SOX2-OT potentiates E2F1-HES6 interaction to suppress natural killer cell activity and mediate immunosuppression in lung adenocarcinoma

Abstract

Lung adenocarcinoma (LUAD) escapes immune surveillance by building an immunosuppressive tumor microenvironment. Within that microenvironment, impaired natural killer (NK) cell function is considered an important mechanism promoting tumor progression and immune escape. However, the molecular networks that control NK cell function in LUAD remain incompletely defined. We therefore examined the role of the SOX2-OT/E2F1/HES6 axis in LUAD immunosuppression and defined its regulatory mechanism. We used the TIMER3.0 database to analyze the correlation between HES6 and NK cell infiltration. Clinical LUAD samples were then used to validate this correlation. The effect of HES6 on NK cell function was assessed by RT-qPCR, Western blotting, flow cytometry, LDH release assay, and ELISA. ChIP, dual-luciferase reporter assays, RNA pull-down, and immunofluorescence were used to define the regulatory relationships among SOX2-OT, E2F1, and HES6. Finally, we used a tumor-bearing mouse model to test how the SOX2-OT/E2F1/HES6 axis affects tumor growth and NK cell infiltration. HES6 expression was prominently downregulated in LUAD and positively correlated with NK cell infiltration levels. Functional assays unveiled that HES6 overexpression potentiated NK cell cytotoxicity directly, elevated the proportion of activated NK cells, and promoted the secretion of effector cytokines IFN-γ and TNF-α. Mechanistic investigations elucidated that the transcription factor E2F1 directly integrated with the HES6 promoter and repressed its transcriptional activity. The lncRNA SOX2-OT served as a molecular scaffold to potentiate the transcriptional repression of E2F1 targeting HES6. In vivo experiments confirmed that SOX2-OT overexpression prominently facilitated tumor growth and attenuated NK cell infiltration, while co-overexpression of HES6 abrogated this effect. SOX2-OT potentiates the E2F1-HES6 interaction via its molecular scaffold function, thereby suppressing NK cell function and driving immunosuppression in LUAD.