Increased PRAME-specific CTL killing of acute myeloid leukemia cells by either a novel histone deacetylase inhibitor chidamide alone or combined treatment with decitabine

Chidamide enhances T-cell-mediated anti-tumor immune function by inhibiting NOTCH1/NFATC1 signaling pathway in ABC-type diffuse large B-cell lymphoma

Chidamide (CS055/HBI-8000, tucidinostat) has shown promising effects in the clinical treatment of various hematologic tumors. Diffuse large B-cell lymphoma (DLBCL) has shown highly heterogeneous biological characteristics. There are complex mechanisms of the role of chidamide in DLBCL for in-depth study. It is essential to probe further into the mechanism of drug-tumor interactions as a guide to clinical application and to understand the occurrence and progression of DLBCL. In vitro and in vivo models were utilized to determine the effects of chidamide on signaling pathways involved in the DLBCL tumor microenvironment. The experimental results show that chidamide inhibited the proliferation of DLBCL cell lines in a dose- and time-dependent manner, and down-regulated the expression of NOTCH1 and NFATC1 in DLBCL cells as well as decreased the concentration of IL-10 in the supernatant. In addition, chidamide significantly lowered the expression of PD1 or TIM3 on CD4+T cells and CD8+T cells and elevated the levels of IL-2, IFN-γ, and TNF-α in the serum of animal models, which augmented the function of circulating T cells and tumor-infiltrating T cells and ultimately significantly repressed the growth of tumors. These findings prove that chidamide can effectively inhibit the cell activity of DLBCL cell lines by inhibiting the activation of NOTCH1 and NFATC1 signaling pathways. It can also improve the abnormal DLBCL microenvironment in which immune escape occurs, and inhibit immune escape. This study provides a new therapeutic idea for the exploration of individualized precision therapy for patients with malignant lymphoma.

Tucidinostat Plus Exemestane as a Neoadjuvant in Early-Stage, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer

BACKGROUND

To assess the efficacy and safety of tucidinostat plus exemestane as a neoadjuvant strategy in early-stage breast cancer.

METHODS

This prospective, open-label, single-arm phase II trial enrolled patients with stage II-III breast cancer with hormone receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative. Eligible patients received tucidinostat plus exemestane, and then breast-conserving surgery (BCS) or modified radical mastectomy.

RESULTS

Among 20 enrolled patients, 3 of them achieved preoperative endocrine prognostic index (PEPI) score of 0. Additionally, complete cell cycle arrest was observed in 7, radiologic objective response rate in 10, and disease control rate in 20 patients, pathological complete response in 1 patient, and 5 patients performed BCS. Ki67 suppression from baseline to surgery was observed in 17 of patients, with the Ki67 change ratio of -73.5%. Treatment-emergent adverse event included neutropenia, leukopenia, thrombocytopenia, lymphopenia, hypoalbuminemia, aspartate aminotransferase elevation, glutamyl transpeptidase elevation, anemia, and alanine aminotransferase elevation.

CONCLUSIONS

Despite the rate of PEPI score 0 was not high, tucidinostat plus exemestane as a neoadjuvant therapy might be well tolerated and showed promising clinical responses in patients with early hormone receptor-positive, HER2-negative breast cancer. To clarify the safety and efficacy of this strategy, further investigation is warranted.

CLINICAL TRIAL REGISTRATION

ChiCTR2100046678.

Chidamide plus envafolimab as subsequent treatment in advanced non-small cell lung cancer patients resistant to anti-PD-1 therapy: A multicohort, open-label, phase II trial with biomarker analysis

BACKGROUND

Combination of chidamide and anti-PD-L1 inhibitor produce synergistic anti-tumor effect in advanced NSCLC patients resistant to anti-PD-1 treatment. However, the effect of chidamide plus envafolimab has not been reported.

AIMS

This study aimed to evaluate the efficacy of chidamide plus envafolimab in advanced NSCLC patients resistant toanti-PD-1 treatment.

MATERIALS AND METHODS

Eligible advanced NSCLC patients after resistant to anti-PD-1 therapy received chidamide and envafolimab. The primary endpoint was objective response rate (ORR). The secondary end points included disease control rate (DCR), progression-free survival (PFS), and safety. The expression of histone deacetylase 2 (HDAC2), PD-L1, and blood TMB (bTMB) was also analyzed.

RESULTS

After a median follow-up of 8.1 (range: 7.6-9.2) months, only two patients achieved partial response. The ORR was 6.7% (2/30), DCR was 50% (15/30), and median PFS (mPFS) was 3.5 (95% confidence interval: 1.9-5.5) months. Biomarker analysis revealed that patients with high-level HDAC2 expression had numerically superior ORR (4.3% vs. 0), DCR (52.2% vs. 0) and mPFS (3.7 vs. 1.4m). Patients with negative PD-L1 had numerically superior DCR (52.2% vs. 33.3%) and mPFS (3.7m vs. 1.8m), so were those with low-level bTMB (DCR: 59.1% vs. 16.7%, mPFS: 3.8 vs.1.9m). Overall safety was controllable.

DISCUSSION

High HDAC2patients showed better ORR, DCR, and PFS. In addition, patient with negative PD-L1 and low-level bTMB had better DCR and PFS. This may be related to the epigenetic function of chidamide. However, the sample size was not big enough, so it is necessary to increase sample size to confirm the conclusion.

CONCLUSION

Combination of chidamide and envafolimab showed efficacy signals in certain NSCLC patients. But further identification of beneficial population is necessary for precision treatment.

Targeting PRAME for acute myeloid leukemia therapy

Despite significant progress in targeted therapy for acute myeloid leukemia (AML), clinical outcomes are disappointing for elderly patients, patients with less fit disease characteristics, and patients with adverse disease risk characteristics. Over the past 10 years, adaptive T-cell immunotherapy has been recognized as a strategy for treating various malignant tumors. However, it has faced significant challenges in AML, primarily because myeloid blasts do not contain unique surface antigens. The preferentially expressed antigen in melanoma (PRAME), a cancer-testis antigen, is abnormally expressed in AML and does not exist in normal hematopoietic cells. Accumulating evidence has demonstrated that PRAME is a useful target for treating AML. This paper reviews the structure and function of PRAME, its effects on normal cells and AML blasts, its implications in prognosis and follow-up, and its use in antigen-specific immunotherapy for AML.

Chidamide plus prednisone, cyclophosphamide, and thalidomide for relapsed or refractory peripheral T-cell lymphoma: A multicenter phase II trial

BACKGROUND

Although the treatment of peripheral T-cell lymphoma (PTCL) has undergone advancements during the past several years, the response rate and long-term effects with respect to patients with PTCL remain unsatisfactory-particularly for relapsed or refractory (R/R) patients. This phase II trial was designed to explore the efficacy and safety of an all-oral regimen of chidamide plus prednisone, cyclophosphamide, and thalidomide (CPCT) for R/R PTCL patients who could not tolerate the standard chemotherapy for a variety of reasons.

METHODS

We conducted a multicenter phase II clinical trial in which we combined chidamide (30 mg twice weekly) with prednisone (20 mg daily after breakfast), cyclophosphamide (50 mg daily after lunch), and thalidomide (100 mg daily at bedtime) (the CPCT regimen) for a total of fewer than 12 cycles as an induction-combined treatment period, and then applied chidamide as single-drug maintenance. Forty-five patients were ultimately enrolled from August 2016 to April 2021 with respect to Chinese patients at nine centers. Our primary objective was to assess the overall response rate (ORR) after the treatment with CPCT.

RESULTS

Of the 45 enrolled patients, the optimal ORR and complete response (CR)/CR unconfirmed (CRu) were 71.1% (32/45) and 28.9% (13/45), respectively, and after a median follow-up period of 56 months, the median progression-free survival (PFS) and overall survival (OS) were 8.5 months and 17.2 months, respectively. The five-year PFS and OS rates were 21.2% (95% confidence interval [CI], 7.9-34.5 %) and 43.8% (95% CI, 28.3-59.3 %), respectively. The most common adverse event was neutropenia (20/45, 44.4%), but we observed no treatment-related death.

CONCLUSION

The all-oral CPCT regimen was an effective and safety regimen for R/R PTCL patients who could not tolerate standard chemotherapy for various reasons.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02879526.

A combined immunopeptidomics, proteomics, and cell surface proteomics approach to identify immunotherapy targets for diffuse intrinsic pontine glioma

Introduction

Diffuse intrinsic pontine glioma (DIPG), recently reclassified as a subtype of diffuse midline glioma, is a highly aggressive brainstem tumor affecting children and young adults, with no cure and a median survival of only 9 months. Conventional treatments are ineffective, highlighting the need for alternative therapeutic strategies such as cellular immunotherapy. However, identifying unique and tumor-specific cell surface antigens to target with chimeric antigen receptor (CAR) or T-cell receptor (TCR) therapies is challenging.

Methods

In this study, a multi-omics approach was used to interrogate patient-derived DIPG cell lines and to identify potential targets for immunotherapy.

Results

Through immunopeptidomics, a range of targetable peptide antigens from cancer testis and tumor-associated antigens as well as peptides derived from human endogenous retroviral elements were identified. Proteomics analysis also revealed upregulation of potential drug targets and cell surface proteins such as Cluster of differentiation 27 (CD276) B7 homolog 3 protein (B7H3), Interleukin 13 alpha receptor 2 (IL-13Rα2), Human Epidermal Growth Factor Receptor 3 (HER2), Ephrin Type-A Receptor 2 (EphA2), and Ephrin Type-A Receptor 3 (EphA3).

