Frequent amplification of HDAC genes and efficacy of HDAC inhibitor chidamide and PD-1 blockade combination in soft tissue sarcoma

Synergistic Immunoregulation: harnessing CircRNAs and PiRNAs to Amplify PD-1/PD-L1 Inhibition Therapy

The utilization of PD-1/PD-L1 inhibitors marks a significant advancement in cancer therapy. However, the efficacy of monotherapy is still disappointing in a substantial subset of patients, necessitating the exploration of combinational strategies. Emerging from the promising results of the KEYNOTE-942 trial, RNA-based therapies, particularly circRNAs and piRNAs, have distinguished themselves as innovative sensitizers to immune checkpoint inhibitors (ICIs). These non-coding RNAs, notable for their stability and specificity, were once underrecognized but are now known for their crucial roles in regulating PD-L1 expression and bolstering anti-cancer immunity. Our manuscript offers a comprehensive analysis of selected circRNAs and piRNAs, elucidating their immunomodulatory effects and mechanisms, thus underscoring their potential as ICIs enhancers. In conjunction with the recent Nobel Prize-awarded advancements in mRNA vaccine technology, our review highlights the transformative implications of these findings for cancer treatment. We also discuss the prospects of circRNAs and piRNAs in future therapeutic applications and research. This study pioneers the synergistic application of circRNAs and piRNAs as novel sensitizers to augment PD-1/PD-L1 inhibition therapy, demonstrating their unique roles in regulating PD-L1 expression and modulating immune responses. Our findings offer a groundbreaking approach for enhancing the efficacy of cancer immunotherapy, opening new avenues for treatment strategies. This abstract aims to encapsulate the essence of our research and the burgeoning role of these non-coding RNAs in enhancing PD-1/PD-L1 inhibition therapy, encouraging further investigation into this promising field.

Regulatory mechanisms of PD-1/PD-L1 in cancers

Immune evasion contributes to cancer growth and progression. Cancer cells have the ability to activate different immune checkpoint pathways that harbor immunosuppressive functions. The programmed death protein 1 (PD-1) and programmed cell death ligands (PD-Ls) are considered to be the major immune checkpoint molecules. The interaction of PD-1 and PD-L1 negatively regulates adaptive immune response mainly by inhibiting the activity of effector T cells while enhancing the function of immunosuppressive regulatory T cells (Tregs), largely contributing to the maintenance of immune homeostasis that prevents dysregulated immunity and harmful immune responses. However, cancer cells exploit the PD-1/PD-L1 axis to cause immune escape in cancer development and progression. Blockade of PD-1/PD-L1 by neutralizing antibodies restores T cells activity and enhances anti-tumor immunity, achieving remarkable success in cancer therapy. Therefore, the regulatory mechanisms of PD-1/PD-L1 in cancers have attracted an increasing attention. This article aims to provide a comprehensive review of the roles of the PD-1/PD-L1 signaling in human autoimmune diseases and cancers. We summarize all aspects of regulatory mechanisms underlying the expression and activity of PD-1 and PD-L1 in cancers, including genetic, epigenetic, post-transcriptional and post-translational regulatory mechanisms. In addition, we further summarize the progress in clinical research on the antitumor effects of targeting PD-1/PD-L1 antibodies alone and in combination with other therapeutic approaches, providing new strategies for finding new tumor markers and developing combined therapeutic approaches.

Advances in molecular targeted drugs in combination with CAR-T cell therapy for hematologic malignancies

Molecular targeted drugs and chimeric antigen receptor (CAR) T cell therapy represent specific biological treatments that have significantly improved the efficacy of treating hematologic malignancies. However, they face challenges such as drug resistance and recurrence after treatment. Combining molecular targeted drugs and CAR-T cells could regulate immunity, improve tumor microenvironment (TME), promote cell apoptosis, and enhance sensitivity to tumor cell killing. This approach might provide a dual coordinated attack on cancer cells, effectively eliminating minimal residual disease and overcoming therapy resistance. Moreover, molecular targeted drugs can directly or indirectly enhance the anti-tumor effect of CAR-T cells by inducing tumor target antigen expression, reversing CAR-T cell exhaustion, and reducing CAR-T cell associated toxic side effects. Therefore, combining molecular targeted drugs with CAR-T cells is a promising and novel tactic for treating hematologic malignancies. In this review article, we focus on analyzing the mechanism of therapy resistance and its reversal of CAR-T cell therapy resistance, as well as the synergistic mechanism, safety, and future challenges in CAR-T cell therapy in combination with molecular targeted drugs. We aim to explore the benefits of this combination therapy for patients with hematologic malignancies and provide a rationale for subsequent clinical studies.

PD-L1 Expression in Neoplastic and Immune Cells of Thymic Epithelial Tumors: Correlations with Disease Characteristics and HDAC Expression

BACKGROUND

Programmed death-ligand 1 (PD-L1) expression in neoplastic and immune cells of the tumor microenvironment determines the efficacy of antitumor immunity, while it can be regulated at the epigenetic level by various factors, including HDACs. In this study, we aim to evaluate the expression patterns of PD-L1 in thymic epithelial tumors (TETs), while we attempt the first correlation analysis between PD-L1 and histone deacetylases (HDACs) expression.

METHODS

Immunohistochemistry was used to evaluate the expression of PD-L1 in tumor and immune cells of 91 TETs with SP263 and SP142 antibody clones, as well as the expressions of HDCA1, -2, -3, -4, -5, and -6.

RESULTS

The PD-L1 tumor proportion score (TPS) was higher, while the immune cell score (IC-score) was lower in the more aggressive TET subtypes and in more advanced Masaoka-Koga stages. A positive correlation between PD-L1 and HDAC-3, -4, and -5 cytoplasmic expression was identified.

CONCLUSIONS

Higher PD-L1 expression in neoplastic cells and lower PD-L1 expression in immune cells of TETs characterizes more aggressive and advanced neoplasms. Correlations between PD-L1 and HDAC expression unravel the impact of epigenetic regulation on the expression of immune checkpoint molecules in TETs, with possible future applications in combined therapeutic targeting.

