Core Viewpoint - Cancer-associated fibroblasts (CAF) play a critical role in supporting tumor growth and metastasis through extracellular matrix remodeling, paracrine signaling, and immune suppression, which limits the efficacy of immune checkpoint blockade (ICB) therapies [2][3]. Group 1 - The study published by researchers from the University of Chicago in the journal Nature reveals that NNMT promotes the recruitment of myeloid-derived suppressor cells (MDSC) into tumors via CAF, leading to the formation of an immunosuppressive tumor microenvironment (TME) [4]. - The research demonstrates that NNMT is expressed in all CAF subtypes and induces H3K27me3 hypomethylation, which facilitates the secretion of complement proteins that recruit MDSC into the tumor [7]. - The team developed a potent and specific NNMT inhibitor (NNMTi) that reduced tumor burden and metastasis in various mouse tumor models by decreasing CAF-mediated MDSC recruitment and reactivating CD8+ T cell activation, thereby restoring the efficacy of ICB therapy [9]. Group 2 - Overall, the study indicates that NNMT is a key regulatory factor of immunosuppression in the tumor microenvironment and represents a promising new target for alleviating immune suppression and enhancing cancer immunotherapy effectiveness [11].