We used serum free medium containing human epidermal growth factor (rhEGF) and basic fibroblast growth factor (rhbFGF) allowing breast tumor cells to grow and form spherical non-adherent mammospheres [11], [19], measured the fold expansion of the breast cancer lines over six to eight passages and calculated their respective Kll (Fig. 4a–b). The gene discussed is EGF; the disease is breast carcinoma.