HDAC inhibitors target IRS4 to enhance anti‑AR therapy in AR‑positive triple‑negative breast cancer

Triple‑negative breast cancer (TNBC) is the most malignant subtype of breast cancer. Androgen receptor (AR) has been identified as a potential therapeutic target for AR‑positive TNBC; however, clinical trials have not yet produced an effective treatment. The present study aimed to identify a novel treatment regimen to improve the prognosis of AR‑positive TNBC. First, a combination of an AR inhibitor (enzalutamide, Enz) and a selective histone deacetylase inhibitor (chidamide, Chid) was used to treat AR‑positive TNBC cell lines, and a synergistic effect of these drugs was observed. The combination treatment inhibited cell proliferation and migration by arresting the cell cycle at the G2/M phase. Subsequently, next‑generation sequencing was performed to detect changes in gene regulation. The results showed that the PI3K/Akt signalling pathway was significantly inhibited by the combination treatment of Enz and Chid. Gene Set Enrichment Analysis revealed that the combination group was significantly enriched in KRAS signalling. Analysis of the associated genes revealed that insulin receptor substrate 4 (IRS4) may have a critical role in blocking the activation of KRAS signalling. In a mouse xenograft model, combination treatment also inhibited the PI3K/Akt signalling pathway by upregulating the expression of IRS4 and thereby suppressing tumour growth. In conclusion, the results of the present study revealed that combination treatment with Enz and Chid can upregulate IRS4, which results in the blocking of KRAS signalling and suppression of tumour growth. It may be hypothesised that the expression levels of IRS4 could be used as a biomarker for screening patients with AR‑positive TNBC using Enz and Chid combination therapy.

HDAC-targeting epigenetic modulators for cancer immunotherapy

HDAC inhibitors, which can inhibit the activity of HDAC enzymes, have been extensively studied in tumor immunotherapy and have shown potential therapeutic effects in cancer immunotherapy. To date, numerous small molecule HDAC inhibitors have been identified, but many of them suffer from limited clinical efficacy and serious toxicity. Hence, HDAC inhibitor-based combination therapies, and other HDAC modulators (e.g. PROTAC degraders, dual-acting agents) have attracted great attention with significant advancements achieved in the past few years due to their superior efficacy compared to single-target HDAC inhibitors. In this review, we overviewed the recent progress on HDAC-based drug discovery with a focus on HDAC inhibitor-based drug combination therapy and other HDAC-targeting strategies (e.g. selective HDAC inhibitors, HDAC-based dual-target inhibitors, and PROTAC HDAC degraders) for cancer immunotherapy. In addition, we also summarized the reported co-crystal structures of HDAC inhibitors in complex with their target proteins and the binding interactions. Finally, the challenges and future directions for HDAC-based drug discovery in cancer immunotherapy are also discussed in detail.

Acetyl-CoA metabolism as a therapeutic target for cancer

Acetyl-coenzyme A (acetyl-CoA), an essential metabolite, not only takes part in numerous intracellular metabolic processes, powers the tricarboxylic acid cycle, serves as a key hub for the biosynthesis of fatty acids and isoprenoids, but also serves as a signaling substrate for acetylation reactions in post-translational modification of proteins, which is crucial for the epigenetic inheritance of cells. Acetyl-CoA links lipid metabolism with histone acetylation to create a more intricate regulatory system that affects the growth, aggressiveness, and drug resistance of malignancies such as glioblastoma, breast cancer, and hepatocellular carcinoma. These fascinating advances in the knowledge of acetyl-CoA metabolism during carcinogenesis and normal physiology have raised interest regarding its modulation in malignancies. In this review, we provide an overview of the regulation and cancer relevance of main metabolic pathways in which acetyl-CoA participates. We also summarize the role of acetyl-CoA in the metabolic reprogramming and stress regulation of cancer cells, as well as medical application of inhibitors targeting its dysregulation in therapeutic intervention of cancers.

Delineating the interplay between oncogenic pathways and immunity in anaplastic Wilms tumors

Wilms tumors are highly curable in up to 90% of cases with a combination of surgery and radio-chemotherapy, but treatment-resistant types such as diffuse anaplastic Wilms tumors pose significant therapeutic challenges. Our multi-omics profiling unveils a distinct desert-like diffuse anaplastic Wilms tumor subtype marked by immune/stromal cell depletion, TP53 alterations, and cGAS-STING pathway downregulation, accounting for one-third of all diffuse anaplastic cases. This subtype, also characterized by reduced CD8 and CD3 infiltration and active oncogenic pathways involving histone deacetylase and DNA repair, correlates with poor clinical outcomes. These oncogenic pathways are found to be conserved in anaplastic Wilms tumor cell models. We identify histone deacetylase and/or WEE1 inhibitors as potential therapeutic vulnerabilities in these tumors, which might also restore tumor immunogenicity and potentially enhance the effects of immunotherapy. These insights offer a foundation for predicting outcomes and personalizing treatment strategies for aggressive pediatric Wilms tumors, tailored to individual immunological landscapes.

HDACs alters negatively to the tumor immune microenvironment in gynecologic cancers

The role of histone deacetylases (HDACs) in the tumor immune microenvironment of gynecologic tumors remains unexplored. We integrated data from The Cancer Genome Atlas and Human Protein Atlas to examine HDAC expression in breast, cervical, ovarian, and endometrial cancers. Elevated HDAC expression correlated with poor prognosis and highly malignant cancer subtypes. Gene Set Enrichment Analysis revealed positive associations between HDAC expression and tumor proliferation signature, while negative associations were found with tumor inflammation signature. Increased HDAC expression was linked to reduced infiltration of natural killer (NK), NKT, and CD8+ T cells, along with negative associations with the expression of PSMB10, NKG7, CCL5, CD27, HLA-DQA1, and HLA-DQB1. In a murine 4T1 breast cancer model, treatment with suberoylanilide hydroxamic acid (SAHA; HDAC inhibitor) and PD-1 antibody significantly inhibited tumor growth and infiltration of CD3+ and CD8+ T cells. Real-time polymerase chain reaction revealed upregulated expressions of Psmb10, Nkg7, Ccl5, Cd8a, Cxcr6, and Cxcl9 genes, while Ctnnb1 and Myc genes were inhibited, indicating tumor suppression and immune microenvironment activation. Our study revealed that HDACs play tumor-promoting and immunosuppressive roles in gynecologic cancers, suggesting HDAC inhibitors as potential therapeutic agents for these cancers.

