DNA damage accumulation and repair defects in FLT3-ITD acute myeloid leukemia: Implications for clonal evolution and disease progression

Reactive oxygen species and aldehyde dehydrogenase 1A as prognosis and theragnostic biomarker in acute myeloid leukaemia patients

Acute myeloid leukaemia (AML) remains a major unmet medical, despite recent progress in targeted molecular therapies. One aspect of leukaemic cell resistance to chemotherapy is the development of clones with increased capacity to respond to cellular stress and the production of reactive oxygen species (ROS), thanks in particular to a high aldehyde dehydrogenases (ALDH) 1A1/2 activity. At diagnosis, ROS level and ALDH1A1/2 activity in AML patients BM are correlated with the different ELN 2022 prognostic groups and overall survival (OS). A significant lower ALDH1A1/2 activity in BM was observed in the favourable ELN2022 subgroup compared to the intermediate and adverse group (p < 0.01). In the same way, the ROS levels were significantly lower in the favourable ELN 2022 subgroup compared to the intermediate group (p < 0.0001) and adverse group (p < 0.0002). ROShigh AML patients had a significantly lower median overall survival (OS) (8.2 months) than ROSlow patients (24.6 months) (p = 0.0368). After first-line therapy, a significant increase of ROS level (p = 0.015) and ALDH1A1/2 activity (0 = 0.0273) in leukaemic blasts was observed, especially in the refractory ones. ABD-3001, a competitive and irreversible inhibitor of ALDHs 1 and 3, can in vitro inhibit the proliferation of patient-derived leukaemic cells in accordance with redox balance. In multivariate analysis, ROS level was the most significant (p < 0.05) and the strongest predictive factor for the sensitivity of cells to ABD-3001. The safety profile of ABD-3001 is currently being assessed through the first inhuman multicenter phase 1 clinical trial "ODYSSEY" (NCT05601726) for patients with relapsed AML.

Effect of AML-exosomes on the cellular and molecular properties of bone marrow mesenchymal stromal cells: Expression of JAK/STAT signaling genes

PURPOSE OF STUDY

Despite the various therapeutic options introduced for AML treatment, therapy resistance and relapse are still the main obstacles. It is well known that alterations in the bone marrow microenvironment (BMM) play a crucial role in leukemia growth and the treatment failure of AML. Evidence shows that exosomes alter the components of BMM in a way that support leukemia survival, leading to chemoresistance. In this study, we evaluated the effect of AML exosomes on the biological functions of human bone marrow mesenchymal stromal cells (h BM-MSCs), especially alteration in the expression of the JAK/STAT signaling genes, as a leukemia-favoring pathway.

METHOD

Exosomes were isolated from the HL-60 cell line and characterized using flow cytometry, Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS) technique. The exosome protein content was assessed using a bicinchoninic acid (BCA) protein assay kit in order to determine the concentration of exosomes. Subsequently, MSCs were treated with varying concentrations of AML exosomes, and data was obtained using MTT, cell cycle, apoptosis, and ki67 assays. Additionally, gene expression analysis was conducted through qRT-PCR.

RESULT

AML exosomes regulated the viability and survival of MSCs in a concentration-dependent manner. The qRT-PCR data revealed that treatment with AML exosomes at a concentration of 50 μg/mL led to a significant upregulation of JAK2, STAT3, and STAT5 genes in MSCs.

CONCLUSION

Because the JAK/STAT signaling pathway has been shown to play a role in the proliferation and survival of leukemic cells, our results suggest that AML exosomes stimulate MSCs to activate this pathway. This activation may impede AML cell apoptosis, potentially leading to chemoresistance and relapse.

Current knowledge about FLT3 gene mutations, exploring the isoforms, and protein importance in AML

Acute myeloid leukaemia (AML) is a complex haematological malignancy characterised by diverse genetic alterations leading to abnormal proliferation of myeloid precursor cells. One of the most significant genetic alterations in AML involves mutations in the FLT3 gene, which plays a critical role in haematopoiesis and haematopoietic homeostasis. This review explores the current understanding of FLT3 gene mutations and isoforms and the importance of the FLT3 protein in AML. FLT3 mutations, including internal tandem duplications (FLT3-ITD) and point mutations in the tyrosine kinase domain (FLT3-TKD), occur in 25-30% in AML and are associated with poor prognosis. FLT3-ITD mutations lead to constitutive activation of the FLT3 signalling pathway, promoting cell survival and proliferation. FLT3-TKD mutations affect the tyrosine kinase domain and affect AML prognosis in various ways. Furthermore, FLT3 isoforms, including shorter variants, contribute to the complexity of FLT3 biology. Additionally, nonpathological polymorphisms in FLT3 are being explored for their potential impact on AML prognosis and treatment response. This review also discusses the development of molecular treatments targeting FLT3, including first-generation and next-generation tyrosine kinase inhibitors, highlighting the challenges of resistance that often arise during therapy. The final chapter describes FLT3 protein domain rearrangements and their relevance to AML pathogenesis.

