MMD2 encodes a member of the progestin and adipoQ receptor (PAQR) family with primary functions in immune signaling and cell differentiation. The protein localizes to the Golgi apparatus and perinuclear cytoplasm, where it regulates Ras/ERK signaling and protein kinase activity involved in neutrophil chemotaxis. MMD2 has emerged as a key player in innate immunity. Monoallelic mutations in MMD2 (p.A116V and p.R126P) cause autosomal dominant aggressive periodontitis by impairing formyl-methionyl-leucyl-phenylalanine (fMLP)-induced activation of Ras/ERK signaling and disrupting Golgi apparatus structure in neutrophils, leading to defective chemotaxis and subsequent periodontal tissue destruction 1. This demonstrates that MMD2-mediated signaling is critical for neutrophil-dependent immune responses. In cancer contexts, MMD2 expression is frequently upregulated and promotes malignant progression. In breast cancer, high MMD2 levels correlate with advanced staging, larger tumors, and worse prognosis; the microRNA miR-1270 suppresses breast cancer malignancy by negatively regulating MMD2 expression 2. Similarly, Helicobacter pylori infection drives gastric cancer aggressiveness through upregulation of the HOXA-AS2/miR-509-3p/MMD2 regulatory axis 3. Across pan-cancer studies, MMD2 expression associates with survival outcomes and drug sensitivity 4. MMD2 represents a potential therapeutic target in immune and malignant diseases, with opportunities for targeted modulation of its signaling function.