头颈部鳞状细胞癌（HNSCC）与重发和转移（R/M HNSCC）设置中显著的治疗相关性发病率和不良无病生存率以及特定疾病生存率有关。程序性死亡-1/配体-1（PD-1/PD-L1）免疫检查点的抑制被接受为R/M HNSCC的一线治疗策略，并扩展至新辅助、明确和辅助治疗设置。为了了解调节HNSCC中PD-L1的细胞信号，我们对一种HNSCC细胞系进行了全基因组开放阅读框（ORF）库的分析，其中包含17,000个单独构建物（14,000个唯一基因）。我们发现有335个ORFs在PD-L1高表达的细胞中富集，并独立验证了其中的五个ORFs（FGF6，IL17A，CD300C，KLR1C和NFKBIA）作为PD-L1上调的驱动因子。我们展示了外源性FGF配体足以诱导多种HNSCC细胞系和人类未成熟树突状细胞中的PD-L1表达。相应地，过表达的FGFR1，FGFR3或在HNSCC肿瘤中常见的FGFR3 S249C和D786N突变体也是诱导肿瘤细胞PD-L1表达的因素。小分子抑制FGF信号可以消除这些模型中PD-L1上调，并以一种STAT1非依赖的方式阻止了“经典”IFNγ调节的PD-L1表达。最后，我们发现FGF特异性上调了我们研究中PD-L1的糖基化形式，并且外源性FGF导致了糖基转移酶的伴随上调，这可能稳定了HNSCC细胞表面的PD-L1。综上所述，我们的研究支持FGF/FGFR信号通路作为驱动免疫逃逸的机制的潜在作用，并且为进一步探索用于改善HNSCC中PD-1/PD-L1轴抑制的临床反应的新型联合治疗提供了理论基础。版权所有©2023年Elsevier Ltd。保留所有权利。

Head and neck squamous cell carcinomas (HNSCC) are associated with significant treatment-related morbidity and poor disease-free and disease-specific survival, especially in the recurrent and metastatic (R/M HNSCC) setting. Inhibition of the programmed death-1/ligand-1 (PD-1/PD-L1) immune checkpoint is accepted as a first-line treatment strategy for R/M HNSCC and has expanded into the neoadjuvant, definitive, and adjuvant settings. To understand cellular signals modulating the PD-L1 in HNSCC, we profiled a HNSCC cell-line with a genome-wide open reading frame (ORF) library of 17,000 individual constructs (14,000 unique genes). We identified 335 ORFs enriched in PD-L1high cells and independently validated five of these ORFs (FGF6, IL17A, CD300C, KLR1C and NFKBIA) as drivers of PD-L1 upregulation. We showed that exogenous FGF ligand is sufficient to induce PD-L1 expression in multiple HNSCC cell lines and human immature dendritic cells. Accordingly, overexpression of FGFR1, FGFR3 or the FGFR3 S249C and D786N mutants common to HNSCC tumors also induced PD-L1 overexpression on tumor cells. Small molecule inhibition of FGF signaling abrogated PD-L1 upregulation in these models and also blocked "classical" IFNγ-regulated PD-L1 expression in a STAT1-independent manner. Finally, we found that FGF specifically upregulated a glycosylated form of PD-L1 in our study, and exogenous FGF led to concomitant upregulation of glycosyltransferases that may stabilize PD-L1 on the surface of HNSCC cells. Taken together, our study supports a potential role for FGF/FGFR pathway signaling as a mechanism driving immune escape and rationalizes further exploration of novel combination therapies to improve clinical responses to PD-1/PD-L1 axis inhibition in HNSCC.Copyright © 2023 Elsevier Ltd. All rights reserved.