checkpoint inhibitors (ICI) in BC. We determined the antitumor effects of CM-1758 in various BC cell lines together with the induction of broad transcriptional changes, with focus on the epigenetic regulation of PD-L1. Using an immunocompetent syngeneic mouse model of metastatic BC, we studied the effects of CM-1758 alone or in combination with anti-PD-L1 not only on tumor cells, but also in the tumor microenvironment. In vitro, we found that CM-1758 has cytotoxic and cytostatic effects either by inducing apoptosis or cell cycle arrest in BC cells at low micromolar levels. PD-L1 is epigenetically regulated by histone acetylation marks and is induced after treatment with CM-1758. We also observed that treatment with CM-1758 led to an important delay in tumor growth and a higher CD8 + T cell tumor infiltration. Moreover, anti-PD-L1 alone or in combination with CM-1758 reprogramed macrophage differentiation towards a M1-like polarization state and increased of pro-inflammatory cytokines systemically, yielding potential further antitumor effects. Our results suggest the possibility of combining HDAC inhibitors with immunotherapies for the management of advanced metastatic BC.

Knowledge-map analysis of bladder cancer immunotherapy

This study aimed to conduct a bibliometric analysis in the field of bladder cancer (BC) immunotherapy, and explore the research trends, hotspots and frontiers from 2000 to 2022. VOSviewer software was used to analyze the collaborative relationships between authors, institutions, countries/regions, and journals through citation, co-authorship, and co-citation analysis, to identify research hotspots and frontiers in this field. Researchers based in the United States of America have published a total of 627 papers with 27,308 citations. Indeed, the USA ranked first among the top 10 most active countries and showed the most extensive collaboration with other countries. The University of Texas MD Anderson CANC CTR has published 58 articles, making it the top most institution in terms of published articles and active collaborative research. Kamat AM and Lamm DL were the most active and co-cited authors with 28 papers and 980 co-citations, respectively. Chang Yuan and Xu le were the most active collaborative authors with a total link strength of 195. The J UROLOGY was the most active and frequently co-cited journal, with 100 papers and 6,668 co-citations. Studies of BC immunotherapy can be broadly classified into three categories: "basic research", "clinical trial", and "prognosis". Our findings provide an overview of the research priorities and future directions of BC immunotherapy. Tumor microenvironment and immune checkpoint inhibitors (ICIs) of BC, as well as the combination of ICIs with other drugs, may become the main direction of future research.

Targeted therapies in bladder cancer: signaling pathways, applications, and challenges

Bladder cancer (BC) is one of the most prevalent malignancies in men. Understanding molecular characteristics via studying signaling pathways has made tremendous breakthroughs in BC therapies. Thus, targeted therapies including immune checkpoint inhibitors (ICIs), antibody-drug conjugates (ADCs), and tyrosine kinase inhibitor (TKI) have markedly improved advanced BC outcomes over the last few years. However, the considerable patients still progress after a period of treatment with current therapeutic regimens. Therefore, it is crucial to guide future drug development to improve BC survival, based on the molecular characteristics of BC and clinical outcomes of existing drugs. In this perspective, we summarize the applications and benefits of these targeted drugs and highlight our understanding of mechanisms of low response rates and immune escape of ICIs, ADCs toxicity, and TKI resistance. We also discuss potential solutions to these problems. In addition, we underscore the future drug development of targeting metabolic reprogramming and cancer stem cells (CSCs) with a deep understanding of their signaling pathways features. We expect that finding biomarkers, developing novo drugs and designing clinical trials with precisely selected patients and rationalized drugs will dramatically improve the quality of life and survival of patients with advanced BC.

Elucidating the direct effects of the novel HDAC inhibitor bocodepsin (OKI-179) on T cells to rationally design regimens for combining with immunotherapy

Histone deacetylase inhibitors (HDACi) are currently being explored for the treatment of both solid and hematological malignancies. Although originally thought to exert cytotoxic responses through tumor-intrinsic mechanisms by increasing expression of tumor suppressor genes, several studies have demonstrated that therapeutic responses depend on an intact adaptive immune system: particularly CD8 T cells. It is therefore critical to understand how HDACi directly affects T cells in order to rationally design regimens for combining with immunotherapy. In this study, we evaluated T cell responses to a novel class-selective HDACi (OKI-179, bocodepsin) by assessing histone acetylation levels, which revealed rapid responsiveness accompanied by an increase in CD4 and CD8 T cell frequencies in the blood. However, these rapid responses were transient, as histone acetylation and frequencies waned within 24 hours. This contrasts with in vitro models where high acetylation was sustained and continuous exposure to HDACi suppressed cytokine production. In vivo comparisons demonstrated that stopping OKI-179 treatment during PD-1 blockade was superior to continuous treatment. These findings provide novel insight into the direct effects of HDAC inhibitors on T cells and that treatment schedules that take into account acute T cell effects should be considered when combined with immunotherapies in order to fully harness the tumor-specific T cell responses in patients.

