Peng Mingjing, Fan Songqing, Li Junjun, Zhou Xiao, Liao Qianjin, Tang Faqing, Liu Wei
Central South University, Xiangya Medical School affiliated Cancer Hospital, Hunan Cancer Hospital, Changsha, 410073, Hunan, People's Republic of China.
Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha, 410078, Hunan, People's Republic of China.
Genes Nutr. 2022 Feb 14;17(1):3. doi: 10.1186/s12263-022-00705-y.
Cancer therapy targeting programmed death receptor-1 (PD-1 or CD279) or programmed death-ligand 1 (PD-L1 or CD274) gives hope to Tongue Squamous Cell Carcinoma (TSCC) treatment. However, the tumor-intrinsic mechanism of PD-L1 is not fully elucidated in TSCC. On the other hand, lycopene showed antitumor effects and chemotherapy/radiotherapy-enhancing effects by mechanisms closely correlated with PD-L1.
We aimed to explore whether the mechanisms of PD-L1 signaling and regulation are reversible by lycopene treatment in TSCC.
We collected TSCC tissues and normal tissues for assessment of PD-L1 expression by immunohistochemical technique and western blotting. We measured the expression of PD-L1 in three TSCC cell lines and constructed cell lines with knockdown and overexpression of PD-L1. Then, we measured the proliferation by CCK-8 assay, migration and invasion by Transwell assay, and apoptosis by TUNEL assay in five groups with treatment of blank control, negative control with vector transfection, PD-L1 knockdown/overexpression, 4 μM lycopene, and combined 4 μM lycopene and PD-L1 knockdown/overexpression. We also systematically analyzed the PD-L1 constitutive signaling pathways and their effect EMT pathways. In order to bring out the mechanism underlying PI3K/AKT depressing Raf/MEK/ERK, we used PI3K inhibitor LY294002.
We detected significant PD-L1 upregulation in biopsies by western blot and immunohistochemistry. Our study demonstrated that PD-L1 upregulation elevated IGF-1R to activate the PI3K/AKT pathway but inactivated the Raf/MEK/ERK pathway in TSCC cell line CAL27, while PD-L1 knockdown decreased IGF-1R to inactivate both PI3K/AKT and Raf/MEK/ERK pathways in cell line SCC9, to increase/decrease p-FOXOs and decrease/increase p-GSK-3β, producing further changes in EMT, proliferation, migration, invasion, and apoptosis. Lycopene reversed PD-L1 signaling and expression by mechanisms opposite to PD-L1 upregulation but similar to PD-L1 knockdown.
Taken together, this study firstly confirmed PD-L1 expression and signaling are reversible by lycopene via PI3K/AKT and Raf/MEK/ERK pathways in TSCC. Our study provides a sounder basis for comprehending PD-L1 signaling and expression and prevention and treatment of TSCC.
针对程序性死亡受体-1（PD-1或CD279）或程序性死亡配体-1（PD-L1或CD274）的癌症治疗为舌鳞状细胞癌（TSCC）的治疗带来了希望。然而，TSCC中PD-L1的肿瘤内在机制尚未完全阐明。另一方面，番茄红素通过与PD-L1密切相关的机制显示出抗肿瘤作用以及化疗/放疗增强作用。
我们旨在探讨番茄红素治疗是否能使TSCC中PD-L1信号传导和调节机制发生逆转。
我们收集了TSCC组织和正常组织，通过免疫组织化学技术和蛋白质印迹法评估PD-L1的表达。我们检测了三种TSCC细胞系中PD-L1的表达，并构建了PD-L1敲低和过表达的细胞系。然后，我们在五组中进行检测，包括空白对照、载体转染阴性对照、PD-L1敲低/过表达、4μM番茄红素以及4μM番茄红素与PD-L1敲低/过表达联合处理，通过CCK-8法检测增殖，Transwell法检测迁移和侵袭，TUNEL法检测凋亡。我们还系统分析了PD-L1组成性信号通路及其对EMT通路的影响。为了揭示PI3K/AKT抑制Raf/MEK/ERK的潜在机制，我们使用了PI3K抑制剂LY294002。
我们通过蛋白质印迹和免疫组织化学在活检组织中检测到显著的PD-L1上调。我们的研究表明，在TSCC细胞系CAL27中，PD-L1上调使IGF-1R升高以激活PI3K/AKT通路，但使Raf/MEK/ERK通路失活，而在细胞系SCC9中，PD-L1敲低使IGF-1R降低，从而使PI3K/AKT和Raf/MEK/ERK通路均失活，导致p-FOXOs增加/减少以及p-GSK-3β减少/增加，进而在EMT、增殖、迁移、侵袭和凋亡方面产生进一步变化。番茄红素通过与PD-L1上调相反但与PD-L1敲低相似的机制逆转了PD-L1信号传导和表达。
综上所述，本研究首次证实番茄红素可通过PI3K/AKT和Raf/MEK/ERK通路使TSCC中的PD-L1表达和信号传导发生逆转。我们的研究为理解PD-L1信号传导和表达以及TSCC的防治提供了更坚实的基础。