Discussion

The results of this study provide a valuable resource for the scientific community to accelerate immunotherapeutic approaches for DIPG. Identifying potential targets for CAR and TCR therapies could open up new avenues for treating this devastating disease.

Chidamide, a novel histone deacetylase inhibitor, inhibits laryngeal cancer progression in vitro and in vivo

Although surgery is an important treatment for laryngeal cancer, surgery has a significant negative impact on the quality of life of patients, and many patients have poor tolerance to surgery. Therefore, alternative chemotherapeutic drugs are an important research hotspot. Chidamide is a histone deacetylase inhibitor that selectively inhibits the expression of type I and IIb histone deacetylases (1, 2, 3 and 10). It has a significant anticancer effect on a variety of solid tumours. This study verified the inhibitory effect of chidamide on laryngeal carcinoma. We conducted a variety of cellular and animal experiments to explore how chidamide inhibits the development of laryngeal cancer. The results showed that chidamide had significant antitumour activity against laryngeal carcinoma cells and xenografts and could induce cell apoptosis, ferroptosis and pyroptosis. This study provides a potential option for the treatment of laryngeal cancer.

Oral HDAC inhibitor tucidinostat in patients with relapsed or refractory peripheral T-cell lymphoma: phase IIb results

Tucidinostat (formerly known as chidamide) is an orally available, novel benzamide class of histone deacetylase (HDAC) inhibitor that selectively blocks class I and class IIb HDAC. This multicenter phase IIb study aimed to investigate the efficacy and safety of tucidinostat, 40 mg twice per week (BIW), in patients with relapsed/refractory (R/R) peripheral T-cell lymphoma (PTCL). The primary endpoint was overall response rate (ORR) assessed by an independent overall efficacy review committee. Between March 2017 and March 2019, 55 patients were treated, and 46 and 55 were evaluated for efficacy and safety, respectively. Twenty-one of 46 patients achieved objective responses with an ORR of 46% (95% confidence interval : 30.9-61.0), including five patients with complete response (CR). Responses were observed across various PTCL subtypes. In angioimmunoblastic T-cell lymphoma, there were two CR and five partial responses (PR) among eight patients, achieving an ORR of 88%. The disease control rate (CR + PR + stable disease) was 72% (33/46). The median progression-free survival, duration of response, and overall survival were 5.6 months, 11.5 months, 22.8 months, respectively. The most common adverse events (AE) (all grades) were thrombocytopenia, neutropenia, leukopenia, anemia, and diarrhea. The grade ≥3 AE emerging in ≥20% of patients included thrombocytopenia (51%), neutropenia (36%), lymphopenia (22%), and leukopenia (20%). Importantly, most of the AE were manageable by supportive care and dose modification. In conclusion, the favorable efficacy and safety profiles indicate that tucidinostat could be a new therapeutic option in patients with R/R PTCL (clinicaltrials gov. Identifier: NCT02953652).

HDAC5-mediated PRAME regulates the proliferation, migration, invasion, and EMT of laryngeal squamous cell carcinoma via the PI3K/AKT/mTOR signaling pathway

Laryngeal squamous cell carcinoma (LSCC) is an aggressive and lethal malignant neoplasm with extremely poor prognoses. Accumulating evidence has indicated that preferentially expressed antigen in melanoma (PRAME) is correlated with several kinds of cancers. However, there is little direct evidence to substantiate the biological function of PRAME in LSCC. The purpose of the current study is to explore the oncogenic role of PRAME in LSCC. PRAME expression was analyzed in 57 pairs of LSCC tumor tissue samples through quantitative real-time PCR, and the correlation between PRAME and clinicopathological features was analyzed. The result indicated that PRAME was overexpressed in the LSCC patients and correlated with the TNM staging and lymphatic metastasis. The biological functions and molecular mechanism of PRAME in LSCC progression were investigated through in vitro and in vivo assays. Functional studies confirmed that PRAME facilitated the proliferation, invasion, migration, and epithelial-mesenchymal transition of LSCC cells, and PRAME also promoted tumor growth in vivo. HDAC5 was identified as an upstream regulator that can affect the expression of PRAME. Moreover, PRAME played the role at least partially by activating PI3K/AKT/mTOR pathways. The above findings elucidate that PRAME may be a valuable oncogene target, contributing to the diagnosis and therapy of LSCC.

A phase II study of chidamide, cytarabine, aclarubicin, granulocyte colony-stimulating factor, and donor lymphocyte infusion for relapsed acute myeloid leukemia and myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation

Chemotherapy followed by donor lymphocyte infusion (DLI) is a promising treatment for relapsed acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the best strategy for administering this therapy is still unclear. This study sought to explore the efficacy and safety of chidamide and CAG (cytarabine, aclarubicin, and granulocyte colony-stimulating factor) (CCAG) regimen followed by DLI in relapsed AML/MDS after allo-HSCT. This was a single-arm, phase II trial in patients with relapsed AML/MDS after allo-HSCT. CCAG regimen followed by DLI was given according to the inclusion and exclusion criteria. Twenty adult patients were enrolled. The median follow-up time was 12 months. The complete remission (CR) rate was 45% and the partial remission (PR) rate was 5%. The 1-year overall survival (OS) was 56.7% (95% confidence interval (95% CI), 31.6-75.6%), and the median OS was 19 months. The 1-year relapse-free survival (RFS) was 83.3% (95% CI, 27.3-97.5%). Patients relapsing more than 6 months after HSCT and achieving CR/PR after CCAG plus DLI regimen attained significantly higher survival rates. The cumulative incidence of grade III-IV acute graft-versus-host disease (aGVHD) was 9.4%. There was no treatment-related mortality (TRM). These data suggest that CCAG plus DLI regimen is safe and induces durable remission and superior survival in patients with relapsed AML/MDS after allo-HSCT. Trial registration number: ChiCTR.org identifier: ChiCTR1800017740 and date of registration: August 12, 2018.

Decitabine enhances targeting of AML cells by NY-ESO-1-specific TCR-T cells and promotes the maintenance of effector function and the memory phenotype

NY-ESO-1 is a well-known cancer-testis antigen (CTA) with re-expression in numerous cancer types, but its expression is suppressed in myeloid leukemia cells. Patients with acute myeloid leukemia (AML) receiving decitabine (DAC) exhibit induced expression of NY-ESO-1 in blasts; thus, we investigated the effects of NY-ESO-1-specific TCR-engineered T (TCR-T) cells combined with DAC against AML. NY-ESO-1-specific TCR-T cells could efficiently eliminate AML cell lines (including U937, HL60, and Kasumi-1cells) and primary AML blasts in vitro by targeting the DAC-induced NY-ESO-1 expression. Moreover, the incubation of T cells with DAC during TCR transduction (designated as dTCR-T cells) could further enhance the anti-leukemia efficacy of TCR-T cells and increase the generation of memory-like phenotype. The combination of DAC with NY-ESO-1-specific dTCR-T cells showed a superior anti-tumor efficacy in vivo and prolonged the survival of an AML xenograft mouse model, with three out of five mice showing complete elimination of AML cells over 90 days. This outcome was correlated with enhanced expressions of IFN-γ and TNF-α, and an increased proportion of central memory T cells (CD45RO⁺CD62L⁺ and CD45RO⁺CCR7⁺). Taken together, these data provide preclinical evidence for the combined use of DAC and NY-ESO-1-specific dTCR-T cells for the treatment of AML.

Outcome of donor-derived TAA-T cell therapy in patients with high-risk or relapsed acute leukemia post allogeneic BMT

Patients with hematologic malignancies relapsing after allogeneic blood or marrow transplantation (BMT) have limited response to conventional salvage therapies, with an expected 1-year overall survival (OS) of <20%. We evaluated the safety and clinical outcomes following administration of a novel T-cell therapeutic targeting 3 tumor-associated antigens (TAA-T) in patients with acute leukemia who relapsed or were at high risk of relapse after allogeneic BMT. Lymphocytes obtained from the BMT donor were manufactured to target TAAs WT1, PRAME, and survivin, which are over-expressed and immunogenic in most hematologic malignancies. Patients received TAA-T infusions at doses of 0.5 to 4 × 107/m2. Twenty-three BMT recipients with relapsed/refractory (n = 11) and/or high-risk (n = 12) acute myeloid leukemia (n = 20) and acute lymphoblastic leukemia (n = 3) were infused posttransplant. No patient developed cytokine-release syndrome or neurotoxicity, and only 1 patient developed grade 3 graft-versus-host disease. Of the patients who relapsed post-BMT and received bridging therapy, the majority (n = 9/11) achieved complete hematologic remission before receiving TAA-T. Relapsed patients exhibited a 1-year OS of 36% and 1-year leukemia-free survival of 27.3% post-TAA-T. The poorest prognosis patients (relapsed <6 months after transplant) exhibited a 1-year OS of 42.8% postrelapse (n = 7). Median survival was not reached for high-risk patients who received preemptive TAA-T posttransplant (n = 12). Although as a phase 1 study, concomitant antileukemic therapy was allowed, TAA-T were safe and well tolerated, and sustained remissions in high-risk and relapsed patients were observed. Moreover, adoptively transferred TAA-T detected by T-cell receptor V-β sequencing persisted up to at least 1 year postinfusion. This trial was registered at clinicaltrials.gov as #NCT02203903.

