Freedom from substrate

Most cells undergo a form of apoptosis called anoikis when they are grown in suspension. Janes and Watt report on page 419 that squamous cell carcinomas (SCCs) avoid this fate by expressing an alternative integrin called α_vβ₆. The pathway may be appropriated from cells that require a temporary reprieve from substrate-dependent growth during differentiation or tissue repair.

The α_vβ₆ integrin is known to favor tumor formation by increasing cell invasion and proliferation and inhibiting matrix assembly, but the new study is the first to demonstrate its ability to confer a survival advantage. The authors introduced α_v into an α_v-null cell line and showed that suspended transfectants died because their α_vβ₅ acted via caspase 8 to suppress activation of an Akt survival signal. Addition of...