Pembrolizumab plus vorinostat induces responses in patients with Hodgkin lymphoma refractory to prior PD-1 blockade

This phase 1 study evaluated the addition of vorinostat to pembrolizumab in patients with relapsed/refractory (RR) classical Hodgkin lymphoma (cHL), diffuse large B-cell lymphoma, and follicular lymphoma. We report the results in cases of cHL. Adult patients with RR cHL who had received ≥1 prior lines of therapy and were ineligible for transplantation were treated in a dose-escalation cohort with 2 dose levels (DLs) and then on an expansion cohort at the recommended phase 2 dose (RP2D) in 21-day cycles. Vorinostat 100 mg twice a day (DL1) and 200 mg twice a day (DL2) was administered orally from days 1 to 5 and 8 to 12; all patients received pembrolizumab 200 mg IV every 3 weeks. The primary end point was safety and determination of RP2D. In total, 32 patients with cHL were enrolled, including 30 at DL2 (RP2D); 78% had received prior anti-programmed cell death 1 (anti-PD-1) therapy, and 56% were PD-1 refractory. Grade ≥3 adverse events (AEs) included hypertension (9%), neutropenia (9%), hypophosphatemia (9%), thrombocytopenia (6%), and lymphopenia (6%). Immune-related AEs included grade 1 or 2 thyroiditis (13%), grade 1 rash (6%), and grade 3 esophagitis/duodenitis (3%). The overall response rate (ORR) was 72% and complete response (CR) rate was 34%. Patients refractory to prior PD-1 blockade (n = 18) had ORR and CR rates of 56% and 11%, respectively. Pembrolizumab and vorinostat was well tolerated with a high ORR rate in RR cHL including in anti-PD-1-refractory disease. This trial was registered at www.clinicaltrials.gov as #NCT03150329.

Mocetinostat activates Krüppel-like factor 4 and protects against tissue destruction and inflammation in osteoarthritis

Osteoarthritis (OA) is the most common joint disorder, and disease-modifying OA drugs (DMOADs) represent a major need in OA management. Krüppel-like factor 4 (KLF4) is a central transcription factor upregulating regenerative and protective functions in joint tissues. This study was aimed to identify small molecules activating KLF4 expression and to determine functions and mechanisms of the hit compounds. High-throughput screening (HTS) with 11,948 clinical-stage compounds was performed using a reporter cell line detecting endogenous KLF4 activation. Eighteen compounds were identified through the HTS and confirmed in a secondary screen. After testing in SW1353 chondrosarcoma cells and human chondrocytes, mocetinostat - a class I selective histone deacetylase (HDAC) inhibitor - had the best profile of biological activities. Mocetinostat upregulated cartilage signature genes in human chondrocytes, meniscal cells, and BM-derived mesenchymal stem cells, and it downregulated hypertrophic, inflammatory, and catabolic genes in those cells and synoviocytes. I.p. administration of mocetinostat into mice reduced severity of OA-associated changes and improved pain behaviors. Global gene expression and proteomics analyses revealed that regenerative and protective effects of mocetinostat were dependent on peroxisome proliferator-activated receptor γ coactivator 1-α. These findings show therapeutic and protective activities of mocetinostat against OA, qualifying it as a candidate to be used as a DMOAD.

The anti-PD-1 era of cervical cancer: achievement, opportunity, and challenge

Cervical cancer is one of the three major female gynecological malignancies, becoming a major global health challenge. Although about 90% of early-stage patients can be cured by surgery, advanced-stage patients still need new treatment methods to improve their efficacy, especially for those with recurrence and metastasis tumors. Anti-PD-1 is currently the most widely used immune checkpoint inhibitor, which has revolutionized cancer therapy for different types of cancer. Pembrolizumab has been approved for second-line treatment of R/M CC but has a modest overall response rate of about 15%. Therefore, multiple types of anti-PD-1 have entered clinical trials successively and evaluated the efficacy in combination with chemotherapy, targeted therapy, and immunotherapy. At the same time, the dual specific antibody of PD-1/CTLA-4 was also used in clinical trials of cervical cancer, and the results showed better than anti-PD-1 monotherapy. In addition, anti-PD-1 has also been shown to sensitize radiotherapy. Therefore, understanding the current research progress of anti-PD-1 will better guide clinical application. This review summarizes ongoing clinical trials and published studies of anti-PD-1 monotherapy and combination therapy in the treatment of cervical cancer, as well as discusses the potential molecular biological mechanisms of combination, aiming to provide the basic evidence for support anti-PD-1 in the treatment of cervical cancer and new insights in combination immunotherapy.

Identification of novel and potent dual-targeting HDAC1/SPOP inhibitors using structure-based virtual screening, molecular dynamics simulation and evaluation of in vitro and in vivo antitumor activity

Cancer is one of the important factors threatening human health. Hence, it is essential to create novel potent drugs to treat it. Due to the strong correlation among histone deacetylase1 (HDAC1), speckle-type POZ protein (SPOP) and cancers, dual inhibition of HDAC1 and SPOP may be a promising strategy for cancer treatment. In this study, we successfully identified four potential dual-targeting HDAC1/SPOP candidate compounds with structure-based virtual screening. In vitro inhibition experiments confirmed that the four compounds had dual inhibitory effects on HDAC1 and SPOP. Among them, compound HS-2 had a stronger inhibitory effect on HDAC1 and SPOP than the positive controls. Further molecular dynamics simulations indicated that HS-2 could stably bind to HDAC1 and SPOP. In addition, MTT assay indicated that HS-2 inhibited the growth of tumor cells in the micromolar range. In vivo evaluation showed that HS-2 could obviously inhibit the growth of tumor in nude mice without obvious toxicity. These findings suggest that HS-2 is a novel and potent dual-targeting HDAC1/SPOP inhibitor for cancer treatment.

