Long noncoding RNA HITT coordinates with RGS2 to inhibit PD-L1 translation in T cell immunity
Qingyu Lin, Tong Liu, Xingwen Wang, Guixue Hou, Zhiyuan Xiang, Wenxin Zhang, Shanliang Zheng, Dong Zhao, Qibin Leng, Xiaoshi Zhang, Minqiao Lu, Tianqi Guan, Hao Liu, Ying Hu
Qingyu Lin, Tong Liu, Xingwen Wang, Guixue Hou, Zhiyuan Xiang, Wenxin Zhang, Shanliang Zheng, Dong Zhao, Qibin Leng, Xiaoshi Zhang, Minqiao Lu, Tianqi Guan, Hao Liu, Ying Hu
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Research Article Immunology Oncology

Long noncoding RNA HITT coordinates with RGS2 to inhibit PD-L1 translation in T cell immunity

Abstract

Programmed cell death ligand 1 (PD-L1) is an immune checkpoint protein frequently expressed in human cancers that contributes to immune evasion through its binding to PD-1 on activated T cells. Unveiling the mechanisms underlying PD-L1 expression is essential for understanding the impact of the immunosuppressive microenvironment and is also crucial for the purpose of reboosting antitumor immunity. However, how PD-L1 is regulated, particularly at translational levels, remains largely unknown. Here, we discovered that a long noncoding RNA (lncRNA), HIF-1α inhibitor at translation level (HITT), was transactivated by E2F transcription factor 1 (E2F1) under IFN-γ stimulation. It coordinated with regulator of G protein signaling 2 (RGS2) in binding to the 5′ UTR of PD-L1, resulting in reduced PD-L1 translation. HITT expression enhanced T cell–mediated cytotoxicity both in vitro and in vivo in a PD-L1–dependent manner. The clinical correlation between HITT/PD-L1 and RGS2/PD-L1 expression was also detected in breast cancer tissues. Together, these findings demonstrate the role of HITT in antitumor T cell immunity, highlighting activation of HITT as a potential therapeutic strategy for enhancing cancer immunotherapy.

Authors

Qingyu Lin, Tong Liu, Xingwen Wang, Guixue Hou, Zhiyuan Xiang, Wenxin Zhang, Shanliang Zheng, Dong Zhao, Qibin Leng, Xiaoshi Zhang, Minqiao Lu, Tianqi Guan, Hao Liu, Ying Hu

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Figure 2

IFN-γ–induced and E2F1-mediated transactivation of HITT attenuates PD-L1 expression.

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IFN-γ–induced and E2F1-mediated transactivation of HITT attenuates PD-L1...
(A and B) PD-L1 and PD-L2 protein levels analyzed by WB assay in HITT stable overexpression (A) or HITT-KO (B) cells. (C and D) HITT levels determined by qRT-PCR in MDA-231 and HeLa cells treated with different concentrations of IFN-γ for 24 hours (C) or treated for the indicated time periods with 10 ng/ml IFN-γ (D). (E) PD-L1 protein levels analyzed by WB in IFN-γ–treated cells with or without HITT KD. (F and G) HITT promoter luciferase activities determined by luciferase reporter assay in MDA-231 and HeLa cells treated with different concentrations of IFN-γ for 24 hours (F) or the indicated time periods with 10 ng/ml IFN-γ (G). (H) Relative binding potentials between different transcription factors and HITT promoter region were analyzed by UCSC ChIP sequence data. (I) E2F1 protein levels were detected by WB in MDA-231 and HeLa cells with different concentrations of IFN-γ for 24 hours or with 10 ng/ml IFN-γ for different time courses. (J) HITT expression levels and HITT promoter luciferase activities were measured by qRT-PCR and luciferase reporter assay in IFN-γ–treated (10 ng/ml for 24 hours) cells after E2F1 KD. E2F1 KD efficiency was validated by WB (bottom). (K) HITT promoter (full length and MT) controlled luciferase activities were determined after transient transfection of the indicated reporter plasmids together with E2F1 expression plasmid. (L) Binding between HITT promoter region and E2F1 was determined by ChIP assay after IFN-γ treatment (10 ng/ml for 24 hours). PCR band intensities were quantified using ImageJ and are presented in the bar graph (bottom). Data are derived from 3 independent experiments and are shown as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; NS, not significant by 1-way ANOVA (C, D, F, G, and J) and Student’s t test (K and L).