Objective: To evaluate androgen receptor (AR) levels to predict endocrine therapy response and prognosis.
Study design: A sepharose microsphere model was employed to establish the relationship between level of immunohistochemical staining density and both antigen and primary antibody (F39.4.1) concentration. Subsequently, the results of the model system were compared with the results in routine prostate sections.
Results: A log-linear relationship was observed between optical density (OD) and primary antibody dilution measured in immunostained, antigen-coated microspheres with moderate antigen density. Similar titration curves were observed in prostate sections at the same dilution range, indicating that the microsphere model can be extrapolated to routine tissue sections. With microspheres with high coating density, the loglinear range of dilutions shifted to higher dilutions.
Conclusion: Differences in AR levels in prostate tissue sections might be more accurately detected by comparison of titration curves of primary antibody than by comparison of OD values at a fixed primary antibody dilution.