Selinexor improves the anti-cancer effect of tucidinostat on TP53 wild-type breast cancer

Histone deacetylase (HDAC) is closely related to the initiation and development of breast cancer (BC). Its inhibitor (HDACi) has been used to treat BC, while the efficacy of clinical trials was not reached expectations. HDACi combined with other drugs may be an effective strategy. This study explored the effect of HDACi tucidinostat combined with selinexor, an exportin 1 (XPO1) inhibitor, on ER⁺Her2^- BC cell lines of MCF-7 (wt-TP53), MDA-MB-175 (wt-TP53), MDA-MB-134 (mut-TP53) and T47D (mut-TP53) in vitro and cell derived xenografts (CDX) of MCF-7 in nude mice in vivo. Results showed that both tucidinostat and selinexor showed better inhibitory activities on wt-TP53 BC (MCF-7 and MDA-MB-175) comparing with mut-TP53 BC (MDA-MB-134 and T47D). Tucidinostat combined with selinexor significantly improved the effects of tucidinostat alone on the proliferation and invasion inhibitions and apoptosis promotions of MCF-7 and MDA-MB-175 cells in vitro. It also significantly enhanced the effects of tucidinostat on up-regulating the expression levels of acetyl-p53, nuclear p53, total p53, p21, Bax and Cleaved Caspase-3, and down-regulating the expression levels of Cyclin D1 and Bcl-2 in MCF-7 or MDA-MB-175 cells. Results consistent with in vitro were also obtained in CDX of MCF-7 in vivo. Taken together, we believe that tucidinostat and selinexor are potentially effective drug combinations for the treatment of wt-TP53 BC, and the molecular mechanism may be through enhancing the activity of p53 in the nucleus of BC cells to suppress proliferation and invasion and promote apoptosis.

CC-01 (chidamide plus celecoxib) modifies the tumor immune microenvironment and reduces tumor progression combined with immune checkpoint inhibitor

Immune checkpoint inhibitors (ICIs) have shown clinical benefit in solid tumors, with modest rates of clinical response. Hence, improved therapeutic approaches need to be investigated. Herein, we assessed a combination of chidamide plus celecoxib (called CC-01) combined with programmed cell death protein 1 (PD-1) blockade in a CT26 model as potent tumor microenvironment (TME) regulator. The antitumor activity was assessed by measuring tumor size, overall response rate, and survival rate. Immune profiling of tumor-infiltrating lymphocytes was performed by flow cytometry. Tumor tissues were assessed by chip assay to predict the possible pathway. Tumor size was significantly reduced in mice treated with CC-01 combined with or without anti-PD-1 antibody, however the triple combination therapy consistently demonstrated that it significantly increased both the ORR and survival rate in term of clinical applications. In the combination group, immune landscape profiling revealed decreased populations of immunosuppressive regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages. Analysis of the mouse tumor chip data using Gene Ontology enrichment analysis of biological processes revealed that the triple combination upregulated genes associated with responses to interferon-gamma. Our results demonstrated that CC-01 possessed potent TME regulatory properties, augmenting the antitumor effect when combined with ICIs. This antitumor effect was achieved by altering the immune landscape in TILs (tumor-infiltrating lymphocytes) and was associated with immune cell activation in the TME. Furthermore, CC-01 demonstrated potent anticancer immune response activity, mainly reducing the number and function of several immunosuppressive cells. The combination of CC-01 with an ICI will further enhance the anticancer effect and boost the immune response rate. Collectively, our results support the clinical evaluation of CC-01 in combination with ICIs in several advanced cancers.

A Multi-Center, Real-World Study of Chidamide for Patients With Relapsed or Refractory Peripheral T-Cell Lymphomas in China

Chidamide has demonstrated significant clinical benefits for patients with relapsed/refractory (R/R) PTCL in previous studies. This multi-center observational study was aimed to evaluate the objective response rate (ORR), overall survival (OS), and safety of chidamide. From February 2015 to December 2017, 548 patients with R/R PTCL from 186 research centers in China were included in the study. Among the 261 patients treated with chidamide monotherapy, ORR was 58.6% and 55 patients (21.1%) achieved complete response (CR). Among the 287 patients receiving chidamide-containing combination therapies, ORR was 73.2% and 73 patients (25.4%) achieved CR. The median OS of all patients was 15.1 months. The median OS of patients receiving chidamide monotherapy and combination therapies was 433 and 463 days, respectively. These results demonstrate a significant survival advantage of chidamide treatments as compared with international historical records. Common adverse effects (AEs) were hematological toxicities. Most AEs in both monotherapy and combined treatments were grade 1–2. No unanticipated AEs occurred. In conclusion, chidamide-based therapy led to a favorable efficacy and survival benefit for R/R PTCL. Future studies should explore the potential advantage of chidamide treatment combined with chemotherapy.

Chidamide combined with cyclophosphamide, doxorubicin, vincristine and prednisone in previously untreated patients with peripheral T-cell lymphoma

Objective

Chidamide is an oral histone deacetylase subtype-selective inhibitor approved for relapsed or refractory peripheral T-cell lymphoma (PTCL). This phase 1b study evaluated the safety, pharmacokinetics, and preliminary efficacy of chidamide in combination with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) for treatment-naïve PTCL patients.

Methods

This study was an open-label, multicenter trial composed of dose escalation and dose expansion. Patients received CHOP for six 21-d cycles and chidamide on d 1, 4, 8 and 11 in each cycle. Four dose levels of chidamide (20, 25, 30 and 35 mg) were evaluated. The primary objective was to evaluate the safety and tolerability of the combination regimen.

Results

A total of 30 patients were evaluated in this study: 15 in the dose-escalation part and 15 in the dose-expansion part. In the dose-escalation study, three patients were enrolled in the 35 mg chidamide cohort. One had dose-limiting toxicity with grade 3 vascular access complications, and one had grade 2 neutropenia with a sustained temperature >38 °C. Dose escalation was stopped at this chidamide dose level. The most common (≥10%) grade 3 or 4 adverse events (AEs) were leukopenia (90.0%), neutropenia (83.3%), vomiting (13.3%), thrombocytopenia (10.0%) and febrile neutropenia (10.0%). No significant changes in chidamide pharmacokinetic properties were observed before and after combination treatment. The objective response rate for the 28 patients evaluable for preliminary efficacy was 89.3% (25/28), with 16 (57.1%) achieving complete response or unconfirmed complete response. The estimated median progression-free survival was 14.0 months. In summary, we chose chidamide 30 mg as the recommended dose for phase 2.

Conclusions

The addition of chidamide to standard CHOP chemotherapy was tolerable with promising preliminary efficacy in previously untreated PTCL patients, which supports further clinical studies with this combination regimen for the frontline treatment of PTCL.

Chidamide triggers BTG1-mediated autophagy and reverses the chemotherapy resistance in the relapsed/refractory B-cell lymphoma

Rituximab/chemotherapy relapsed and refractory B cell lymphoma patients have a poor overall prognosis, and it is urgent to develop novel drugs for improving the therapy outcomes. Here, we examined the therapeutic effects of chidamide, a new histone deacetylase (HDAC) inhibitor, on the cell and mouse models of rituximab/chemotherapy resistant B-cell lymphoma. In Raji-4RH/RL-4RH cells, the rituximab/chemotherapy resistant B-cell lymphoma cell lines (RRCL), chidamide treatment induced growth inhibition and G0/G1 cell cycle arrest. The primary B-cell lymphoma cells from Rituximab/chemotherapy relapsed patients were sensitive to chidamide. Interestingly, chidamide triggered the cell death with the activation of autophagy in RRCLs, likely due to the lack of the pro-apoptotic proteins. Based on the RNA-seq and chromatin immunoprecipitation (ChIP) analysis, we identified BTG1 and FOXO1 as chidamide target genes, which control the autophagy and the cell cycle, respectively. Moreover, the combination of chidamide with the chemotherapy drug cisplatin increased growth inhibition on the RRCL in a synergistic manner, and significantly reduced the tumor burden of a mouse lymphoma model established with engraftment of RRCL. Taken together, these results provide a theoretic and mechanistic basis for further evaluation of the chidamide-based treatment in rituximab/chemotherapy relapsed and refractory B-cell lymphoma patients.

Epigenetic Therapy Promotes the Ratio of Th1/Th17 Lineage to Reverse Immune Evasion and Treat Leukemia Relapse Post-allogeneic Stem Cell Transplantation in Non-APL AML Patients

To reverse the early-stage relapse post-hematopoietic stem cell transplantation, we investigated the safety and efficacy of a new epigenetic regimen (chidamide and decitabine plus thymalfasin simultaneously) on acute myeloid leukemia patients (excluding acute promyelocytic leukemia). Twenty-four patients were enrolled in this observational study during April 2015 to May 2018. The most common adverse event was reversible CTCAE grade 2 thrombocytopenia (20/24). Strikingly, all 24 patients had response to this epigenetic regimen accompanied with decreased measurable residual disease. The overall survival rate is 79.2% (19/24), with a relapse-free survival rate of 79.2% (19/24). During this regimen treatment, Th1 cells and CD3+CD4-CD8+T cells increased, and Th17 cells decreased gradually. The status of high Th1 and low Th17 cells was still observed on the 3rd month after discontinuation of this regimen. Interestingly, the significantly elevated ratio of Th1/Th17 seemed to reflect the treatment-related immune effect, which may be a valuable marker to be monitored in the early-relapse stage for evaluating the efficacy and prognosis.