HDAC inhibitors enhance the anti-tumor effect of immunotherapies in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common liver malignancy with a poor prognosis and increasing incidence, remains a serious health problem worldwide. Immunotherapy has been described as one of the ideal ways to treat HCC and is transforming patient management. However, the occurrence of immunotherapy resistance still prevents some patients from benefiting from current immunotherapies. Recent studies have shown that histone deacetylase inhibitors (HDACis) can enhance the efficacy of immunotherapy in a variety of tumors, including HCC. In this review, we present current knowledge and recent advances in immunotherapy-based and HDACi-based therapies for HCC. We highlight the fundamental dynamics of synergies between immunotherapies and HDACis, further detailing current efforts to translate this knowledge into clinical benefits. In addition, we explored the possibility of nano-based drug delivery system (NDDS) as a novel strategy to enhance HCC treatment.

Undifferentiated pleomorphic sarcoma of the breast with neoplastic fever: case report and genomic characterization

PURPOSE

Primary breast sarcomas are extraordinary rare, in particular undifferentiated pleomorphic sarcoma (UPS). UPS with neoplastic fever (UPS-NF) of the breast has not been reported yet. Here, we present an extended UPS-NF of the breast including its comprehensive molecular workup.

METHODS

A 58-year-old female presented with general malaise, fever spikes, weight loss, and a massively swollen left breast. C-reactive protein and blood leucocytes were significantly increased. However, repeated blood cultures and smears were all sterile. Histopathology of the abscess-forming tumor revealed an undifferentiated malignancy with numerous of tumor giant cells as well as spindle-shaped cells with nuclear pleomorphism and hyperchromasia. Immunohistochemistry demonstrated partial, patchy desmin staining and weak heterogonous neuron-specific enolase immunoreactivity of tumor cells, but a focal staining for Melan-A.

RESULTS

Neither common melanoma driver mutations nor an ultraviolet mutational signature was detected by whole genome sequencing. Using FISH and RT-PCR we also excluded translocations characteristic for clear cell sarcoma. Thus, the diagnosis of inflammatory UPS-NF of the breast was considered highly probable. Despite a complete mastectomy, the tumor recurred after only three months. This recurrence was treated with a combination of ipilimumab and nivolumab based on the primary tumor's TPS score for PD-L1 of 30%. After an initial response, however, the tumor was progressive again.

CONCLUSION

We describe here the first case of UPS-NF of the breast, which shows great clinical and histopathologic resemblances to previously reported UPS-NF of other anatomic localizations.

Case report: Targeting the PD-1 receptor and genetic mutations validated in primary histiocytic sarcoma with hemophagocytic lymphohistiocytosis

Histiocytic sarcoma (HS) is a rare hematological malignancy with limited treatment options, and it is also prone to complications such as hemophagocytic lymphohistiocytosis (HLH) in the later stages of the disease, leading to difficulties in treatment and poor prognosis. It highlights the importance of developing novel therapeutic agents. Herein, we present a case of a 45-year-old male patient who was diagnosed with PD-L1-positive HS with HLH. The patient was admitted to our hospital with recurrent high fever, multiple skin rashes with pruritus throughout the body and enlarged lymph nodes. Subsequently, pathological biopsy of the lymph nodes revealed high expression of CD163, CD68, S100, Lys and CD34 in the tumor cells and no expression of CD1a and CD207, confirming this rare clinical diagnosis. Concerning the low remission rate by conventional treatment in this disease, the patient was administered with sintilimab (an anti-programmed cell death 1 [anti-PD-1] monoclonal antibody) at 200 mg/d combined with a first-line chemotherapy regimen for one cycle. Further exploration of pathological biopsy by using next-generation gene sequencing led to the use of targeted therapy of chidamide. After one cycle of combination therapy (chidamide+sintilimab, abbreviated as CS), the patient achieved a favorable response. The patient showed remarkable improvement in the general symptoms and laboratory examination results (e.g., elevated indicators of inflammation); even the clinical benefits was not persistent, he survived one more month after his cessation of treatment by himself due to economic difficulty. Our case suggests that PD-1 inhibitor coupled with targeted therapy might constitute a potential therapeutic option for primary HS with HLH.

Targeted Epigenetic Interventions in Cancer with an Emphasis on Pediatric Malignancies

Over the past two decades, novel hallmarks of cancer have been described, including the altered epigenetic landscape of malignant diseases. In addition to the methylation and hyd-roxymethylation of DNA, numerous novel forms of histone modifications and nucleosome remodeling have been discovered, giving rise to a wide variety of targeted therapeutic interventions. DNA hypomethylating drugs, histone deacetylase inhibitors and agents targeting histone methylation machinery are of distinguished clinical significance. The major focus of this review is placed on targeted epigenetic interventions in the most common pediatric malignancies, including acute leukemias, brain and kidney tumors, neuroblastoma and soft tissue sarcomas. Upcoming novel challenges include specificity and potential undesirable side effects. Different epigenetic patterns of pediatric and adult cancers should be noted. Biological significance of epigenetic alterations highly depends on the tissue microenvironment and widespread interactions. An individualized treatment approach requires detailed genetic, epigenetic and metabolomic evaluation of cancer. Advances in molecular technologies and clinical translation may contribute to the development of novel pediatric anticancer treatment strategies, aiming for improved survival and better patient quality of life.

Histone Deacetylase Inhibitor Panobinostat Benefits the Therapeutic Efficacy of Oncolytic Herpes Simplex Virus Combined with PD-1/PD-L1 Blocking in Glioma and Squamous Cell Carcinoma Models

BACKGROUND

Combination therapy has been widely explored for oncolytic virus (OV), as it can be met with tumor resistance. The HDAC inhibitor (HDACi) panobinostat is a potent pan-deacetylase inhibitor which blocks multiple cancer-related pathways and reverses epigenetic events in cancer progression.

METHODS

In this study, oncolytic activity in vitro and antitumor therapeutic efficacy in vivo when combined with oHSV and panobinostat were investigated.

