Loss of the histone methyltransferase EZH2 induces resistance to multiple drugs in acute myeloid leukemia

Proteasome inhibition enhances the anti-leukemic efficacy of chimeric antigen receptor (CAR) expressing NK cells against acute myeloid leukemia

BACKGROUND

Relapsed and refractory acute myeloid leukemia (AML) carries a dismal prognosis. CAR T cells have shown limited efficacy in AML, partially due to dysfunctional autologous T cells and the extended time for generation of patient specific CAR T cells. Allogeneic NK cell therapy is a promising alternative, but strategies to enhance efficacy and persistence may be necessary. Proteasome inhibitors (PI) induce changes in the surface proteome which may render malignant cells more vulnerable to NK mediated cytotoxicity. Here, we investigated the potential benefit of combining PIs with CAR-expressing allogeneic NK cells against AML.

METHODS

We established the IC50 concentrations for Bortezomib and Carfilzomib against several AML cell lines. Surface expression of class-I HLA molecules and stress-associated proteins upon treatment with proteasome inhibitors was determined by multiparameter flow cytometry. Using functional in vitro assays, we explored the therapeutic synergy between pre-treatment with PIs and the anti-leukemic efficacy of NK cells with or without expression of AML-specific CAR constructs against AML cell lines and primary patient samples. Also, we investigated the tolerability and efficacy of a single PI application strategy followed by (CAR-) NK cell infusion in two different murine xenograft models of AML.

RESULTS

AML cell lines and primary AML patient samples were susceptible to Bortezomib and Carfilzomib mediated cytotoxicity. Conditioned resistance to Azacitidine/Venetoclax did not confer primary resistance to PIs. Treating AML cells with PIs reduced the surface expression of class-I HLA molecules on AML cells in a time-and-dose dependent manner. Stress-associated proteins were upregulated on the transcriptional level and on the cell surface. NK cell mediated killing of AML cells was enhanced in a synergistic manner. PI pre-treatment increased effector-target cell conjugate formation and Interferon-γ secretion, resulting in enhanced NK cell activity against AML cell lines and primary samples in vitro. Expression of CD33- and CD70-specific CARs further improved the antileukemic efficacy. In vivo, Bortezomib pre-treatment followed by CAR-NK cell infusion reduced AML growth, leading to prolonged overall survival.

CONCLUSIONS

PIs enhance the anti-leukemic efficacy of CAR-expressing allogeneic NK cells against AML in vitro and in vivo, warranting further exploration of this combinatorial treatment within early phase clinical trials.

HOXA9 versus HOXB9; particular focus on their controversial role in tumor pathogenesis

The Homeobox (HOX) gene family is essential to regulating cellular processes because it maintains the exact coordination required for tissue homeostasis, cellular differentiation, and embryonic development. The most distinctive feature of this class of genes is the presence of the highly conserved DNA region known as the homeobox, which is essential for controlling their regulatory activities. Important players in the intricate process of genetic regulation are the HOX genes. Many diseases, especially in the area of cancer, are linked to their aberrant functioning. Due to their distinctive functions in biomedical research-particularly in the complex process of tumor advancement-HOXA9 and HOXB9 have drawn particular attention. HOXA9 and HOXB9 are more significant than what is usually connected with HOX genes since they have roles in the intricate field of cancer and beyond embryonic processes. The framework for a focused study of the different effects of HOXA9 and HOXB9 in the context of tumor biology is established in this study.

Epigenetic alterations in AML: Deregulated functions leading to new therapeutic options

Acute myeloid leukemia (AML) results in disruption of the hematopoietic differentiation process. Crucial progress has been made, and new therapeutic strategies for AML have been developed. Induction chemotherapy, however, remains the main option for the majority of AML patients. Epigenetic dysregulation plays a central role in AML pathogenesis, supporting leukemogenesis and maintenance of leukemic stem cells. Here, we provide an overview of the intricate interplay of altered epigenetic mechanisms, including DNA methylation, histone modifications, and chromatin remodeling, in AML development. We explore the role of epigenetic regulators, such as DNMTs, HMTs, KDMs, and HDACs, in mediating gene expression patterns pushing towards leukemic cell transformation. Additionally, we discuss the impact of cytogenetic lesions on epigenomic remodeling and the potential of targeting epigenetic vulnerabilities as a therapeutic strategy. Understanding the epigenetic landscape of AML offers insights into novel therapeutic avenues, including epigenetic modifiers and particularly their use in combination therapies, to improve treatment outcomes and overcome drug resistance.

Identification of novel biomarkers and potential molecular targets for uterine cancer using network-based approach

A better understanding of incidences at the cellular level in uterine cancer is necessary for its effective treatment and favourable prognosis. Till date, it lacks appropriate molecular target-based treatment because of unknown molecular mechanisms that proceed to cancer and no drug has shown the required results of treatment with less severe side effects. Uterine Cancer is one of the top five cancer diagnoses and among the ten most common death-causing cancer in the United States of America. There is no FDA-approved drug for it yet. Therefore, it became necessary to identify the molecular targets for molecular targeted therapy of this widely prevalent cancer type. For this study, we used a network-based approach to the list of the deregulated (both up and down-regulated) genes taking adjacent p-Value ≤ 0.05 as significance cut off for the mRNA data of uterine cancer. We constructed the protein-protein interaction (PPI) network and analyzed the degree, closeness, and betweenness centrality-like topological properties of the PPI network. Then we traced the top 30 genes listed from each topological property to find the key regulators involved in the endometrial cancer (ECa) network. We then detected the communities and sub-communities from the PPI network using the Cytoscape network analyzer and Louvain modularity optimization method. A set of 26 (TOP2A, CENPE, RAD51, BUB1, BUB1B, KIF2C, KIF23, KIF11, KIF20A, ASPM, AURKA, AURKB, PLK1, CDC20, CDKN2A, EZH2, CCNA2, CCNB1, CDK1, FGF2, PRKCA, PGR, CAMK2A, HPGDS, and CDCA8) genes were found to be key genes of ECa regulatory network altered in disease state and might be playing the regulatory role in complex ECa network. Our study suggests that among these genes, KIF11 and H PGDS appeared to be novel key genes identified in our research. We also identified these key genes interactions with miRNAs.

Telomere dysfunction alters intestinal stem cell dynamics to promote cancer

Telomere dynamics are linked to aging hallmarks, and age-associated telomere loss fuels the development of epithelial cancers. In Apc-mutant mice, the onset of DNA damage associated with telomere dysfunction has been shown to accelerate adenoma initiation via unknown mechanisms. Here, we observed that Apc-mutant mice engineered to experience telomere dysfunction show accelerated adenoma formation resulting from augmented cell competition and clonal expansion. Mechanistically, telomere dysfunction induces the repression of EZH2, resulting in the derepression of Wnt antagonists, which causes the differentiation of adjacent stem cells and a relative growth advantage to Apc-deficient telomere dysfunctional cells. Correspondingly, in this mouse model, GSK3β inhibition countered the actions of Wnt antagonists on intestinal stem cells, resulting in impaired adenoma formation of telomere dysfunctional Apc-mutant cells. Thus, telomere dysfunction contributes to cancer initiation through altered stem cell dynamics, identifying an interception strategy for human APC-mutant cancers with shortened telomeres.

EZH2-mediated development of therapeutic resistance in cancer

Enhancer of zeste homolog 2 (EZH2) regulates gene expression and plays a definite role in cell proliferation, apoptosis, and senescence. Overexpression of EZH2 has been found in various human malignancies, including prostate, breast, and ovarian cancers, and is associated with increased metastasis and poor prognosis. EZH2 catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) as a canonical role in a PRC2-dependent manner. This mechanism silences various tumor suppressor genes through EZH2-mediated histone lysine methyltransferase activity. As a non-canonical role, EZH2 partners with other signaling molecules to undergo post-translational modification to orchestrate its function as a co-activator playing a critical role in cancer progression. Dysregulation of EZH2 has also been associated with therapeutic resistance in cancer cells. Given the role of EZH2 in promoting carcinogenesis and therapy resistance, both canonical and non-canonical EZH2 inhibitors have been used to combat multiple cancer types. Moreover, combining EZH2 inhibitors with other therapeutic modalities have shown to enhance the therapeutic efficacy and overcome potential resistance mechanisms in these cancerous cells. Therefore, targeting EZH2 through canonical and non-canonical modes appears to be a promising therapeutic strategy to enhance efficacy and overcome resistance in multiple cancers.