Chidamide induces long-term remission in rare subcutaneous panniculitis-like T-cell lymphoma: An unusual case report and literature review

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare primary cutaneous lymphoma composed of CD8⁺ cytotoxic T-cell that is primarily localized in the subcutaneous tissue. No standard treatments are currently available for SPTCL due to its rarity. Chemotherapy, radiotherapy, immunosuppressive agents, and hematopoietic stem cell transplantation (HSCT) have been used frequently, however, the effects of these treatment approaches remain controversial. In this report, we present an unusual case of SPTCL in a 47-year-old woman whose initial symptoms were atypical. The patient was started on etoposide, vincristine, cyclophosphamide, doxorubicin, and prednisone (EPOCH) chemotherapy once diagnosed. After two cycles of chemotherapy, her clinical symptoms were not significantly improved. Subsequently, histone deacetylase (HDAC) inhibitor chidamide was added to the chemotherapy from the third cycle. She recovered gradually and achieved complete remission (CR) after four cycles of chemotherapy combined with chidamide, followed by chidamide monotherapy for maintenance. More than 1 year after the therapy, she remained in CR. Our case illustrates, for the first time, chidamide can be an effective agent to induce long-term remission for rare SPTCL.

Hypomethylating Agents and Immunotherapy: Therapeutic Synergism in Acute Myeloid Leukemia and Myelodysplastic Syndromes

Decitabine and guadecitabine are hypomethylating agents (HMAs) that exert inhibitory effects against cancer cells. This includes stimulation of anti-tumor immunity in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) patients. Treatment of AML and MDS patients with the HMAs confers upregulation of cancer/testis antigens (CTAs) expression including the highly immunogenic CTA NY-ESO-1. This leads to activation of CD4⁺ and CD8⁺ T cells for elimination of cancer cells, and it establishes the feasibility to combine cancer vaccine with HMAs to enhance vaccine immunogenicity. Moreover, decitabine and guadecitabine induce the expression of immune checkpoint molecules in AML cells. In this review, the accumulating knowledge on the immunopotentiating properties of decitabine and guadecitabine in AML and MDS patients are presented and discussed. In summary, combination of decitabine or guadecitabine with NY-ESO-1 vaccine enhances vaccine immunogenicity in AML patients. T cells from AML patients stimulated with dendritic cell (DC)/AML fusion vaccine and guadecitabine display increased capacity to lyse AML cells. Moreover, decitabine enhances NK cell-mediated cytotoxicity or CD123-specific chimeric antigen receptor-engineered T cells antileukemic activities against AML. Furthermore, combination of either HMAs with immune checkpoint blockade (ICB) therapy may circumvent their resistance. Finally, clinical trials of either HMAs combined with cancer vaccines, NK cell infusion or ICB therapy in relapsed/refractory AML and high-risk MDS patients are currently underway, highlighting the promising efficacy of HMAs and immunotherapy synergy against these malignancies.

Oncolytic Viruses and Hematological Malignancies: A New Class of Immunotherapy Drugs

The use of viruses for tumour treatment has been imagined more than one hundred years ago, when it was reported that viral diseases were occasionally leading to a decrease in neoplastic lesions. Oncolytic viruses (OVs) seem to have a specific tropism for tumour cells. Previously, it was hypothesised that OVs’ antineoplastic actions were mainly due to their ability to contaminate, proliferate and destroy tumour cells and the immediate destructive effect on cells was believed to be the single mechanism of action of OVs’ action. Instead, it has been established that oncolytic viruses operate via a multiplicity of systems, including mutation of tumour milieu and a composite change of the activity of immune effectors. Oncolytic viruses redesign the tumour environment towards an antitumour milieu. The aim of our work is to evaluate the findings present in the literature about the use of OVs in the cure of haematological neoplastic pathologies such as multiple myeloma, acute and chronic myeloid leukaemia, and lymphoproliferative diseases. Further experimentations are essential to recognize the most efficient virus or treatment combinations for specific haematological diseases, and the combinations able to induce the strongest immune response.

HMGB1: an important regulator of myeloid differentiation and acute myeloid leukemia as well as a promising therapeutic target

Abstract

High mobility group box 1 (HMGB1) is a non-histone nuclear protein which has been intensively studied in various physiological and pathological processes including leukemia. Here in this study, we further demonstrated that HMGB1 presents higher expression in the bone marrow mononuclear cells of acute myeloid leukemia (AML) patients compared with the normal controls and contributes to the AML pathogenesis and progression by inhibiting apoptosis, facilitating proliferation, and inducing myeloid differentiation blockade of AML cells. Mechanistic investigation revealed that transforming growth factor beta-induced (TGFBI) acts as a potential downstream target of HMGB1 and lentivirus-mediated knockdown of TGFBI expression impaired phorbol-12-myristate-13-acetate (PMA) and all-trans retinoic acid (ATRA)–induced myeloid differentiation of AML cell lines. On the other hand, chidamide, an orally histone deacetylase inhibitor, decreases HMGB1 expression significantly in AML cells with concomitant upregulation of TGFBI expression, and confers therapeutic effect on AML by inducing cell differentiation, apoptosis and inhibiting cell proliferation. In conclusion, our findings provide additional insights that HMGB1 is a promising therapeutic target of AML, and also present experimental evidence for the clinical application of chidamide as a novel agent in AML therapy by downregulating HMGB1 expression.

Key messages

HMGB1 induces cell proliferation and myeloid differentiation blockade and inhibits apoptosis of AML cells.

TGFBI acts as a potential target of HMGB1.

Chidamide, a selective HDAC inhibitor, confers promising therapeutic effect for AML via downregulating HMGB1 expression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-020-01998-5.

Effective Treatment with PD-1 Antibody, Chidamide, Etoposide, and Thalidomide (PCET) for Relapsed/Refractory Natural Killer/T-Cell Lymphoma: A Report of Three Cases

Extranodal natural killer (NK)/T-cell lymphoma, nasal type (ENKTL) is a specific subtype of peripheral T cell lymphoma (PTCL) with a poor prognosis. To date, there exist no standard therapeutic regimens for relapsed/refractory (R/R) ENKTL. More potent treatment strategies are urgently needed to improve the survival of these patients with R/R ENKTL. Herein, we present three R/R ENKTL patients who failed prior therapies (L-asparaginase containing chemotherapy, radiotherapy or biological-cell therapy, etc.) benefited from the combination regimen comprised of anti-programmed-death-1 (PD-1) antibody toripalimab, chidamide, etoposide, and thalidomide. They received the treatment regimen continuously until the disease progression occurs. As of data collection, two patients achieved complete remission (CR) after 4, 6 cycles of treatment, respectively, and another patient was evaluated as partial remission (PR) after 2 cycles. Treatment-related adverse events (AEs) mainly presented grade 2~3 leukocytopenia and anemia, which were controllable. It follows that PD-1 antibody, chidamide, etoposide, and thalidomide (PCET) regimen may be a promising choice for patients with R/R ENKTL and warrants further investigation.

Toll-like receptor 7/8-matured RNA-transduced dendritic cells as post-remission therapy in acute myeloid leukaemia: results of a phase I trial

Objectives

Innovative post‐remission therapies are needed to eliminate residual AML cells. DC vaccination is a promising strategy to induce anti‐leukaemic immune responses.

Methods

We conducted a first‐in‐human phase I study using TLR7/8‐matured DCs transfected with RNA encoding the two AML‐associated antigens WT1 and PRAME as well as CMVpp65. AML patients in CR at high risk of relapse were vaccinated 10× over 26 weeks.

Results

Despite heavy pretreatment, DCs of sufficient number and quality were generated from a single leukapheresis in 11/12 cases, and 10 patients were vaccinated. Administration was safe and resulted in local inflammatory responses with dense T‐cell infiltration. In peripheral blood, increased antigen‐specific CD8⁺ T cells were seen for WT1 (2/10), PRAME (4/10) and CMVpp65 (9/10). For CMVpp65, increased CD4⁺ T cells were detected in 4/7 patients, and an antibody response was induced in 3/7 initially seronegative patients. Median OS was not reached after 1057 days; median RFS was 1084 days. A positive correlation was observed between clinical benefit and younger age as well as mounting of antigen‐specific immune responses.

Conclusions

Administration of TLR7/8‐matured DCs to AML patients in CR at high risk of relapse was feasible and safe and resulted in induction of antigen‐specific immune responses. Clinical benefit appeared to occur more likely in patients <65 and in patients mounting an immune response. Our observations need to be validated in a larger patient cohort. We hypothesise that TLR7/8 DC vaccination strategies should be combined with hypomethylating agents or checkpoint inhibition to augment immune responses.

Trial registration

The study was registered at https://clinicaltrials.gov on 17 October 2012 (NCT01734304) and at https://www.clinicaltrialsregister.eu (EudraCT‐Number 2010‐022446‐24) on 10 October 2013.

A combination of low-dose decitabine and chidamide resulted in synergistic effects on the proliferation and apoptosis of human myeloid leukemia cell lines

Two of the most common and well-characterized epigenetic changes, DNA methylation and histone modifications, occur in leukemia. Decitabine (5-aza-2'-deoxycytidine, DAC), as a hypomethylating agent (HMA), and chidamide (CS055), as a histone deacetylase inhibitor (HDACi), each demonstrate effects against leukemia. However, whether the combination of low-dose DAC with chidamide constitutes an effective epigenetic regimen for the treatment of myeloid leukemia is currently unknown. In this study, the combination of DAC at low doses and chidamide showed enhanced inhibition of myeloid leukemia cell (K562, THP-1) growth. As a novel HDACi, chidamide increased the level of ace-H3K18 expression. Combined use of low-dose DAC and chidamide arrested the cell cycle at the G0/G1 phase by upregulating p21 expression, and the combination also suppressed PI3K/AKT/mTOR signaling pathway. Furthermore, chidamide enhanced the apoptotic effect of DAC by downregulating expression of Bcl-2 and pro-caspase-3 and upregulating that of Bax, cleaved PARP-1, and caspase-9. Moreover, the mitochondrial transmembrane potential was significantly decreased in DAC-, chidamide-, or combination-treated leukemia cells. These results suggest that targeting the leukemia epigenome through the combination of low-dose DAC and chidamide is a promising approach.

