Evolving insights on histone methylome regulation in human acute myeloid leukemia pathogenesis and targeted therapy

Constitutive activation of the Src-family kinases Fgr and Hck enhances the tumor burden of acute myeloid leukemia cells in immunocompromised mice

Overexpression of the myeloid Src-family kinases Fgr and Hck has been linked to the development of acute myeloid leukemia (AML). Here we characterized the contribution of active forms of these kinases to AML cell cytokine dependence, inhibitor sensitivity, and AML cell engraftment in vivo. The human TF-1 erythroleukemia cell line was used as a model system as it does not express endogenous Hck or Fgr. To induce constitutive kinase activity, Hck and Fgr were fused to the coiled-coil (CC) oligomerization domain of the breakpoint cluster region protein associated with the Bcr-Abl tyrosine kinase in chronic myeloid leukemia. Expression of CC-Hck or CC-Fgr transformed TF-1 cells to a granulocyte-macrophage colony-stimulating factor (GM-CSF)-independent phenotype that correlated with enhanced phosphorylation of the kinase domain activation loop. Both CC-Hck and CC-Fgr cell populations became sensitized to growth arrest by Src-family kinase inhibitors previously shown to suppress the growth of bone marrow cells from AML patients in vitro and decrease AML cell engraftment in immunocompromised mice. Methionine substitution of the 'gatekeeper' residue (Thr338) also stimulated Hck and Fgr kinase activity and transformed TF-1 cells to GM-CSF independence without CC fusion. TF-1 cells expressing either active form of Hck or Fgr engrafted immunocompromised mice faster and developed more extensive tumors compared to mice engrafted with the parent cell line, resulting in shorter survival. Expression of wild-type Hck also significantly enhanced bone marrow engraftment without an activating mutation. Reverse phase protein array analysis linked active Hck and Fgr to the mammalian target of rapamycin complex-1/p70 S6 ribosomal protein (mTORC-1/S6) kinase and focal adhesion kinase (Fak) signaling pathways. Combining Hck and Fgr inhibitors with existing mTORC-1/S6 kinase or Fak inhibitors may improve clinical responses and reduce the potential for acquired resistance.

Can O-GIcNAc Transferase (OGT) Complex Be Used as a Target for the Treatment of Hematological Malignancies?

The circulatory system is a closed conduit system throughout the body and consists of two parts as follows: the cardiovascular system and the lymphatic system. Hematological malignancies usually grow and multiply in the circulatory system, directly or indirectly affecting its function. These malignancies include multiple myeloma, leukemia, and lymphoma. O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) regulates the function and stability of substrate proteins through O-GlcNAc modification. Abnormally expressed OGT is strongly associated with tumorigenesis, including hematological malignancies, colorectal cancer, liver cancer, breast cancer, and prostate cancer. In cells, OGT can assemble with a variety of proteins to form complexes to exercise related biological functions, such as OGT/HCF-1, OGT/TET, NSL, and then regulate glucose metabolism, gene transcription, cell proliferation, and other biological processes, thus affecting the development of hematological malignancies. This review summarizes the complexes involved in the assembly of OGT in cells and the role of related OGT complexes in hematological malignancies. Unraveling the complex network regulated by the OGT complex will facilitate a better understanding of hematologic malignancy development and progression.

Acute myeloid leukemia: from NGS, through scRNA-seq, to CAR-T. dissect cancer heterogeneity and tailor the treatment

Acute myeloid leukemia (AML) is a malignant blood cancer with marked cellular heterogeneity due to altered maturation and differentiation of myeloid blasts, the possible causes of which are transcriptional or epigenetic alterations, impaired apoptosis, and excessive cell proliferation. This neoplasm has a high rate of resistance to anticancer therapies and thus a high risk of relapse and mortality because of both the biological diversity of the patient and intratumoral heterogeneity due to the acquisition of new somatic changes. For more than 40 years, the old gold standard "one size fits all" treatment approach included intensive chemotherapy treatment with anthracyclines and cytarabine.The manuscript first traces the evolution of the understanding of the pathology from the 1970s to the present. The enormous strides made in its categorization prove to be crucial for risk stratification, enabling an increasingly personalized diagnosis and treatment approach.Subsequently, we highlight how, over the past 15 years, technological advances enabling single cell RNA sequencing and T-cell modification based on the genomic tools are affecting the classification and treatment of AML. At the dawn of the new millennium, the advent of high-throughput next-generation sequencing technologies has enabled the profiling of patients evidencing different facets of the same disease, stratifying risk, and identifying new possible therapeutic targets that have subsequently been validated. Currently, the possibility of investigating tumor heterogeneity at the single cell level, profiling the tumor at the time of diagnosis or after treatments exist. This would allow the identification of underrepresented cellular subclones or clones resistant to therapeutic approaches and thus responsible for post-treatment relapse that would otherwise be difficult to detect with bulk investigations on the tumor biopsy. Single-cell investigation will then allow even greater personalization of therapy to the genetic and transcriptional profile of the tumor, saving valuable time and dangerous side effects. The era of personalized medicine will take a huge step forward through the disclosure of each individual piece of the complex puzzle that is cancer pathology, to implement a "tailored" therapeutic approach based also on engineered CAR-T cells.