Regulation of EZH2 protein stability: new mechanisms, roles in tumorigenesis, and roads to the clinic

The importance of EZH2 as a key methyltransferase has been well documented theoretically. Practically, the first EZH2 inhibitor Tazemetostat (EPZ6438), was approved by FDA in 2020 and is used in clinic. However, for most solid tumors it is not as effective as desired and the scope of clinical indications is limited, suggesting that targeting its enzymatic activity may not be sufficient. Recent technologies focusing on the degradation of EZH2 protein have drawn attention due to their potential robust effects. This review focuses on the molecular mechanisms that regulate EZH2 protein stability via post-translational modifications (PTMs), mainly including ubiquitination, phosphorylation, and acetylation. In addition, we discuss recent advancements of multiple proteolysis targeting chimeras (PROTACs) strategies and the latest degraders that can downregulate EZH2 protein. We aim to highlight future directions to expand the application of novel EZH2 inhibitors by targeting both EZH2 enzymatic activity and protein stability.

Epigenetic vulnerabilities of leukemia harboring inactivating EZH2 mutations

Epigenetic regulators, such as the polycomb repressive complex 2 (PRC2), play a critical role in both normal development and carcinogenesis. Mutations and functional dysregulation of PRC2 complex components, such as EZH2, are implicated in various forms of cancer and associated with poor prognosis. This study investigated the epigenetic vulnerabilities of acute myeloid leukemia (AML) and myelodysplastic/myeloproliferative disorders (MDS/MPN) by performing a chemical probe screen in patient cells. Paradoxically, we observed increased sensitivity to EZH2 and embryonic ectoderm development (EED) inhibitors in AML and MDS/MPN patient cells harboring EZH2 mutations. Expression analysis indicated that EZH2 inhibition elicited upregulation of pathways responsible for cell death and growth arrest, specifically in patient cells with mutant EZH2. The identified EZH2 mutations had drastically reduced catalytic activity, resulting in lower cellular H3K27me3 levels, and were associated with decreased EZH2 and PRC2 component EED protein levels. Overall, this study provides an important understanding of the role of EZH2 dysregulation in blood cancers and may indicate disease etiology for these poor prognosis AML and MDS/MPN cases.

FLT3 tyrosine kinase inhibition modulates PRC2 and promotes differentiation in acute myeloid leukemia

Internal tandem duplication mutations in fms-like tyrosine kinase 3 (FLT3-ITD) are recurrent in acute myeloid leukemia (AML) and increase the risk of relapse. Clinical responses to FLT3 inhibitors (FLT3i) include myeloid differentiation of the FLT3-ITD clone in nearly half of patients through an unknown mechanism. We identified enhancer of zeste homolog 2 (EZH2), a component of polycomb repressive complex 2 (PRC2), as a mediator of this effect using a proteomic-based screen. FLT3i downregulated EZH2 protein expression and PRC2 activity on H3K27me3. FLT3-ITD and loss-of-function mutations in EZH2 are mutually exclusive in human AML. We demonstrated that FLT3i increase myeloid maturation with reduced stem/progenitor cell populations in murine Flt3-ITD AML. Combining EZH1/2 inhibitors with FLT3i increased terminal maturation of leukemic cells and reduced leukemic burden. Our data suggest that reduced EZH2 activity following FLT3 inhibition promotes myeloid differentiation of FLT3-ITD leukemic cells, providing a mechanistic explanation for the clinical observations. These results demonstrate that in addition to its known cell survival and proliferation signaling, FLT3-ITD has a second, previously undefined function to maintain a myeloid stem/progenitor cell state through modulation of PRC2 activity. Our findings support exploring EZH1/2 inhibitors as therapy for FLT3-ITD AML.

MIR143HG promotes methylation of transcription factor HOXB7 promoter by recruiting methyltransferase DNMT1 to prevent the progression of colon cancer

In recent years, accumulating evidence has demonstrated the role of long noncoding RNAs (lncRNAs) in colon cancer. We aim to investigate the role of MIR143HG, also known as CARMN (Cardiac mesoderm enhancer-associated noncoding RNA) in colon cancer and explore the related mechanisms. An RNAseq data analysis was performed to screen differentially expressed lncRNAs associated with colon cancer. Next, MIR143HG expression was quantified in colon cancer cells. Moreover, the contributory roles of MIR143HG in the progression of colon cancer with the involvement of DNMT1 and HOXB7 (Homeobox B7) were evaluated after restored MIR143HG or depleted HOXB7. Finally, the effects of MIR143HG were investigated in vivo by measuring tumor formation in nude mice. High-throughput transcriptome sequencing was employed to validate the specific mechanisms by which MIR143HG and HOXB7 affect tumor growth in vivo. MIR143HG was found to be poorly expressed, while HOXB7 was highly expressed in colon cancer. MIR143HG could promote HOXB7 methylation by recruiting DNMT1 to reduce HOXB7 expression. Upregulation of MIR143HG or downregulation of HOXB7 inhibited cell proliferation, invasion and migration and facilitated apoptosis in colon cancer cells so as to delay the progression of colon cancer. The same trend was identified in vivo. Our study provides evidence that restoration of MIR143HG suppressed the progression of colon cancer via downregulation of HOXB7 through DNMT1-mediated HOXB7 promoter methylation. Thus, MIR143HG may be a potential candidate for the treatment of colon cancer.

Deciphering signaling pathways in hematopoietic stem cells: the molecular complexity of Myelodysplastic Syndromes (MDS) and leukemic progression

Myelodysplastic Syndromes, a heterogeneous group of hematological disorders, are characterized by abnormalities in phosphoinositide-dependent signaling, epigenetic regulators, apoptosis, and cytokine interactions within the bone marrow microenvironment, contributing to disease pathogenesis and neoplastic growth. Comprehensive knowledge of these pathways is crucial for the development of innovative therapies that aim to restore normal apoptosis and improve patient outcomes.

Inhibition of PLK4 remodels histone methylation and activates the immune response via the cGAS-STING pathway in TP53-mutated AML

Acute myeloid leukemia (AML) with TP53 mutation is one of the most lethal cancers and portends an extremely poor prognosis. Based on in silico analyses of druggable genes and differential gene expression in TP53-mutated AML, we identified pololike kinase 4 (PLK4) as a novel therapeutic target and examined its expression, regulation, pathogenetic mechanisms, and therapeutic potential in TP53-mutated AML. PLK4 expression was suppressed by activated p53 signaling in TP53 wild-type AML and was increased in TP53-mutated AML cell lines and primary samples. Short-term PLK4 inhibition induced DNA damage and apoptosis in TP53 wild-type AML. Prolonged PLK4 inhibition suppressed the growth of TP53-mutated AML and was associated with DNA damage, apoptosis, senescence, polyploidy, and defective cytokinesis. A hitherto undescribed PLK4/PRMT5/EZH2/H3K27me3 axis was demonstrated in both TP53 wild-type and mutated AML, resulting in histone modification through PLK4-induced PRMT5 phosphorylation. In TP53-mutated AML, combined effects of histone modification and polyploidy activated the cGAS-STING pathway, leading to secretion of cytokines and chemokines and activation of macrophages and T cells upon coculture with AML cells. In vivo, PLK4 inhibition also induced cytokine and chemokine expression in mouse recipients, and its combination with anti-CD47 antibody, which inhibited the "don't-eat-me" signal in macrophages, synergistically reduced leukemic burden and prolonged animal survival. The study shed important light on the pathogenetic role of PLK4 and might lead to novel therapeutic strategies in TP53-mutated AML.

