Purpose: The monoclonal antibody (mAb) 323/A3, a second generation high aff
inity antibody of the 17-1A antibody family, recognizes a 40 kDa transmembr
ane glycoprotein that has been referred to as Ep-CAM, 17-1A recognized anti
gen, or EGP40. While Ep-CAM is expressed on the basolateral surface of a va
riety of epithelia, the strongest expression is frequently detected among s
everal types of carcinoma. In this regard, Ep-CAM may be useful in therapy,
in diagnosis, and/or in prognosis. We examined the distribution of Ep-CAM
in normal, dysplastic, and malignant prostatic epithelium.
Materials and Methods: Paraffin sections of prostate tissue from 76 patient
s with clinically localized (pT2) prostatic adenocarcinoma were immunostain
ed with mouse mAb 323/A3 using the avidin-biotin horseradish peroxidase met
hod.
Results: Within benign prostatic epithelium, immunoreactivity typically was
low and frequently was restricted to the luminal cells. In contrast, moder
ate to strong immunostaining was detected frequently in the luminal cells o
f high grade prostatic intraepithelial neoplasia (PIN). Furthermore, strong
immunostaining usually was detected in the cells of adenocarcinomas. The i
mmunostaining in PIN (p <0.0001) and in adenocarcinoma (p <0.0001) was sign
ificantly greater than that observed in the normal epithelium. Expression o
f Ep-CAM did not vary significantly with the Gleason score of tumors or the
clinical outcome of patients. Expression of Ep-CAM was demonstrated also i
n the malignant prostatic cell Lines LNCaP, DU145 and PC3 using immunohisto
chemistry and an immunoblot technique.
Conclusions: These findings suggest that increased levels of Ep-CAM represe
nt an early event in the development of prostatic adenocarcinoma.