PTEN and neoplasm: Negative immunostaining was detected with all anti-PTEN mAb in a variable number of prostate or urothelial bladder samples positive for FISH analysis (Table 2, Table S1), suggesting the frequent loss of PTEN protein expression in these tumor types without deletion of the PTEN gene, in agreement with previous observations by others.17,71,72 Sensitivity of the anti-PTEN mAb was tested by immunoblot using decreasing amounts of cell lysates containing ectopically expressed recombinant PTEN from transfected COS-7 cells.