Umemura Shigeki, Zhu Jianquan, Chahine Joeffrey J, Kallakury Bhaskar, Chen Vincent, Kim In-Kyu, Zhang Yu-Wen, Goto Koichi, He Yongfeng, Giaccone Giuseppe
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, 20057, USA; Department of Thoracic Oncology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, 20057, USA; Department of Lung Cancer, Tianjin Medical University Cancer Institute and Hospital, Tianjin Lung Cancer Center, Tianjin Key Laboratory of Cancer Prevention and Therapy, National Clinical Research Center for Cancer, Tianjin, People's Republic of China.
Lung Cancer. 2020 Sep;147:221-228. doi: 10.1016/j.lungcan.2020.07.018. Epub 2020 Jul 22.
Recent genomic studies suggest the biological significance of the cylindromatosis (CYLD) gene in thymic epithelial tumors (TETs). CYLD is a crucial regulator of immune response, and we previously reported that CYLD mutation is associated with high PD-L1 expression in thymic carcinoma. Therefore, we wanted to explore the role and mechanism of CYLD in regulating PD-L1 expression in TETs.
The role of CYLD in PD-L1 expression was assessed by knockdown of CYLD in TET cells upon stimulation with interferon gamma (IFN-γ), tumor necrosis factor-α (TNF-α) or polyinosinic-polycytidylic acid (poly I:C). The molecular mechanism was investigated through analysis of downstream molecules in the STAT1/IRF1 pathway. Moreover, the clinical correlation between low CYLD and high PD-L1 expression, and the clinical impact of CYLD expression were evaluated in tissue microarrays of 105 TET cases.
CYLD knockdown significantly enhanced the expression of PD-L1 in presence of IFN-γ stimulation in most TET cell lines. However, this phenomenon was not observed in presence of TNF-α stimulation. CYLD knockdown upregulated IFN-γ mediated activation of the STAT1/IRF1 axis, which in turn induced PD-L1 expression. Interestingly, we found a significant association between low CYLD expression and ≥ 50 % PD-L1 expression (p = 0.001). In addition, the average proportion of tumor cells exhibiting PD-L1 staining was significantly higher in the low CYLD expression group (24.7 %) than in the high CYLD expression group (5.2 %) (p = 0.005). There was no correlation between CYLD expression and the frequency of pre-existing paraneoplastic auto-immune diseases. In advanced stages (III/IV), the low CYLD expressing group had numerically worse survival than the high CYLD group (log-rank p = 0.089).
Our findings provide insight into the mechanism of regulation of PD-L1 expression by CYLD in TET cells. Tumors with low CYLD expression could be potential targets for PD-1/PD-L1 inhibitors.
近期的基因组研究表明圆柱瘤（CYLD）基因在胸腺上皮肿瘤（TETs）中具有生物学意义。CYLD是免疫反应的关键调节因子，我们之前报道CYLD突变与胸腺癌中高PD-L1表达相关。因此，我们想探讨CYLD在调节TETs中PD-L1表达的作用及机制。
通过在γ干扰素（IFN-γ）、肿瘤坏死因子-α（TNF-α）或聚肌苷酸-聚胞苷酸（poly I:C）刺激下敲低TET细胞中的CYLD来评估CYLD在PD-L1表达中的作用。通过分析STAT1/IRF1途径中的下游分子来研究分子机制。此外，在105例TET病例的组织芯片中评估低CYLD与高PD-L1表达之间的临床相关性以及CYLD表达的临床影响。
在大多数TET细胞系中，CYLD敲低在IFN-γ刺激下显著增强了PD-L1的表达。然而，在TNF-α刺激下未观察到这种现象。CYLD敲低上调了IFN-γ介导的STAT1/IRF1轴的激活，进而诱导了PD-L1的表达。有趣的是，我们发现低CYLD表达与≥50%的PD-L1表达之间存在显著关联（p = 0.001）。此外，低CYLD表达组中显示PD-L1染色的肿瘤细胞平均比例（24.7%）显著高于高CYLD表达组（5.2%）（p = 0.005）。CYLD表达与既往副肿瘤性自身免疫性疾病的发生率之间无相关性。在晚期（III/IV期），低CYLD表达组的生存数值上比高CYLD组差（对数秩检验p = 0.089）。
我们的研究结果为CYLD在TET细胞中调节PD-L1表达的机制提供了见解。CYLD表达低的肿瘤可能是PD-1/PD-L1抑制剂的潜在靶点。
