Abstract A direct link between chronic inflammation and development of Acute Myeloid Leukemia (AML) has been highlighted in the past few years, demonstrating an interconnection between marked inflammatory phenotype and aberrant myeloproliferation in AML patients. Treating AML patients exhibiting a higher inflammatory signature with anti-inflammatory molecules resulted in significant increase of overall survival. Protein Arginine Methyltransferases (PRMTs) are epigenetic factors known to regulate gene expression through methylation of histone tails. It has been previously reported that PRMT1, 4, and 5 inhibition exhibit anti-proliferative effects on AML models. In this study, we investigated the role of another PRMT, called PRMT2, in the development of AML through its regulatory roles in inflammatory pathways. We first determined from an AML cohort (The Leucegene project, IRIC, Montréal, QC, Canada) that patients with a low PRMT2 expression display an enrichment of proinflammatory pathways compared to patients with a high PRMT2 expression. Therefore, we hypothesized that PRMT2 could be a key regulator of inflammatory processes in AML. We thus used a PRMT2 knockout mouse model (Prmt2 KO) and a PRMT2 knockout human AML cell line to validate our hypothesis. Although we demonstrated no difference in the bone marrow progenitors or mature cell populations of Prmt2 KO mice compared to control, we observed that Prmt2 KO Bone-Marrow Derived Macrophages (BMDMs) are more sensitive to LPS stimulation and express higher levels of pro-inflammatory cytokines, supporting our previous findings for a role of PRMT2 in the negative regulation of inflammatory processes. PRMT2 depleted human AML cells displayed an increased pro-inflammatory signature due to overactivation of STAT3, which is caused by an enhanced activation of the NFkB signaling pathway, leading to an overproduction of IL6. Together, these findings demonstrate that PRMT2 is a key regulator of the control of inflammation in AML. Recognition of PRMT2 as a biomarker of inflammation in AML would help to adapt treatment possibly through the synergistic use of anti-inflammatory molecules with other cytotoxic drugs. Citation Format: Camille Sauter, Thomas Morin, Fabien Guidez, John Simonet, Cyril Fournier, Céline Row, Denis Masnikov, Baptiste Pernon, Anne Largeot, Aziza Aznague, Yann Herault, Guy Sauvageau, Marc Maynadie, Mary Callanan, Jean-Noël Bastie, Romain Aucagne, Laurent Levadny Delva. Protein Arginine Methyltransferase 2 is involved in the control of inflammatory processes in acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5588.

Arginine methylation is catalyzed by protein arginine methyltransferases (PRMTs) and is involved in various cellular processes, including cancer development. PRMT2 expression is increased in several cancer types although its role in acute myeloid leukemia (AML) remains unknown. Here, we investigate the role of PRMT2 in a cohort of patients with AML, PRMT2 knockout AML cell lines as well as a Prmt2 knockout mouse model. In patients, low PRMT2 expressors are enriched for inflammatory signatures, including the NF-κB pathway, and show inferior survival. In keeping with a role for PRMT2 in control of inflammatory signaling, bone marrow-derived macrophages from Prmt2 KO mice display increased pro-inflammatory cytokine signaling upon LPS treatment. In PRMT2-depleted AML cell lines, aberrant inflammatory signaling has been linked to overproduction of IL6, resulting from a deregulation of the NF-κB signaling pathway, therefore leading to hyperactivation of STAT3. Together, these findings identify PRMT2 as a key regulator of inflammation in AML.

