CASP3 and carcinoma: When 4T1 carcinoma cells were treated with gamma‐irradiation in fractions of 6 Gy for up to three times, the population of cells positive for Sca‐1 was found to increase with escalating dose (Fig. 1A, B) and similar changes were observed using immunocytochemical (ICC) staining (Fig. 1C–F).