Therapeutic Discovery A Novel Kinase Inhibitor of FADD Phosphorylation Chemosensitizes through the Inhibition of NF-kB

Fas-associated protein with death domain (FADD) is a cytosolic adapter protein essential for mediating death receptor–induced apoptosis. It has also been implicated in a number of nonapoptotic activities including embryogenesis, cell-cycle progression, cell proliferation, and tumorigenesis. Our recent studies have shown that high levels of phosphorylated FADD (p-FADD) in tumor cells correlate with increased activation of the antiapoptotic transcription factor NF-kB and is a biomarker for aggressive disease and poor clinical outcome. These findings suggest that inhibition of FADD phosphorylation is a viable target for cancer therapy. A high-throughput screen using a cell-based assay for monitoring FADD-kinase activity identified NSC 47147 as a small molecule inhibitor of FADD phosphorylation. The compoundwas evaluated in live cells and mouse tumors for its efficacy as an inhibitor of FADD-kinase activity through the inhibition of casein kinase 1a. NSC 47147 was shown to decrease levels of p-FADD and NF-kB activity such that combination therapy leads to greater induction of apoptosis and enhanced tumor control than either agent alone. The studies described here show the utility of bioluminescent cell–based assays for the identification of active compounds and the validation of drug–target interaction in a living subject. In addition, the presented results provide proof-of-principle studies as to the validity of targeting FADD-kinase activity as a novel cancer therapy strategy. Mol Cancer Ther; 10(10); 1807–17. 2011 AACR.