Journal of Clinical and Cellular Immunology
Open Access
ISSN: 2155-9899
ISSN: 2155-9899
Shikha Saini, Aditi Mathur, Ajay V Maker and Bellur S Prabhakar
University of Illinois College of Medicine, USA
Posters & Accepted Abstracts: J Clin Cell Immunol
Thyroid cancer is the most frequently occurring endocrine cancer. Anaplastic thyroid cancer (ATC) shows very poor prognosis (mean survival <6 months) and have limited treatment options. TNF-related apoptosis-inducing ligand (TRAIL) can induce tumor cell specific apoptosis in multiple cancers without affecting non-tumor cells. We have previously demonstrated that Map kinase Activating Death Domain containing protein (MADD), is a cancer cell survival factor, its knockdown leads to cancer cell apoptosis and Akt-mediated MADD phosphorylation confers resistance to TRAIL induced apoptosis in thyroid cancer. Therefore, we hypothesized that ATC TRAIL sensitivity could be enhanced by preventing MADD phosphorylation. MADD expression and TRAIL resistance was determined by Western blotting and active caspase 3 staining in several ATC cell lines harboring mutations in cancer driver genes including BRAF, Akt and PTEN. MADD phosphorylation was inhibited by site directed mutagenesis of Akt phosphorylation sites and exogenously expressing the mutant constructs to determine the effect on TRAIL induced apoptosis. MADD was overexpressed in all ATC cells compared to the normal thyroid tissues irrespective of the underlying genetic mutation and/or inherent TRAIL resistance. Further, preventing MADD phosphorylation by site directed mutagenesis in ATC lines resulted in significantly increased TRAIL-induced apoptosis accompanied by the activation of both intrinsic and extrinsic apoptotic pathways. Additionally, we inhibited endogenous MADD phosphorylation by using AKT inhibitors. PI3-kinase inhibitor which acts upstream of AKT and MADD in combination with TRAIL showed increased apoptosis in ATC cell lines in comparison to TRAIL or PI3K inhibitor alone. Thus, we conclude that prevention of MADD phosphorylation by site directed mutagenesis or PI3K inhibitors improves TRAIL susceptibility of ATC cells. Further studies are warranted to delineate the underlying mechanism of action and determine the clinical utility of this approach to treat ATC.
Email: ssaini@uic.edu