CHUK/IKK-α loss in lung epithelial cells enhances NSCLC growth associated with HIF up-regulation

Through the progressive accumulation of genetic and epigenetic alterations in cellular physiology, non-small-cell lung cancer (NSCLC) evolves in distinct steps involving mutually exclusive oncogenic mutations in K-Ras or EGFR along with inactivating mutations in the p53 tumor suppressor. Herein, we show two independent in vivo lung cancer models in which CHUK/IKK-alpha acts as a major NSCLC tumor suppressor. In a novel transgenic mouse strain, wherein IKK alpha ablation is induced by tamoxifen (Tmx) solely in alveolar type II (AT-II) lung epithelial cells, IKKa loss increases the number and size of lung adenomas in response to the chemical carcinogen urethane, whereas IKK-beta instead acts as a tumor promoter in this same context. IKKa knockdown in three independent human NSCLC lines (independent of K-Ras or p53 status) enhances their growth as tumor xenografts in immune-compromised mice. Bioinformatics analysis of whole transcriptome profiling followed by quantitative protein and targeted gene expression validation experiments reveals that IKKa loss can result in the up-regulation of activated HIF-1-alpha protein to enhance NSCLC tumor growth under hypoxic conditions in vivo.