RESULTS

(1) Treatment with panobinostat enhanced oHSV propagation and cytotoxicity in human glioma A172 and squamous cell carcinoma SCC9 cells. (2) Combined treatment with oHSV and panobinostat enhanced virus replication mediated by the transcriptional downregulation of IFN-β- and IFN-responsive antiviral genes in human glioma A172 and squamous cell carcinoma SCC9 cells. (3) Panobinostat treatment induced upregulation of PD-L1 expression in both glioma and squamous cell carcinoma cells. (4) A significantly enhanced therapeutic efficacy was shown in vivo for the murine glioma CT-2A and squamous cell carcinoma SCC7 models when treated with a combination of oHSV, including PD-1/PD-L1 blockade and HDAC inhibition.

CONCLUSIONS

Consequently, these data provide some new clues for the clinical development of combination therapy with OVs, epigenetic modifiers, and checkpoint blockades for glioma and squamous cell carcinoma.

Strategies to enhance CAR-T persistence

Chimeric antigen receptor T (CAR-T) cell therapy has significantly improved the life expectancy for patients with refractory or relapse B cell lymphoma. As for B cell acute lymphoblastic leukemia (B-ALL), although the primary response rate is promising, the high incidence of early relapse has caused modest long-term survival with CAR-T cell alone. One of the main challenges is the limited persistence of CAR-T cells. To further optimize the clinical effects of CAR-T cells, many studies have focused on modifying the CAR structure and regulating CAR-T cell differentiation. In this review, we focus on CAR-T cell persistence and summarize the latest progress and strategies adopted during the in vitro culture stage to optimize CAR-T immunotherapy by improving long-term persistence. Such strategies include choosing a suitable cell source, improving culture conditions, combining CAR-T cells with conventional drugs, and applying genetic manipulations, all of which may improve the survival of patients with hematologic malignancies by reducing the probability of recurrence after CAR-T cell infusion and provide clues for solid tumor CAR-T cell therapy development.

Optimized dose selective HDAC inhibitor tucidinostat overcomes anti-PD-L1 antibody resistance in experimental solid tumors

BACKGROUND

Although immune checkpoint inhibitors (ICIs) have influenced the treatment paradigm for multiple solid tumors, increasing evidence suggests that primary and adaptive resistance may limit the long-term efficacy of ICIs. New therapeutic strategies with other drug combinations are hence warranted to enhance the antitumor efficacy of ICIs. As a novel tumor suppressor, histone deacetylase (HDAC) inhibitor tucidinostat has been successfully confirmed to act against hematological malignancies. However, the underlying mechanisms of action for tucidinostat and whether it can manipulate the tumor microenvironment (TME) in solid tumors remain unclear.

METHODS

Three murine tumor models (4T1, LLC, and CT26) were developed to define the significant role of different doses of tucidinostat in TME. The immunotherapeutic effect of tucidinostat combined with anti-programmed cell death ligand 1 antibody (aPD-L1) was demonstrated. Furthermore, the effect of tucidinostat on phenotypic characteristics of peripheral blood mononuclear cells (PBMCs) from lung cancer patients was investigated.

RESULTS

With an optimized dose, tucidinostat could alter TME and promote the migration and infiltration of CD8⁺ T cells into tumors, partially by increasing the activity of C-C motif chemokine ligand 5 (CCL5) via NF-κB signaling. Moreover, tucidinostat significantly promoted M1 polarization of macrophages and increased the in vivo antitumor efficacy of aPD-L1. Tucidinostat also enhanced the expression of the costimulatory molecules on human monocytes, suggesting a novel and improved antigen-presenting function.

CONCLUSIONS

A combination regimen of tucidinostat and aPD-L1 may work synergistically to reduce tumor burden in patients with cancer by enhancing the immune function and provided a promising treatment strategy to overcome ICI treatment resistance.

FOXP3+ regulatory T cells and the immune escape in solid tumours

FOXP3+ regulatory T (Treg) cells play critical roles in establishing the immunosuppressive tumour microenvironment, which is achieved and dynamically maintained with the contribution of various stromal and immune cell subsets. However, the dynamics of non-lymphoid FOXP3+ Treg cells and the mutual regulation of Treg cells and other cell types in solid tumour microenvironment remains largely unclear. In this review, we summarize the latest findings on the dynamic connections and reciprocal regulations of non-lymphoid Treg cell subsets in accordance with well-established and new emerging hallmarks of cancer, especially on the immune escape of tumour cells in solid tumours. Our comprehension of the interplay between FOXP3+ Treg cells and key hallmarks of cancer may provide new insights into the development of next-generation engineered T cell-based immune treatments for solid tumours.

Sintilimab combined with chidamide in the treatment of extranodal nature killer/T-cell lymphoma with secondary hemophagocytic lymphohistiocytosis: Two case reports and literature review

RATIONALE

Extranodal nature killer/T-cell lymphoma (ENKTL) failing in asparaginase-containing treatments is fatal, it has a higher mortality rate when accompanied by secondary hemophagocytic lymphohistiocytosis (HLH). The study reported 2 ENKTL-related HLH patients.

PATIENT CONCERNS

Patient 1 visited for nasal congestion and runny nose for 6 months then got a fever and serious myelosuppression after P-GEP (pegaspargase, gemcitabine, etoposide, and methylprednisolone) chemotherapy. Patient 2 complained of painless lymphadenectasis in the right neck for 4 months and experienced recurrent fever and poor performance status after 3 cycles of P-Gemox (pegaspargase, gemcitabine, and oxaliplatin) chemotherapy.

DIAGNOSES

Patient 1 and patient 2 were diagnosed as ENKTL failing in asparaginase-based chemotherapy and involving secondary HLH.

INTERVENTIONS

The dose of chidamide was 20 mg twice a week for 2 weeks and sintilimab was 200 mg once every 3 weeks.

OUTCOMES

ENKTL was relieved and the HLH was resolved after the therapy of sintilimab and chidamide. The patients had achieved durable survival without immune-related adverse events.

LESSONS

ENKTL-related HLH needs early diagnosis and treatment. The combined strategy of sintilimab plus chidamide help deal with HLH and solve ENKTL, it may be a useful treatment option for ENKTL-related HLH.

