Abstract / Summary
Myelodysplastic syndromes/neoplasms (MDS) are clonal hematopoietic disorders characterized by ineffective hematopoiesis, cytopenias, and an immunosuppressive bone marrow microenvironment. Although immunogenic cell death (ICD) holds therapeutic promise by activating antitumor immunity, the role of endogenous ICD inducers in MDS pathogenesis and immune evasion remains poorly understood. By integrating methylome and transcriptome analyses of MDS patient samples, we identified PRSS33 as a candidate tumor suppressing gene frequently silenced by promoter hypermethylation, with low expression correlating with poor survival. Hypomethylating agents restored PRSS33 expression, confirming epigenetic regulation. Functionally, PRSS33 restoration suppressed proliferation, induced cell cycle arrest and apoptosis, promoted myeloid differentiation in vitro, and inhibited tumor growth in vivo. Mechanistically, PRSS33 triggered endoplasmic reticulum stress, leading to a robust ICD response characterized by calreticulin exposure, ATP and HMGB1 release, and CD47 downregulation. This cascade enhanced macrophage phagocytosis, promoted M1 polarization, and stimulated dendritic cell maturation. Conversely, PRSS33 knockdown in NHD13 MDS mice aggravated cytopenias and erythroid dysplasia and fostered an immunosuppressive microenvironment with myeloid-derived suppressor cell expansion and T-cell loss. Importantly, vaccination with PRSS33-overexpressing cells elicited immune-associated effects and altered in vitro responsiveness to the PD-1/PD-L1 inhibitor BMS-1. Our study identifies PRSS33 as an epigenetically silenced tumor suppressor and a potent endogenous ICD inducer in MDS. These findings support PRSS33 reactivation as a rational strategy to remodel the immunosuppressive microenvironment and enhance existing therapies for MDS. PRSS33 is frequently silenced by promoter hypermethylation in MDS. Restoration of PRSS33 expression triggers a robust, ER stress-dependent ICD program. Genetic loss of PRSS33 in vivo (NHD13 model) directly links epigenetic silencing to immune escape.