The Identification of New c-FLIP Inhibitors for Restoring Apoptosis in TRAIL-Resistant Cancer Cells

Area of Science:

• Molecular Biology
• Cancer Research
• Drug Discovery

Background:

• The anti-apoptotic protein c-FLIP is highly expressed in cancers, inhibiting the extrinsic apoptotic pathway by competing with caspase-8 for FADD binding.
• Inhibiting c-FLIP could enhance tumor cell apoptosis and overcome resistance to anticancer therapies.

Purpose of the Study:

• To identify novel small molecules that selectively inhibit c-FLIP's anti-apoptotic activity.
• To explore the potential of these inhibitors as anticancer agents.

Main Methods:

• In silico screening of 1880 compounds from the NCI database using a homology 3D model of c-FLIP.
• In vitro validation of selected compounds using the H1703 lung cancer cell line.
• Assays included molecular pull-down and DISC immunoprecipitation to assess FADD/c-FLIP interactions.

Main Results:

• Nine compounds showed selective binding to c-FLIP's DED2 domain.
• Six compounds effectively prevented FADD/c-FLIP interactions.
• Combination therapy with TRAIL and selected inhibitors restored TRAIL-induced apoptosis in H1703 cells by reactivating caspase cleavage and activation.

Conclusions:

• New small molecules were identified that inhibit c-FLIP by preventing its recruitment into the DISC complex.
• These inhibitors restore the caspase-8-dependent apoptotic cascade, demonstrating potential as anticancer agents for c-FLIP-overexpressing tumors.