Therapeutic potential of tucidinostat, a subtype-selective HDAC inhibitor, in cancer treatment

Histone deacetylase (HDAC) is one of the most characterized epigenetic modifiers, modulating chromatin structure and gene expression, which plays an important role in cell cycle, differentiation and apoptosis. Dysregulation of HDAC promotes cancer progression, thus inhibitors targeting HDACs have evidently shown therapeutic efficacy in multiple cancers. Tucidinostat (formerly known as chidamide), a novel subtype-selective HDAC inhibitor, inhibits Class I HDAC1, HDAC2, HDAC3, as well as Class IIb HDAC10. Tucidinostat is approved in relapsed or refractory (R/R) peripheral T-cell lymphoma (PTCL), advanced breast cancer and R/R adult T-cell leukemia-lymphoma (ATLL). Compared with other HDAC inhibitors, tucidinostat shows notable antitumor activity, remarkable synergistic effect with immunotherapy, and manageable toxicity. Here, we comprehensively summarize recent advances in tucidinostat as both monotherapy and a regimen of combination therapy in both hematological and solid malignancies in clinic. Further studies will endeavor to identify more combination strategies with tucidinostat and to identify specific clinical biomarkers to predict the therapeutic effect.

Panobinostat enhances NK cell cytotoxicity in soft tissue sarcoma

Sarcoma is a rare and heterogeneous class of mesenchymal malignancies with poor prognosis. Panobinostat (LBH589) as one of histone deacetylase (HDAC) inhibitors, has demonstrated anti-tumor activity in patients with sarcoma, but its mechanisms remains unclear. Here, we found that LBH589 alone inhibited the proliferation and colony formation of soft tissue sarcoma(STS) cell lines. Transcriptome analysis showed that treatment with LBH589 augmented the NK cell mediated cytotoxicity. Quantitative real-time PCR and flow cytometric analysis (FACS) further confirmed that LBH589 increased the expression of NKG2D ligands MICA/MICB. Mechanistically, LBH589 activated the Wnt/β-catenin pathway by upregulating the histone acetylation in β-catenin promoter. In vitro co-culture experiments and in vivo animal experiments showed that LBH589 increased the cytotoxicity of natural killer (NK) cells while Wnt/β-catenin inhibitor decreased the effects. Our findings suggests that LBH589 facilitates the anti-tumor effect of NK cells, highlights LBH589 an effective assistance drug in NK cell-based immunotherapies.

Chidamide and sintilimab combination in diffuse large B-cell lymphoma progressing after chimeric antigen receptor T therapy

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is curable with first-line chemoimmunotherapy but patients with relapsed/refractory (R/R) DLBCL still face a poor prognosis. For patients with R/R DLBCL, the complete response rate to traditional next-line therapy is only 7% and the median overall survival is 6.3 mo. Recently, CD19-targeting chimeric antigen receptor T cells (CAR-T) have shown promise in clinical trials. However, approximately 50% of patients treated with CAR-T cells ultimately progress and few salvage therapies are effective.

CASE SUMMARY

Here, we report on 7 patients with R/R DLBCL whose disease progressed after CAR-T infusion. They received a PD-1 inhibitor (sintilimab) and a histone deacetylase inhibitor (chidamide). Five of the 7 patients tolerated the treatment without any serious adverse events. Two patients discontinued the treatment due to lung infection and rash. At the 20-mo follow-up, the median overall survival of these 7 patients was 6 mo. Of note, there were 2 complete response rates (CRs) and 2 partial response rates (PRs) during this novel therapy, with an overall response rate (ORR) of 57.1%, and one patient had a durable CR that lasted at least 20 mo.

CONCLUSION

In conclusion, chidamide combined with sintilimab may be a choice for DLBCL patients progressing after CD19-targeting CAR-T therapy.

DNTTIP1 promotes nasopharyngeal carcinoma metastasis via recruiting HDAC1 to DUSP2 promoter and activating ERK signaling pathway

Background

Distant metastasis remains the leading cause of treatment failure in patients with nasopharyngeal carcinoma (NPC), making it critical to identify efficient therapeutic targets for metastatic NPC. Previous studies have demonstrated that deoxynucleotidyltransferase terminal-interacting protein 1 (DNTTIP1) is associated with the development of various types of cancer. However, its role and mechanism in NPC have not been explored.

Methods

RNA-seq profiling was performed for three pairs of NPC and normal nasopharynx tissues. DNTTIP1 expression in NPC specimens was detected by immunohistochemistry. In vitro and in vivo assays were used to investigate the function of DNTTIP1. The molecular mechanism was determined using RT-qPCR, western blotting, RNA-seq, luciferase reporter assays, ChIP assays, and co-IP assays.

Findings

DNTTIP1 was found to be significantly upregulated in NPC tissues. Furthermore, DNTTIP1 promoted NPC growth and metastasis in vitro and in vivo. Upregulation of DNTTIP1 in NPC indicated poor clinical outcomes. Mechanistically, DNTTIP1 suppressed DUSP2 gene expression via recruiting HDAC1 to its promoter and maintaining a deacetylated state of histone H3K27. The downregulation of DUSP2 resulted in aberrant activation of the ERK signaling and elevated MMP2 levels, promoting NPC metastasis. Chidamide, an HDAC inhibitor, was shown to suppress NPC metastasis by regulating the DNTTIP1/HDAC1-DUSP2 axis.

Interpretation

Our findings demonstrate that DNTTIP1 not only regulates NPC metastasis but also independently predicts NPC prognosis. Furthermore, targeting DNTTIP1/HDAC1 by Chidamide may benefit NPC patients with metastasis.

Funding

This work was supported by the National Natural Science Foundation of China (No. 81872464, 82073243).

Local hyperthermia combined with chemotherapy for the treatment of multiple recurrences of undifferentiated pleomorphic sarcoma: A case report

BACKGROUND

Undifferentiated pleomorphic sarcoma (UPS) is a type of soft tissue sarcoma, the histologic origin and differentiation direction of which are still unclear. There are few treatment options for UPS other than surgery. Herein we describe a patient who had multiple recurrences of UPS postoperatively, but R0 resection was achieved by local hyperthermia combined with chemotherapy, thus providing a new treatment approach for similar situations.

