Jul 2026· Leukemia research : a Forum for Studies on Leukemia and Normal Hemopoiesis· Vol 168, pp.
108286
· 0 citations· 43 references
Medicine
TL;DR
The data indicate that MA4 alone drives aberrantly high expression of only a few target genes, whereas A4M counteracts this detrimental effect, and suggests that A4M is crucial through its chromatin-opening activity, which strongly expands the pool of MA4 target genes and thereby promotes the establishment of pre-leukemogenic and leukemogenic gene expression programs.
Abstract
The chromosomal translocation t(4;11)(q21;q23) is the most common genetic aberration in KMT2A-rearranged acute leukemia. Although the molecular functions of wild-type KMT2A and AFF1 complexes are well characterized, little is known about the interplay between the reciprocal fusion proteins KMT2A::AFF1 (MA4) and AFF1::KMT2A (A4M). Here, we established model systems to investigate this interplay and the role of the RNA-binding proteins IGF2BP1-3. We also compared the murinized fusion KMT2A::mAff1 (MmA4) with the authentic human KMT2A::AFF1 fusion. Our data indicate that MA4 alone drives aberrantly high expression of only a few target genes, whereas A4M counteracts this detrimental effect. Under these conditions, MA4 induces genes encoding RNA-binding proteins as a counterregulatory response. Both reciprocal fusion transcripts are bound by IGF2BP3, resulting in reduced MA4 protein abundance but increased A4M levels. This effect was not observed for the artificial MmA4 fusion, likely because it cannot recruit the SL-1 complex. Together with previous findings, our results suggest that A4M is crucial through its chromatin-opening activity, which strongly expands the pool of MA4 target genes and thereby promotes the establishment of pre-leukemogenic and leukemogenic gene expression programs.
The t(4;11) translocation, which drives KMT2A::AFF1 fusion gene expression, is associated with poor prognosis in pediatric and adult B-cell Acute Lymphoblastic Leukemia (B-ALL). KMT2A::AFF1 fusion circular RNAs (f-circRNAs) have been identified in B-ALL, though their contribution to leukemia has not yet been outlined. We identified a novel recurrent KMT2A::AFF1-derived back-splicing junction joining AFF1 exon 7 to KMT2A exon 3 (AK_7_3) in SEM, RS4;11, and ALL-PO B-ALL cell lines, all of which carry the t(4;11)(q24;q23)/KMT2A::AFF1 translocation. This sequence was observed in RT-PCR products encompassing two splicing variants of KMT2A exon 4, which are also present in the linear KMT2A::AFF1 chimera. AK_7_3 was also found in 12/18 pediatric and 17/24 adult t(4;11)-positive B-ALL patients, including three paired diagnosis/relapse samples, whereas it was absent in 23 t(4;11)-negative B-ALL patients. Whole-transcriptome analysis of AK_7_3-knockdown SEM cells identified upregulated genes involved in oxidative stress response and regulation of apoptosis. Cell death analysis confirmed the pro-apoptotic impact of AK_7_3 silencing. Confocal analyses, Seahorse bioenergetic profiling, and electron microscopy revealed an overproduction of reactive oxygen species, increased mitochondrial membrane potential, mitochondrial respiration, and dysmorphic mitochondria after AK_7_3 knockdown in KMT2A::AFF1 cell lines. In summary, we identified AK_7_3 as a novel f-circRNA back-splicing junction recurrent in t(4;11)-positive B-ALL patients at both diagnosis and relapse. Our data provide evidence for a functional role of this molecule as an anti-apoptotic agent that affects mitochondrial function, suggesting its potential involvement in KMT2A::AFF1-driven B-ALL leukemogenesis.