Histone deacetylases inhibitor chidamide synergizes with humanized PD1 antibody to enhance T-cell chemokine expression and augment Ifn-γ response in NK-T cell lymphoma

BACKGROUND

Whether immunotherapy combined with different histone deacetylases (HDAC) inhibitors in refractory or relapsed natural killer/T-cell lymphoma (NKTCL) is superior to each agent is still lacking in head-to-head clinical trials or preclinical evidence.

METHODS

NKTCL cell line xenograft models (CDX) in immunocompetent, human programmed cell death protein 1 (PD1) knock-in genetically engineered mice were used to investigate the combination effects. Different types and dosages of HDAC inhibitors were investigated. We explored the underlying mechanisms by RNA-sequencing and ChIP-sequencing. Two clinical cases treated with anti-PD1/chidamide were presented.

FINDINGS

Anti-PD1/chidamide shows significant tumour rejection in two CDX models. RNA-seq and CHIP-seq revealed that chidamide is synergistic to enhance T-cell chemokine expression, augment the Ifn-γ response, and increase CD8 T-cell infiltration via histone modification. Ifn-γ neutralizing antibody can attenuate the efficacy of combination drugs. However, the anti-PD1/romidepsin failed to augment the Ifn-γ response. The expressions of Ifn-γ related gene set signatures are significantly correlated with tumour rejection in anti-PD1/chidamide. In the clinic, two NKTCL patients treated with the PD1/chidamide show promising efficacy and limited toxicity.

INTERPRETATION

Anti-PD1/chidamide enhances T-cell chemokine expression and augments the IFN-γ response in preclinical NKTCL immunocompetent models. IFN-γ signatures may be good response biomarkers for the selection of potentially benefit patients.

FUNDING

This study was supported by the Chinese National Major Project for New Drug Innovation (2017ZX09304015) and the Chinese Society of Clinical Oncology Research Fund (Y-BMS2019-026).

Plant-Derived Sulforaphane Suppresses Growth and Proliferation of Drug-Sensitive and Drug-Resistant Bladder Cancer Cell Lines In Vitro

Simple Summary

The natural compound sulforaphane is highly popular among tumor patients, since it is suggested to prevent oncogenesis and cancer progression. However, knowledge about its precise mode of action, particularly when drug resistance has been established, remains poor. The present study demonstrates the proliferation-blocking effects of SFN on a panel of drug-resistant bladder cancer cell lines.

Abstract

Combined cisplatin–gemcitabine (GC) application is standard for treating muscle-invasive bladder cancer. However, since rapid resistance to treatment often develops, many patients turn to supplements in the form of plant-based compounds. Sulforaphane (SFN), derived from cruciferous vegetables, is one such compound, and the present study was designed to investigate its influence on growth and proliferation in a panel of drug-sensitive bladder cancer cell lines, as well as their gemcitabine- and cisplatin-resistant counterparts. Chemo-sensitive and -resistant RT4, RT112, T24, and TCCSUP cell lines were exposed to SFN in different concentrations, and tumor growth, proliferation, and clone formation were evaluated, in addition to apoptosis and cell cycle progression. Means of action were investigated by assaying cell-cycle-regulating proteins and the mechanistic target of rapamycin (mTOR)/AKT signaling cascade. SFN significantly inhibited growth, proliferation, and clone formation in all four tumor cell lines. Cells were arrested in the G2/M and/or S phase, and alteration of the CDK–cyclin axis was closely associated with cell growth inhibition. The AKT/mTOR signaling pathway was deactivated in three of the cell lines. Acetylation of histone H3 was up-regulated. SFN, therefore, does exert tumor-suppressive properties in cisplatin- and gemcitabine-resistant bladder cancer cells and could be beneficial in optimizing bladder cancer therapy.