CASE SUMMARY

A 65-year-old man sought evaluation from a physician for a mass on his right back. After surgery, the pathologic diagnosis was fibrosarcoma. During the follow-up evaluations until 2021, the patient had four relapses of varying degrees. Postoperative pathology confirmed the recurrence of UPS on the right back. In March 2021, he underwent local hyperthermia combined with two cycles of chemotherapy for recurring lesions. After magnetic resonance imaging re-examination and preoperative examination, the patient chose surgery again. During the operation, the tumors were easy to excise, the amount of bleeding decreased significantly, and the pathologic evaluation confirmed that one of the specimens was an R0 excision.

CONCLUSION

Local hyperthermia combined with chemotherapy enables R0 resection to be achieved in patients with advanced UPS recurrence.

Local hyperthermia combined with chemotherapy for the treatment of multiple recurrences of undifferentiated pleomorphic sarcoma: A case report

BACKGROUND

Undifferentiated pleomorphic sarcoma (UPS) is a type of soft tissue sarcoma, the histologic origin and differentiation direction of which are still unclear. There are few treatment options for UPS other than surgery. Herein we describe a patient who had multiple recurrences of UPS postoperatively, but R0 resection was achieved by local hyperthermia combined with chemotherapy, thus providing a new treatment approach for similar situations.

CASE SUMMARY

A 65-year-old man sought evaluation from a physician for a mass on his right back. After surgery, the pathologic diagnosis was fibrosarcoma. During the follow-up evaluations until 2021, the patient had four relapses of varying degrees. Postoperative pathology confirmed the recurrence of UPS on the right back. In March 2021, he underwent local hyperthermia combined with two cycles of chemotherapy for recurring lesions. After magnetic resonance imaging re-examination and preoperative examination, the patient chose surgery again. During the operation, the tumors were easy to excise, the amount of bleeding decreased significantly, and the pathologic evaluation confirmed that one of the specimens was an R0 excision.

CONCLUSION

Local hyperthermia combined with chemotherapy enables R0 resection to be achieved in patients with advanced UPS recurrence.

Epigenetic Modification of PD-1/PD-L1-Mediated Cancer Immunotherapy against Melanoma

Malignant melanoma is one of the representative skin cancers with unfavorable clinical behavior. Immunotherapy is currently used for the treatment, and it dramatically improves clinical outcomes in patients with advanced malignant melanoma. On the other hand, not all these patients can obtain therapeutic efficacy. To overcome this limitation of current immunotherapy, epigenetic modification is a highlighted issue for clinicians. Epigenetic modification is involved in various physiological and pathological conditions in the skin. Recent studies identified that skin cancer, especially malignant melanoma, has advantages in tumor development, indicating that epigenetic manipulation for regulation of gene expression in the tumor can be expected to result in additional therapeutic efficacy during immunotherapy. In this review, we focus on the detailed molecular mechanism of epigenetic modification in immunotherapy, especially anti-PD-1/PD-L1 antibody treatment for malignant melanoma.

Establishment and Characterization of NCC-MFS5-C1: A Novel Patient-Derived Cell Line of Myxofibrosarcoma

Myxofibrosarcoma (MFS) is a highly aggressive malignancy with complex karyotypes and a postoperative recurrence tendency, owing to its strong invasiveness. Although systemic chemotherapy is considered in patients with unresectable MFS, the efficacy of conventional chemotherapy is hitherto unclear. Recently, drug screening analysis using a large number of tumor cell lines has been attempted to discover novel therapeutic candidate drugs for common cancers. However, the number of MFS cell lines is extremely small because of its low incidence-this hinders the conduction of screening studies and slows down the development of therapeutic drugs. To overcome this problem, we established a novel MFS cell line, NCC-MFS5-C1, which was shown to harbor typical MFS genetic abnormalities and thus had useful properties for in vitro studies. We conducted the largest integrated screening analysis of 210 drugs using NCC-MFS5-C1 cells along with four MFS cell lines, which we previously reported. Bortezomib (a proteasome inhibitor) and romidepsin (a histone deacetylase inhibitor) showed stronger antitumor effects than the standard drug, doxorubicin. Therefore, the NCC-MFS5-C1 cell line can potentially contribute to elucidating MFS pathogenesis and developing a novel MFS treatment.

The diagnostic utility of DNA copy number analysis of core needle biopsies from soft tissue and bone tumors

Morphologic and immunohistochemical analysis of preoperative core needle biopsies (CNB) is important in the management of patients with soft tissue and bone tumors (STBTs). Most SBTB subtypes have more or less extensive DNA copy number aberrations (CNA), potentially providing useful diagnostic information. To evaluate the technical feasibility of single nucleotide polymorphism (SNP) array analysis and the diagnostic usefulness of the copy number profiles, we studied CNBs from 171 patients with suspected STBTs. SNP array analysis could be performed on 168 (98%) of the samples. The CNA profile was compatible with the CNB diagnosis in 87% of the cases. Discrepant cases were dominated by false-negative results due to nonrepresentative material or contamination with normal cells. 70 genomic profiles were indicative of specific histopathologic tumor entities and in agreement with the corresponding CNB diagnoses in 83%. In 96 of the cases with aberrant CNA profiles, the SNP profiles were of sufficient quality for segmentation, allowing clustering analysis on the basis of the Jaccard similarity index. The analysis of these segment files showed three major CNA clusters, based on the complexity levels and the predominance of gains versus losses. For 43 of these CNB samples, we had SNP array data also from their corresponding surgical samples. In 33 of these pairs, the two corresponding samples clustered next to each other, with Jaccard scores ranging from 0.61 to 0.99 (median 0.96). Also, for those tumor pairs that did not cluster together, the Jaccard scores were relatively high (median 0.9). 10 cases showed discrepant results, mainly due to varying degrees of normal cell contamination or technical issues. Thus, the copy number profile seen in a CNB is typically highly representative of the major cell population in the tumor.

