Dysregulated Epiregulin (EREG) can activate epidermal growth factor receptor (EGFR) and promote tumor progression in head and neck squamous cell carcinoma (HNSCC). However, the mechanisms underlying EREG dysregulation remain largely unknown. Here, we showed that dysregulated EREG was highly associated with enhanced PDL1 in HNSCC tissues. Treatment of HNSCC cells with EREG resulted in upregulated PDL1 via the c-myc pathway. Of note, we found that N-glycosylation of EREG was essential for its stability, membrane location, biological function, and upregulation of its downstream target PDL1 in HNSCC. EREG was glycosylated at N47 via STT3B glycosyltransferases, whereas mutations at N47 site abrogated N-glycosylation and destabilized EREG. Consistently, knockdown of STT3B suppressed glycosylated EREG and inhibited PDL1 in HNSCC cells. Moreover, treatment of HNSCC cells with NGI-1, an inhibitor of STT3B, blocked STT3B-mediated glycosylation of EREG, leading to its degradation and suppression of PDL1. Finally, combination of NGI-1 treatment with anti-PDLl therapy synergistically enhanced the efficacy of immunotherapy of HNSCC in vivo. Taken together, STT3B-mediated N-glycosylation is essential for stabilization of EREG, which mediates PDL1 upregulation and immune evasion in HNSCC.

失调的上皮调节蛋白（EREG）可以激活表皮生长因子受体（EGFR）并促进头颈鳞状细胞癌（HNSCC）的肿瘤进展。然而，EREG 失调的机制仍然很大程度上未知。在这里，我们发现，HNSCC 组织中 EREG 失调与 PDL1 增强高度相关。用 EREG 处理 HNSCC 细胞可通过 c-myc 途径上调 PDL1。值得注意的是，我们发现 EREG 的 N-糖基化对其稳定性、膜定位、生物学功能及其下游靶点 PDL1 在 HNSCC 中的上调至关重要。 EREG 通过 STT3B 糖基转移酶在 N47 位点糖基化，而 N47 位点的突变消除了 N-糖基化并使 EREG 不稳定。一致地，敲低 STT3B 会抑制 HNSCC 细胞中的糖基化 EREG 并抑制 PDL1。此外，用STT3B抑制剂NGI-1处理HNSCC细胞，可阻断STT3B介导的EREG糖基化，导致其降解并抑制PDL1。最后，NGI-1治疗与抗PDL1治疗的组合协同增强了HNSCC体内免疫治疗的功效。总而言之，STT3B 介导的 N-糖基化对于 EREG 的稳定至关重要，而 EREG 介导 HNSCC 中 PDL1 上调和免疫逃避。