Circ_0074158 and QKI6: A regulatory axis for PD-L1 ubiquitination and immune evasion in NSCLC

OBJECTIVE: CircRNAs are involved in cancer progression. However, their role in immune escape in non-small cell lung cancer (NSCLC) remains poorly understood. METHODS: This study employed RIP-seq for the targeted enrichment of circRNAs, followed by Western blotting and RT-qPCR to confirm their expression. Specific binding was assessed using electrophoretic mobility shift assays. Transwell and wound healing assays were performed to evaluate the invasive and migratory capacities of NSCLC cells. The secretion of TNF-α, IFN-γ, GzmB, and perforin by CD8(+) T cells co-cultured with peripheral blood mononuclear cells (PBMCs) was quantitatively measured using enzyme-linked immunosorbent assays. The PD-L1 phenotype and apoptosis levels were determined by flow cytometry, while cell proliferation and apoptosis were evaluated through CCK-8, EdU, and TUNEL assays. The in vivo role of circ_0074158 was investigated using a mouse subcutaneous tumour implantation model. RESULTS: QKI6 modulates the level of PD-L1 ubiquitination in NSCLC. Both hsa_circ_0074158 and QKI6 influence the proliferation, invasion, and migration of NSCLC cells. Circ_0074158 regulates PD-L1 ubiquitination by modulating QKI6 expression, thus affecting PD-L1 expression. Furthermore, circ_0074158 activates CD8(+) T cells in PBMCs, inhibits immune escape, and promotes tumour cell apoptosis, suppressing tumour growth. CONCLUSION: The circ_0074158/QKI6 axis regulates PD-L1 ubiquitination in NSCLC, limiting tumour cell proliferation and invasion. Our findings reveal a novel function for circ_0074158 in NSCLC, suggesting its potential as a therapeutic target.