A Therapeutic Perspective of HDAC8 in Different Diseases: An Overview of Selective Inhibitors

Histone deacetylases (HDACs) are epigenetic enzymes which participate in transcriptional repression and chromatin condensation mechanisms by removing the acetyl moiety from acetylated ε-amino group of histone lysines and other non-histone proteins. In recent years, HDAC8, a class I HDAC, has emerged as a promising target for different disorders, including X-linked intellectual disability, fibrotic diseases, cancer, and various neuropathological conditions. Selective HDAC8 targeting is required to limit side effects deriving from the treatment with pan-HDAC inhibitors (HDACis); thus, many endeavours have focused on the development of selective HDAC8is. In addition, polypharmacological approaches have been explored to achieve a synergistic action on multi-factorial diseases or to enhance the drug efficacy. In this frame, proteolysis-targeting chimeras (PROTACs) might be regarded as a dual-targeting approach for attaining HDAC8 proteasomal degradation. This review highlights the most relevant and recent advances relative to HDAC8 validation in various diseases, providing a snapshot of the current selective HDAC8is, with a focus on polyfunctional modulators.

Small-Molecule PROTACs for Cancer Immunotherapy

Unsatisfactory physicochemical properties of macromolecular drugs seriously hinder their application in tumor immunotherapy. However, these problems can be effectively solved by small-molecule compounds. In the promising field of small-molecule drug development, proteolysis targeting chimera (PROTAC) offers a novel mode of action in the interactions between small molecules and therapeutic targets (mainly proteins). This revolutionary technology has shown considerable impact on several proteins related to tumor survival but is rarely exploited in proteins associated with immuno-oncology up until now. This review attempts to comprehensively summarize the well-studied and less-developed immunological targets available for PROTAC technology, as well as some targets to be explored, aiming to provide more options and opportunities for the development of small-molecule-based tumor immunotherapy. In addition, some novel directions that can magnify and broaden the protein degradation efficiency are mentioned to improve PROTAC design in the future.

Case Report: Outcome and Adverse Events of Anti-PD-1 Antibody Plus Chidamide for Relapsed/Refractory Sézary Syndrome: Case Series and A Literature Review

Sézary syndrome (SS) is an aggressive leukemic variant of cutaneous T-cell lymphoma with a poor prognosis and survival rate. Existing therapies for relapsed/refractory (R/R) SS have a low response rate with a short duration time. Herein, we presented three cases of R/R SS treated with the anti-PD-1 antibody and chidamide. Case 1 and case 2 showed the potential efficacy of this combination therapy with a long duration time. Case 2 and case 3 both showed that the patients developed acute and transient worsening of erythroderma and pruritus after anti-PD-1 antibody infusion, and this flare reaction was associated with transient decreased leukocytes and lymphocytes in peripheral blood. To the best of our knowledge, this is the first report of the anti-PD-1 antibody combined with chidamide for treatment of R/R SS. This report suggests that the combination therapy may be a new and effective treatment and that further clinical trials are needed to prove it and elucidate the mechanism of this combination therapy and its flare reaction.

Combination of atezolizumab and chidamide to maintain long-term remission in refractory metastatic extranodal natural killer/T-cell lymphoma: A case report

BACKGROUND

The prognosis of refractory extranodal natural killer/T-cell lymphoma (ENKTL) is poor. Recent data have indicated that immune checkpoint blockade with a programmed cell death protein-1 (PD-1) antibody in combination with administration of histone deacetylase inhibitors represents a potentially effective treatment strategy. Compared with PD-1 antibodies, programmed death-ligand 1 antibodies have fewer side effects. Here, we present a rare case of a patient with refractory metastatic ENKTL who achieved sustained remission of approximately 10 mo with minor adverse effects after combination therapy with atezolizumab, chidamide, and radiotherapy.

CASE SUMMARY

A 56-year-old woman underwent resection of a tumour in her left nasal cavity and was diagnosed with ENKTL (nasal type). Medical examination revealed tumours observed in the bilateral nasal mucosa, the subcutaneous soft tissue of the inner side of the left eye, the soft tissue of the nasopharynx, the bilateral tonsils, and the left preauricular, right hilar, bilateral neck lymph nodes and bone marrow. However, tomography/computed tomography showed increased metabolism of the bilateral nasal mucosa and subcutaneous soft tissue of the inner side of the left eye and newly increased metabolism of the left cervical lymph node after chemotherapy. Therefore, combination therapy with chidamide, atezolizumab, and radiotherapy was performed. Fortunately, the patient achieved a complete response following 10 mo of combination therapy.

