Original Article Induction of epithelial-mesenchymal transition (EMT) by hypoxia-induced lncRNA RP11-367G18.1 through regulating the histone 4 lysine 16 acetylation (H4K16Ac) mark

Hypoxia activates various long noncoding RNAs (lncRNAs) to induce the epithelial-mesenchymal transition (EMT) and tumor metastasis. The hypoxia/HIF-1 alpha-regulated lncRNAs that also regulate a specific histone mark and promote EMT and metastasis have not been identified. We performed RNA-sequencing dataset analysis to search for such lncRNAs and lncRNA RP11-367G18.1 was the hypoxia-induced lncRNA with the highest hazard ratio. High expression of lncRNA RP11-367G18.1 is correlated with a worse survival of head and neck cancer patients. We further showed that lncRNA RP11-367G18.1 is induced by hypoxia and directly regulated by HIF-1 alpha in cell lines. Overexpression of lncRNA RP11-367G18.1 induces the EMT and increases the in vitro migration and invasion and in vivo metastatic activity. Knockdown experiments showed that lncRNA RP11-367G18.1 plays an essential role in hypoxia-induced EMT. LncRNA RP11-367G18.1 specifically regulates the histone 4 lysine 16 acetylation (H4K16Ac) mark that is located on the promoters of two "core" EMT regulators, Twist1 and SLUG, and VEGF genes. These re-sults indicate that lncRNA RP11-367G18.1 regulates the deposition of H4K16Ac on the promoters of target genes to activate their expression. This report identifies lncRNA RP11-367G18.1 as a key player in regulating the histone mark H4K16Ac through which activates downstream target genes to mediate hypoxia-induced EMT.