Hypoxia-induced adaptations of N-glycomes and proteomes in breast cancer cells and their secreted extracellular vesicles

The hypoxic tumor microenvironment significantly impacts cellular behavior and intercellular communication, with extracellular vesicles (EVs) playing a crucial in promoting angiogenesis, metastasis, and host immunosuppression. Aberrant surface N-glycan expression in EVs is closely associated with cancer progression and metastasis. We hypothesize that hypoxic tumors synthesize specific hypoxia-induced N-glycans, which are packaged into EVs to modulate the tumor microenvironment and drive cancer progression. This study utilized nano-LC-MS/MS to integrate quantitative proteomic and N-glycomic analyses of both cells and EVs derived from the MDA-MB-231 breast cancer cell line, cultured under normoxic and hypoxic conditions. Whole N-glycome and proteome profiling revealed that hypoxia changes the expression of asparagine N-linked glycosylation and glycolysis/gluconeogenesis proteins in cells to altered N-glycosylation for their adaptation to low oxygen conditions. Distinct N-glycan types, high-mannose glycans like Man3 and Man9 were highly abundant in hypoxic cells. On the other hand, alterations in sialylation and fucosylation patterns were observed in hypoxic cells. Furthermore, hypoxia-induced EVs exhibit a signature consisting of mono-antennary structures and specific N-glycans (H4N3F1S2, H3N3F1S0, and H7N4F3S2, H8N4F1S0 and H8N6F1S2), which significantly associated with a poor prognosis for breast tumor, potentially altering interactions within the tumor microenvironment to promote tumorigenesis and metastasis. Our findings provide an overview of N-glycan profiles, particularly under hypoxic conditions, offer insights into potential biomarkers for tracking tumor microenvironment dynamics and for developing precision medicine approaches in oncology.