To assess the ability of Bmi1+ cells to serve as prostate cancer initiating cells, we specifically deleted Pten in Bmi1-expressing cells by treating Bmi1-CreER;R26R-confetti;Ptenf/f mice (hereafter BC-Pten mice) with tamoxifen (Fig. 6a). The gene discussed is BMI1; the disease is prostate carcinoma.