Chromothripsis in hematologic malignancies

Chromotrypsis, a phenomenon resulting from catastrophic mitotic errors and genomic instability, is defined by the occurrence of multiple DNA double-strand breaks in one or more chromosomes, subsequently subject to error-prone repair mechanisms. This unique process results in extensive rearrangements in the affected chromosomes, leading to loss of tumor suppressor function, the creation of fusion genes, and/or activation of oncogenes. The importance of chromothripsis in cancer, especially in the field of hematologic disorders, underscores the intricate interplay between genomic instability and the genesis of alterations that contribute to cancer. This accentuates the critical need to unravel these complex processes for the targeted development of specific therapeutic interventions. This review delves into the analysis of chromothripsis cases in various hematologic diseases, such as leukemia, lymphoma, and myeloma, with the aim of unveiling its profound impact on patient prognosis. Furthermore, the study explores the intricate molecular mechanisms underlying chromothripsis and investigates its consequences.

Targeting chemoresistance and mitochondria-dependent metabolic reprogramming in acute myeloid leukemia

Chemoresistance often complicates the management of cancer, as noted in the instance of acute myeloid leukemia (AML). Mitochondrial function is considered important for the viability of AML blasts and appears to also modulate chemoresistance. As mitochondrial metabolism is aberrant in AML, any distinct pathways could be directly targeted to impact both cell viability and chemoresistance. Therefore, identifying and targeting those precise rogue elements of mitochondrial metabolism could be a valid therapeutic strategy in leukemia. Here, we review the evidence for abnormalities in mitochondria metabolic processes in AML cells, that likely impact chemoresistance. We further address several therapeutic approaches targeting isocitrate dehydrogenase 2 (IDH2), CD39, nicotinamide phosphoribosyl transferase (NAMPT), electron transport chain (ETC) complex in AML and also consider the roles of mesenchymal stromal cells. We propose the term "mitotherapy" to collectively refer to such regimens that attempt to override mitochondria-mediated metabolic reprogramming, as used by cancer cells. Mounting evidence suggests that mitotherapy could provide a complementary strategy to overcome chemoresistance in liquid cancers, as well as in solid tumors.

Improved efficacy of quizartinib in combination therapy with PI3K inhibition in primary FLT3-ITD AML cells

Acute myeloid leukemia is a heterogeneous hematopoietic malignancy, characterized by uncontrolled clonal proliferation of abnormal myeloid progenitor cells, with poor outcomes. The internal tandem duplication (ITD) mutation of the Fms-like receptor tyrosine kinase 3 (FLT3) (FLT3-ITD) represents the most common genetic alteration in AML, detected in approximately 30% of AML patients, and is associated with high leukemic burden and poor prognosis. Therefore, this kinase has been regarded as an attractive druggable target for the treatment of FLT3-ITD AML, and selective small molecule inhibitors, such as quizartinib, have been identified and trialled. However, clinical outcomes have been disappointing so far due to poor remission rates, also because of acquired resistance. A strategy to overcome resistance is to combine FLT3 inhibitors with other targeted therapies. In this study, we investigated the preclinical efficacy of the combination of quizartinib with the pan PI3K inhibitor BAY-806946 in FLT3-ITD cell lines and primary cells from AML patients. We show here that BAY-806946 enhanced quizartinib cytotoxicity and, most importantly, that this combination increases the ability of quizartinib to kill CD34+ CD38-leukemia stem cells, whilst sparing normal hematopoietic stem cells. Because constitutively active FLT3 receptor tyrosine kinase is known to boost aberrant PI3K signaling, the increased sensitivity of primary cells to the above combination can be the mechanistic results of the disruption of signaling by vertical inhibition.

How ITD Insertion Sites Orchestrate the Biology and Disease of FLT3-ITD-Mutated Acute Myeloid Leukemia

Mutations of the FLT3 gene are among the most common genetic aberrations detected in AML and occur mainly as internal tandem duplications (FLT3-ITD). However, the specific sites of FLT3-ITD insertion within FLT3 show marked heterogeneity regarding both biological and clinical features. In contrast to the common assumption that ITD insertion sites (IS) are restricted to the juxtamembrane domain (JMD) of FLT3, 30% of FLT3-ITD mutations insert at the non-JMD level, thereby integrating into various segments of the tyrosine kinase subdomain 1 (TKD1). ITDs inserted within TKD1 have been shown to be associated with inferior complete remission rates as well as shorter relapse-free and overall survival. Furthermore, resistance to chemotherapy and tyrosine kinase inhibition (TKI) is linked to non-JMD IS. Although FLT3-ITD mutations in general are already recognized as a negative prognostic marker in currently used risk stratification guidelines, the even worse prognostic impact of non-JMD-inserting FLT3-ITD has not yet been particularly considered. Recently, the molecular and biological assessment of TKI resistance highlighted the pivotal role of activated WEE1 kinase in non-JMD-inserting ITDs. Overcoming therapy resistance in non-JMD FLT3-ITD-mutated AML may lead to more effective genotype- and patient-specific treatment approaches.

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.