CONCLUSION

The outcome in this case suggests that the combination of atezolizumab, chidamide, and radiotherapy is a promising regimen for treating refractory metastatic ENKTL following chemotherapy treatment failure.

Epigenetic Drugs and Their Immune Modulating Potential in Cancers

Epigenetic drugs are used for the clinical treatment of hematologic malignancies; however, their therapeutic potential in solid tumors is still under investigation. Current evidence suggests that epigenetic drugs may lead to antitumor immunity by increasing antigen presentation and may enhance the therapeutic effect of immune checkpoint inhibitors. Here, we highlight their impact on the tumor epigenome and discuss the recent evidence that epigenetic agents may optimize the immune microenvironment and promote antiviral response.

Acetylation in Tumor Immune Evasion Regulation

Acetylation is considered as one of the most common types of epigenetic modifications, and aberrant histone acetylation modifications are associated with the pathological process of cancer through the regulation of oncogenes and tumor suppressors. Recent studies have shown that immune system function and tumor immunity can also be affected by acetylation modifications. A comprehensive understanding of the role of acetylation function in cancer is essential, which may help to develop new therapies to improve the prognosis of cancer patients. In this review, we mainly discussed the functions of acetylase and deacetylase in tumor, immune system and tumor immunity, and listed the information of drugs targeting these enzymes in tumor immunotherapy.

Sintilimab and Chidamide for Refractory Transformed Diffuse Large B Cell Lymphoma: A Case Report and A Literature Review

Patients with relapsed/refractory (R/R) transformed diffused large B cell lymphoma (tDLBCL) have a poor prognosis and a low survival rate. In addition, no standard therapy has yet been established for R/R tDLBCL. Herein we presented a single case of a patient with R/R tDLBCL who was successfully treated with sintilimab and chidamide. The patient was a 71-year-old man with pulmonary mucosa-associated lymphoid tissue lymphoma. He did not receive any treatment until tDLBCL was confirmed 2 years later. The tDLBCL was primary refractory to R2-CHOP, R2-MTX, and Gemox regimens. However, the patient achieved sustained complete remission after the combination therapy of sintilimab and chidamide. To the best of our knowledge, this is the first report of sintilimab combined with chidamide for the treatment of R/R tDLBCL, which opens up new therapeutic possibilities for this new combination therapy in future prospective clinical trials.

Tumor-Associated Macrophages in Bladder Cancer: Biological Role, Impact on Therapeutic Response and Perspectives for Immunotherapy

Tumor-associated macrophages (TAMs) are one of the most abundant infiltrating immune cells of solid tumors. Despite their possible dual role, i.e., pro- or anti-tumoral, there is considerable evidence showing that the accumulation of TAMs promotes tumor progression rather than slowing it. Several strategies are being developed and clinically tested to target these cells. Bladder cancer (BCa) is one of the most common cancers, and despite heavy treatments, including immune checkpoint inhibitors (ICIs), the overall patient survival for advanced BCa is still poor. TAMs are present in bladder tumors and play a significant role in BCa development. However, few investigations have analyzed the effect of targeting TAMs in BCa. In this review, we focus on the importance of TAMs in a cancerous bladder, their association with patient outcome and treatment efficiency as well as on how current BCa treatments impact these cells. We also report different strategies used in other cancer types to develop new immunotherapeutic strategies with the aim of improving BCa management through TAMs targeting.

Characterization of Histone Deacetylase Mechanisms in Cancer Development

Over decades of studies, accumulating evidence has suggested that epigenetic dysregulation is a hallmark of tumours. Post-translational modifications of histones are involved in tumour pathogenesis and development mainly by influencing a broad range of physiological processes. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are pivotal epigenetic modulators that regulate dynamic processes in the acetylation of histones at lysine residues, thereby influencing transcription of oncogenes and tumour suppressor genes. Moreover, HDACs mediate the deacetylation process of many nonhistone proteins and thus orchestrate a host of pathological processes, such as tumour pathogenesis. In this review, we elucidate the functions of HDACs in cancer.

