Institute of Experimental Endocrinology and Oncology (IEOS), CNR, Naples, Italy.
Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy.
J Exp Clin Cancer Res. 2021 Jan 7;40(1):22. doi: 10.1186/s13046-020-01818-1.
The programmed cell death-1 (PD-1) receptor and its ligands PD-L1 and PD-L2 are immune checkpoints that suppress anti-cancer immunity. Typically, cancer cells express the PD-Ls that bind PD-1 on immune cells, inhibiting their activity. Recently, PD-1 expression has also been found in cancer cells. Here, we analysed expression and functions of PD-1 in thyroid cancer (TC).
PD-1 expression was evaluated by immunohistochemistry on human TC samples and by RT-PCR, western blot and FACS on TC cell lines. Proliferation and migration of TC cells in culture were assessed by BrdU incorporation and Boyden chamber assays. Biochemical studies were performed by western blot, immunoprecipitation, pull-down and phosphatase assays. TC cell tumorigenicity was assessed by xenotransplants in nude mice.
Human TC specimens (47%), but not normal thyroids, displayed PD-1 expression in epithelial cells, which significantly correlated with tumour stage and lymph-node metastasis. PD-1 was also constitutively expressed on TC cell lines. PD-1 overexpression/stimulation promoted TC cell proliferation and migration. Accordingly, PD-1 genetic/pharmacologic inhibition caused the opposite effects. Mechanistically, PD-1 recruited the SHP2 phosphatase to the plasma membrane and potentiated its phosphatase activity. SHP2 enhanced Ras activation by dephosphorylating its inhibitory tyrosine 32, thus triggering the MAPK cascade. SHP2, BRAF and MEK were necessary for PD-1-mediated biologic functions. PD-1 inhibition decreased, while PD-1 enforced expression facilitated, TC cell xenograft growth in mice by affecting tumour cell proliferation.
PD-1 circuit blockade in TC, besides restoring anti-cancer immunity, could also directly impair TC cell growth by inhibiting the SHP2/Ras/MAPK signalling pathway.
程序性细胞死亡受体-1（PD-1）及其配体 PD-L1 和 PD-L2 是抑制抗肿瘤免疫的免疫检查点。通常，癌细胞表达 PD-Ls，与免疫细胞上的 PD-1 结合，抑制其活性。最近，也发现癌细胞表达 PD-1。在这里，我们分析了甲状腺癌（TC）中 PD-1 的表达和功能。
通过免疫组化分析人 TC 样本、RT-PCR、western blot 和 FACS 分析 TC 细胞系中 PD-1 的表达。通过 BrdU 掺入和 Boyden 室测定评估 TC 细胞在培养中的增殖和迁移。通过 western blot、免疫沉淀、下拉和磷酸酶测定进行生化研究。通过裸鼠异种移植评估 TC 细胞的致瘤性。
人 TC 标本（47%），而不是正常甲状腺，上皮细胞表达 PD-1，与肿瘤分期和淋巴结转移显著相关。PD-1 也在 TC 细胞系中持续表达。PD-1 过表达/刺激促进 TC 细胞增殖和迁移。相应地，PD-1 基因/药物抑制产生相反的效果。在机制上，PD-1 将 SHP2 磷酸酶募集到质膜并增强其磷酸酶活性。SHP2 通过去磷酸化其抑制性酪氨酸 32 来增强 Ras 的激活，从而触发 MAPK 级联反应。SHP2、BRAF 和 MEK 是 PD-1 介导的生物学功能所必需的。PD-1 抑制减少，而 PD-1 强制表达通过影响肿瘤细胞增殖，促进 TC 细胞异种移植在小鼠中的生长。
TC 中的 PD-1 电路阻断，除了恢复抗肿瘤免疫外，还可以通过抑制 SHP2/Ras/MAPK 信号通路直接损害 TC 细胞的生长。