Mutations in the histone methyltransferase Ezh2 drive context-dependent leukemia in Xenopus tropicalis

CRISPR-mediated simultaneous targeting of candidate tumor suppressor genes in Xenopus tropicalis allows fast functional assessment of co-driver genes for various solid tumors. Genotyping of tumors that emerge in the mosaic mutant animals rapidly exposes the gene mutations under positive selection for tumor establishment. However, applying this simple approach to the blood lineage has not been attempted. Multiple hematologic malignancies have mutations in EZH2, encoding the catalytic subunit of the Polycomb Repressive Complex 2. Interestingly, EZH2 can act as an oncogene or a tumor suppressor, depending on cellular context and disease stage. We show here that mosaic CRISPR/Cas9 mediated ezh2 disruption in the blood lineage resulted in early and penetrant acute myeloid leukemia (AML) induction. While animals were co-targeted with an sgRNA that induces notch1 gain-of-function mutations, sequencing of leukemias revealed positive selection towards biallelic ezh2 mutations regardless of notch1 mutational status. Co-targeting dnm2, recurrently mutated in T/ETP-ALL, induced a switch from myeloid towards acute T-cell leukemia. Both myeloid and T-cell leukemias engrafted in immunocompromised hosts. These data underline the potential of Xenopus tropicalis for modeling human leukemia, where mosaic gene disruption, combined with deep amplicon sequencing of the targeted genomic regions, can rapidly and efficiently expose co-operating driver gene mutations.

DNA methylation of HOX genes and its clinical implications in cancer

Homeobox (HOX) genes encode highly conserved transcription factors that play vital roles in embryonic development. DNA methylation is a pivotal regulatory epigenetic signaling mark responsible for regulating gene expression. Abnormal DNA methylation is largely associated with the aberrant expression of HOX genes, which is implicated in a broad range of human diseases, including cancer. Numerous studies have clarified the mechanisms of DNA methylation in both physiological and pathological processes. In this review, we focus on how DNA methylation regulates HOX genes and briefly discuss drug development approaches targeting these mechanisms.

Tumor-suppressive functions of protein lysine methyltransferases

Protein lysine methyltransferases (PKMTs) play crucial roles in histone and nonhistone modifications, and their dysregulation has been linked to the development and progression of cancer. While the majority of studies have focused on the oncogenic functions of PKMTs, extensive evidence has indicated that these enzymes also play roles in tumor suppression by regulating the stability of p53 and β-catenin, promoting α-tubulin-mediated genomic stability, and regulating the transcription of oncogenes and tumor suppressors. Despite their contradictory roles in tumorigenesis, many PKMTs have been identified as potential therapeutic targets for cancer treatment. However, PKMT inhibitors may have unintended negative effects depending on the specific cancer type and target enzyme. Therefore, this review aims to comprehensively summarize the tumor-suppressive effects of PKMTs and to provide new insights into the development of anticancer drugs targeting PKMTs.

A guide to epigenetics in leukaemia stem cells

Leukaemia stem cells (LSCs) are the critical seed for the growth of haematological malignancies, driving the clonal expansion that enables disease initiation, relapse and often resistance. Specifically, they display inherent phenotypic and epigenetic plasticity resulting in complex heterogenic diseases. In this review, we discuss the key principles of deregulation of epigenetic processes that shape this disease evolution. We consider measures to define and quantify clonal heterogeneity, combining information from recent studies assessing mutational, transcriptional and epigenetic landscapes at single cell resolution in myeloid neoplasms (MN). We highlight the importance of integrating epigenetic and genetic information to better understand inter- and intra-patient heterogeneity and discuss how this understanding further informs evolution and progression trajectories and subsequent clinical response in MN. Under this topic, we also discuss efforts to identify mechanisms of resistance, by longitudinal analyses of patient samples. Finally, we highlight how we might target these aberrant epigenetic processes for better therapeutic outcomes and to potentially eradicate LSCs.

Comprehensive analysis of HOXC8 associated with tumor microenvironment characteristics in colorectal cancer

Background

Accumulating evidence have highlighted the essential roles of HOX genes in embryonic development and carcinogenesis. As a member of the HOX gene family, the abnormal expression of HOXC8 gene is associated with the progression and metastasis of various tumors. However, potential roles of HOXC8 in colorectal cancer (CRC) prognosis and tumor microenvironment (TME) remodeling remain unclear.

Methods

We conducted an integrated analysis of clinical and molecular characteristics, relevant oncogenic and immune regulation roles and drug sensitivity features of HOXC8 in CRC.

Results

HOXC8 expression was markedly high expressed in CRC samples compared to normal samples, and the upregulated expression of HOXC8 was associated with poor prognosis. High HOXC8 expression was significantly associated with invasion-related pathways especially epithelial-mesenchymal transition (EMT). In vitro experiments showed significantly up-regulated HOXC8 expression in some CRC cell lines and its promoting effect on EMT and cell proliferation. TME categorization through transcriptomic analysis of CRC patients with high HOXC8 expression identified two different TME subtypes known as immune-enriched with fibrotic subtype and immune-depleted subtype. Patients with immune-enriched, fibrotic subtype exhibited significantly longer progression-free survival (PFS), upregulated PD-L1 and CTLA4 expression and higher TMB than those with the immune-depleted subtype.

Conclusions

HOXC8 overexpression was associated with poor prognosis and specific TME subtypes in CRC. This study provided valuable resource for further exploring the potential mechanisms and therapeutic targets of HOX genes in CRC.

TRIM21 enhances bortezomib sensitivity in multiple myeloma by halting prosurvival autophagy

Bortezomib (bort) is an effective therapeutic agent for patients with multiple myeloma (MM); however, most patients develop drug resistance. Autophagy, a highly conserved process that recycles cytosol or entire organelles via lysosomal activity, is essential for the survival, homeostasis, and drug resistance in MM. Growing evidence has highlighted that E3 ligase tripartite motif-containing protein 21 (TRIM21) not only interacts with multiple autophagy regulators but also participates in drug resistance in various cancers. However, to date, the direct substrates and additional roles of TRIM21 in MM remain unexplored. In this study, we demonstrated that low TRIM21 expression is a factor for relapse in MM. TRIM21 knockdown (KD) made MM cells more resistant to bort, whereas TRIM21 overexpression (OE) resulted in increased MM sensitivity to bort. Proteomic and phosphoproteomic studies of TRIM21 KD MM cells showed that bort resistance was associated with increased oxidative stress and elevated prosurvival autophagy. Our results showed that TRIM21 KD MM cell lines induced prosurvival autophagy after bort treatment, suppressing autophagy by 3-methyladenine treatment or by the short hairpin RNA of autophagy-related gene 5 (ATG5)-restored-bort sensitivity. Indeed, ATG5 expression was increased and decreased by TRIM21 KD and OE, respectively. TRIM21 affected autophagy by ubiquitinating ATG5 through K48 for proteasomal degradation. Importantly, we confirmed that TRIM21 could potentiate the antimyeloma effect of bort through in vitro and in vivo experiments. Overall, our findings define the key role of TRIM21 in MM bort resistance and provide a foundation for a novel targeted therapeutic approach.

