Continued expression of Notch^IC, but not c-Myc, is required for tumor maintenance. (Left) Tumors generated by inducible Notch^IC and constitutive c-Myc regress when Notch expression is extinguished. (Right) Tumors generated by inducible c-Myc and constitutive Notch^IC do not regress when c-Myc expression is extinguished.