The CXC chemokine interleukin-8 (IL-8) is an angiogenic growth factor that is overexpressed in various cancers, including non-small cell lung cancer (NSCLC). Previously, IL-8 was shown as a transcriptional target of RAS signaling, raising the possibility of its role in oncogenic KRAS-driven NSCLC. Using microarray analysis, we identified IL-8 as the most downregulated gene by shRNA-mediated KRAS knockdown in NCI-H1792 NSCLC cells where IL-8 is overexpressed. NSCLC cell lines harboring KRAS or EGFR mutations overexpressed IL-8, while IL-8 levels were more prominent in KRAS mutants compared to EGFR mutants. IL-8 expression was downregulated by shRNA-mediated KRAS knockdown in KRAS mutants or by treatment with EGFR tyrosine kinase inhibitors and EGFR siRNAs in EGFR mutants. In our analysis of the relationship of IL-8 expression with clinical parameters and mutation status of KRAS or EGFR in 89 NSCLC surgical specimens, IL-8 expression was shown to be significantly higher in NSCLCs of males, smokers, and elderly patients and those with pleural involvement and KRAS mutated adenocarcinomas. In KRAS mutant cells, the MEK inhibitor markedly decreased IL-8 expression, while the p38 inhibitor increased IL-8 expression. Attenuation of IL-8 function by siRNAs or a neutralizing antibody inhibited cell proliferation and migration of KRAS mutant/IL-8 overexpressing NSCLC cells. These results indicate that activating mutations of KRAS or EGFR upregulate IL-8 expression in NSCLC; IL-8 is highly expressed in NSCLCs from males, smokers, elderly patients, NSCLCs with pleural involvement, and KRAS-mutated adenocarcinomas; and IL-8 plays a role in cell growth and migration in oncogenic KRAS-driven NSCLC.

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