D. Tolomeo, M. Bardini, Santina Venuto et al.· Haematologica· 0 citations
Patients with acute leukemias harboring translocations involving gene lysine methyltransferase 2A (KMT2A) have a poor prognosis due to chemotherapy resistance with rapid relapse following standard treatments. The resulting KMT2A fusion proteins dysregulate gene expression, leading to an upregulation of leukemogenic transcription factors such as HOXA9 and MEIS1, which drives leukemic transformation. Although Menin inhibitors are proving to be promising new therapeutics for patients with KMT2A-rearranged (KMT2Ar) acute leukemia, resistance mechanisms have already been described and new therapeutic approaches for this patient subgroup must be identified. Here, a genome-wide CRISPR/Cas9 screen in a KMT2Ar B-cell acute lymphoblastic leukemia (ALL) cell line identified the deubiquitinase USP22 as a novel regulator of MEIS1 protein stability. USP22 is a member of the Spt-Ada-Gcn5 acetyltransferase (SAGA) multiprotein complex, which has crucial functions in shaping the chromatin landscape and modulating transcription. Genetic depletion of USP22 impaired cellular growth and proliferation in KMT2Ar acute leukemia models. Chromatin immunoprecipitation revealed cooperative binding between USP22 and MEIS1 at critical oncogenic target genes suggesting that USP22 safeguards leukemogenic transcription by protecting MEIS1 from proteasomal degradation. Genetic or chemical inhibition of USP22 led to polyubiquitination of MEIS1 resulting in proteasomal degradation and downregulation of the expression of target genes. Our study identifies USP22 as a novel regulator of MEIS1 protein stability, that could potentially be exploited as a therapeutic target in the future in KMT2Ar leukemias.
Sarah Bröchtel, C. Schneider, Marius Müller et al.· Blood· 0 citations
Summary Lung adenocarcinoma (LUAD) remains a leading cause of cancer-related death, underscoring the need for an improved molecular understanding. This study investigated the regulatory mechanism of the long non-coding RNA deoxyguanosine kinase antisense RNA 1 (DGUOK-AS1) in LUAD. DGUOK-AS1 was significantly upregulated in LUAD cells and serum samples, and its elevated expression showed a preliminary association with LUAD. Functional experiments demonstrated that DGUOK-AS1 promoted LUAD proliferation and migration both in vitro and in vivo, partly by acting as a competing endogenous RNA for miR-2467-5p to modulate PRMT5 expression. Mechanistically, RNA-binding motif protein 15 (RBM15) enhanced DGUOK-AS1 stability through m6A modification, which in turn enabled heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1) binding in an m6A-dependent manner via its RNA recognition motif 3 (RRM3) domain, promoting degradation. RBM15 knockdown attenuated the malignant phenotype through the miR-2467-5p/PRMT5 axis. These findings reveal an m6A-dependent mechanism governing DGUOK-AS1 stability and provide insights into its contribution to LUAD progression.
Menghao Yang, Jiaen Wu, Youjie Li et al.· iScience· 0 citations
Mutations in splicing factors (SF3B1, SRSF2, and U2AF1) are recurrent in myelodysplastic syndromes (MDS) and related hematologic malignancies, where they occur in a mutually exclusive manner that create a vulnerability when a second wild-type splicing factor is therapeutically targeted. However, the feasibility of this approach and mechanisms underlying selective toxicity of splicing factor–mutant cells remain incompletely defined. We developed AP-232, a small-molecule inhibitor of U2AF1, and investigated its mechanism of action in K562 cells (wild-type splicing factors) and HNT-34 cells, an MDS-derived AML model harboring the SF3B1K700E mutation. We found that AP-232 induces two temporally distinct and mechanistically opposing cellular states. Cell viability assays showed that at 24 hours, it drives acute cytotoxicity (up to ∼83% for K562 and ∼100% for HNT-34), while at later timepoints it shifts to sustained cytostatic effects. The cytotoxic effect of AP-232 diminished to ∼10% in K562 cells (IC50 of ∼17 uM) but remained ∼40% in HNT-34 cells (IC50 of ∼7 uM) at 72h, indicating greater sensitivity to U2AF1 inhibition in HNT-34 cells. Mechanistically, early responses in K562 are characterized by inflammatory, non-apoptotic cell death. LDH release, pyroptosis-associated markers, and Necrostatin-1 co-treatment implicate the involvement of necrosis or non-canonical pyroptosis. RNA-seq analysis at 48 h revealed strong induction of inflammatory pathways, which may result from inflammatory cell death. We previously showed that AP-232 induces transient autophagy inhibition, suggesting the contribution of lysosomal dysfunction and impaired autophagic flux to this early inflammatory cytotoxicity. Western blot analysis at 24 h demonstrated that K562 cells undergo replication stress, as indicated by increased levels of PCNA, Chk1, PARP, and c-Myc. In contrast, at 48 hours, replication collapses. All four markers are markedly reduced, and cells undergo G1 arrest accompanied by suppression of proliferative programs. Transcriptomic analysis revealed downregulation of c-Myc and E2F target genes, which was confirmed at the protein level by decreased expression of c-Myc, PCNA, Cdc6, MCM7, CDC20, and PLK1. Despite reduced checkpoint signaling at 48 hours, no DNA damage was detected by comet assay or immunoblotting for γ-H2AX, a marker of double-strand breaks, indicating that this state exhibits diminished replication activity without genotoxic stress. Collectively, AP-232 exerts a dual mechanism of action: an early inflammatory, non-apoptotic cell death program linked to autophagy disruption and replication stress, followed by sustained cytostatic repression of c-Myc/E2F-driven cell cycle programs. Enhanced activity in SF3B1-mutant cells suggests that simultaneous targeting of splicing and autophagy dependencies may represent a therapeutic strategy for SF3B1–mutant hematological malignancies, potentially driven by increased reliance on autophagy as a survival mechanism in this genetic context.