Chidamide in combination with chemotherapy in refractory and relapsed T lymphoblastic lymphoma/leukemia

Chidamide, a novel histone deacetylase inhibitor, has exerted effects in T-cell tumors through various mechanisms. Seventeen patients with refractory or relapsed T-cell acute lymphoblastic lymphoma/leukemia (T-LBL/ALL) received Chidamide combined with chemotherapy as salvage treatment. Historical data was analyzed as comparison as chemotherapy group. Complete response (CR) rate and overall response rate (ORR) of Chidamide + chemotherapy group were higher than that of chemotherapy group after one course. Chidamide + chemotherapy group had a better progress-free survival (PFS) compared to chemotherapy group. No difference in overall survival (OS) was observed. Grade 3/4 nonhematological adverse events (>10%) of patients in Chidamide + chemotherapy group included febrile neutropenia (64.7%), drug-induced liver failure (17.6%), decreased fibrinogen (11.8%), sepsis (11.8%), pneumonitis (11.8%), and oral mucositis (11.8%). This study demonstrates that Chidamide included regimen may be a new treatment strategy with an acceptable safety profile for refractory or relapsed T-LBL/ALL patients but requires further investigation.

Phenotype of mesenchymal stem cells from patients with myelodyplastic syndrome maybe partly modulated by decitabine

Mesenchymal stem cells (MSCs) derived from myelodysplastic syndromes (MDSs) have been demonstrated to accelerate the progression of MDS. However, whether the phenotype of MSCs derived from MDS (MDS-MSCs) may be reversed and serve as a potential target for the treatment of MDS remains unclear. The present study investigated the functional alternations of MDS-MSCs following in vitro decitabine-treatment. Primary MSCs were cultured from the bone marrow aspirates of 28 patients with MDS. The impact on the growth of MDS-MSCs treated with decitabine was analyzed using the MTT assay. Changes in the gene expression levels of runt related transcription factor 2 (RUNX2), Sp7 transcription factor (SP7), cyclin dependent kinase inhibitor 1A (CDKN1A) and CD274 in MDS-MSCs following treatment with decitabine were analyzed by reverse transcription-quantitative polymerase chain reaction. The effects of decitabine on apoptosis and the cell cycle were examined using flow cytometry. The effect of decitabine on the immune regulation of MDS-MSCs was tested by the co-culture of MSCs with activated T cells in vitro. The results revealed that proliferation, apoptosis and the mRNA expression levels of RUNX2 and SP7 in MDS-MSCs did not significantly change following treatment with decitabine compared with control MDS-MSCs. However, treatment with decitabine resulted in a smaller population of cells in the G1 phase and an increase in the number of cells in the G2/M phase compared with control MDS-MSCs. This change was associated with decreased expression of CDKN1A in cells treated with decitabine compared with control cells. Notably, the ability of MDS-MSCs treated with decitabine to induce the differentiation of T cells into regulatory T cells was significantly reduced compared with control MDS-MSCs. This was associated with a decreased expression of CD274 in MDS-MSCs treated with decitabine compared with control MDS-MSCs. In conclusion, the phenotype of MSCs derived from patients with MDS was partially reversed by treatment with decitabine, presenting a potential therapeutic intervention.

Cancer Testis Antigens and Immunotherapy: Where Do We Stand in the Targeting of PRAME?

PRAME or PReferentially expressed Antigen in Melanoma is a testis-selective cancer testis antigen (CTA) with restricted expression in somatic tissues and re-expression in various cancers. It is one of the most widely studied CTAs and has been associated with the outcome and risk of metastasis. Although little is known about its pathophysiological function, PRAME has gained interest as a candidate target for immunotherapy. This review provides an update on our knowledge on PRAME expression and function in healthy and malignant cells and the current immunotherapeutic strategies targeting PRAME with their specific challenges and opportunities. We also highlight some of the features that position PRAME as a unique cancer testis antigen to target.

Plasmacytoid dendritic cells orchestrate innate and adaptive anti-tumor immunity induced by oncolytic coxsackievirus A21

BACKGROUND

The oncolytic virus, coxsackievirus A21 (CVA21), has shown promise as a single agent in several clinical trials and is now being tested in combination with immune checkpoint blockade. Combination therapies offer the best chance of disease control; however, the design of successful combination strategies requires a deeper understanding of the mechanisms underpinning CVA21 efficacy, in particular, the role of CVA21 anti-tumor immunity. Therefore, this study aimed to examine the ability of CVA21 to induce human anti-tumor immunity, and identify the cellular mechanism responsible.

METHODS

This study utilized peripheral blood mononuclear cells from i) healthy donors, ii) Acute Myeloid Leukemia (AML) patients, and iii) patients taking part in the STORM clinical trial, who received intravenous CVA21; patients receiving intravenous CVA21 were consented separately in accordance with local institutional ethics review and approval. Collectively, these blood samples were used to characterize the development of innate and adaptive anti-tumor immune responses following CVA21 treatment.

RESULTS

An Initial characterization of peripheral blood mononuclear cells, collected from cancer patients following intravenous infusion of CVA21, confirmed that CVA21 activated immune effector cells in patients. Next, using hematological disease models which were sensitive (Multiple Myeloma; MM) or resistant (AML) to CVA21-direct oncolysis, we demonstrated that CVA21 stimulated potent anti-tumor immune responses, including: 1) cytokine-mediated bystander killing; 2) enhanced natural killer cell-mediated cellular cytotoxicity; and 3) priming of tumor-specific cytotoxic T lymphocytes, with specificity towards known tumor-associated antigens. Importantly, immune-mediated killing of both MM and AML, despite AML cells being resistant to CVA21-direct oncolysis, was observed. Upon further examination of the cellular mechanisms responsible for CVA21-induced anti-tumor immunity we have identified the importance of type I IFN for NK cell activation, and demonstrated that both ICAM-1 and plasmacytoid dendritic cells were key mediators of this response.

CONCLUSION

This work supports the development of CVA21 as an immunotherapeutic agent for the treatment of both AML and MM. Additionally, the data presented provides an important insight into the mechanisms of CVA21-mediated immunotherapy to aid the development of clinical biomarkers to predict response and rationalize future drug combinations.

Tucidinostat plus exemestane for postmenopausal patients with advanced, hormone receptor-positive breast cancer (ACE): a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Tucidinostat (formerly known as chidamide) is an oral subtype-selective histone deacetylase inhibitor. In an exploratory study, the combination of tucidinostat with exemestane showed preliminary signs of encouraging anti-tumour activity in patients with advanced hormone receptor-positive breast cancer. To build on these findings, we aimed to assess the efficacy and safety of this combination in a randomised trial in a larger population of postmenopausal patients with advanced, hormone receptor-positive breast cancer.

METHODS

We did the randomised, double-blind, placebo-controlled, phase 3 ACE trial at 22 specialist cancer centres in China. Eligible patients were postmenopausal women (aged ≥60 years or aged <60 years if their serum follicle-stimulating hormone and oestradiol concentrations were within postmenopausal ranges) with hormone receptor-positive, HER2-negative breast cancer, whose disease had relapsed or progressed after at least one endocrine therapy (either in advanced or metastatic or adjuvant setting), and who had at least one measurable lesion, adequate organ function, Eastern Cooperative Oncology Group (ECOG) performance status of 0-1, and adequate haematological and biochemical parameters. Endocrine therapy did not have to be the most recent therapy before randomisation, but recurrence or progression after the most recent therapy was a prerequisite. Patients were randomly assigned (2:1) by a dynamic randomisation scheme via an interactive web-response system to receive 30 mg oral tucidinostat or placebo twice weekly. All patients in both groups also received 25 mg oral exemestane daily. Randomisation was stratified according to the presence of visceral metastases (yes vs no). Patients, investigators, study site staff, and the sponsor were masked to treatment assignment. The primary endpoint was investigator-assessed progression-free survival. Efficacy analyses were done in the full analysis set population, comprising all patients who received at least one dose of any study treatment, and safety analyses were done in all patients who received at least one dose of any study treatment and for whom at least one safety case report form was available. This study is registered with ClinicalTrials.gov, number NCT02482753. The study has reached the required number of events for final analysis of the primary endpoint. The trial is no longer enrolling patients, but follow-up for investigation of overall survival is ongoing.

FINDINGS

Between July 20, 2015, and June 26, 2017, 365 patients were enrolled and randomly assigned, 244 to the tucidinostat group and 121 to the placebo group. The median duration of follow-up was 13·9 months (IQR 9·8-17·5). Investigator-assessed median progression-free survival was 7·4 months (95% CI 5·5-9·2) in the tucidinostat group and 3·8 months (3·7-5·5) in the placebo group (HR 0·75 [95% CI 0·58-0·98]; p=0·033). The most common grade 3 or 4 adverse events in either group were neutropenia (124 [51%] of 244 patients in the tucidinostat group vs three [2%] of 121 patients in the placebo group), thrombocytopenia (67 [27%] vs three [2%]), and leucopenia (46 [19%] vs three [2%]). Serious adverse events of any cause occurred in 51 (21%) of 244 patients in the tucidinostat group and seven (6%) of 121 patients in the placebo group. No treatment-related deaths were reported.

