FOXA2 Loss in TGF-β1-Induced EMT Suppresses Bisecting-GlcNAc N-Glycan Synthesis in Lung Adenocarcinoma

Glycosylation, a major posttranslational modification (PTM), is often dysregulated in cancer due to altered glycosyltransferase activity. Studies have shown specific changes in glycan structures associated with epithelial-mesenchymal transition (EMT) in cancer cells. However, the specific mechanism by which glycosyltransferases contribute to EMT remains unclear. In this study, we used bronchoalveolar lavage fluid (BALF) from lung adenocarcinoma (LUAD) patients to comparatively characterize glycopatterns and identify dysregulated glycosyltransferases in LUAD. We found a significant reduction in N-glycans containing the bisecting GlcNAc structure and confirmed by Western blot that N-acetylglucosaminyltransferase-III (MGAT3) is downregulated in LUAD. We observed a notable downregulation of both messenger RNA (mRNA) and protein expression of Forkhead box protein A2 (FOXA2) in early-stage LUAD, with FOXA2 loss emerging as an EMT promoter. Interestingly, cellular EMT models demonstrated that FOXA2 deficiency decreased MGAT3 expression during TGF-β1-driven EMT, leading to reduced levels of bisecting-GlcNAc N-glycans in LUAD cells. Our findings unveil a novel mechanism underlying the downregulation of MGAT3 and bisecting GlcNAc N-glycan expression during EMT, a process crucial for tumor metastasis.