Minocycline inhibits angiogenesis in vitro through the translational suppression of HIF-1α

Minocycline was recently found to be effective against cancer. However, the precise molecular mechanisms of minocycline in cancer are poorly understood. Hypoxia-inducible factor-1 (HIF-1, a heterodimeric transcription factor composed of HIF-1α and β) activates the transcription of genes that are involved in angiogenesis in cancer. In this study, we found that minocycline significantly inhibits HIF-1α protein expression and suppresses HIF-1 transcriptional activity. The tube formation assay showed that minocycline has anti-angiogenic activity and suppresses hypoxia-induced vascular endothelial growth factor (VEGF) expression. The metabolic labeling assay showed that minocycline reduces HIF-1α protein translation and global protein synthesis. In addition, minocycline suppresses mTOR signaling and increases the phosphorylation of eIF2α, which is known to be related to the translational regulation of HIF-1α expression. These findings collectively indicate that minocycline is a potential inhibitor of HIF-1α and provide new insight into the discovery of drugs for cancer treatment.