A novel IFNα-induced long noncoding RNA negatively regulates immunosuppression by interrupting H3K27 acetylation in head and neck squamous cell carcinoma

Background Interferon alpha (IFN alpha) is a well-established regulator of immunosuppression in head and neck squamous cell carcinoma (HNSCC), while the role of long noncoding RNAs (lncRNAs) in immunosuppression remains largely unknown. Methods Differentially expressed lncRNAs were screened under IFN alpha stimulation using lncRNA sequencing. The role and mechanism of lncRNA in immunosuppression were investigated in HNSCC in vitro and in vivo. Results We identified a novel IFN alpha-induced upregulated lncRNA, lncMX1-215, in HNSCC. LncMX1-215 was primarily located in the cell nucleus. Ectopic expression of lncMX1-215 markedly inhibited expression of the IFN alpha-induced, immunosuppression-related molecules programmed cell death 1 ligand 1 (PD-L1) and galectin-9, and vice versa. Subsequently, histone deacetylase (HDAC) inhibitors promoted the expression of PD-L1 and galectin-9. Binding sites for H3K27 acetylation were found on PD-L1 and galectin-9 promoters. Mechanistically, we found that lncMX1-215 directly interacted with GCN5, a known H3K27 acetylase, to interrupt its binding to H3K27 acetylation. Clinically, negative correlations between lncMX1-215 and PD-L1 and galectin-9 expression were observed. Finally, overexpression of lncMX1-215 suppressed HNSCC proliferation and metastasis capacity in vitro and in vivo. Conclusions Our results suggest that lncMX1-215 negatively regulates immunosuppression by interrupting GCN5/H3K27ac binding in HNSCC, thus providing novel insights into immune checkpoint blockade treatment.