RIP shuttles between CD95/Fas death and FAK survival signaling to mediate anoikis.

Anoikis-apoptotic cell death triggered by loss of extracellular matrix (ECM) contacts-is dysregulated in many chronic debilitating and fatal diseases. Mechanisms rendering tumor cells resistant to anoikis, although not completely understood, possess significant therapeutic promise. In death receptor-mediated anoikis mechanisms, FAK and RIP dissociate, leading to association of RIP with Fas, formation of the death-inducing signaling complex (DISC), activation of caspase-3, and propagation of anoikis. In contrast, anoikis resistance is accomplished through constitutive activation of survival pathways that include integrin-dependent activation of focal adhesion kinase (FAK) and extracellular-signal-regulated kinase (ERK). In addition, FAK and receptor-interacting protein (RIP) association confers anoikis resistance by inhibiting the association of RIP with Fas and formation of the death signaling complex, which allows cells to escape anoikis. Up-regulation of CD44 also contributes to survival signals and promotes anoikis resistance. This review will focus on the roles of death receptors, pro-survival pathways, and the molecular players involved in anoikis escalation and resistance in OSCC.