Department of Maxillofacial Surgery, Aichi Gakuin University School of Dentistry, Nagoya 464-0821, Japan.
Research Creation Support Center, Aichi Medical University School of Medicine, Nagakute 480-1195, Japan.
Int J Mol Sci. 2022 Apr 7;23(8):4077. doi: 10.3390/ijms23084077.
The expression of programmed death ligand-1 (PD-L1) is controlled by complex mechanisms. The elucidation of the molecular mechanisms of PD-L1 expression is important for the exploration of new insights into PD-1 blockade therapy. Detailed mechanisms of the in situ expression of PD-L1 in tissues of oral squamous cell carcinomas (OSCCs) have not yet been clarified. We examined the mechanisms of PD-L1 expression focusing on the phosphorylation of downstream molecules of epidermal growth factor (EGF) and interferon gamma (IFN-γ) signaling in vitro and in vivo by immunoblotting and multi-fluorescence immunohistochemistry (MF-IHC), respectively. The in vitro experiments demonstrated that PD-L1 expression in OSCC cell lines is upregulated by EGF via the EGF receptor (EGFR)/PI3K/AKT pathway, the EGFR/STAT1 pathway, and the EGFR/MEK/ERK pathway, and by IFN-γ via the JAK2/STAT1 pathway. MF-IHC demonstrated that STAT1 and EGFR phosphorylation was frequently shown in PD-L1-positive cases and STAT1 phosphorylation was correlated with lymphocyte infiltration and EGFR phosphorylation. Moreover, the phosphorylation pattern of the related molecules in PD-L1-positive cells differed among the cases investigated. These findings indicate that PD-L1 expression mechanisms differ depending on the tissue environment and suggest that the examination of the tissue environment and molecular alterations of cancer cells affecting PD-L1 expression make it necessary for each patient to choose the appropriate combination drugs for PD-1 blockade cancer treatment.
程序性死亡配体 1（PD-L1）的表达受复杂机制的控制。阐明 PD-L1 表达的分子机制对于探索 PD-1 阻断治疗的新见解很重要。口腔鳞状细胞癌（OSCC）组织中 PD-L1 的原位表达的详细机制尚未阐明。我们通过免疫印迹和多荧光免疫组织化学（MF-IHC）分别在体外和体内检查了 PD-L1 表达的机制，重点研究了表皮生长因子（EGF）和干扰素γ（IFN-γ）信号下游分子的磷酸化。体外实验表明，EGF 通过表皮生长因子受体（EGFR）/PI3K/AKT 通路、EGFR/STAT1 通路和 EGFR/MEK/ERK 通路上调 OSCC 细胞系中的 PD-L1 表达，IFN-γ 通过 JAK2/STAT1 通路上调 PD-L1 表达。MF-IHC 表明 PD-L1 阳性病例中频繁出现 STAT1 和 EGFR 磷酸化，STAT1 磷酸化与淋巴细胞浸润和 EGFR 磷酸化相关。此外，PD-L1 阳性细胞中相关分子的磷酸化模式在不同病例中存在差异。这些发现表明 PD-L1 表达机制因组织环境而异，并表明检查影响 PD-L1 表达的癌细胞的组织环境和分子改变对于为每位患者选择合适的 PD-1 阻断癌症治疗联合药物很有必要。
