Abstract
Epigenetic dysregulation plays a pivotal role in mixed-lineage leukemia (MLL) pathogenesis, therefore serving as a suitable therapeutic target. S-adenosylmethionine (SAM) is the universal methyl donor in human cells and is synthesized by methionine adenosyltransferase 2A (MAT2A), which is deregulated in different cancer types. Here, we used our human CRISPR/Cas9-MLL-rearranged (CRISPR/Cas9-MLLr) leukemia model, faithfully mimicking MLLr patients’ pathology with indefinite growth potential in vitro, to evaluate the unknown role of MAT2A. Comparable to publicly available patient data, we detected MAT2A to be significantly overexpressed in our CRISPR/Cas9-MLLr model compared to healthy controls. By using non-MLLr and MLLr cell lines and our model, we detected an MLLr-specific enhanced response to PF-9366, a new MAT2A inhibitor, and small interfering (si) RNA-mediated knockdown of MAT2A, by alteration of the proliferation, viability, differentiation, apoptosis, cell cycling, and histone methylation. Moreover, the combinational treatment of PF-9366 with chemotherapy or targeted therapies against the SAM-dependent methyltransferases, disruptor of telomeric silencing 1 like (DOT1L) and protein arginine methyltransferase 5 (PRMT5), revealed even more pronounced effects. In summary, we uncovered MAT2A as a key regulator in MLL leukemogenesis and its inhibition led to significant anti-leukemic effects. Therefore, our study paves the avenue for clinical application of PF-9366 to improve the treatment of poor prognosis MLLr leukemia.
Highlights
Rearrangements of the mixed-lineage leukemia (MLL) or lysine methyltransferase 2A (KMT2A) gene with over 100 known partner genes like ALL1-fused gene from chromosome (AF) 4 or AF9 are frequently found in leukemia with a dismal prognosis [1]
We reported the generation of a reliable human CRISPR/Cas9-MLLr model based on patient sequences under endogenous oncogene expression [6]
This model is convincing by both indefinite growth potential in in vitro culture systems and the possibility to identify therapeutically relevant downstream effects of MLL-AF4 and -AF9 translocations
Summary
Rearrangements of the mixed-lineage leukemia (MLL) or lysine methyltransferase 2A (KMT2A) gene with over 100 known partner genes like ALL1-fused gene from chromosome (AF) 4 or AF9 are frequently found in leukemia with a dismal prognosis [1]. Uncovering the pathogenic mechanisms that maintain MLL-rearranged (MLLr) leukemogenesis is crucial to develop new targeted therapies. For this purpose, reliable human models are urgently needed as a platform to study new drugs on their way to clinical translation [3]. We developed representative human MLLr models using CRISPR/Cas based on patient-specific sequences with complete translocation between the MLL and AF4 or AF9 gene modeling the consequences of endogenous oncogene activation and hereby mimicking the patient’s disease [6]. In contrast to primary leukemic cells leading to rapid differentiation in in vitro cultures, our CRISPR/Cas9-MLLr model demonstrates unlimited in vitro growth potential amenable to fast and efficiently conduct pharmacological studies with high translational character
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