INTERPRETATION

Tucidinostat plus exemestane improved progression-free survival compared with placebo plus exemestane in patients with advanced, hormone receptor-positive, HER2-negative breast cancer that progressed after previous endocrine therapy. Grade 3-4 haematological adverse events were more common in the tucidinostat plus exemestane group than in the placebo plus exemestane group. Tucidinostat plus exemestane could represent a new treatment option for these patients.

FUNDING

Chipscreen Biosciences.

Antigenic Targets for the Immunotherapy of Acute Myeloid Leukaemia

One of the most promising approaches to preventing relapse is the stimulation of the body’s own immune system to kill residual cancer cells after conventional therapy has destroyed the bulk of the tumour. In acute myeloid leukaemia (AML), the high frequency with which patients achieve first remission, and the diffuse nature of the disease throughout the periphery, makes immunotherapy particularly appealing following induction and consolidation therapy, using chemotherapy, and where possible stem cell transplantation. Immunotherapy could be used to remove residual disease, including leukaemic stem cells from the farthest recesses of the body, reducing, if not eliminating, the prospect of relapse. The identification of novel antigens that exist at disease presentation and can act as targets for immunotherapy have also proved useful in helping us to gain a better understand of the biology that belies AML. It appears that there is an additional function of leukaemia associated antigens as biomarkers of disease state and survival. Here, we discuss these findings.

Secondary skin involvement in gastric diffuse large B-cell lymphoma treated with chidamide: A case report

RATIONALE

Diffuse large B-cell lymphoma (DLBCL) is a neoplasm of large B lymphoid cells that exhibits diffuse growth patterns. Patients may present with nodal and/or extranodal disease. The most common extranodal site is the gastrointestinal tract, while skin is less common.

PATIENT CONCERNS

We report a case of secondary skin involvement of an original gastric DLBCL, which has achieved a complete response after treatment with chidamide.

DIAGNOSES

Initially, the diagnosis of gastric DLBCL is clear, and this patient responded well to systemic chemotherapy (rituximab + cyclophosphamide + epirubicin + vincristine + prednisone) after 8 cycles. Thirty months later, some rapidly enlarging skin nodules on his arm were found. These skin nodules were diagnosed as secondary cutaneous DLBCL based on the clinical features, positron emission tomography-computed tomography, and histomorphologic and immunohistochemical expression.

INTERVENTIONS

Steroids, interferon-α, and radiation had little therapeutic effect. We treated the patient with chidamide at 30 mg twice per week in combination with dexamethasone.

OUTCOMES

The skin nodules regressed 3 weeks later. During the 1-year follow-up period, the patient is still in treatment with chidamide without adverse reactions.

LESSONS

To the best of our knowledge, this is the first case of secondary skin DLBCL reported to exhibit a complete response to chidamide, which provides a novel therapeutic strategy for secondary skin DLBCL. However, more cases are still needed to further validate its efficacy.

Determination of chidamide in rat plasma and cerebrospinal fluid

Chidamide is a new subtype-selective histone deacetylase inhibitor (HDACi), which has been approved for the treatment of recurrent or refractory peripheral T-cell lymphoma (PTCL) in China. However, there are few studies about the application of chidamide in PTCL with central nervous system (CNS) involvement. It is essential to investigate the penetration of chidamide in the blood brain barrier (BBB). LC-MS methods were established firstly to determine the concentration of chidamide in rat plasma and CSF. Then five rats were anaesthetized and the plasma and CSF samples were collected at the time of 5, 15, 30, 60, 120, 180, 240, 360 and 480 min after being administered 1 mg/kg chidamide by intravenous injection, respectively. All samples were analyzed with the established LC-MS method by using the precursor/product transitions (m/z) of 391.1/265.1 for chidamide and 441.1/138.2 for internal standard (IS). The PK parameters were calculated after both of the concentrations of chidamide in plasma and CSF were determined. The penetration ratio of chidamide in BBB ranged from 0.19% to 0.67%. Result indicated chidamide could pass through the BBB, enter into the CNS and have the potential to be utilized in PTCL with CNS involvement.

Successful treatment of high-risk myelodysplastic syndrome with decitabine-based chemotherapy followed by haploidentical lymphocyte infusion: A case report and literature review

RATIONALE

The current therapy for elderly patients with high-risk myelodysplastic syndromes (MDSs) remains unsatisfactory. Decitabine, which has been approved to treat MDS, cannot eliminate malignant clones of MDS.

PATIENT CONCERNS

A 68-year-old woman presented with multiple divergent bleeding points in the subcutaneous tissue of the limb. Two years earlier, she had been diagnosed with invasive ductal carcinoma of the left breast and had undergone left modified radical mastectomy and local radiation therapy.

DIAGNOSES

The patient was diagnosed with MDS refractory anemia with excess of blast II and was classified as very high risk according to the revised international prognostic scoring system.

INTERVENTIONS

The chemotherapy regimen consisted of decitabine (20 mg/m intravenously on days 1-5), cytarabine (10 mg/m every 12 hours subcutaneously on days 1-5), aclarubicin hydrochloride (20 mg intravenously on days 1, 3, and 5), and recombinant human granulocyte colony-stimulating factor (250 μg/d subcutaneously from day 0 to day 5). Peripheral mononuclear cells from her son were infused at 36 hours after the end of each chemotherapy cycle. The patient received a total of 4 cycles of the therapy.

OUTCOMES

The patient achieved complete remission after the first cycle of the treatment. There was no clinical evidence of MDS relapse as of 4 years after the completion of the treatment.

LESSONS

The results suggested that decitabine-based chemotherapy and haploidentical lymphocyte infusion may be act synergistically. Combination therapy is a suitable, safe, and effective treatment regimen for elderly patients with high-risk MDS.

PRAME expression and promoter hypomethylation in epithelial ovarian cancer

PRAME is a cancer-testis antigen (CTA) and potential immuno-therapeutic target, but has not been well-studied in epithelial ovarian cancer (EOC) or its high grade serous (HGSC) subtype. Compared to normal ovary, PRAME expression was significantly increased most EOC, regardless of stage and grade. Interestingly, PRAME mRNA expression was associated with improved survival in the HGSC subtype. The PRAME locus was a frequent target for copy number alterations (CNA) in HGSC but most changes were heterozygous losses, indicating that elevated PRAME expression is not typically due to CNA. In contrast, PRAME promoter DNA hypomethylation was very common in EOC and HGSC and correlated with increased PRAME expression. PRAME expression and promoter hypomethylation both correlated with LINE-1 hypomethylation, a biomarker of global DNA hypomethylation. Pharmacologic or genetic disruption of DNA methyltransferase (DNMT) enzymes activated PRAME expression in EOC cells. Immunohistochemistry (IHC) of PRAME in EOC revealed frequent, but low level, protein expression, and expression was confined to epithelial cells and localized to the cytoplasm. Cytoplasmic PRAME expression was positively associated with PRAME mRNA expression and negatively associated with promoter methylation, but the latter correlation was not statistically significant. PRAME protein expression did not correlate with EOC clinicopathology or survival. In summary, PRAME is frequently expressed in EOC at the mRNA and protein levels, and DNA methylation is a key mechanism regulating its expression. These data support PRAME as an immunotherapy target in EOC, and suggest treatment with DNMT inhibitors as a means to augment PRAME immunotherapy.

Exploratory clinical study of chidamide, an oral subtype-selective histone deacetylase inhibitor, in combination with exemestane in hormone receptor-positive advanced breast cancer

Objective

The recurrence or progression under endocrine therapy in hormone receptor-positive (HR+) advanced breast cancer (ABC) remained a critical clinical challenge. Chidamide is an oral subtype-selective histone deacetylase (HDAC) inhibitor with multiple functions in tumor growth inhibition and microenvironment modulation via epigenetic reprogramming. The purpose of this study was to evaluate the safety, pharmacokinetics (PK), and preliminary efficacy of chidamide in combination with exemestane in HR+ ABC patients.

Methods

Eligible patients were postmenopausal women with HR+ ABC recurrent or progressed to at least one endocrine therapy. Blood samples were obtained in the run-in period and the first day of combination treatment for PK analysis. In combination treatment, patients were given exemestane 25 mg daily and chidamide 30 mg twice a week (BIW) until progression of disease or intolerable toxicities. A treatment cycle was defined as 4 weeks. Safety, PK parameters, and preliminary efficacy were evaluated.

Results

A total of 20 patients were enrolled between July and December, 2015. The median number of treatments cycle was 5.2 (20.8 weeks) with 2 patients still on treatment at the data cut-off date of October, 2017. The treatment-related adverse events (AE) ≥ grade 3 in more than 2 patients were neutropenia (35%), thrombocytopenia (30%), and leucopenia (20%). The plasma exposure of exemestane was consistent in the presence or absence of chidamide. A slight increase in chidamide exposure was noted in the presence of exemestane, probably due to the inter- and intra-patient variations. The best response in 16 evaluable patients was assessed by Response Evaluation Criteria in Solid Tumors (RECIST), including 4 patients with partial response, 10 patients with stable disease. The median progression-free survival (PFS) was 7.6 months.

Conclusions

The combination of chidamide with exemestane was generally well tolerated with promising preliminary efficacy in HR+ ABC patients. The overall results from this study encourage further pivotal trial in this patient population.