Epigenetics of Cutaneous Sarcoma

Epigenetic changes influence various physiological and pathological conditions in the human body. Recent advances in epigenetic studies of the skin have led to an appreciation of the importance of epigenetic modifications in skin diseases. Cutaneous sarcomas are intractable skin cancers, and there are no curative therapeutic options for the advanced forms of cutaneous sarcomas. In this review, we discuss the detailed molecular effects of epigenetic modifications on skin sarcomas, such as dermatofibrosarcoma protuberans, angiosarcoma, Kaposi's sarcoma, leiomyosarcoma, and liposarcoma. We also discuss the application of epigenetic-targeted therapy for skin sarcomas.

Preclinical Evaluation of the HDAC Inhibitor Chidamide in Transformed Follicular Lymphoma

The key factors leading to transformed follicular lymphoma (t-FL) include the aberrations of epigenetic modifiers as early and driving events, especially mutations in the gene encoding for histone acetyltransferase. Therefore, reversal of this phenomenon by histone deacetylase (HDAC) inhibitors is essential for the development of new treatment strategies in t-FL. Several t-FL cell lines were treated with various doses of chidamide and subjected to cell proliferation, apoptosis and cell cycle analyses with CCK-8 assay, Annexin V/PI assay and flow cytometry, respectively. Chidamide dose-dependently inhibited cell proliferation, caused G0/G1 cycle arrest and triggered apoptosis in t-FL cells. In addition, the effects of chidamide on tumor growth were evaluated in vivo in xenograft models. RNA-seq analysis revealed gene expression alterations involving the PI3K-AKT signaling pathway might account for the mechanism underlying the antitumor activity of chidamide as a single agent in t-FL. These findings provide a basis for further clinical exploration of chidamide as a promising treatment for FL.

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.

Establishment and Characterization of NCC-DDLPS4-C1: A Novel Patient-Derived Cell Line of Dedifferentiated Liposarcoma

Dedifferentiated liposarcoma (DDLPS) is a highly malignant sarcoma characterized by the co-amplification of MDM2 and CDK4. Although systemic chemotherapy is recommended for unresectable or metastatic cases, DDLPS is insensitive to conventional chemotherapy, leading to an unfavorable prognosis. Therefore, novel treatment methods are urgently required. Patient-derived cell lines are essential in preclinical studies. Recently, large-scale screening studies using a number of cell lines have been actively conducted for the development of new therapeutic drugs. However, the DDLPS cell line cannot be obtained from public cell banks owing to its rarity, hindering screening studies. As such, novel DDLPS cell lines need to be established. Accordingly, this study aimed to establish a novel DDLPS cell line from surgical specimens. The cell line was named NCC-DDLPS4-C1. NCC-DDLPS4-C1 cells retained copy number alterations corresponding to the original tumors. Further, the cells demonstrated constant growth, spheroid formation, and equivalent invasiveness to MG63 osteosarcoma cells. We also conducted drug screening and integrated the results with those of the previously reported DDLPS cell lines. Consequently, we identified the histone deacetylase inhibitor romidepsin as a novel candidate drug. In conclusion, the NCC-DDLPS4-C1 cell line is a useful tool for the basic study of DDLPS.

Glycogen Metabolism Predicts the Efficacy of Immunotherapy for Urothelial Carcinoma

Urothelial cancer (UC) is one of the common refractory tumors and chemotherapy is the primary treatment for it. The advent of immune checkpoint inhibitors (ICI) has facilitated the development of treatment strategies for UC patients. To screen out UC patients sensitive to ICI, researchers have proposed that PD-L1, tumor mutation burden and TCGA molecular subtypes can be used as predictors of ICI efficacy. However, the performance of these predictors needs further validation. We need to identify novel biomarkers to screen out UC patients sensitive to ICI. In our study, we collected the data of two clinical cohorts: the ICI cohort and the TCGA cohort. The result of the multivariate Cox regression analysis showed that glycogen metabolism score (GMS) (HR = 1.26, p = 0.017) was the negative predictor of prognosis for UC patients receiving ICI treatment. Low-GMS patients had a higher proportion of patients achieving complete response or partial response to ICI. After the comparison of gene mutation status between high-GMS and low-GMS patients, we identified six genes with significant differences in mutation frequencies, which may provide new directions for potential drug targets. Moreover, we analyzed the immune infiltration status and immune-related genes expression between high-GMS and low-GMS patients. A reduced proportion of tumor-associated fibroblasts and elevated proportion of CD8⁺ T cells can be observed in low-GMS patients while several immunosuppressive molecules were elevated in the high-GMS patients. Using the sequencing data of the GSE164042 dataset, we also found that myeloid-derived suppressor cell and neutrophil related signature scores were lower in α-glucosidase knockout bladder carcinoma cells when compared to the control group. In addition, angiogenesis, classic carcinogenic pathways, immunosuppressive cells related pathways and immunosuppressive cytokine secretion were mainly enriched in high-GMS patients and cell samples from the control group. Finally, we suspected that the combination treatment of ICI and histone deacetylase inhibitors may achieve better clinical responses in UC patients based on the analysis of drug sensitivity data. In conclusion, our study revealed the predictive value of GMS for ICI efficacy of UC patients, providing a novel perspective for the exploration of new drug targets and potential treatment strategies.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Unraveling the Epigenetic Role and Clinical Impact of Histone Deacetylases in Neoplasia

Histone deacetylases (HDACs) have long been implicated in tumorigenesis and tumor progression demonstrating their important participation in neoplasia. Therefore, numerous studies have been performed, highlighting the mechanism of HDACs action in tumor cells and demonstrating the potential role of HDAC inhibitors in the treatment of different cancer types. The outcome of these studies further delineated and strengthened the solid role that HDACs and epigenetic modifications exert in neoplasia. These results have spread promise regarding the potential use of HDACs as prospective therapeutic targets. Nevertheless, the clinical significance of HDAC expression and their use as biomarkers in cancer has not been extensively elucidated. The aim of our study is to emphasize the clinical significance of HDAC isoforms expression in different tumor types and the correlations noted between the clinicopathological parameters of tumors and patient outcomes. We further discuss the obstacles that the next generation HDAC inhibitors need to overcome, for them to become more potent.

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.