Epigenetic targeting to enhance acute myeloid leukemia-directed immunotherapy

AML is a malignant disease of hematopoietic progenitor cells with unsatisfactory treatment outcome, especially in patients that are ineligible for intensive chemotherapy. Immunotherapy, comprising checkpoint inhibition, T-cell engaging antibody constructs, and cellular therapies, has dramatically improved the outcome of patients with solid tumors and lymphatic neoplasms. In AML, these approaches have been far less successful. Discussed reasons are the relatively low mutational burden of AML blasts and the difficulty in defining AML-specific antigens not expressed on hematopoietic progenitor cells. On the other hand, epigenetic dysregulation is an essential driver of leukemogenesis, and non-selective hypomethylating agents (HMAs) are the current backbone of non-intensive treatment. The first clinical trials that evaluated whether HMAs may improve immune checkpoint inhibitors' efficacy showed modest efficacy except for the anti-CD47 antibody that was substantially more efficient against AML when combined with azacitidine. Combining bispecific antibodies or cellular treatments with HMAs is subject to ongoing clinical investigation, and efficacy data are awaited shortly. More selective second-generation inhibitors targeting specific chromatin regulators have demonstrated promising preclinical activity against AML and are currently evaluated in clinical trials. These drugs that commonly cause leukemia cell differentiation potentially sensitize AML to immune-based treatments by co-regulating immune checkpoints, providing a pro-inflammatory environment, and inducing (neo)-antigen expression. Combining selective targeted epigenetic drugs with (cellular) immunotherapy is, therefore, a promising approach to avoid unintended effects and augment efficacy. Future studies will provide detailed information on how these compounds influence specific immune functions that may enable translation into clinical assessment.

Verification of fasting-mimicking diet to assist monotherapy of human cancer-bearing models

The efficacy of a single clinical nanodrug for cancer treatment is still unsatisfactory, especially for drug-resistant cancer. Herein, we applied a fasting-mimicking diet (FMD) approach via dietary intervention to assist single clinical nanodrug for breast or ovarian cancer treatments instead of using multi-drug therapies which might cause adverse side effects. Specifically, we adopted Doxil or Abraxane to treat human breast tumor-bearing nude mice and Doxil to treat the human ovarian tumor and drug-resistant ovarian tumor-bearing nude mice under FMD conditions, respectively. According to the results, the FMD condition can promote the cellular uptake and cytotoxicity of a single nanodrug, reduce the ATP level in drug-resistant tumor cells to hinder drug efflux, normalize tumor blood vessels, relieve tumor hypoxia, and increase the accumulation of nanodrugs at tumor sites, thereby enhancing the therapeutic effects on these types of human cancers. Collectively, these results demonstrate that the FMD strategy of significance can become a practical, alternative, and promising assistant for single nanodrug for enhancing cancer therapy and clinical translation.

EZH2 can be used as a therapeutic agent for inhibiting endothelial dysfunction

Enhancer of zeste homolog 2 (EZH2) is a catalytic subunit of polycomb repressor complex 2 and plays important roles in endothelial cell homeostasis. EZH2 functionally methylates lysine 27 of histone H3 and represses gene expression through chromatin compaction. EZH2 mediates the effects of environmental stimuli by regulating endothelial functions, such as angiogenesis, endothelial barrier integrity, inflammatory signaling, and endothelial mesenchymal transition. Numerous studies have been conducted to determine the significance of EZH2 in endothelial function. The aim of this review is to provide a concise summary of the roles EZH2 plays in endothelial function and elucidate its therapeutic potential in cardiovascular diseases.

SAM-Competitive EZH2-Inhibitors Induce Platinum Resistance by EZH2-Independent Induction of ABC-Transporters

T-cell lymphomas are heterogeneous and rare lymphatic malignancies with unfavorable prognosis. Consequently, new therapeutic strategies are needed. The enhancer of zeste homologue 2 (EZH2) is the catalytic subunit of the polycomb repressive complex 2 and responsible for lysine 27 trimethylation of histone 3. EZH2 is overexpressed in several tumor entities including T-cell neoplasms leading to epigenetic and consecutive oncogenic dysregulation. Thus, pharmacological EZH2 inhibition is a promising target and its clinical evaluation in T-cell lymphomas shows favorable results. We have investigated EZH2 expression in two cohorts of T-cell lymphomas by mRNA-profiling and immunohistochemistry, both revealing overexpression to have a negative impact on patients' prognosis. Furthermore, we have evaluated EZH2 inhibition in a panel of leukemia and lymphoma cell lines with a focus on T-cell lymphomas characterized for canonical EZH2 signaling components. The cell lines were treated with the inhibitors GSK126 or EPZ6438 that inhibit EZH2 specifically by competitive binding at the S-adenosylmethionine (SAM) binding site in combination with the common second-line chemotherapeutic oxaliplatin. The change in cytotoxic effects under pharmacological EZH2 inhibition was evaluated revealing a drastic increase in oxaliplatin resistance after 72 h and longer periods of combinational incubation. This outcome was independent of cell type but associated to reduced intracellular platinum. Pharmacological EZH2 inhibition revealed increased expression in SRE binding proteins, SREBP1/2 and ATP binding cassette subfamily G transporters ABCG1/2. The latter are associated with chemotherapy resistance due to increased platinum efflux. Knockdown experiments revealed that this was independent of the EZH2 functional state. The EZH2 inhibition effect on oxaliplatin resistance and efflux was reduced by additional inhibition of the regulated target proteins. In conclusion, pharmacological EZH2 inhibition is not suitable in combination with the common chemotherapeutic oxaliplatin in T-cell lymphomas revealing an EZH2-independent off-target effect.

Post-translational modifications of histones: Mechanisms, biological functions, and therapeutic targets

Histones are DNA-binding basic proteins found in chromosomes. After the histone translation, its amino tail undergoes various modifications, such as methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, and lactylation, which together constitute the "histone code." The relationship between their combination and biological function can be used as an important epigenetic marker. Methylation and demethylation of the same histone residue, acetylation and deacetylation, phosphorylation and dephosphorylation, and even methylation and acetylation between different histone residues cooperate or antagonize with each other, forming a complex network. Histone-modifying enzymes, which cause numerous histone codes, have become a hot topic in the research on cancer therapeutic targets. Therefore, a thorough understanding of the role of histone post-translational modifications (PTMs) in cell life activities is very important for preventing and treating human diseases. In this review, several most thoroughly studied and newly discovered histone PTMs are introduced. Furthermore, we focus on the histone-modifying enzymes with carcinogenic potential, their abnormal modification sites in various tumors, and multiple essential molecular regulation mechanism. Finally, we summarize the missing areas of the current research and point out the direction of future research. We hope to provide a comprehensive understanding and promote further research in this field.

High-throughput approaches to uncover synergistic drug combinations in leukemia

We report a comprehensive drug synergy study in acute myeloid leukemia (AML). In this work, we investigate a panel of cell lines spanning both MLL-rearranged and non-rearranged subtypes. The work comprises a resource for the community, with many synergistic drug combinations that could not have been predicted a priori, and open source code for automation and analyses. We base our definitions of drug synergy on the Chou-Talalay method, which is useful for visualizations of synergy experiments in isobolograms, and median-effects plots, among other representations. Our key findings include drug synergies affecting the chromatin state, specifically in the context of regulation of the modification state of histone H3 lysine-27. We report open source high throughput methodology such that multidimensional drug screening can be accomplished with equipment that is accessible to most laboratories. This study will enable preclinical investigation of new drug combinations in a lethal blood cancer, with data analysis and automation workflows freely available to the community.

The Molecular Context of Oxidant Stress Response in Cancer Establishes ALDH1A1 as a Critical Target: What This Means for Acute Myeloid Leukemia

The protein family of aldehyde dehydrogenases (ALDH) encompasses nineteen members. The ALDH1 subfamily consists of enzymes with similar activity, having the capacity to neutralize lipid peroxidation products and to generate retinoic acid; however, only ALDH1A1 emerges as a significant risk factor in acute myeloid leukemia. Not only is the gene ALDH1A1 on average significantly overexpressed in the poor prognosis group at the RNA level, but its protein product, ALDH1A1 protects acute myeloid leukemia cells from lipid peroxidation byproducts. This capacity to protect cells can be ascribed to the stability of the enzyme under conditions of oxidant stress. The capacity to protect cells is evident both in vitro, as well as in mouse xenografts of those cells, shielding cells effectively from a number of potent antineoplastic agents. However, the role of ALDH1A1 in acute myeloid leukemia has been unclear in the past due to evidence that normal cells often have higher aldehyde dehydrogenase activity than leukemic cells. This being true, ALDH1A1 RNA expression is significantly associated with poor prognosis. It is hence imperative that ALDH1A1 is methodically targeted, particularly for the acute myeloid leukemia patients of the poor prognosis risk group that overexpress ALDH1A1 RNA.

