Correlation of Survivin and KI-67 Immunoreactivity in Canine Urinary Bladder Tissues
Survivin is an inhibitor of apoptosis that we have previously identified in canine urinary bladder transitional cell carcinoma (TCC), abnormal bladder and cystitis tissues. The purpose of this study was to correlate survivin expression with cell proliferation (assessed by Ki-67 immunoreactivity) in canine urinary bladder tissues.
Murine anti-Ki-67 antibody was used on formalin-fixed, paraffin-embedded TCC, normal urinary bladder and cystitis samples which had been previously evaluated for nuclear and cytoplasmic survivin immunoreactivity. The total number of epithelial cells and cells positive for Ki-67 were manually counted in ten 400X fields per sample; counts were expressed as a percentage of total cells.
TCC samples without nuclear survivin (n=8) had an average Ki-67 score of 18% compared to 31.2% for those samples with nuclear survivin (n=11) (P=0.02). Cystitis tissues without nuclear survivin (n=11) had an average Ki-67 score of 7.1% compared to 44.6% in those with nuclear survivin (n=12) (P<0.001). Normal bladder tissues lacked nuclear survivin immunoreactivity. Tumor samples without (n=12) cytoplasmic survivin and those with cytoplasmic survivin (n=7) had no significant difference in average Ki-67 scores (23% versus 27.2%, P=0.5). Normal tissues without (n=26) and with (n=16) cytoplasmic survivin had average Ki-67 scores of 2.2% and 2.7% (P=0.4). Only one cystitis sample had cytoplasmic survivin.
Urinary bladder samples with nuclear survivin have higher Ki-67 immunoreactivity compared to those without nuclear survivin. Prospective studies are warranted to determine if nuclear survivin is associated with more aggressive disease and its potential as a prognostic tool or therapeutic target in canine urinary bladder TCC.