ABSTRACT
The eukaryotic translation initiation factor 4E (eIF4E) is considered as a key survival protein involved in cell cycle progression, transformation and apoptosis resistance. Herein, we demonstrate that medicinal plant derivative 3-AWA (from Withaferin A) suppressed the proliferation and metastasis of CaP cells through abrogation of eIF4E activation and expression via c-FLIP dependent mechanism. This translational attenuation prevents the de novo synthesis of major players of metastatic cascades viz. c-FLIP, c-Myc and cyclin D1. Moreover, the suppression of c-FLIP due to inhibition of translation initiation complex by 3-AWA enhanced FAS trafficking, BID and caspase 8 cleavage. Further ectopically restored c-Myc and GFP-HRas mediated activation of eIF4E was reduced by 3-AWA in transformed NIH3T3 cells. Detailed underlying mechanisms revealed that 3-AWA inhibited Ras-Mnk and PI3-AKT-mTOR, two major pathways through which eIF4E converges upon eIF4F hub. In addition to in vitro studies, we confirmed that 3-AWA efficiently suppressed tumor growth and metastasis in different mouse models. Given that 3-AWA inhibits c-FLIP through abrogation of translation initiation by co-targeting mTOR and Mnk-eIF4E, it (3-AWA) can be exploited as a lead pharmacophore for promising anti-cancer therapeutic development.
Subject(s)
Adenosine Triphosphatases/metabolism , Cation Transport Proteins/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , TOR Serine-Threonine Kinases/metabolism , ras Proteins/metabolism , Adaptor Proteins, Signal Transducing , Animals , CASP8 and FADD-Like Apoptosis Regulating Protein/genetics , CASP8 and FADD-Like Apoptosis Regulating Protein/metabolism , Carcinoma, Ehrlich Tumor/genetics , Carcinoma, Ehrlich Tumor/metabolism , Carcinoma, Ehrlich Tumor/pathology , Carrier Proteins/metabolism , Caspase 8/metabolism , Cell Cycle Proteins , Cell Line, Tumor , Cell Movement/genetics , Copper-Transporting ATPases , Disease Models, Animal , Eukaryotic Initiation Factor-4E/metabolism , Eukaryotic Initiation Factors , Humans , Male , Mice , Neoplasm Metastasis , Phosphoproteins/metabolism , Phosphorylation , Protein Biosynthesis/drug effects , Protein Transport , Withanolides/pharmacology , fas Receptor/metabolismABSTRACT
Sclareol, a promising anticancer labdane diterpene, was isolated from Salvia sclarea. Keeping the basic stereochemistry-rich framework of the molecule intact, a method for the synthesis of novel sclareol analogues was designed using palladium(II)-catalyzed oxidative Heck coupling reaction in order to study their structure-activity relationship. Both sclareol and its derivatives showed an interesting cytotoxicity profile, with 15-(4-fluorophenyl)sclareol (SS-12) as the most potent analogue, having IC50 = 0.082 µM against PC-3 cells. It was found that SS-12 commonly interacts with Bcl-2 and Beclin 1 BH3 domain proteins and enhances autophagic flux by modulating autophagy-related proteins. Moreover, inhibition of autophagy by autophagy inhibitors protected against SS-12-induced apoptosis. Finally, SS-12 effectively suppressed tumor growth in vivo in Ehrlich's ascitic and solid Sarcoma-180 mouse models.
