Downregulation of CYLD promotes IFN-γ mediated PD-L1 expression in thymic epithelial tumors.

Abstract

OBJECTIVES:

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.

MATERIALS AND METHODS:

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.

RESULTS:

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).

CONCLUSIONS:

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.

• Authors: Shigeki Umemura, Jianquan Zhu, Joeffrey J Chahine, Bhaskar Kallakury, Vincent Chen, In-Kyu Kim, Yu-Wen Zhang, Koichi Goto, Yongfeng He, Giuseppe Giaccone
• Journal: Lung cancer (Amsterdam, Netherlands) (Lung Cancer) Vol. 147 Pg. 221-228 (09 2020) ISSN: 1872-8332 [Electronic] Ireland
• PMID: 32738418 (Publication Type: Journal Article)
• Copyright: Copyright © 2020 Elsevier B.V. All rights reserved.

Chemical References

• B7-H1 Antigen
• CD274 protein, human
• Interferon-gamma
• CYLD protein, human
• Deubiquitinating Enzyme CYLD

Topics

• B7-H1 Antigen (genetics, metabolism)
• Deubiquitinating Enzyme CYLD (genetics)
• Down-Regulation
• Humans
• Interferon-gamma (metabolism)
• Lung Neoplasms
• Neoplasms, Glandular and Epithelial
• Thymus Neoplasms (genetics)