Autophagy related 4B, upregulated by HIF-1α, attenuates the sensitivity to cisplatin in nasopharyngeal carcinoma cells

J. Huang, H.-B. Li, S. Yu, F. Yuan, Z.-P. Lou

Department of Otolaryngology, Zhuji Affiliated Hospital of Shaoxing University, Zhuji City, Zhejiang Province, China. jiajiaamao@163.com

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• Oncology

OBJECTIVE: Increasing evidence has shown that autophagy related proteins and hypoxia-inducible factor-1α (HIF-1α) are both involved in the malignant progress of nasopharyngeal carcinoma (NPC), and HIF-1α plays an emerging role in the chemosensitivity of NPC cells. However, it is still unknown whether autophagy related proteins are associated with HIF-1α in regulating the chemosensitivity of NPC cells.

MATERIALS AND METHODS: Quantitative Real-time PCR (qPCR) was applied to determine mRNA levels of HIF-1α and the autophagy related proteins, such as ATG3, ATG4B, ATG5, Beclin1, ATG7, ATG10, ATG12 and ATG16L1. Western blot was applied to determine protein levels of HIF-1α, ATG4B and cleaved Caspase-3. Cell viability and death were investigated by cell counting kit-8 and trypan blue exclusion assay. In addition, Caspase-3 activity was detected to reflect apoptosis. Furthermore, Luciferase reporter assay was applied to explore the mechanism by which HIF-1α transcriptionally upregulated ATG4B expression.

RESULTS: Our study reveals that HIF-1α increased ATG4B expression in NPC cells, and in turn upregulated the cisplatin (DDP)-induced protective autophagy, resulting in enhanced killing effect of DDP to NPC cells. In mechanism, reporter assay showed that HIF-1α upregulated ATG4B expression by activating its gene promoter region. The binding site (-225 to -216) was required for HIF-1α-induced increase of ATG4B gene promoter activity.

CONCLUSIONS: These results indicate that HIF-1α elevates ATG4B via promoting its transcription, which alleviates the sensitivity of DDP in NPC cells through enhancing protective autophagy, suggesting that ATG4B, upregulated by HIF-1α, may be a novel target for DDP sensitization in the treatment of NPC in clinic.

 

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