TRAF2 Cooperates with Focal Adhesion Signaling to Regulate Cancer Cell Susceptibility to Anoikis

TRAF2, a RING finger adaptor protein, plays an important function in tumor necrosis factor (TNF)- and TNF-like weak inducer of apoptosis (TWEAK)-dependent signaling, in particular during inflammatory and immune responses. We identified a functional interaction of TRAF2 with focal adhesion (FA) signaling involving the focal adhesion kinase (FAK) in the regulation of cell susceptibility to anoikis. Comparison of TRAF2-proficient (TRAF2 +/+ ) versus TRAF2-deficient (TRAF2 −/− ), and FAK-proficient (FAK +/+ ) versus FAK-deficient (FAK −/− ) mouse embryonic fibroblasts and their matched reconstituted cells demonstrated that TRAF2 interacts physically with the N-terminal portion of FAK and colocalizes to cell membrane protrusions. This interaction was found to be critical for promoting resistance to cell anoikis. Similar results were confirmed in the human breast cancer cell line MDA-MB-231, where TRAF2 and FAK downregulation promoted cell susceptibility to anoikis. In human breast cancer tissues, genomic analysis of The Cancer Genome Atlas database revealed coamplification of TRAF2 and FAK in breast cancer tissues with a predictive value for shorter survival, further supporting a potential role of TRAF2–FAK cooperative signaling in cancer progression.