Targeting WD repeat domain 5 enhances chemosensitivity and inhibits proliferation and programmed death-ligand 1 expression in bladder cancer

Background

Chemotherapy and/or immunotherapy are first-line treatments for advanced muscle-invasive bladder cancer (BCa), but the unsatisfactory objective response rate to these treatments yields poor 5-year patient survival. Discovery of therapeutic targets essential for BCa maintenance is critical to improve therapy response in clinic. This study evaluated the role of targeting WD repeat domain 5 (WDR5) with the small molecule compound OICR-9429 and whether it could be used to treat bladder cancer.

Methods

We analysed the expression and clinical prognosis of WDR5 in a TCGA cohort. The pharmacological role of OICR-9429 was further investigated in vitro and in vivo. RNA sequencing, western blot, and chromatin immunoprecipitation (ChIP) were utilized to explored the mechanism underlying OICR-9429-induced WDR5 inhibition.

Results

First, we found that WDR5 expression was upregulated in BCa and was associated with histologic grade, metastasis status, histologic subtype, and molecular subtype. High WDR5 expression level was also correlated with shorter overall survival (OS) in BCa. The WDR5 inhibitor OICR-9429 reduced cell viability by decreasing H3K4me3 levels but not WDR5 levels in T24, UM-UC-3, and TCCSUP BCa cells. OICR-9429 suppressed the proliferation of BCa cells by blocking the G1/S phase transition. Next, OICR-9429 enhanced apoptosis and chemosensitivity to cisplatin in BCa cells. In addition, OICR-9429 independently inhibited the motility and metastatic behaviour of BCa cells. In vivo experiments further revealed that OICR-9429 suppressed tumour growth, enhanced chemosensitivity, and reduced the toxicity of cisplatin in BCa. Notably, WDR5 was positively correlated with programmed death-ligand 1 (PD-L1) expression, and OICR-9429 suppressed immune evasion by blocking PD-L1 induced by IFN-γ. Mechanistically, some cell cycle-, antiapoptosis-, DNA repair-, metastasis-, and immune evasion-related genes, including BIRC5, XRCC2, CCNB1, CCNE2, PLK1, AURKA, FOXM1, and PD-L1 were identified to be directly regulated by OICR-9429 in a H3K4me3-dependent manner.

Conclusions

Our novel finding is that the WDR5 inhibitor, OICR-9429, suppressed proliferation, metastasis and PD-L1-based immune evasion while enhancing apoptosis and chemosensitivity to cisplatin in BCa by blocking the WDR5-MLL complex mediating H3K4me3 in target genes. Hence, our findings offer insight into a multipotential anticancer compound, OICR-9429, which enhances the antitumour effect of cisplatin or immunotherapy in BCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01989-5.

Epigenetic Silencing of Immune-Checkpoint Receptors in Bone Marrow- Infiltrating T Cells in Acute Myeloid Leukemia

Background

Immune-checkpoint (IC) inhibitors have revolutionized the treatment of multiple solid tumors and defined lymphomas, but they are largely ineffective in acute myeloid leukemia (AML). The reason why especially PD1/PD-L1 blocking agents are not efficacious is not well-understood but it may be due to the contribution of different IC ligand/receptor interactions that determine the function of T cells in AML.

Methods

To analyze the interactions of IC ligands and receptors in AML, we performed a comprehensive transcriptomic analysis of FACS-purified leukemia stem/progenitor cells and paired bone marrow (BM)-infiltrating CD4⁺ and CD8⁺ T cells from 30 patients with AML. The gene expression profiles of activating and inhibiting IC ligands and receptors were correlated with the clinical data. Epigenetic mechanisms were studied by inhibiting the histone deacetylase with valproic acid or by gene silencing of PAC1.

Results

We observed that IC ligands and receptors were mainly upregulated in leukemia stem cells. The gene expression of activating IC ligands and receptors correlated with improved prognosis and vice versa. In contrast, the majority of IC receptor genes were downregulated in BM-infiltrating CD8⁺ T cells and partially in CD4⁺ T cells, due to pathological chromatin remodeling via histone deacetylation. Therefore, treatment with histone deacetylase inhibitor (HDACi) or silencing of PAC1, as a T cell-specific epigenetic modulator, significantly increased the expression of IC receptors and defined effector molecules in CD8⁺ T cells.

Conclusions

Our results suggest that CD8⁺ T cells in AML are dysfunctional mainly due to pathological epigenetic silencing of activating IC receptors rather than due to signaling by immune inhibitory IC receptors, which may explain the limited efficacy of antibodies that block immune-inhibitory ICs in AML.

