NOVEL NUCLEAR PHOSPHOPROTEIN PP32 IS HIGHLY EXPRESSED IN INTERMEDIATE-GRADE AND HIGH-GRADE PROSTATE-CANCER

BACKGROUND. pp32 is a differentiation-regulated nuclear phosphoprotein that is highly expressed in many cancers, but is restricted to self-r enewing and long-lived normal cell populations. During murine embryoge nesis, pp32 is expressed in primitive cell populations, diminishing as tissues terminally differentiate. Functionally, pp32 confers resistan ce to programmed cell death and, paradoxically, inhibits transformatio n mediated in vitro by a broad range of oncogenes, suggesting that pp3 2 is a multifunctional molecule with potentially complex activities in cancer. METHODS. We studied pp32 expression in prostatic adenocarcino mas and benign prostatic hyperplasia by in situ hybridization. RESULTS . In benign prostatic tissues, moderate pp32 expression occurs only in the basal cells. This study found elevated pp32 expression in 98% (54 /55) of prostatic adenocarcinomas of Gleason score greater than or equ al to 5 (P < 0.0001). CONCLUSIONS. These results suggest that pp32 may be diagnostically useful and may contribute mechanistically to prosta te tumor development. In comparison to other molecular alterations, in creased pp32 expression is one of the most frequent events in primary prostate cancer. (C) 1998 Wiley-Liss, Inc.