Malignant transformation of human prostatic epithelium is associated with the loss of androgen receptor immunoreactivity in the surrounding stroma.

The cellular pathways involved in the pathogenesis of hormone resistance remain unclear. Studies evaluating the role of changes in human androgen receptor (hAR) expression in the progression of prostatic tumors have been inconclusive. Androgenic influence over prostatic growth is mediated via the regulation of interactions between stromal and epithelial cells. We hypothesized that neoplastic transformation of the prostate would be associated with alterations in hAR expression in the adjacent stroma. Using immunohistochemical techniques, we determined hAR positivity in the epithelium and adjacent stroma of sections from 17 benign and 39 malignant prostatic glands. We found that whereas the expression of the receptor decreased in both cellular compartments as the tissues dedifferentiated, the depletion was more pronounced in the stromal nuclei (P<0.0001). However, in sections from both untreated and hormone-resistant prostate cancer tissues, although heterogeneity of hAR expression in malignant epithelia was increased, there appeared to be a unique field effect around the cancerous prostate glands that resulted in a decreased expression of the receptor in the adjacent benign glands and its total loss in the surrounding stroma. The loss of hAR in the stroma adjacent to malignant prostatic epithelium may play an important role in prostate cancer progression. Furthermore, the similarity of the lack of stromal hAR expression in newly diagnosed and hormone-resistant prostate cancer (P = 0.85) may be an indication that the mechanisms responsible for the acquisition of hormone independence are established early in the malignant transformation process.