SUSD2 hypersialylation promotes early lung adenocarcinoma progression by driving ECM remodeling and pro-tumorigenic fibroblast activation

Cancer-associated fibroblasts (CAFs) play a crucial role in promoting the invasion and metastasis of lung adenocarcinoma (LUAD). The mechanism by which CAFs promote this process remains unclear. We employed glycoproteomics to investigate the dynamic changes in glycosylation between normal and early-stage LUAD tissues, and explore the roles of related glycoproteins and site-specific polysaccharides through in vitro and in vivo experiments. Using mass spectrometry-based glycoproteomics, we identified 242 N-glycosylated proteins with significantly increased expression and 17 with decreased expression in LUAD tissues. Sialylated modifications constitute the largest proportion of N-glycosylation and promote extracellular matrix (ECM) release by CAFs, enhancing their pro-cancer potential. Stage I LUAD patients with high levels of sialylation modifications have poor overall survival (OS) rates. Further findings revealed that ST3GAL4-mediated sialylation in CAFs is a key driver of ECM secretion, and that early-stage LUAD patients with high infiltration of ST3GAL4-positive CAFs have poor OS. Quantitative analysis of intact glycopeptides showed that core sialylation of SUSD2-Asn(N)162 was significantly upregulated and correlated with the ability of CAFs to secrete ECM. Sialylated SUSD2 binds to AKT and Smad2, enhancing their phosphorylation and ECM secretion, thereby increasing the pro-tumorigenic effects of CAFs. These findings offer new directions for developing glycosylation-centric therapies and biomarkers to treat early-stage LUAD, to improve patient outcomes by targeting CAF-driven drug resistance mechanisms.