Combination Therapies with Kinase Inhibitors for Acute Myeloid Leukemia Treatment

Targeting kinase activity is considered to be an attractive therapeutic strategy to overcome acute myeloid leukemia (AML) since aberrant activation of the kinase pathway plays a pivotal role in leukemogenesis through abnormal cell proliferation and differentiation block. Although clinical trials for kinase modulators as single agents remain scarce, combination therapies are an area of therapeutic interest. In this review, the author summarizes attractive kinase pathways for therapeutic targets and the combination strategies for these pathways. Specifically, the review focuses on combination therapies targeting the FLT3 pathways, as well as PI3K/AKT/mTOR, CDK and CHK1 pathways. From a literature review, combination therapies with the kinase inhibitors appear more promising than monotherapies with individual agents. Therefore, the development of efficient combination therapies with kinase inhibitors may result in effective therapeutic strategies for AML.

Crosstalk between Noncoding RNAs and the Epigenetics Machinery in Pediatric Tumors and Their Microenvironment

According to the World Health Organization, every year, an estimated 400,000+ new cancer cases affect children under the age of 20 worldwide. Unlike adult cancers, pediatric cancers develop very early in life due to alterations in signaling pathways that regulate embryonic development, and environmental factors do not contribute much to cancer development. The highly organized complex microenvironment controlled by synchronized gene expression patterns plays an essential role in the embryonic stages of development. Dysregulated development can lead to tumor initiation and growth. The low mutational burden in pediatric tumors suggests the predominant role of epigenetic changes in driving the cancer phenotype. However, one more upstream layer of regulation driven by ncRNAs regulates gene expression and signaling pathways involved in the development. Deregulation of ncRNAs can alter the epigenetic machinery of a cell, affecting the transcription and translation profiles of gene regulatory networks required for cellular proliferation and differentiation during embryonic development. Therefore, it is essential to understand the role of ncRNAs in pediatric tumor development to accelerate translational research to discover new treatments for childhood cancers. This review focuses on the role of ncRNA in regulating the epigenetics of pediatric tumors and their tumor microenvironment, the impact of their deregulation on driving pediatric tumor progress, and their potential as effective therapeutic targets.

The roles of EZH2 in cancer and its inhibitors

The enhancer of zeste homolog 2 (EZH2) is encoded by the Enhancer of zeste 2 polycomb repressive complex 2 subunit gene. EZH2 is involved in the cell cycle, DNA damage repair, cell differentiation, autophagy, apoptosis, and immunological modulation. The main function of EZH2 is to catalyze the methylation of H3 histone of H3K27Me3, which inhibits the transcription of target genes, such as tumor suppressor genes. EZH2 also forms complexes with transcriptions factors or directly binds to the promoters of target genes, leading to regulate gene transcriptions. EZH2 has been as a prominent target for cancer therapy and a growing number of potential targeting medicines have been developed. This review summarized the mechanisms that EZH2 regulates gene transcription and the interactions between EZH2 and important intracellular signaling molecules (Wnt, Notch, MEK, Akt) and as well the clinical applications of EZH2-targeted drugs.

Sunitinib attenuates reactive MDSCs enhancing anti-tumor immunity in HNSCC

Enhancer of zeste homolog 2 (EZH2) is implicated in promoting HNSCC malignant progression. However, EZH2 inhibitors, when used alone, increase the number of myeloid-derived suppressor cells (MDSCs), which are responsible for enhancing tumor stemness and promoting tumor immune escape. We aimed to determine whether combining tazemetostat (an EZH2 inhibitor) and sunitinib (a MDSC inhibitor) can improve the response rate to an immune-checkpoint-blocking (ICB) therapy. We evaluated the efficacy of the above treatment strategies by bioinformatics analysis and animal experiments. EZH2 overexpression and abundant MDSCs in patients with HNSCC are associated with tumor progression. Tazemetostat treatment alone had limited inhibitory effect on HNSCC progression in the mouse models, accompanied by a surge in the number of MDSCs in the tumor microenvironment. Conversely, the combined use of tazemetostat and sunitinib reduced the number of MDSCs and regulatory T cell populations, promoting intratumoral infiltration of T cells and inhibiting of T cell exhausting, regulating of wnt/β-catenin signaling pathway and tumor stemness, promoting the intratumoral PD-L1 expression and improved the response rate to anti-PD-1 therapy. The combined use of EZH2 and MDSC inhibitors effectively reverses HNSCC-specific immunotherapeutic resistance and is a promising strategy for overcoming resistance to ICB therapy.

Dual inhibition of EZH2 and G9A/GLP histone methyltransferases by HKMTI-1-005 promotes differentiation of acute myeloid leukemia cells

All-trans-retinoic acid (ATRA)-based differentiation therapy of acute promyelocytic leukemia (APL) represents one of the most clinically effective examples of precision medicine and the first example of targeted oncoprotein degradation. The success of ATRA in APL, however, remains to be translated to non-APL acute myeloid leukemia (AML). We previously showed that aberrant histone modifications, including histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) methylation, were associated with this lack of response and that epigenetic therapy with small molecule inhibitors of the H3K4 demethylase LSD1/KDM1A could reprogram AML cells to respond to ATRA. Serving as the enzymatic component of Polycomb Repressive Complex 2, EZH2/KMT6A methyltransferase plays a critical role in normal hematopoiesis by affecting the balance between self-renewal and differentiation. The canonical function of EZH2 is methylation of H3K27, although important non-canonical roles have recently been described. EZH2 mutation or deregulated expression has been conclusively demonstrated in the pathogenesis of AML and response to treatment, thus making it an attractive therapeutic target. In this study, we therefore investigated whether inhibition of EZH2 might also improve the response of non-APL AML cells to ATRA-based therapy. We focused on GSK-343, a pyridone-containing S-adenosyl-L-methionine cofactor-competitive EZH2 inhibitor that is representative of its class, and HKMTI-1-005, a substrate-competitive dual inhibitor targeting EZH2 and the closely related G9A/GLP H3K9 methyltransferases. We found that treatment with HKMTI-1-005 phenocopied EZH2 knockdown and was more effective in inducing differentiation than GSK-343, despite the efficacy of GSK-343 in terms of abolishing H3K27 trimethylation. Furthermore, transcriptomic analysis revealed that in contrast to treatment with GSK-343, HKMTI-1-005 upregulated the expression of differentiation pathway genes with and without ATRA, while downregulating genes associated with a hematopoietic stem cell phenotype. These results pointed to a non-canonical role for EZH2, which was supported by the finding that EZH2 associates with the master regulator of myeloid differentiation, RARα, in an ATRA-dependent manner that was enhanced by HKMTI-1-005, possibly playing a role in co-regulator complex exchange during transcriptional activation. In summary, our results strongly suggest that addition of HKMTI-1-005 to ATRA is a new therapeutic approach against AML that warrants further investigation.

Polycomb Alterations in Acute Myeloid Leukaemia: From Structure to Function

Epigenetic dysregulation is a hallmark of many haematological malignancies and is very frequent in acute myeloid leukaemia (AML). A cardinal example is the altered activity of the Polycomb Repressive Complex 2 (PRC2) due to somatic mutations and deletions in genes encoding PRC2 core factors that are necessary for correct complex assembly. These genetic alterations typically lead to reduced histone methyltransferase activity that, in turn, has been strongly linked to poor prognosis and chemoresistance. In this review, we provide an overview of genetic alterations of PRC components in AML, with particular reference to structural and functional features of PRC2 factors. We further review genetic interactions between these alterations and other AML-associated mutations in both adult and paediatric leukaemias. Finally, we discuss reported prognostic links between PRC2 mutations and deletions and disease outcomes and potential implications for therapy.