Epigenetic modulation and understanding of HDAC inhibitors in cancer therapy

The role of genetic and epigenetic factors in tumor initiation and progression is well documented. Histone deacetylases (HDACs), histone methyl transferases (HMTs), and DNA methyl transferases. (DNMTs) are the main proteins that are involved in regulating the chromatin conformation. Among these, histone deacetylases (HDAC) deacetylate the histone and induce gene repression thereby leading to cancer. In contrast, histone acetyl transferases (HATs) that include GCN5, p300/CBP, PCAF, Tip 60 acetylate the histones. HDAC inhibitors are potent drug molecules that can induce acetylation of histones at lysine residues and induce open chromatin conformation at tumor suppressor gene loci and thus resulting in tumor suppression. The key processes regulated by HDAC inhibitors include cell-cycle arrest, chemo-sensitization, apoptosis induction, upregulation of tumor suppressors. Even though FDA approved drugs are confined mainly to haematological malignancies, the research on HDAC inhibitors in glioblastoma multiforme and triple negative breast cancer (TNBC) are providing positive results. Thus, several combinations of HDAC inhibitors along with DNA methyl transferase inhibitors and histone methyl transferase inhibitors are in clinical trials. This review focuses on how HDAC inhibitors regulate the expression of coding and non-coding genes with specific emphasis on their anti-cancer potential.

Immune modulation underpins the anti-cancer activity of HDAC inhibitors

Aberrant protein acetylation is strongly linked to tumorigenesis, and modulating acetylation through targeting histone deacetylase (HDAC) with small‐molecule inhibitors has been the focus of clinical trials. However, clinical success on solid tumours, such as colorectal cancer (CRC), has been limited, in part because the cancer‐relevant mechanisms through which HDAC inhibitors act remain largely unknown. Here, we have explored, at the genome‐wide expression level, the effects of a novel HDAC inhibitor CXD101. In human CRC cell lines, a diverse set of differentially expressed genes were up‐ and downregulated upon CXD101 treatment. Functional profiling of the expression data highlighted immune‐relevant concepts related to antigen processing and natural killer cell‐mediated cytotoxicity. Similar profiles were apparent when gene expression was investigated in murine colon26 CRC cells treated with CXD101. Significantly, these changes were also apparent in syngeneic colon26 tumours growing in vivo. The ability of CXD101 to affect immune‐relevant gene expression coincided with changes in the tumour microenvironment (TME), especially in the subgroups of CD4 and CD8 tumour‐infiltrating T lymphocytes. The altered TME reflected enhanced antitumour activity when CXD101 was combined with immune checkpoint inhibitors (ICIs), such as anti‐PD‐1 and anti‐CTLA4. The ability of CXD101 to reinstate immune‐relevant gene expression in the TME and act together with ICIs provides a powerful rationale for exploring the combination therapy in human cancers.

Sustained remission of multi-line relapsed extranodal NK/T-cell lymphoma, nasal type, following sintilimab and chidamide: A case report

INTRODUCTION

There is currently no optimal treatment modality for refractory or relapsed Extranodal NK/T-cell lymphoma, nasal type (ENKTL). In recent years, programmed cell death protein 1 (PD-1)/programmed cell - ligand 1 pathway blockade and histone deacetylase inhibitors have emerged as promising strategies for refractory or relapsed ENKTL. Accumulating evidence has shown that therapeutic effects of anti-PD-1 antibody could be enhanced by histone deacetylase inhibitors.

PATIENT CONCERNS

A 52-year-old male patient was diagnosed with stage I ENKTL by biopsy on February 2010.

DIAGNOSIS

positron emission tomography-computed tomography (PET-CT) and biopsy were used to diagnose relapsed ENKTL in 2014.

