LINC01140 promotes the progression and tumor immune escape in lung cancer by sponging multiple microRNAs

BACKGROUND: Long intergenic non-protein coding RNA 1140 (LINC01140), a long non-coding RNA, is highly expressed in various cancers; however, its biological functions in lung cancer (LC) progression and immune escape are still unclear. METHODS: Here, to elucidate LINC01140 function, 79 paired LC and paracancerous tissues were collected. LINC01140 expression levels were determined using fluorescence in situ hybridization and qPCR analysis. Cell counting kit-8 (CCK-8) assay and transwell assays were performed. The interaction between microRNAs (miRNAs) and LINC01140 was confirmed using an RNA immunoprecipitation assay. Cytokine-induced killer (CIK) cell phenotypes were analyzed by flow cytometry. Cytokine secretion levels were determined by ELISA. CIK cytotoxicity was assessed by measuring lactate dehydrogenase release. Besides, xenograft tumor mouse models were used to unveil the in vivo function of LINC01140. RESULTS: We found that LINC01140 was highly expressed in human LC tissues and cell lines. High LINC01140 levels were associated with poor survival in patients with LC. LINC01140 upregulation promoted the proliferation, migration, and invasion of LC cells through direct interaction with miR-33a-5p and miR-33b-5p, thereby contributing to c-Myc expression and also inhibited cisplatin-induced cell apoptosis. In subcutaneous tumor xenograft mice, LINC01140 knockdown markedly reduced tumor growth and lung metastasis. Additionally, LINC01140 directly repressed miR-377-3 p and miR-155-5 p expression levels, resulting in the upregulation of their common downstream target programmed death-ligand 1 (PD-L1), a crucial target in LC immunotherapy. Notably, we proved that LINC01140 knockdown, along with CIK administration, suppressed the growth of subcutaneous LC xenografts by decreasing PD-L1 expression in severe combined immunodeficient mice. CONCLUSIONS: Taken together, LINC01140 overexpression protects c-Myc and PD-L1 mRNA from miRNA-mediated inhibition and contributes to the proliferation, migration, invasion, and immune escape of LC cells. These results provide a theoretical basis that LINC01140 is a promising target for LC treatment.