Measurement of cellular proliferation in human prostate by AgNOR, PCNA, and SPF

Tumor differentiation and proliferative activity are important predictors of biological behavior. While routine histological evaluation is fairly adequate to assess differentiation, tumor proliferative activity is difficult to measure. Silver staining for nucleolar organizer regions (AgNORs) is reported to be helpful for assessing tumor proliferation. We investigated the AgNOR counts in 20 formalin fixed, paraffin embedded human prostate tissues in three microscopic fields of 330X, using an image analysis system. A total of 200-700 nuclei were evaluated on histologically controlled areas of nonneoplastic prostate tissue, prostatic intraepithelial neoplasia (PIN), and invasive carcinoma. The values were compared to flow cytometrically obtained synthesis phase fractions (SPF) and immunohistochemically semi-quantitated, proliferative cell nuclear antigen (PCNA) patterns. AgNOR counts were also compared to tumor stage and Gleason's score. The pattern of PCNA staining in formalin fixed specimens was widely variable, probably due to differences in preservation of antigen. The positive counts varied from 0 to 55%, with a mean value of 8.55 +/- 15.9. The SPF values ranged from 5 to 13% with a mean value of 8.50 +/- 2.37. Two of 20 tumors were aneuploid and 18 were of diploid range. The mean AgNOR values in nonneoplastic nuclei (1.836 +/- 0.299), PIN (3.129 +/- 0.295), and invasive tumor cell nuclei (4.737 +/- 0.369) were highly significant (P < 0.0001) when paired differences were compared. AgNOR counts correlated significantly with tumor Gleason's score (P < 0.0145). However, the correlation coefficient for SPF and AgNOR values was not significant (P > 0.24), possibly because of the small number of samples examined. The highest AgNOR counts were found in the two aneuploid tumors. We conclude that AgNOR count may be a potential indicator of cellular proliferation, and possibly a marker of tumor differentiation.