MYC and cancer: Despite not imposing hard concentration cutoffs for the rheostat-like regulation of the Bcl-2 family proteins by c-Myc, the predicted regulatory functions still led to an identifiable “cancer zone”, consisting of a range of c-Myc concentrations wherein the predominant function of c-Myc is to promote cell growth, as well as an “apoptosis zone”, wherein the primary function of c-Myc is to promote cell death, see Fig 3D.