Mona Kazemi Sabzvar, Amol D. Patil, Eun Bee Cho, Arda Durmaz, Daniel M. Collier, Jianxiong Jiang, Valeria Visconte, Chao-Yie Yang. Evaluation of a small molecule, AP-232, as a splicing factor inhibitor of U2 auxiliary factor 1 (U2AF1) in leukemia cells [abstract]. In: Proceedings of AACR Drug Discovery and Development (AACR D3) Conference; 2026 Jul 21-24; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(14_Suppl):Abstract nr B074.
Mona Kazemi Sabzvar, Amol D Patil, Eun Bee Cho et al.· Clinical Cancer Research· 0 citations
OtUD6B-AS1 suppresses EAC progression by sponging miR-145-5p and upregulating AIF to induce parthanatos activation, and Targeting this ceRNA regulatory axis may be a therapeutic strategy for EAC.
Qingfeng Zheng, Qiu-ping Wu, Yuling Lin et al.· American journal of translat...· 0 citations
INTRODUCTION
The t(2;11)(p21;q23) translocation without KMT2A rearrangement has been reported in ~16 hematologic neoplasms, but its molecular target(s) remain unknown. We aimed to identify the genes disrupted by this translocation and to clarify its contribution to Acute Myeloid Leukemia (AML) pathogenesis.
METHODS
We performed Whole-Genome Sequencing (WGS), targeted RNA next-generation sequencing (86-gene panel), and transcriptome profiling on diagnostic bone-marrow samples from a 64-year-old male with AML. Karyotype analysis and Sanger sequencing confirmed chromosomal breakpoints and fusion junctions. CAMKMT expression and correlations with glycolysis-related genes were validated in TCGA (n = 173) and GTEx (n = 70) datasets.
RESULTS
Karyotyping revealed a main clone with sole t(2;11)(p21;q23) and a subclone with an additional del(5q). WGS uncovered an inverted, tail-to-tail fusion between CAMKMT (2p21) and GRIA4 (11q22.3) that truncates both genes. RNA-seq showed marked CAMKMT down-regulation (p < 0.01) and up-regulation of ENO1, PGK1, GPI, TPI1, and CXCL2 (all p < 0.05). Public datasets confirmed that low CAMKMT expression inversely correlates with these glycolytic genes (r = -0.18 to -0.31; p < 0.05). No functional chimeric protein is predicted.
DISCUSSION
CAMKMT truncation, rather than a gain-of-function fusion, appears to drive leukemogenesis by reprogramming energy metabolism. This mechanism aligns with CAMKMT's role as a negative regulator of glycolysis and calmodulin signaling. However, a major limitation of the present study is the lack of protein-level evidence, which precludes definitive confirmation that functional loss of CAMKMT occurs at the cellular level.
CONCLUSION
We demonstrate that the t(2;11)(p21;q23) translocation is associated with disruption of CAMKMT at the genetic level and may promote leukemogenesis through metabolic reprogramming. These findings broaden the molecular spectrum of AML and suggest CAMKMT loss as a potential therapeutic vulnerability. However, our conclusions are based on transcriptomic evidence, and protein-level validation will be required in future studies to confirm the functional consequences of CAMKMT disruption.
Shujun Li, Xiaoshan Yang, Peng Fang et al.· Current Medicinal Chemistry· 0 citations
