Multiple myeloma (MM) is a heterogeneous haematological disease that remains clinically challenging. Increased activity of the epigenetic silencer EZH2 is a common feature in patients with poor prognosis. Previous findings have demonstrated that metabolic profiles can be sensitive markers for response to treatment in cancer. While EZH2 inhibition (EZH2i) has proven efficient in inducing cell death in a number of human MM cell lines, we hereby identified a subset of cell lines that despite a global loss of H3K27me3, remains viable after EZH2i. By coupling liquid chromatography-mass spectrometry with gene and miRNA expression profiling, we found that sensitivity to EZH2i correlated with distinct metabolic signatures resulting from a dysregulation of genes involved in methionine cycling. Specifically, EZH2i resulted in a miRNA-mediated downregulation of methionine cycling-associated genes in responsive cells. This induced metabolite accumulation and DNA damage, leading to G2 arrest and apoptosis. Altogether, we unveiled that sensitivity to EZH2i in human MM cell lines is associated with a specific metabolic and gene expression profile post-treatment.

Aberrant DNA methylation, dysregulation of chromatin-modifying enzymes, and microRNAs (miRNAs) play a crucial role in haematological malignancies. These epimutations, with an impact on chromatin accessibility and transcriptional output, are often associated with genomic instability and the emergence of drug resistance, disease progression, and poor survival. In order to exert their functions, epigenetic enzymes utilize cellular metabolites as co-factors and are highly dependent on their availability. By affecting the expression of metabolic enzymes, epigenetic modifiers may aid the generation of metabolite signatures that could be utilized as targets and biomarkers in cancer. This interdependency remains often neglected and poorly represented in studies, despite well-established methods to study the cellular metabolome. This review critically summarizes the current knowledge in the field to provide an integral picture of the interplay between epigenomic alterations and the cellular metabolome in haematological malignancies. Our recent findings defining a distinct metabolic signature upon response to enhancer of zeste homolog 2 (EZH2) inhibition in multiple myeloma (MM) highlight how a shift of preferred metabolic pathways may potentiate novel treatments. The suggested link between the epigenome and the metabolome in haematopoietic tumours holds promise for the use of metabolic signatures as possible biomarkers of response to treatment.

Multiple myeloma (MM) is a hematological disease of the plasma cell that remains clinically challenging despite the development of novel therapies. Epigenetic alterations have been demonstrated to contribute to MM pathogenesis, yet comprehensive studies into the links between different epigenetic regulatory systems in myeloma progression and drug resistance, though clinically relevant, are largely lacking. G9a and the DNA methyltransferases (DNMTs) are epigenetic modifiers that exhibit increased activity in MM, correlating with poor prognosis. To investigate the partnership between G9a and DNMTs, we used a combinatorial treatment approach involving small-molecule inhibitors. In-depth molecular analysis of the histone H3 lysine dimethylation distribution, the DNA methylome and the transcriptome of MM revealed a silencing mechanism involving G9a and DNMTs that represses key tumor suppressor genes. Moreover, dual inhibition of G9a and DNMTs reduced cell viability in primary MM cells and induced apoptosis in MM cell lines. This was accompanied by increased expression of apoptosis-related genes and decreased protein levels of the MM-associated oncoproteins IRF4, XBP1, and MYC. To assess the translational relevance of our in vitro findings, we evaluated the combination therapy in an in vivo preclinical xenograft MM model. Specifically, we demonstrate that the G9a inhibitor A366 synergizes with the DNMTs inhibitor decitabine to promote a robust tumor regression in vivo. Together, these data provide new insights into the cooperative role of G9a and the DNMTs in regulating gene silencing in MM, and support dual epigenetic inhibition as a promising therapeutic strategy.

Summary: Validation of biobanks and large cancer cohorts is essential in ensuring high‐quality research results. We examined the coverage, generalisability and validity of the lymphoma collection of the Uppsala‐Umeå Comprehensive Cancer Consortium (U‐CAN) biobank in Sweden, one of the largest cancer biobanks in Europe. Up until 2022, 889 lymphoma patients in U‐CAN Uppsala had available samples, and 329 in U‐CAN Umeå. Patients diagnosed in the U‐CAN Uppsala area 2011–2021 (n = 843) were linked to the nationwide Swedish Lymphoma Register, and a subset diagnosed before 2019 (n = 727) to population‐based registers. The coverage was 39% of all lymphoma patients between 2011 and 2019 diagnosed in the U‐CAN Uppsala area, with a pandemic decline to 10% during 2020–2021. The patients included had superior overall survival (hazard ratio = 0.70 [95% confidence interval, CI: 0.60–0.82]) than all lymphoma patients in Sweden. They had better performance status, were younger (odds ratio [OR] = 0.21 [95% CI: 0.13–0.34]) and had less comorbidities (OR = 0.66 [95% CI: 0.56–0.78]). However, cause‐specific survival and stage distribution were similar. The questionnaire data captured less comorbidities compared to the national registers. Evaluations of biobanks are important, as even population‐based biobanks such as U‐CAN select younger patients with higher socioeconomical status and better performance status. However, the similar cause‐specific survival as in the registries suggests U‐CANs usefulness for prognostic biomarker studies.