Heat-Shock Proteins in Leukemia and Lymphoma: Multitargets for Innovative Therapeutic Approaches

Heat-shock proteins (HSPs) are powerful chaperones that provide support for cellular functions under stress conditions but also for the homeostasis of basic cellular machinery. All cancer cells strongly rely on HSPs, as they must continuously adapt to internal but also microenvironmental stresses to survive. In solid tumors, HSPs have been described as helping to correct the folding of misfolded proteins, sustain oncogenic pathways, and prevent apoptosis. Leukemias and lymphomas also overexpress HSPs, which are frequently associated with resistance to therapy. HSPs have therefore been proposed as new therapeutic targets. Given the specific biology of hematological malignancies, it is essential to revise their role in this field, providing a more adaptable and comprehensive picture that would help design future clinical trials. To that end, this review will describe the different pathways and functions regulated by HSP27, HSP70, HSP90, and, not least, HSP110 in leukemias and lymphomas.

Tumor-derived miRNAs as tumor microenvironment regulators for synergistic therapeutic options

MicroRNAs (miRNAs) are a class of non-coding RNAs that perform post-transcriptional gene regulation. This review focuses on the role of tumor cell-derived miRNAs in the regulation of the tumor microenvironment (TME) via receptor cell recoding, including angiogenesis, expression of immunosuppressive molecules, formation of radiation resistance, and chemoresistance. Furthermore, we discuss the potential of these molecules as adjuvant therapies in combination with chemotherapy, radiotherapy, or immunotherapy, as well as their advantages as efficacy predictors for personalized therapy. MiRNA-based therapeutic agents for tumors are currently in clinical trials, and while challenges remain, additional research on tumor-derived miRNAs is warranted, which may provide significant clinical benefits to cancer patients.

Polycomb Repressive Complex 2 in Oncology

Dynamic regulation of the chromatin state by Polycomb Repressive Complex 2 (PRC2) provides an important mean for epigenetic gene control that can profoundly influence normal development and cell lineage specification. PRC2 and PRC2-induced methylation of histone H3 lysine 27 (H3K27) are critically involved in a wide range of DNA-templated processes, which at least include transcriptional repression and gene imprinting, organization of three-dimensional chromatin structure, DNA replication and DNA damage response and repair. PRC2-based genome regulation often goes wrong in diseases, notably cancer. This chapter discusses about different modes-of-action through which PRC2 and EZH2, a catalytic subunit of PRC2, mediate (epi)genomic and transcriptomic regulation. We will also discuss about how alteration or mutation of the PRC2 core or axillary component promotes oncogenesis, how post-translational modification regulates functionality of EZH2 and PRC2, and how PRC2 and other epigenetic pathways crosstalk. Lastly, we will briefly touch on advances in targeting EZH2 and PRC2 dependence as cancer therapeutics.

Acute myeloid leukemia: novel mutations and their clinical implications

Acute myeloid leukemia (AML) is a heterogenous and challenging hematological malignancy with suboptimal outcomes. The implications of advanced technologies in the genetic characterization of AML have enhanced the understanding of individualized patient risk, which has also led to the development of new therapeutic strategies. A comprehensive study of novel mutations is essential to moderate the complicacies in patient management and achieve optimal outcomes in AML. In this review, we summarized the clinical relevance of important novel mutations, including TET2, ETV6, SATB1, EZH2, PTPN11, and U2AF1, which impact the prognosis of AML. TET2 mutation can lead to DNA hypermethylation, and gene fusion, and mutation in ETV6 disrupts hematopoietic transcription machinery, SATB1 downregulation aggravates the disease, and EZH2 mutation confers resistance to chemotherapy. PTPN11 mutation influences the RAS-MAPK signaling pathway, and U2AF1 alters the splicing of downstream mRNA. The systemic influence of these mutations has adverse consequences. Therefore, extensive research on novel mutations and their mechanism of action in the pathogenesis of AML is vital. This study lays out the perspective of expanding the apprehension about AML and novel drug targets. The combination of advanced genetic techniques, risk stratification, ongoing improvements, and innovations in treatment strategy will undoubtedly lead to improved survival outcomes in AML.

The epigenome and the many facets of cancer drug tolerance

The use of chemotherapeutic agents and the development of new cancer therapies over the past few decades has consequently led to the emergence of myriad therapeutic resistance mechanisms. Once thought to be explicitly driven by genetics, the coupling of reversible sensitivity and absence of pre-existing mutations in some tumors opened the way for discovery of drug-tolerant persisters (DTPs): slow-cycling subpopulations of tumor cells that exhibit reversible sensitivity to therapy. These cells confer multi-drug tolerance, to targeted and chemotherapies alike, until the residual disease can establish a stable, drug-resistant state. The DTP state can exploit a multitude of distinct, yet interlaced, mechanisms to survive otherwise lethal drug exposures. Here, we categorize these multi-faceted defense mechanisms into unique Hallmarks of Cancer Drug Tolerance. At the highest level, these are comprised of heterogeneity, signaling plasticity, differentiation, proliferation/metabolism, stress management, genomic integrity, crosstalk with the tumor microenvironment, immune escape, and epigenetic regulatory mechanisms. Of these, epigenetics was both one of the first proposed means of non-genetic resistance and one of the first discovered. As we describe in this review, epigenetic regulatory factors are involved in most facets of DTP biology, positioning this hallmark as an overarching mediator of drug tolerance and a potential avenue to novel therapies.

Mechanisms of myeloid leukemogenesis: Current perspectives and therapeutic objectives

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic neoplasm which results in clonal proliferation of abnormally differentiated hematopoietic cells. In this review, mechanisms contributing to myeloid leukemogenesis are summarized, highlighting aberrations of epigenetics, transcription factors, signal transduction, cell cycling, and the bone marrow microenvironment. The mechanisms contributing to AML are detailed to spotlight recent findings that convey clinical impact. The applications of current and prospective therapeutic targets are accentuated in addition to reviews of treatment paradigms stratified for each characteristic molecular lesion - with a focus on exploring novel treatment approaches and combinations to improve outcomes in AML.

Molecular regulators of HOXA9 in acute myeloid leukemia

Dysregulation of the oncogenic transcription factor HOXA9 is a prominent feature for most aggressive acute myeloid leukemia cases and a strong indicator of poor prognosis in patients. Leukemia subtypes with hallmark overexpression of HOXA9 include those carrying MLL gene rearrangements, NPM1c mutations, and other genetic alternations. A growing body of evidence indicates that HOXA9 dysregulation is both sufficient and necessary for leukemic transformation. The HOXA9 mRNA and protein regulation includes multilayered controls by transcription factors (such as CDX2/4 and USF2/1), epigenetic factors (such as MLL-menin-LEDGF, DOT1L, ENL, HBO1, NPM1c-XPO1, and polycomb proteins), microRNAs (such as miR-126 and miR-196b), long noncoding RNAs (such as HOTTIP), three-dimensional chromatin interactions, and post-translational protein modifications. Recently, insights into the dynamic regulation of HOXA9 have led to an advanced understanding of the HOXA9 regulome and provided new cancer therapeutic opportunities, including developing inhibitors targeting DOT1L, menin, and ENL proteins. This review summarizes recent advances in understanding the molecular mechanisms controlling HOXA9 regulation and the pharmacological approaches that target HOXA9 regulators to treat HOXA9-driven acute myeloid leukemia.

CRISPR-Cas9-mediated gene therapy in lung cancer

As the largest cause of cancer-related deaths worldwide, pulmonary cancer is the most common form of the disease. Several genetic, epigenetic, and environmental factors come into play during the multi-step mechanism of tumorigenesis. The heterogeneity that makes discovering successful therapeutics for pulmonary cancer problematic is significantly influenced by the epigenetic landscape, including DNA methylation, chromatin architecture, histone modifications, and noncoding RNA control. Clinical activity of epigenetic-targeted medicines has been reported in hematological tumors, and these compounds may also have therapeutic effects in solid tumors. Over the course of the past few years, some researchers have successfully modified the expression of genes in cells using the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated proteins) technique. The utilization of this technology allows for the induction of site-specific mutagenesis, epigenetic alterations, and the regulation of gene expression. This study will present an overview of the primary epigenetic alterations seen in pulmonary cancer, as well as a summary of therapeutic implications for targeting epigenetics in the management of pulmonary cancer, with a particular emphasis on the technique known as CRISPR/Cas9.

