HOXA11-AS1 Promotes PD-L1-Mediated Immune Escape and Metastasis of Hypopharyngeal Carcinoma by Facilitating PTBP1 and FOSL1 Association

Abstract

Background: The metastatic characteristics of hypopharyngeal squamous cell carcinoma (HSCC) lead to many diagnostic and therapeutic challenges, while functional long non-coding RNAs (lncRNAs) can provide effective strategies for its diagnosis and treatment. Methods: RT-qPCR, Western blot, immunohistochemistry, and an immunofluorescence assay were used to detect the related gene expression. Flow cytometry was used to measure the percentage of CD8+ and CD4+ T cells. CCK-8 and transwell assays were performed to analyze the role of HOXA11-AS1. The targeted relationship of the FOSL1/PD-L1 promoter was measured by ChIP and dual-luciferase reporter assays. RNA pulldown and RIP assays were used to measure the interaction between HOXA11-AS1, FOSL1, and PTBP1. A tumor xenograft study was used to analyze HOXA11-AS1 function in vivo. Results: HOXA11-AS1, PD-L1, and FOSL1 were upregulated in HSCC, and HOXA11-AS1 positively correlated with PD-L1. HOXA11-AS1 knockdown upregulated CD8+ T cells through an increase in IFN-γ concentration while decreasing the proliferation, migration, and invasion of HSCC cells. FOSL1 bound the PD-L1 promoter, increasing gene expression. HOXA11-AS1 enhanced the stability of FOSL1 mRNA by binding to PTBP1. HOXA11-AS1 or PTBP1 overexpression increased FOSL1 and PD-L1 expression. PD-L1 knockdown arrested the inhibiting function of HOXA11-AS1 overexpression on CD8+ T cell content. HOXA11-AS1 knockdown inhibited immune escape and metastasis through PD-L1 regulation by downregulating FOSL1 in vivo. Conclusion: HOXA11-AS1 promoted PD-L1 expression by upregulating FOSL1 levels through PTBP1, thereby facilitating immune escape, proliferation, and metastasis of HSCC cells.