Quantitative analysis of the decay of immunoreactivity in stored prostate needle biopsy sections

Application of immunohistochemistry to assess the presence of prognostic tissue markers is used widely. The quantitation of these markers may be hampered by a time-related loss of antigenicity in formalin-fixed paraffin- embedded tissue stored on glass slides. Potential loss of immunohistochemical staining intensity was studied on prostatic needle biopsy sections stored for a maximum of 4 years with antibodies against p27(kip1), CD-44s, MIB-1, and androgen receptor (AR). In benign tissue, the positive/total ratio for p27(kip1) was determined, while CD-44s staining intensity was assessed semiquantitatively. For MIB-1 and AR, nuclear staining intensity was assessed using computed image analysis. An exponential and significant decay of immunoreactivity was seen for p27(kip1), CD-44s, MIB-1, and AR, with half- lives of 587 days, 214 days, and 290 days for p27(kip1), MIB-1, and AR, respectively. Immunohistochemical assessment of prognostic tissue markers on stored slides must be considered with care in research and clinical settings.