Impaired glycosylation of gastric mucins drives gastric tumorigenesis and serves as a novel therapeutic target.

Gastric cancer is often accompanied by a loss of MUC6, but its pathogenic role in gastric carcinogenesis remains unclear.Muc6 knockout (Muc6-/-) mice and Muc6-dsRED mice were newly generated. Tff1Cre, Golph3-/-, R26-Golgi-mCherry, Hes1flox/flox, Cosmcflox/flox, A4gnt-/- mice were also used. Histology, DNAs and RNAs, proteins, and sugar chains were analyzed by whole exon DNA sequence, RNA sequence, immunohistochemistry, lectin-binding assays, and LC-MS analysis. Gastric organoids and cell lines were used for in vitro assays and xenograft experiments.Deletion of Muc6 in mice spontaneously causes pan-gastritis and invasive gastric cancers. Muc6-deficient tumor growth was dependent on MAPK activation, mediated by Golgi stress-induced upregulation of GOLPH3. Glycomic profiling revealed aberrant expression of mannose-rich N-linked glycans in gastric tumors, detected with Banana lectin in association with lack of MUC6 expression. We identified a precursor of clusterin as a binding partner of mannose glycans. MAPK activation, Golgi stress responses, aberrant mannose expression are found in a separate Cosmc- and A4gnt-deficient mouse models which lack normal O-glycosylation. Banana lectin-drug conjugates proved an effective treatment for mannose-rich murine and human gastric cancer.We propose that Golgi stress responses and aberrant glycans are important drivers of, and promising new therapeutic targets for gastric cancer.