GUSB and head and neck squamous cell carcinoma: Finally, to determine whether GUSB‐H351Q‐promoted N‐glycosylation of PD‐L1 is predominantly mediated by STT3B, we cotransfected the HNSCC cell line with GUSB and STT3B, and knockdown of STT3B substantially decreased the binding of PD‐L1 with Con A in the GUSB‐H351Q group, suggesting that the GUSB mutation facilitated PD‐L1 glycosylation primarily through STT3B (Figure 6D).