KDM6 demethylases integrate DNA repair gene regulation and loss of KDM6A sensitizes human acute myeloid leukemia to PARP and BCL2 inhibition

Acute myeloid leukemia (AML) is a heterogeneous, aggressive malignancy with dismal prognosis and with limited availability of targeted therapies. Epigenetic deregulation contributes to AML pathogenesis. KDM6 proteins are histone-3-lysine-27-demethylases that play context-dependent roles in AML. We inform that KDM6-demethylase function critically regulates DNA-damage-repair-(DDR) gene expression in AML. Mechanistically, KDM6 expression is regulated by genotoxic stress, with deficiency of KDM6A-(UTX) and KDM6B-(JMJD3) impairing DDR transcriptional activation and compromising repair potential. Acquired KDM6A loss-of-function mutations are implicated in chemoresistance, although a significant percentage of relapsed-AML has upregulated KDM6A. Olaparib treatment reduced engraftment of KDM6A-mutant-AML-patient-derived xenografts, highlighting synthetic lethality using Poly-(ADP-ribose)-polymerase-(PARP)-inhibition. Crucially, a higher KDM6A expression is correlated with venetoclax tolerance. Loss of KDM6A increased mitochondrial activity, BCL2 expression, and sensitized AML cells to venetoclax. Additionally, BCL2A1 associates with venetoclax resistance, and KDM6A loss was accompanied with a downregulated BCL2A1. Corroborating these results, dual targeting of PARP and BCL2 was superior to PARP or BCL2 inhibitor monotherapy in inducing AML apoptosis, and primary AML cells carrying KDM6A-domain mutations were even more sensitive to the combination. Together, our study illustrates a mechanistic rationale in support of a novel combination therapy for AML based on subtype-heterogeneity, and establishes KDM6A as a molecular regulator for determining therapeutic efficacy.

Mechanisms of carcinogenic activity triggered by lysine-specific demethylase 1A

Epigenetics has emerged as a prime focus area in the field of cancer research. Lysine-specific demethylase 1A (LSD1), the first discovered histone demethylase, is mainly responsible for catalysing demethylation of histone 3 lysine 4 (H3K4) and H3K9 to activate or inhibit gene transcription. LSD1 is abnormally expressed in various cancers and participates in cancer proliferation, apoptosis, metastasis, invasion, drug resistance and other processes by interacting with regulatory factors. Therefore, it may serve as a potential therapeutic target for cancer. This review summarises the major oncogenic mechanisms mediated by LSD1 and provides a reference for developing novel and efficient anticancer strategies targeting LSD1.

LukS-PV Induces Apoptosis via the SET8-H4K20me1-PIK3CB Axis in Human Acute Myeloid Leukemia Cells

Evidence suggests that histone modification disorders are involved in leukemia pathogenesis. We previously reported that LukS-PV, a component of Panton-Valentine leukocidin (PVL), has antileukemia activities that can induce differentiation, increase apoptosis, and inhibit proliferation of acute myeloid leukemia (AML) cells. Furthermore, LukS-PV inhibited hepatoma progression by regulating histone deacetylation, speculating that LukS-PV may exert antileukemia activity by targeting histone modification regulators. In this study, the results showed that LukS-PV induced apoptosis by downregulating the methyltransferase SET8 and its target histone H4 monomethylated at Lys 20 (H4K20me1). Furthermore, chromatin immunoprecipitation sequencing and polymerase chain reaction identified the kinase PIK3CB as a downstream target gene for apoptosis mediated by SET8/H4K20me1. Finally, our results indicated that LukS-PV induced apoptosis via the PIK3CB-AKT-FOXO1 signaling pathway by targeting SET8. This study indicates that SET8 downregulation is one of the mechanisms by which LukS-PV induces apoptosis in AML cells, suggesting that SET8 may be a potential therapeutic target for AML. Furthermore, LukS-PV may be a drug candidate for the treatment of AML that targets epigenetic modifications.

Roles of Histone Deacetylases in Acute Myeloid Leukemia With Fusion Proteins

Accurate orchestration of gene expression is critical for the process of normal hematopoiesis, and dysregulation is closely associated with leukemogenesis. Epigenetic aberration is one of the major causes contributing to acute myeloid leukemia (AML), where chromosomal rearrangements are frequently found. Increasing evidences have shown the pivotal roles of histone deacetylases (HDACs) in chromatin remodeling, which are involved in stemness maintenance, cell fate determination, proliferation and differentiation, via mastering the transcriptional switch of key genes. In abnormal, these functions can be bloomed to elicit carcinogenesis. Presently, HDAC family members are appealing targets for drug exploration, many of which have been deployed to the AML treatment. As the majority of AML events are associated with chromosomal translocation resulting in oncogenic fusion proteins, it is valuable to comprehensively understand the mutual interactions between HDACs and oncogenic proteins. Therefore, we reviewed the process of leukemogenesis and roles of HDAC members acting in this progress, providing an insight for the target anchoring, investigation of hyperacetylated-agents, and how the current knowledge could be applied in AML treatment.