The roles of histone modifications in tumorigenesis and associated inhibitors in cancer therapy

Histone modifications are key factors in chromatin packaging, and are responsible for gene regulation during cell fate determination and development. Abnormal alterations in histone modifications potentially affect the stability of the genome and disrupt gene expression patterns, leading to many diseases, including cancer. In recent years, mounting evidence has shown that various histone modifications altered by aberrantly expressed modifier enzymes contribute to tumor development and metastasis through the induction of epigenetic, transcriptional, and phenotypic changes. In this review, we will discuss the existing histone modifications, both well-studied and rare ones, and their roles in solid tumors and hematopoietic cancers, to identify the molecular pathways involved and investigate targeted therapeutic drugs to reorganize the chromatin and enhance cancer treatment efficiency. Finally, clinical inhibitors of histone modifications are summarized to better understand the developmental stage of cancer therapy in using these drugs to inhibit the histone modification enzymes.

High HOXA9 gene expression predicts response to chemotherapy and prognosis of high-grade serous ovarian cancer patients

Objective

High-grade serous ovarian cancer (HGSOC) is a deadly malignancy. Homeobox protein A9 ( HOXA9) is linked with serous papillary histotype differentiation, and inappropriate HOXA9 expression is a step in ovarian cancer that induces aberrant differentiation. This study aimed to reveal the significance of HOXA9 in HGSOC.

Methods

HOXA9 mRNA and protein expression were examined by quantitative PCR and immunohistochemistry, respectively. The chi-square test was used to evaluate associations between HOXA9 expression and clinical characteristics. The prognostic value of HOXA9 was calculated by the Kaplan–Meier method. The Kaplan–Meier Plotter database was used to assess the prognostic value of HOXA9.

Results

The mRNA and protein expression of HOXA9 were significantly upregulated in chemotherapy-resistant HGSOC compared with chemotherapy-sensitive HGSOC. The chi-square test showed that high HOXA9 expression was significantly related with grade, clinical stage, and residual disease. High HOXA9 expression was significantly associated with poor prognosis. The Kaplan–Meier Plotter database further confirmed these results. Cox hazard regression showed that high HOXA9 expression was an independent prognostic factor for survival in HGSOC patients.

Conclusion

This study showed that HOXA9 expression was associated with chemotherapy resistance and poor outcomes in HGSOC patients. High HOXA9 expression might be a prognostic indicator for HGSOC.

Inhibition of the CtBP complex and FBXO11 enhances MHC class II expression and anti-cancer immune responses

There is increasing recognition of the prognostic significance of tumor cell major histocompatibility complex (MHC) class II expression in anti-cancer immunity. Relapse of acute myeloid leukemia (AML) following allogeneic stem cell transplantation (alloSCT) has recently been linked to MHC class II silencing in leukemic blasts; however, the regulation of MHC class II expression remains incompletely understood. Utilizing unbiased CRISPR-Cas9 screens, we identify that the C-terminal binding protein (CtBP) complex transcriptionally represses MHC class II pathway genes, while the E3 ubiquitin ligase complex component FBXO11 mediates degradation of CIITA, the principal transcription factor regulating MHC class II expression. Targeting these repressive mechanisms selectively induces MHC class II upregulation across a range of AML cell lines. Functionally, MHC class II+ leukemic blasts stimulate antigen-dependent CD4+ T cell activation and potent anti-tumor immune responses, providing fundamental insights into the graft-versus-leukemia effect. These findings establish the rationale for therapeutic strategies aimed at restoring tumor-specific MHC class II expression to salvage AML relapse post-alloSCT and also potentially to enhance immunotherapy outcomes in non-myeloid malignancies.

Real-world experience in treating pediatric relapsed/refractory or therapy-related myeloid malignancies with decitabine, vorinostat, and FLAG therapy based on a phase 1 study run by the TACL consortium

Current therapies for relapsed/refractory (R/R) pediatric myeloid neoplasms are inadequately effective. Real-world data (RWD) can improve care by augmenting traditional studies and include individuals not eligible for clinical trials. The Therapeutic Advances in Childhood Leukemia and Lymphoma (TACL) consortium recently completed T2016-003, a phase 1 study of decitabine, vorinostat, fludarabine, cytarabine, and granulocyte colony-stimulating factor (G-CSF) in R/R acute myeloid leukemia (AML), which added epigenetic drugs to a cytotoxic backbone. We report results of RWD from six centers that treated 28 pediatric patients (26 with AML, two with other myeloid neoplasms) identically to the TACL study but who were not enrolled. This allowed unique analyses and the ability to compare data with the 35 TACL study patients. The overall response rate (ORR) (complete response [CR] plus CR with incomplete count recovery) among 26 RWD evaluable patients was 65%. The ORR of 13 patients with relapsed AML with epigenetic alterations was 69% (T2016-003 + RWD: 68%, n = 25), of eight patients with refractory AML was 38% (T2016-003 + RWD: 41%, n = 17) and of five patients with therapy-related AML (t-AML) was 80% (T2016-003 + RWD: 75%, n = 8). The mean number of Grade 3/4 toxicities experienced by the T2016-003-eligible RWD population (n = 22) (one per patient-cycle) was not meaningfully different than those (n = 6) who would have been TACL study-ineligible secondary to comorbidities (two per patient-cycle). Overall, this therapy was well tolerated and effective in pediatric patients with R/R myeloid neoplasms, particularly those with epigenetic alterations, t-AML, and refractory disease.

Low expression of the metabolism-related gene SLC25A21 predicts unfavourable prognosis in patients with acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease associated with poor outcomes. To identify AML-specific genes with prognostic value, we analysed transcriptome and clinical information from The Cancer Genome Atlas (TCGA) database, Gene Expression Omnibus (GEO) datasets, and Genotype-Tissue Expression (GTEx) project. The metabolism-related gene, SLC25A21 was found to be significantly downregulated in AML, and was associated with high white blood cell (WBC) counts, high pretrial blood (PB) and bone marrow (BM) blast abundance, FLT3 mutation, NPM1 mutation, and death events (all p value <0.05). We validated the expression of SLC25A21 in our clinical cohort, and found that SLC25A21 was downregulated in AML. Moreover, we identified low expression of SLC25A21 as an independent prognostic factor by univariate Cox regression (hazard ratio [HR]: 0.550; 95% Confidence interval [CI]: 0.358–0.845; p value = 0.006) and multivariate Cox regression analysis (HR: 0.341; 95% CI: 0.209–0.557; p value <0.05). A survival prediction nomogram was established with a C-index of 0.735, which indicated reliable prognostic prediction. Subsequently, based on the median SLC25A21 expression level, patients in the TCGA-LAML cohort were divided into low- and high-expression groups. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs highlighted growth factor binding, extracellular structure organization, cytokine‒cytokine receptor interaction, etc. The results of gene set enrichment analysis (GSEA) indicated that the epithelial-mesenchymal transition, KRAS signalling, oxidative phosphorylation, and reactive oxygen species pathways were enriched. Through gene coexpression and protein‒protein interaction (PPI) network analysis, we identified two hub genes, EGFR and COL1A2, which were linked to worse clinical outcomes. Furthermore, we found that lower SLC25A21 expression was closely associated with a significant reduction in the levels of infiltrating immune cells, which might be associated with immune escape of AML cells. A similar trend was observed for the expression of checkpoint genes (CTLA4, LAG3, TIGIT, and HAVCR2). Finally, drug sensitivity testing suggested that the low-expression SLC25A21 group is sensitive to doxorubicin, mitomycin C, linifanib but resistant to JQ1, belinostat, and dasatinib. Hence, our study demonstrated that a low expression level of SLC25A21 predicts an unfavourable prognosis in patients with AML.

