O-linked β-N-acetylglucosamine transferase (O-GlcNAc transferase, OGT) is a key enzyme that regulates O-GlcNAc modification, which is significantly up-regulated and participates in the regulation of tumorigenesis. Although previous research indicated that OGT promotes epithelial-mesenchymal transition (EMT) of lung cancer, the underlying molecular mechanisms, especially within the tumor inflammatory microenvironment, require further elucidation.
The role of the inflammatory signaling Interleukin 6/Signal Transducer and activator of transcription 3 (IL-6/STAT3) in Non-small cell lung cancer (NSCLC) cells A549 were confirmed by Transwell assay, Scratch wound healing assay, Western blot, Immunofluorescence staining, and Nuclear and cytoplasmic extraction experiment. Western blot detected OGT expression and whole protein O-GlcNacylation after IL-6 stimulation in NSCLCs cells. The biological effects and related mechanism of OGT in NSCLC cells were investigated by Western blot, Transwell assay, Immunofluorescence staining and Immunoprecipitation. The up-stream mechanism of OGT expression was explored by employing the specific chemical inhibitors, and the expression and distribution of OGT and phosphorylated STAT3 in NSCLC samples were confirmed by immunohistochemical analysis.
IL-6/STAT3 promoted the migration and invasion of NSCLC cells. IL-6 stimulation elevated OGT expression and the total protein O-GlcNacylation in A549 cells. Silencing OGT by shRNA significantly inhibited the IL-6 induced EMT marker (N-cadherin and Slug) expression, migration and invasion in A549 cells. OGT interacted with and mediated O-GlcNacylation of STAT3, which promoted STAT3 Y705 phosphorylation in IL-6 treated NSCLC cells. OGT expression was positively regulated by NF-κB p65 signaling pathway after IL-6 stimulation, instead of STAT3 signaling. OGT and phosphorylated STAT3 had an obviously higher expression in human NSCLC tissues, and phosphorylated STAT3 was mainly expressed in the nucleus.
The above results showed that OGT regulated O-GlcNacylation promoted migration and invasion by activating IL-6/STAT3 signaling in lung cancer.

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