Tumor necrosis factor-alpha (TNFα) is an inflammatory cytokine that regulates inflammation and tumor progression in non-small cell lung cancer (NSCLC). The higher levels of TNF α are known to induce expression of several genes such as TNFα-induced protein 2 (TNFAIP2) with a largely unknown role in NSCLC. We provide the preliminary evidence for the role of TNFAIP2 in NSCLC progression and its epigenetic regulation mediated by microRNA, miR-145-5p. The expression of TNFAIP2 was confirmed using quantitative real-time PCR, immunohistochemistry, and Western blot in NSCLC tissue and paired adjacent normal tissue. All in vitro assays were undertaken in A549 and H23 cells and chemoresistance assays were undertaken in A549/Cisplatin (DDP) and H23/DDP cell types. TNFAIP2 silencing was undertaken using lipofectamine transfection of specific siRNA. Cells were co-transfected with miR-145-5p, and TNFAIP2-3' untranslated region (UTR) or TNFAIP2 with mutated 3'UTR using the luciferase vector pGL. Cell viability, transwell migration, and invasion were assessed. The role of caspase 3 proteins in cell viability was ascertained using Western blot. The tumor tissues (and cisplatin-resistant cell lines A549/DDP and H23/DDP) expressed significantly higher levels of TNAIP2 mRNA and protein. Silencing of TNFAIP2 resulted in reduced cell viability, reduced invasion, and migration in vitro. Silencing of TNFAIP2 in A549/DDP and H23/DDP had higher expression of TNFAIP2, reduced cell viability, and increased induction of caspase 3. MiR-145-5p binds to the 3'UTR of TNFAIP2. Overexpression of MiR-145-5p reduced expression of TNFAIP2, decreased cell viability, reduced cell migration and invasion, and significantly reduced expression of caspase 3 protein. TNFAIP2 mediates tumorigenesis in NSCLC through, not completely known pathways. miR-145-5p negatively regulates TNFAIP2 expression. miR-145-5p-mediated therapies may be explored in NSCLC.

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