DISCREPANCIES BETWEEN DETECTION OF BCL-2 BY IN-SITU HYBRIDIZATION ANDIMMUNOCYTOCHEMISTRY IN HUMAN PROSTATE-CANCER TISSUES

Extensive study of Bcl-2 protein expression in prostate cancer (CaP) t issues by means of immunocytochemistry (IC) has provided evidence that it positively correlates with high grade and stage of Cap and is asso ciated with resistance to anti-androgen hormone therapy. In the presen t study, we investigated the expression of bcl-2 mRNA by non-isotopic in situ hybridization (ISH) in a series of 36 Cap with or without prev ious anti-androgen hormone treatment and performed a comparison with I C-detected Bcl-2 protein expression. Expression of Bcl-2 mRNA detected by ISH consistently differed from that detected by IC, especially in lymph node metastases (whereas no relevant variations of Bcl-2 mRNA le vels were found in treated vs. untreated Cap patients). In particular, high content of Bcl-2 mRNA was found in 25/36 cases of Cap (in 13/18 hormone-treated and 12/18 untreated patients). Conversely, Bcl-2(+) im munostaining was observed in only 7/36 Cap (in 4/18 hormone-treated an d 3/18 untreated patients). Furthermore, ISH revealed Bcl-2 mRNA in 4/ 7 lymph node metastases, all 7 of which were Bcl-2(-) by IC. We conclu de that, in the absence of a demonstrated posttranscriptional control of the bcl-2 gene, detection of mRNA by ISH in prostate archival tissu es appears to be a reliable alternative method to assess differential expressions of the bcl-2 gene. (C) 1998 Wiley-Liss, Inc.