Hypoxia induces sorafenib resistance mediated by autophagy via activating FOXO3a in hepatocellular carcinoma

Chao Liang,Miaozun Zhang,Weiming Yu,Yuan Xu,Wei Chen,Xianlei Cai,Zhebin Dong,Jie Shen,Hong Li

doi:10.1038/s41419-020-03233-y

Abstract

Sorafenib, a multikinase inhibitor, is considered as the only approved drug to cure the advanced hepatocellular carcinoma (HCC); however, the acquired chemoresistance caused by intratumoral hypoxia through sorafenib long term therapy induces sorafenib inefficacy. We demonstrated here that hypoxia significantly attenuated sensitivity of HCC cells to sorafenib treatment and reduced its proliferation. Autophagy was observed in sorafenib-treated HCC cells in hypoxia, and inhibition of autophagy by 3-MA eliminated hypoxia-induced sorafenib resistance. Further study revealed hypoxia-activated FOXO3a, an important cellular stress transcriptional factor, via inducing its dephosphorylation and nuclear location; and FOXO3a-dependent transcriptive activation of beclin-1 was responsible for hypoxia-induced autophagy in HCC cells. Knockout of FOXO3a inhibited the autophagy induced by sorafenib itself in normoxia and significantly enhanced the cytotoxicity of sorafenib in HCC cells; and it also inhibited the hypoxia-induced autophagy and achieved the same effect in sorafenib sensitivity-enhancement in HCC cells as it in normoxia. Finally, knockout of intratumoral FOXO3a significantly enhanced curative efficacy of sorafenib via inhibition of autophagy in xenograft tumors in nude mice. Collectively, our study suggests that FOXO3a plays a key role in regulating hypoxia-induced autophagy in sorafenib-treated HCC, and FOXO3-targeted therapy may serve as a promising approach to improve clinical prognosis of patients suffering from HCC.

Highlights

Hepatocellular carcinoma (HCC), the most common type of liver cancer, is still a major medical burden worldwide so far[1,2]
These results indicated that hypoxia attenuated the cytotoxicity of sorafenib to HCC cells in vitro
Western blot assay result revealed that expression of autophagy marker LC-3 was significantly increased after 15 μM sorafenib treatment for 48 h in 4 HCC cells compared to control group, accompanied by the significantly decreased in the expression of substrate recognitive factor p62 in autophagy process (Fig. 2A)

Summary

Introduction

Hepatocellular carcinoma (HCC), the most common type of liver cancer, is still a major medical burden worldwide so far[1,2]. HCC represents the fifth most commonly diagnosed cancer and is often diagnosed at advanced stages with high recurrence and mortality rate[3]. A multikinase inhibitor which suppresses HCC angiogenesis and proliferation, is considered the only effective systemic drug to cure patients with advanced. Multiple intracellular and extracellular factors were considered accounting for sorafenib resistance in HCC6,7; the precise underlying mechanism is still not understood and, revealing which undoubtedly will benefit for patients with HCC8. The interactions between hypoxic microenvironment and HCC cells are considered as a key factor causing sorafenib chemotherapy failure[11]. Combination of inhibitor of Official journal of the Cell Death Differentiation Association

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