Immunohistochemical quantitation of androgen receptor expression using color video image analysis

Background: The immunostaining features of the androgen receptor (AR) have been studied in prostate cancer (CaP) to predict the outcome of androgen de privation therapies. We have developed an automatic video color image analy sis system for quantitation of AR expression in large samples of prostatic nuclei. Methods: Essential criteria of immunostaining have been examined to establi sh a linear relationship between AR protein content and mean optical densit y (MOD) of the immunoperoxidase-substrate reaction product. Titration of mo noclonal AR antibody, F39.4.1, and concentration and reaction time of subst rate were optimized using color video image analysis. The methodology was t ested twice. First, CWR22 human CaP xenograft specimens, harvested from tes tosterone (T)-stimulated, castrated and T-resupplemented mice, were immunos tained to demonstrate the dependence of AR expression on serum androgen lev els. Second, AR expression was measured in archived clinical specimens. Results: In CWR22 tumor-bearing mice castrated for 6 days, AR MOD decreased to 57% of T-stimulated, intact mice. After 72 hrs of T treatment, AR MOD r eturned to the level measured in T-stimulated, intact mice. Sixteen radical prostatectomy specimens and 16 transurethral resection of prostate (TURP) specimens were double-labeled with F39.4.1 and anti-cytokeratin MAb (13 bet a E12) specific for basal epithelial cells. Benign epithelial cells exhibit ed lower AR MOD in prostatectomy compared to TURF specimens (P < 0.01). Dif ferences in AR immunostaining intensity may have resulted from differences in tissue fixation of whole organ versus small tissue specimens. Conclusions: AR immunostaining can be quantitated accurately using optimize d immunohistochemical criteria and video image analysis. Cytometry 35:2-10, 1999. (C) 1999 Wiley-Liss, Inc.