Regulation of PD-1/PD-L1 pathway and resistance to PD-1/PD-L1 blockade

Immune checkpoint blockades, such as inhibitors against programmed death 1 (PD-1) and its ligand (PD-L1), have received extensive attention in the past decade because of their dramatic clinical outcomes in advanced malignancies. However, both primary and acquired resistance becomes one of the major obstacles, which greatly limits the long-lasting effects and wide application of PD-1/PD-L1 blockade therapy. PD-1/PD-L1 both regulates and is regulated by cellular signaling pathways and epigenetic modification, thus inhibiting the proliferation and effector function of T and B cells. The lack of tumor antigens and effective antigen presentation, aberrant activation of oncogenic pathways, mutations in IFN-γ signaling, immunosuppressive tumor microenvironment such as regulatory T cells, myeloid-derived suppressor cells, M2 macrophages, and immunoinhibitory cytokines can lead to resistance to PD-1/PD-L1 blockade. In this review, we describe PD-1 related signaling pathways, essential factors contributing to the resistance of PD-1 blockade, and discuss strategies to increase the efficacy of immunotherapy. Furthermore, we discuss the possibility of combined epigenetic therapy with PD-1 blockade as a potential promising approach for cancer treatment.

Progesterone impairs antigen-non-specific immune protection by CD8 T memory cells via interferon-γ gene hypermethylation

Pregnant women and animals have increased susceptibility to a variety of intracellular pathogens including Listeria monocytogenes (LM), which has been associated with significantly increased level of sex hormones such as progesterone. CD8 T memory(Tm) cell-mediated antigen-non-specific IFN-γ responses are critically required in the host defense against LM. However, whether and how increased progesterone during pregnancy modulates CD8 Tm cell-mediated antigen-non-specific IFN-γ production and immune protection against LM remain poorly understood. Here we show in pregnant women that increased serum progesterone levels are associated with DNA hypermethylation of IFN-γ gene promoter region and decreased IFN-γ production in CD8 Tm cells upon antigen-non-specific stimulation ex vivo. Moreover, IFN-γ gene hypermethylation and significantly reduced IFN-γ production post LM infection in antigen-non-specific CD8 Tm cells are also observed in pregnant mice or progesterone treated non-pregnant female mice, which is a reversible phenotype following demethylation treatment. Importantly, antigen-non-specific CD8 Tm cells from progesterone treated mice have impaired anti-LM protection when adoptive transferred in either pregnant wild type mice or IFN-γ-deficient mice, and demethylation treatment rescues the adoptive protection of such CD8 Tm cells. These data demonstrate that increased progesterone impairs immune protective functions of antigen-non-specific CD8 Tm cells via inducing IFN-γ gene hypermethylation. Our findings thus provide insights into a new mechanism through which increased female sex hormone regulate CD8 Tm cell functions during pregnancy.

Increased female sex hormones during pregnancy generate a temporary immune suppression status in the pregnant that protect the developing fetus from maternal rejection but renders the pregnant highly susceptible to various pathogens. However, molecular mechanisms underlying such an increased maternal susceptibility to pathogens during pregnancy remain to be further understood. Here we show in pregnant women that increased progesterone levels are associated with IFN-γ gene hypermethylation and reduced IFN-γ production in peripheral CD8 Tm cells. By using murine models of LM infection, for the first time we show a causal relationship between increased level of progesterone, a characteristic female sex hormone of pregnancy, and increased susceptibility to Listeria monocytogenes, an intracellular bacterium that endangers both the pregnant and the fetus. Such an impact on anti-listeria host defense is mediated through progesterone-induced IFN-γ gene hypermethylation in CD8 Tm cells, resulting in impaired IFN-γ production and reduced immune protection by antigen-non-specific CD8 Tm cells. This study provides new insights into molecular mechanisms underlying the increased susceptibility to intracellular pathogens during pregnancy.

Complete molecular remission in relapsed and refractory acute myeloid leukaemia with MLL-AF9 treated with chidamide-based chemotherapy

WHAT IS KNOWN AND OBJECTIVE

The mixed lineage leukaemia (MLL) gene translocations are found in approximately 10% of adults with acute myeloid leukaemia (AML) and are markers of poor prognosis. As the best reported response in relapsed and refractory MLL-rearranged AML is around 40%, reinduction treatment is very challenging for those patients.

CASE DESCRIPTION

We report a case of relapsed and refractory AML with MLL-AF9, who did not respond to FLAG (fludarabine, cytarabine, granulocyte colony stimulating factor) regimen reinduction treatment, but achieved complete response and molecular remission after chidamide-based chemotherapy.

WHAT IS NEW AND CONCLUSION

Chidamide (CS055/HBI-8000) is a new histone deacetylase (HDAC) inhibitor that is clinically active in relapsed and refractory peripheral T-cell lymphomas. To the best of our knowledge, successful reinduction treatment on relapsed MLL-AF9 by chidamide-based regimen has not been previously reported.

Epigenetics and immunotherapy: The current state of play

Cancer cells employ a number of mechanisms to escape immunosurveillance and facilitate tumour progression. The recent explosion of interest in immunotherapy, especially immune checkpoint blockade, is a result of discoveries about the fundamental ligand-receptor interactions that occur between immune and cancer cells within the tumour microenvironment. Distinct ligands expressed by cancer cells engage with cell surface receptors on immune cells, triggering inhibitory pathways (such as PD-1/PD-L1) that render immune cells immunologically tolerant. Importantly, recent studies on the role of epigenetics in immune evasion have exposed a key role for epigenetic modulators in augmenting the tumour microenvironment and restoring immune recognition and immunogenicity. Epigenetic drugs such as DNA methyltransferase and histone deacetylase inhibitors can reverse immune suppression via several mechanisms such as enhancing expression of tumour-associated antigens, components of the antigen processing and presenting machinery pathways, immune checkpoint inhibitors, chemokines, and other immune-related genes. These discoveries have established a highly promising basis for studies using combined epigenetic and immunotherapeutic agents as anti-cancer therapies. In this review, we discuss the exciting role of epigenetic immunomodulation in tumour immune escape, emphasising its significance in priming and sensitising the host immune system to immunotherapies through mechanisms such as the activation of the viral defence pathway. With this background in mind, we highlight the promise of combined epigenetic therapy and immunotherapy, focusing on immune checkpoint blockade, to improve outcomes for patients with many different cancer types.

The double-edged sword of (re)expression of genes by hypomethylating agents: from viral mimicry to exploitation as priming agents for targeted immune checkpoint modulation

Hypomethylating agents (HMAs) have been widely used over the last decade, approved for use in myelodysplastic syndrome (MDS), chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML). The proposed central mechanism of action of HMAs, is the reversal of aberrant methylation in tumor cells, thus reactivating CpG-island promoters and leading to (re)expression of tumor suppressor genes. Recent investigations into the mode of action of azacitidine (AZA) and decitabine (DAC) have revealed new molecular mechanisms that impinge on tumor immunity via induction of an interferon response, through activation of endogenous retroviral elements (ERVs) that are normally epigenetically silenced. Although the global demethylation of DNA by HMAs can induce anti-tumor effects, it can also upregulate the expression of inhibitory immune checkpoint receptors and their ligands, resulting in secondary resistance to HMAs. Recent studies have, however, suggested that this could be exploited to prime or (re)sensitize tumors to immune checkpoint inhibitor therapies. In recent years, immune checkpoints have been targeted by novel therapies, with the aim of (re)activating the host immune system to specifically eliminate malignant cells. Antibodies blocking checkpoint receptors have been FDA-approved for some solid tumors and a plethora of clinical trials testing these and other checkpoint inhibitors are under way. This review will discuss AZA and DAC novel mechanisms of action resulting from the re-expression of pathologically hypermethylated promoters of gene sets that are related to interferon signaling, antigen presentation and inflammation. We also review new insights into the molecular mechanisms of action of transient, low-dose HMAs on various tumor types and discuss the potential of new treatment options and combinations.

Demethylating agent decitabine disrupts tumor-induced immune tolerance by depleting myeloid-derived suppressor cells

PURPOSE

The immunoregulatory effect of demethylating agent decitabine (DAC) has been recognized recently. However, little is known about its impact on immune tolerance. In this study, we aimed to determine the impact of DAC on the immune tolerance induced by tumor cells.

METHODS

The effects of DAC on immune cells in vivo were measured by flow cytometry. Myeloid-derived suppressor cells (MDSCs) were sorted using magnetic beads and cultured in vitro. The mixed lymphocyte reaction was used to determine the immunoregulatory effect of DAC in vitro. An adoptive transfusion mouse model was established to evaluate the effect in vivo.

RESULTS

We found that DAC treatment significantly depleted MDSCs in vivo by inducing MDSCs apoptosis. When given at a low dose, the immune effector cells were less affected by the treatment, except for MDSCs. The mixed lymphocyte reaction in vitro showed that T-cell responses were enhanced when MDSCs were depleted. Supplementation of MDSCs would attenuate this T-cell activation effect. Using an adoptive transfusion mouse model, we further demonstrated in vivo that DAC treatment could induce autologous anti-tumor immune response by depleting MDSCs.

CONCLUSIONS

This study is the first to illustrate DAC's immunoregulatory effect on immune tolerance. The disruption of immune tolerance is due to MDSCs depletion that induces an autologous immune response in vivo. By depleting MDSCs, DAC treatment removes one of the obstacles affecting anti-tumor immune activation and warrants further experimental and clinical studies to explore its potential utility in combination with various anti-tumor immunotherapies in the future.