Arginine methylation is a common post-translational modification affecting protein activity and the transcription of target genes when methylation occurs on histone tails. There are nine protein arginine methyltransferases (PRMTs) in mammals, divided into subgroups depending on the methylation they form on a molecule of arginine. During the formation and maturation of the different types of blood cells, PRMTs play a central role by controlling cell differentiation at the transcriptional level. PRMT enzymatic activity is necessary for many cellular processes in hematological malignancies, such as the activation of cell cycle and proliferation, inhibition of apoptosis, DNA repair processes, RNA splicing, and transcription by methylating histone tails' arginine. Chemical tools have been developed to inhibit the activity of PRMTs and have been tested in several models of hematological malignancies, including primary samples from patients, xenografts into immunodeficient mice, mouse models, and human cell lines. They show a significant effect by reducing cell viability and increasing the overall survival of mice. PRMT5 inhibitors have a strong therapeutic potential, as phase I clinical trials in hematological malignancies that use these molecules show promising results, thus, underlining PRMT inhibitors as useful therapeutic tools for cancer treatment in the future.

The human genome is composed of unique DNA sequences that encode proteins and unique sequence noncoding RNAs that are essential for normal development and cellular differentiation. The human genome also contains over 50% of genome sequences that are repeat in nature (tandem and interspersed repeats) that are now known to contribute dynamically to genetic diversity in populations, to be transcriptionally active under certain physiological conditions, and to be aberrantly active in disease states including cancer, where consequences are pleiotropic with impact on cancer cell phenotypes and on the tumor immune microenvironment. Repeat element-derived RNAs play unique roles in exogenous and endogenous cell signaling under normal and disease conditions. A key component of repeat element-derived transcript-dependent signaling occurs via triggering of innate immune receptor signaling that then feeds forward to inflammatory responses through interferon and NFκB signaling. It has recently been shown that cancer cells display abnormal transcriptional activity of repeat elements and that this is linked to either aggressive disease and treatment failure or to improved prognosis/treatment response, depending on cell context and the amplitude of the so-called 'viral mimicry' response that is engaged. 'Viral mimicry' refers to a cellular state of active antiviral response triggered by endogenous nucleic acids often derived from aberrantly transcribed endogenous retrotransposons and other repeat elements. In this paper, the literature regarding transcriptional activation of repeat elements and engagement of inflammatory signaling in normal (focusing on hematopoiesis) and cancer is reviewed with an emphasis on the role of innate immune receptor signaling, in particular by dsRNA receptors of the RIG-1 like receptor family and interferons/NFκB. How repeat element-derived RNA reprograms cell identity through RNA-guided chromatin state modulation is also discussed.

Diagnosis of B-cell chronic lymphocytic leukemia (B-CLL) is usually straightforward, involving clinical, immunophenotypic (Matutes score), and (immuno)genetic analyses (to refine patient prognosis for treatment). CLL cases with atypical presentation (e.g., Matutes ≤ 3) are also encountered, and for these diseases, biology and prognostic impact are less clear. Here we report the genomic characterization of a case of atypical B-CLL in a 70-yr-old male patient; B-CLL cells showed a Matutes score of 3, chromosomal translocation t(14;18)(q32;q21) (BCL2/IGH), mutated IGHV, deletion 17p, and mutations in BCL2, NOTCH1 (subclonal), and TP53 (subclonal). Quite strikingly, a novel PAX5 mutation that was predicted to be loss of function was also seen. Exome sequencing identified, in addition, a potentially actionable BRAF mutation, together with novel somatic mutations affecting the homeobox transcription factor NKX2-3, known to control B-lymphocyte development and homing, and the epigenetic regulator LRIF1, which is implicated in chromatin compaction and gene silencing. Neither NKX2-3 nor LRIF1 mutations, predicted to be loss of function, have previously been reported in B-CLL. Sequencing confirmed the presence of these mutations together with BCL2, NOTCH1, and BRAF mutations, with the t(14;18)(q32;q21) translocation, in the initial diagnostic sample obtained 12 yr prior. This is suggestive of a role for these novel mutations in B-CLL initiation and stable clonal evolution, including upon treatment withdrawal. This case extends the spectrum of atypical B-CLL with t(14;18)(q32;q21) and highlights the value of more global precision genomics for patient follow-up and treatment in these patients.