Tissue sections were deparaffinized in xylene and microwaved in 10 mM citrate buffer (pH 6.0) to unmask the epitopes. Endogenous peroxidase activity was blocked by incubation for 10 min with 0.03% hydrogen peroxide in methanol. Immunohistochemical staining was performed using the indirect avidin biotin-enhanced HRP method according to the manufacturer’s instructions (Vector Laboratories, Burlingame, CA). After developing with 3,3′-diaminobenzidine, all sections were counterstained with hematoxylin and observed by microscope (200×). Quantitative analysis of IHC staining was performed using the Image-Pro Plus software (v.6.0) program (Media Cybernetics, Inc. Rockville, MD).