Senescence of Mesenchymal Stromal Cells in Myelofibrosis Tumor Microenvironemnt Is Mediated By Glutamate-Induced Intracellular Fumarate Accumulation

Primary myelofibrosis (PMF) is a type of myeloproliferative neoplasm characterized by ineffective blood cell production. The growth of malignant cells is influenced by their interaction with the tumor microenvironment (TME), which is marked by significant fibrosis and inflammation. In this setting, mesenchymal stromal cells (MSCs) are reprogrammed to become senescent, releasing proinflammatory cytokines as part of the senescence-associated secretory phenotype (SASP), thereby worsening the inflammatory state of the PMF-TME. Additionally, the PMF-TME is rich in various metabolites that reshape the microenvironment to support the growth of malignant cells.

To investigate the metabolic changes in PMF, we analyzed several metabolites in peripheral blood using HPLC and found an accumulation of Glutamate (Glu) and its byproduct fumarate. Both Glu and fumarate are known to induce cell senescence. To explore their impact on the mesenchymal compartment, we used an in vitro model of healthy MSCs. Treatment with Glu and fumarate led to increased accumulation of reactive oxygen species (ROS), causing elevated DNA damage and fumarate-associated epigenetic modification H3K36me2. Moreover, fumarate inhibited cell proliferation, as shown by clonogenic assays and triphosphate accumulation. Importantly, supplementation with Glu and fumarate induced cell senescence, as evidenced by increased β-Galactosidase activity. This senescent phenotype was further supported by the accumulation of phospho-p53 and increased expression of SASP-associated genes IL6, TNF, and TGFβ. Senescent cells also showed increased 5mC levels, similar to those observed in primary PMF-MSCs. Additionally, fumarate supplementation led to enhanced expression of Col1a1, highlighting its role in promoting the characteristic fibrotic environment of the PMF-TME.

In conclusion, our findings reveal that Glu metabolism plays a critical role in the onset of PMF. The conversion of Glu to fumarate induces a senescent profile in MSCs, contributing to the fibrotic TME typical of PMF. Future studies aiming to inhibit Glu uptake could lead to novel therapeutic strategies against PMF.

Palumbo:Novartis: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AOP: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Incyte,: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Morphosys: Consultancy, Honoraria.