Primary screening results. (a) Summary of the primary screen in LNCaP-S14 cells. From 7368 compounds analysed in duplicates, 176 were positive in the primary screening. They were classified according to their Z-score as strong (Z > 5), medium (Z = 3-5) and weak (Z = 2-3). (b) Effect of increasing concentrations (18 h treatment) of the positive screening hit camptothecin (CPT) on p27 and SKP2 levels in LNCaP-S14 cells by regular immunofluorescence and immunoblotting (c). (d) 109 strong and medium compounds were selected for secondary screening. Of those 60 compounds were still positive.