BackgroundAs one of the most common malignancies worldwide, Hepatocellular carcinoma (HCC) has been treated by Sorafenib, which is the first approved target drug by FDA for advanced HCC. However, drug resistance is one of the obstacles to its application. As a typical characteristic of most solid tumors, hypoxia has become a key cause for resistant to chemotherapy and radiotherapy. It is important to elucidate the underlying mechanisms of Sorafenib resistance under hypoxia. 17-AAG, an inhibitor of HSP90α, and is in clinical test at present in anticancer. MethodsRoutine laboratory experimental methods including cell culture, cell transfection, western blot, immunohistochemistry (IHC), and immunofluorescence (IF) were used; the morphological changes of hepatocellular carcinoma cell was observed by Live Cell Imaging System and Transmission Electron Microscope; coimmunoprecipitation (Co-IP) were used for confirmation of interactions of RIPK3/MLKL/HSP90α and HSP70/LAMP2/HSP90α/MLKL. Patient-derived tumor xenograft (PDX) model and human HCC cells xenograft model have been established, and primary resistant cell line was induced to investigate the potential therapeutic strategies to overcome Sorafenib resistance.ResultsIn this study, Sorafenib was found to induce necroptosis in liver cancer. Under hypoxia, the distribution of necroptosis related proteins was changed, which contributed to Sorafenib resistance. HSP90α binds with RIPK1/RIPK3/MLKL complex and promotes chaperone-mediated autophagy (CMA) degradation, which leads necroptosis blocking. Ultimately, the decrease of necroptosis resulted in Sorafenib resistance. 17-AAG inhibited HSP90α and presented obvious reversal effects of Sorafenib resistance in vivo and in vitro. All the results emphasized that the blockage of HSP90α can significantly improve the effect of Sorafenib under hypoxia. ConclusionsHSP90α plays a critical role in Sorafenib resistance under hypoxia by blocking necroptosis. 17-AAG combining with Sorafenib is a promising therapy for hepatocellular carcinoma.

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