Q6, a novel hypoxia-targeted drug, regulates hypoxia-inducible factor signaling via an autophagy-dependent mechanism in hepatocellular carcinoma.
Tumor hypoxia underlies treatment failure and yields more aggressive and metastatic cancer phenotypes. Although therapeutically targeting these hypoxic environments has been proposed for many years, to date no approaches have shown the therapeutic value to gain regulatory approval. Here, we demonstrated that a novel hypoxia-activated prodrug, Q6, exhibits potent antiproliferative efficacy under hypoxic conditions and induces caspase-dependent apoptosis in 2 hepatocellular carcinoma (HCC) cell lines, with no obvious toxicity being detected in 2 normal liver cell lines. Treatment with Q6 markedly downregulated HIF1A [hypoxia inducible factor 1, α subunit (basic helix-loop-helix transcription factor)] expression and transcription of the downstream target gene, VEGFA (vascular endothelial growth factor A). This dual hypoxia-targeted modulation mechanism leads to high potency in suppressing tumor growth and vascularization in 2 in vivo models. Intriguingly, it is the autophagy-dependent degradation pathway that plays a crucial role in Q6-induced attenuation of HIF1A expression, rather than the proteasome-dependent pathway, which is normally regarded as the predominant mechanism underlying posttranslational regulation of HIF1A. Inhibition of autophagy, either by short interfering RNA (siRNA) or by chemical inhibitors, blocked Q6-induced HIF1A degradation. Autophagic degradation of HIF1A was further confirmed by the observation that HIF1A coimmunoprecipitated with the ubiquitin-binding adaptor protein, SQSTM1, which is degraded through autophagy. Additionally, silencing of SQSTM1 inhibited Q6-induced HIF1A degradation. These findings suggest that the novel hypoxia-targeted agent, Q6, has potential clinical value in the therapy of HCC. Furthermore, the identification of autophagy as a crucial regulator of HIF1A provides new insights into hypoxia-related treatments.
['Liu|Xiao-Wen|XW|', 'Cai|Tian-Yu|TY|', 'Zhu|Hong|H|', 'Cao|Ji|J|', 'Su|Yi|Y|', 'Hu|Yong-Zhou|YZ|', 'He|Qiao-Jun|QJ|', 'Yang|Bo|B|']
D048868:Adaptor Proteins, Signal Transducing D000818:Animals D000970:Antineoplastic Agents D017209:Apoptosis D001343:Autophagy D000071187:Autophagy-Related Protein 5 D006528:Carcinoma, Hepatocellular D020169:Caspases D015687:Cell Hypoxia D045744:Cell Line, Tumor D049109:Cell Proliferation D015536:Down-Regulation D051795:Hypoxia-Inducible Factor 1, alpha Subunit D008113:Liver Neoplasms D008247:Lysosomes D051379:Mice D008819:Mice, Nude D008869:Microtubule-Associated Proteins D059748:Proteolysis D011810:Quinoxalines D000071456:Sequestosome-1 Protein D015398:Signal Transduction D014158:Transcription, Genetic
hypoxia-activated prodrug posttranslational regulation autophagy dual modulation mechanisms targeting treatment