Chidamide in the treatment of peripheral T-cell lymphoma

Mature T-cell lymphomas are aggressive malignancies. Treatment outcome is poor with conventional chemotherapy. They are about twice as common in Asia as compared with other non-Asian countries. Histone proteins form the basic structure of chromatin, and their acetylation at lysine residues relaxes chromatin structure, facilitating gene transcription. Conversely, histone deacetylation, catalyzed by histone deacetylases, compacts chromatin and represses gene transcription. Histone deacetylase inhibitors are an important class of antineoplastic agents. Chidamide is a novel orally active benzamide-type histone deacetylase inhibitor that has shown in vitro activities against a wide array of neoplasms. In Phase I trials, chidamide showed preferential efficacy in mature T-cell lymphomas. In a pivotal Phase II trial of chidamide in 79 patients with relapsed or refractory mature T-cell lymphomas, an overall response rate of 28% (complete remission/complete remission unconfirmed: 14%) was achieved, with most responses occurring within the first 6 weeks of treatment. The median duration of response (DOR) was 9.9 (1.1–40.8) months. Of 22 responders, 19 patients (86%) had a DOR of ≥3 months and eight patients (36%) had a DOR of >12 months. Angioimmunoblastic T-cell lymphoma and anaplastic large cell lymphoma (anaplastic lymphoma kinase-negative) showed better response rates, with the most durable responses observed in angioimmunoblastic T-cell lymphoma patients. Safety profile was favorable, with very few cases of grade 3/4 toxicities observed. Chidamide is approved by the China Food and Drug Administration for the treatment of relapsed and refractory peripheral T-cell lymphomas.

The prevalence of expression of MAGE-A3 and PRAME tumor antigens in East and South East Asian non-small cell lung cancer patients

INTRODUCTION

Treatment of non-small cell lung cancer (NSCLC) is an important and often unmet medical need regardless of the disease stage at the time of first diagnosis. Antigen-specific immunotherapy may be a feasible therapeutic option if tumor associated antigens (TAAs) that can be targeted by the patient's immune system are identified. The study objective (NCT01837511) was to investigate the expression rates of MAGE-A3 and PRAME in tumors from East Asian NSCLC patients, and the associations between TAA expression and clinico-pathologic patient characteristics.

METHODS

Archived formalin-fixed paraffin-embedded tumor tissue specimens were tested for MAGE-A3 and PRAME expression by quantitative reverse transcription polymerase chain reaction. Exploratory analyses of the impact of patient and tumor characteristics on antigen expression were performed by multivariate logistic regression analyses.

RESULTS

A total of 377 specimens were tested and a valid expression result was obtained for 86.5% and 92.6% for MAGE-A3 and PRAME, respectively. Of the specimens with valid test results, 26.4% expressed MAGE-A3, 49.9% PRAME, 20.0% both and 57.5% expressed at least one TAA. The same pattern of associations between antigen expression and patient and tumor characteristics was found for both TAAs: higher rates of antigen-positive tumors were found in squamous cell carcinomas compared to adenocarcinomas, and for smokers compared to non-smokers.

CONCLUSIONS

Expression of MAGE-A3 and PRAME suggests an association with tumor histology and the patient's smoking status. The rates of TAA-positive tumors found in these East and South East Asian NSCLC patients indicate that both antigens may serve as targets for antigen-specific immunotherapies.

A phase I trial of an oral subtype-selective histone deacetylase inhibitor, chidamide, in combination with paclitaxel and carboplatin in patients with advanced non-small cell lung cancer

Objective

This phase I study was to evaluate safety, maximum tolerated dose, pharmacokinetics and preliminary antitumor activity of chidamide, a novel subtype-selective histone deacetylase (HDAC) inhibitor, in combination with paclitaxel and carboplatin in patients with advanced non-small cell lung cancer (NSCLC).

Methods

Ten patients received oral chidamide 20, 25, or 30 mg twice per week continuously with paclitaxel (175 mg/m²) and carboplatin [area under the curve (AUC) 5 mg/mL/min] administered in a 3-week cycle. Patients with response and stable disease after four cycles maintained chidamide monotherapy until disease progression or unacceptable toxicity. Blood samples were collected for pharmacokinetic analysis after the first single oral of chidamide and first combination treatment in cycle 1 from all patients.

Results

Two dose-limiting toxicities were recorded in the 30 mg cohort, including thrombocytopenia and prolonged neutropenia in the first cycle. Grade 3/4 neutropenia in any cycle was observed in all patients, but was not associated with significant complications. Other grade 3/4 hematologic toxicities included thrombocytopenia and leucopenia. No significant changes were observed in pharmacokinetic parameters for both chidamide and paclitaxel. One patient in the 20 mg cohort had confirmed partial response (PR). Two out of 5 patients with brain metastases had intracranial complete remission after 4-cycle treatment.

Conclusions

Chidamide combined with paclitaxel and carboplatin was generally tolerated without unanticipated toxicities or clinically relevant pharmacokinetic interactions. The recommended dose for chidamide in this combination was established at 20 mg, and a phase II trial is ongoing with this regimen in patients with advanced NSCLC.

Diverse HLA-I Peptide Repertoires of the APC Lines MUTZ3-Derived Immature and Mature Dendritic Cells and THP1-Derived Macrophages

Dendritic cells (DCs) and macrophages are specialized APCs that process and present self-Ags for induction of tolerance and foreign Ags to initiate T cell-mediated immunity. Related to differentiation states they have specific phenotypes and functions. However, the impact of these differentiations on Ag processing and presentation remains poorly defined. To gain insight into this, we analyzed and compared the HLA-I peptidomes of MUTZ3-derived human immature and mature DC lines and THP1-derived macrophages by liquid chromatography tandem mass spectrometry. We found that the HLA-I peptidomes were heterogeneous and individualized and were dominated by nonapeptides with similar HLA-I binding affinities and anchor residues. MUTZ3-derived DCs and THP1-derived macrophages were able to sample peptides from source proteins of almost all subcellular locations and were involved in various cellular functions in similar proportion, with preference to proteins involved in cell communication, signal transduction, protein metabolism, and transcription factor/regulator activity.

Development of chidamide for peripheral T-cell lymphoma, the first orphan drug approved in China

Peripheral T-cell lymphoma (PTCL) is a set of rare and highly heterogeneous group of mature T- and NK-cell neoplasms associated with poor outcomes and lack of standard and effective therapies. The total number of newly diagnosed cases of PTCL yearly in China is estimated about 50,000. Chidamide (CS055) is a novel and orally active benzamide class of histone deacetylase (HDAC) inhibitor that selectively inhibits activity of HDAC1, 2, 3 and 10, the enzymes that are involved and play an important role in tumor initiation and development in both tumor cells and their surrounding micro-environment. Functioning as a genuine epigenetic modulator, chidamide induces growth arrest and apoptosis in tumor cells and enhances cellular antitumor immunity. Based on the overall results from preclinical and phase I clinical studies, exploratory and pivotal phase II trials of chidamide for relapsed or refractory PTCL were conducted from March 2009 to May 2012, and the results led to CFDA approval of chidamide for the indication in December 2014, being the first approved orphan drug according to the research & development approach of orphan drugs in China, as well as the first orally active drug for PTCL in China and worldwide.

The cancer/testis-antigen PRAME supports the pluripotency network and represses somatic and germ cell differentiation programs in seminomas

BACKGROUND

Cancer/testis-antigens (CTAs) are specifically expressed in human malignancies and testis tissue, but their molecular functions are poorly understood. CTAs serve as regulators of gene expression, cell cycle and spermatogenesis, as well as targets for immune-based therapies. The CTA PRAME is expressed in various cancers, antagonises retinoic acid signalling and is regulated by DNA methylation and histone acetylation.

METHODS

We analysed the molecular function of the CTA PRAME in primordial germ cells (PGC) and testicular germ cell cancers (GCC). GCCs arise from a common precursor lesion termed germ cell neoplasia in situ (GCNIS), which itself is thought to originate from a defective PGC. GCNIS cells eventually develop into unipotent seminomas or totipotent embryonal carcinomas (ECs), which are capable of differentiation into teratomas, yolk-sac tumours and choriocarcinomas.

RESULTS

PRAME is, like the master regulator of PGCs SOX17 expressed in human PGCs, GCNIS and seminomas but absent in ECs. shRNA-mediated knockdown of PRAME in seminomatous TCam-2 cells left SOX17 levels unchanged, but resulted in downregulation of pluripotency- and PGC-related genes (LIN28, PRDM14, ZSCAN10), whereas somatic and germ cell differentiation markers were upregulated. So, PRAME seems to act downstream of SOX17 by mediating the regulation of the germ cell differentiation and pluripotency programme. Endoderm differentiation is triggered in somatic cells by SOX17, suggesting that in PGCs, PRAME represses this programme and modulates SOX17 to function as a PGC-master regulator. Surprisingly, knockdown of PRAME in TCam-2 cells did not render the cells sensitive towards retinoic acid, despite the fact that PRAME has been described to antagonise retinoic acid signalling. Finally, we demonstrate that in non-seminomas PRAME expression is silenced by DNA methylation, which can be activated by formation of euchromatin via histone-deacetylase-inhibitors.

CONCLUSIONS

We identified the CTA PRAME as a downstream factor of SOX17 and LIN28 in regulating pluripotency and suppressing somatic/germ cell differentiation in PGC, GCNIS and seminomas.