PTL induces apoptosis in primitive cancer cells. Percent viability of prostate cancer cells and cells from a patient with BPH treated with increasing concentrations of PTL. Cells were cultured for 1 h with 100 ng/ml TNFα prior to treatment with PTL for 18 h. Cells were subsequently labeled with CD133-APC, Annexin-V-FITC and DAPI. Viability was defined as annexin-V-/DAPI- on total cells. Three prostate cancer patients' samples were analyzed and a representative profile is shown of normal CD133+ (open circles), cancer CD133+ (filled squares), normal progenitor (filled circles) and cancer progenitor (open squares).