Purpose
Aurora kinase A (AURKA) is overexpressed in several cancer types, making it an attractive druggable target in clinical trials. In this study, we investigated the role of AURKA in regulating EIF4E, cap-dependent translation, and resistance to mTOR inhibitor, RAD001 (everolimus).
Experimental design
Tumor xenografts and in vitro cell models of upper gastrointestinal adenocarcinomas (UGCs) were used to determine the role of AURKA in activation of EIF4E and cap-dependent translation. Overexpression, knockdown, and pharmacologic inhibition of AURKA were used in vitro and in vivo.
Results
Using in vitro cell models, we found that high protein levels of AURKA mediate phosphorylation of EIF4E and upregulation of c-MYC. Notably, we detected overexpression of endogenous AURKA in everolimus-resistant UGC cell models. AURKA mediated phosphorylation of EIF4E, activation of cap-dependent translation, and an increase in c-MYC protein levels. Targeting AURKA using genetic knockdown or a small molecule inhibitor, alisertib, reversed these molecular events, leading to a decrease in cancer cell survival in acquired and intrinsic resistant cell models. Mechanistic studies demonstrated that AURKA binds to and inactivates protein phosphatase 2A (PP2A), a negative regulator of EIF4E, leading to activation of EIF4E and resistance to everolimus in an AKT-, ERK1/2-, and mTOR-independent manner. Data from tumor xenograft mouse models confirmed that everolimus-resistant cancer cells are sensitive to alisertib.
Conclusion
Our results indicate that AURKA plays an important role in activation of EIF4E and cap-dependent translation. Targeting AURKA-EIF4E-c-MYC axis using alisertib is a novel therapeutic strategy that can be applicable for everolimus-resistant tumors and/or subgroups of cancers that show overexpression of AURKA and activation of EIF4Eand c-MYC.