SMYD3 regulates gastric cancer progression and macrophage polarization through EZH2 methylation

SET and MYND domain-containing protein 3 (SMYD3), a known histone methyltransferase, was reported to regulate cancer pathogenesis. However, its role in gastric development and progression remains unclear. EZH2 methylation had been associated with cancer metastasis, but the EZH2 methylation status in gastric cancer (GC) is unknown. Here, we report that EZH2 K421 methylation was responsible for gastric cancer cell soft agar colony formation, in vivo metastasis, and macrophage polarization. Mechanically, we identified SMYD3 as the methyltransferase of EZH2 at K421 residue which accelerates EZH2 Ubiquitin proteasome degradation. Cell harboring non-methylated EZH2 mutants promotes gastric cancer cell metastasis. Taken together, our results showed that SMYD3-EZH2 axis restricts gastric cancer metastasis via integrating epigenetic signaling.

Protein tyrosine kinase 2b inhibition reverts niche-associated resistance to tyrosine kinase inhibitors in AML

FLT3 tyrosine kinase inhibitor (TKI) therapy evolved into a standard therapy in FLT3-mutated AML. TKI resistance, however, develops frequently with poor outcomes. We analyzed acquired TKI resistance in AML cell lines by multilayered proteome analyses. Leupaxin (LPXN), a regulator of cell migration and adhesion, was induced during early resistance development, alongside the tyrosine kinase PTK2B which phosphorylated LPXN. Resistant cells differed in cell adhesion and migration, indicating altered niche interactions. PTK2B and LPXN were highly expressed in leukemic stem cells in FLT3-ITD patients. PTK2B/FAK inhibition abrogated resistance-associated phenotypes, such as enhanced cell migration. Altered pathways in resistant cells, assessed by nascent proteomics, were largely reverted upon PTK2B/FAK inhibition. PTK2B/FAK inhibitors PF-431396 and defactinib synergized with different TKIs or daunorubicin in FLT3-mutated AML. Midostaurin-resistant and AML cells co-cultured with mesenchymal stroma cells responded particularly well to PTK2B/FAK inhibitor addition. Xenograft mouse models showed significant longer time to leukemia symptom-related endpoint upon gilteritinib/defactinib combination treatment in comparison to treatment with either drug alone. Our data suggest that the leupaxin-PTK2B axis plays an important role in acquired TKI resistance in AML. PTK2B/FAK inhibitors act synergistically with currently used therapeutics and may overcome emerging TKI resistance in FLT3-mutated AML at an early timepoint.

Immunohistochemical loss of enhancer of Zeste Homolog 2 (EZH2) protein expression correlates with EZH2 alterations and portends a worse outcome in myelodysplastic syndromes

EZH2 coding mutation (EZH2^MUT), resulting in loss-of-function, is an independent predictor of overall survival in MDS. EZH2 function can be altered by other mechanisms including copy number changes, and mutations in other genes and non-coding regions of EZH2. Assessment of EZH2 protein can identify alterations of EZH2 function missed by mutation assessment alone. Precise evaluation of EZH2 function and gene-protein correlation in clinical MDS cohorts is important in the context of upcoming targeted therapies aimed to restore EZH2 function. In this study, we evaluated the clinicopathologic characteristics of newly diagnosed MDS patients with EZH2^MUT and correlated the findings with protein expression using immunohistochemistry. There were 40 (~6%) EZH2^MUT MDS [33 men, seven women; median age 74 years (range, 55-90)]. EZH2 mutations spanned the entire coding region. Majority had dominant EZH2 clone [median VAF, 30% (1-92)], frequently co-occurring with co-dominant TET2 (38%) and sub-clonal ASXL1 (55%) and RUNX1 (43%) mutations. EZH2^MUT MDS showed frequent loss-of-expression compared to EZH2^WT (69% vs. 27%, p = 0.001). Interestingly, NINE (23%) EZH2^WT MDS also showed loss-of-expression. EZH2^MUT and loss-of-expression significantly associated with male predominance and chr(7) loss. Further, only EZH2 loss-of-expression patients showed significantly lower platelet counts, a trend for higher BM blast% and R-IPSS scores. Over a 14-month median follow-up, both EZH2^MUT (p = 0.027) and loss-of-expression (p = 0.0063) correlated with poor survival, independent of R-IPSS, age and gender. When analyzed together, loss-of-expression showed a stronger correlation than mutation (p = 0.061 vs. p = 0.43). In conclusion, immunohistochemical assessment of EZH2 protein, alongside mutation, is important for prognostic workup of MDS.

Ultra-deep sequencing validates safety of CRISPR/Cas9 genome editing in human hematopoietic stem and progenitor cells

As CRISPR-based therapies enter the clinic, evaluation of safety remains a critical and active area of study. Here, we employ a clinical next generation sequencing (NGS) workflow to achieve high sequencing depth and detect ultra-low frequency variants across exons of genes associated with cancer, all exons, and genome wide. In three separate primary human hematopoietic stem and progenitor cell (HSPC) donors assessed in technical triplicates, we electroporated high-fidelity Cas9 protein targeted to three loci (AAVS1, HBB, and ZFPM2) and harvested genomic DNA at days 4 and 10. Our results demonstrate that clinically relevant delivery of high-fidelity Cas9 to primary HSPCs and ex vivo culture up to 10 days does not introduce or enrich for tumorigenic variants and that even a single SNP in a gRNA spacer sequence is sufficient to eliminate Cas9 off-target activity in primary, repair-competent human HSPCs.

Targeting histone methylation to reprogram the transcriptional state that drives survival of drug-tolerant myeloid leukemia persisters

Although chemotherapy induces complete remission in the majority of acute myeloid leukemia (AML) patients, many face a relapse. This relapse is caused by survival of chemotherapy-resistant leukemia (stem) cells (measurable residual disease; MRD). Here, we demonstrate that the anthracycline doxorubicin epigenetically reprograms leukemia cells by inducing histone 3 lysine 27 (H3K27) and H3K4 tri-methylation. Within a doxorubicin-sensitive leukemia cell population, we identified a subpopulation of reversible anthracycline-tolerant cells (ATCs) with leukemic stem cell (LSC) features lacking doxorubicin-induced H3K27me3 or H3K4me3 upregulation. These ATCs have a distinct transcriptional landscape than the leukemia bulk and could be eradicated by KDM6 inhibition. In primary AML, reprogramming the transcriptional state by targeting KDM6 reduced MRD load and survival of LSCs residing within MRD, and enhanced chemotherapy response in vivo. Our results reveal plasticity of anthracycline resistance in AML cells and highlight the potential of transcriptional reprogramming by epigenetic-based therapeutics to target chemotherapy-resistant AML cells.

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Reversible anthracycline-tolerant leukemia cells (ATCs) have low H3K27me3 or H3K4me3

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ATCs exhibit stem cell features similar to leukemic stem cells

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Reprogramming the transcriptional state by inhibition of KDM6 depletes ATCs

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Inhibiting KDM6 adds to doxorubicin treatment and eradicates AML MRD (stem) cells

How Genetics Can Drive Initial Therapy Choices for Older Patients with Acute Myeloid Leukemia

OPINION STATEMENT

Treatment of older adults with acute myeloid leukemia (AML) is challenging. Therapy decisions must be guided by multiple factors including aging-related conditions (e.g., comorbidities, functional impairment), therapy benefits and risks, patient preferences, and disease characteristics. Balancing these factors requires understanding the unique, and frequently higher-risk cytogenetic and molecular characteristics of AML in older adult populations, which should caution providers not to reduce therapy intensity on the basis of age alone. Instead, geriatric assessments should be employed to determine fitness for therapy. Treatment options in AML are increasingly targeted to specific mutations or recognized to have differential benefits on the basis of genomics, and representation of older adults and geriatric outcome reporting in clinical trials is improving. Additionally, newer studies have begun to explore personalized therapy strategies on the basis of initial genetic testing. Review and refinement of practice guidelines for older patients on the basis of these advances is needed and is anticipated to remain an important topic in ongoing hematology/oncology clinical education.