Roles of PRRs in orchestrating myeloid-derived suppressor cell (MDSC) function across different cancers. PRRs represent the primary MDSC receptors for integrating signals from pathogens or damaged cells. By recognizing different ligands, PRRs orchestrate MDSC immunosuppressive function, survival, migration, accumulation, differentiation, and soluble molecule release, thus exerting protumor or antitumor effects in mice and humans. PRRs, pattern recognition receptors; TLR, Toll-like receptor; NLRP3, NLR family pyrin domain containing 3; NOD1, nucleotide oligomerization domain; RIG-I, retinoic acid-inducible gene-I; BLP, bacterial lipoprotein; HSP70, heat shock protein 70; BCG, Bacille–Calmette–Guerín; LPS, lipopolysaccharide; S100A9, S100 calcium-binding protein A9; CARD9, caspase activation and recruitment domain 9; Gem, gemcitabine; 5FU, 5-fluorouracil; PD-L1, programmed death-ligand 1; RLH, RIG-I-like helicases. All listed PRRs were demonstrated to regulate MDSC function in mice, whereas only the PRRs indicated with lines were proven to modulate MDSC function in human cancers. The role of ALRs is not shown above due to the lack of relevant reports.