INTERVENTIONS

The patient was treated with radiotherapy and six cycles of etoposide, prednisone, vincristine (Oncovin), cyclophosphamide and doxorubicin hydrochloride and achieved complete remission (CR) by PET-CT in August 2010. In November 2014, the patient was diagnosed with relapsed stage IV ENKTL and was treated with six cycles of alternative chemotherapy with the regimen of steroid (dexamethasone), methotrexate, ifosfamide, L-asparaginase, and etoposide and pegaspargase plus Gemcitabine, Oxaliplatin along with radiotherapy. The patient achieved remission and was placed on thalidomide maintenance treatment. Upon suspicion of relapse suggested by PET-CT, Autologous stem cell transplant was performed after BCNU, etoposide, Ara-C, and melphalan preconditioning on February 2016. Following relapse again in December 2016, the lesions of left femur were treated with radiotherapy and he received anti-PD-1 antibody. He was treated with 4 cycles of pegaspargase plus Gemcitabine, Oxaliplatin on August 2017. The patient's condition improved. He received maintenance and consolidation therapy including lenalidomide, radiotherapy of the right nasal cavity and paranasal sinuses and antigen-specific reactive T cell infusions. PET-CT imaging showed there was high metabolic activity signal in the distal end of right femoral on August 2018 and the treatment regimen was adjusted to radiotherapy of the distal end of right femoral and systemic treatment of PD-1 antibody Sintilimab and chidamide 30 mg. After 5 months post-treatment, biopsy of nasopharynx showed no lymphoma cells. The patient continued the treatment of Sintilimab and chidamide 20 mg.

OUTCOMES

PET-CT imaging showed his lesions obtained remission after 8 months post-treatment.

CONCLUSION

Thus, combination of sintilimab and chidamide can be used to treat relapsed ENKTL following treatment failure from chemo-, radio-, and immuno-therapy. A clinical trial has been launched.

The Roles of T cells in Bladder Pathologies

T lymphocytes play important roles in the skin and mucosal surfaces such as the gut and lung. Until recently the contributions of T cells to mammalian bladder immunity were largely unknown. With newer techniques, including single-cell RNA sequencing and reporter mice, an understanding is emerging of T cell roles in bladder diseases (bacterial infections, bladder cancer, chronic inflammation). In these pathologies, many bladder T cell responses can be harmful to the host through suboptimal clearance of bacteria or cancer cells, or by modulating autoinflammation. Recent findings suggest that T cell behavior might be influenced by resident T cell interactions with the bladder microbiota and other immunostimulants. Thus, regulating bladder T cell functions could emerge as a putative immunotherapy to treat some bladder diseases.

Anticancer Therapy with HDAC Inhibitors: Mechanism-Based Combination Strategies and Future Perspectives

The increasing knowledge of molecular drivers of tumorigenesis has fueled targeted cancer therapies based on specific inhibitors. Beyond "classic" oncogene inhibitors, epigenetic therapy is an emerging field. Epigenetic alterations can occur at any time during cancer progression, altering the structure of the chromatin, the accessibility for transcription factors and thus the transcription of genes. They rely on post-translational histone modifications, particularly the acetylation of histone lysine residues, and are determined by the inverse action of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Importantly, HDACs are often aberrantly overexpressed, predominantly leading to the transcriptional repression of tumor suppressor genes. Thus, histone deacetylase inhibitors (HDACis) are powerful drugs, with some already approved for certain hematological cancers. Albeit HDACis show activity in solid tumors as well, further refinement and the development of novel drugs are needed. This review describes the capability of HDACis to influence various pathways and, based on this knowledge, gives a comprehensive overview of various preclinical and clinical studies on solid tumors. A particular focus is placed on strategies for achieving higher efficacy by combination therapies, including phosphoinositide 3-kinase (PI3K)-EGFR inhibitors and hormone- or immunotherapy. This also includes new bifunctional inhibitors as well as novel approaches for HDAC degradation via PROteolysis-TArgeting Chimeras (PROTACs).

Durable Response to Sintilimab and Chidamide in a Patient With Pegaspargase- and Immunotherapy-Resistant NK/T-Cell Lymphoma: Case Report and Literature Review

The prognosis of patients with relapsed/refractory NK/T-cell lymphoma (NKTCL) is dismal. Immunotherapy has showed encouraging anti-tumor activity in patients with asparaginase-resistant NKTCL; however, only a portion of patients benefit and the median response duration is rather short. Treatment strategies have not been identified for immunotherapy-resistant NKTCL. We describe a patient with primary cutaneous NKTCL experienced disease progression after pegaspargase-based chemotherapy and PD-1 inhibitor (sintilimab)-based immunotherapy. Following a combined treatment of sintilimab and the HDAC inhibitor chidamide, the patient achieved a durable complete molecular response with mild toxicity. This case indicates that the combination of PD-1 inhibitor and HDAC inhibitor might be a treatment choice for immunotherapy-resistant NKTCL.