[695] Expression Patterns of Lewis Y Antigen in Prostate Tissue: Non-Neoplastic, Primary Adenocarcinoma and Bone Metastasis

IC Soares, K Simoes, A Wakamatsu, OK Okamoto, J Pontes, AA Jungbluth, VAF Alves, LJ Old. University of Sao Paulo School of Medicine, Sao Paulo, Brazil; Sao Paulo Federal University, Sao Paulo, Brazil; Ludwig Institute for Cancer Research, New York

Background: Despite recent progress in reducing prostate cancer mortality due to improvement of surgical treatment and screening strategies for organ-confined tumors, this is still the most common cancer in males, with few therapeutical options in advanced metastatic disease. Monoclonal antibody (mAb) 3S193 was raised as a reagent against the Lewis Y (LeY) antigen, a potential target for immunotherapy. To assess a possible relevance of LeY in metastases, we searched for its immuno-expression pattern in non-neoplastic prostatic tissue (NNPT), primary prostatic adenocarcinoma (PPA) and prostatic adenocarcinoma bone metastasis (PABM) with mAb3S193.
Design: Formalin-fixed, paraffin-embedded tissue was retrieved from the files of the Dept of Pathology, Hospital das Clinicas, Sao Paulo University of Sao Paulo School of Medicine and tissue micro-arrays generated as follows: 40 cases of NNPT; 97 cases of PPA, and 22 cases of PABM. An average of 3 cores/case were arrayed. Immunohistochemistry (IHC): primary antibody: 3S193; amplification system: Novolink, polymer-base peroxidase method; semi-quantitation: estimation of percentage of positive cells , classifying according to 10% increments. Cytoplasmic and membranous immunoreactivity was individually graded . Comparison of reactivities in each compartment was assessed by non-parametric Kruskal-Wallis test.
Results: Twenty eight out of 40 NNPT (70%), 24/97 PPA (24.7%) and 13/22 (59.1%) PABM cases showed variable degrees of cytoplasmic LeY expression. For NNPT, PPA, and PABM scores for cytoplasmic LeY immunoreactivity were 12.5%9.5, 3.4%6.5 and 25.0%31.4, respectively (mean + S.D., p<0,001). Regarding membranous expression, 34/40 NNPT (85%), 19/97 PPA (19.6%) and 5/22 PABM cases (22.7%) showed some degree of LeY immunostaining, with mean percentages of 12.7%12.8, 2.1%4.6 and 5.0%13.3, respectively (mean + S.D., p<0,001).
Conclusions: Immunodetection of LeY by mAb3S193 occurs in larger number of cases and in higher number of cells from bone metastases than primary prostatic adenocarcinomas, both in cytoplasm and in membrane. This study further point for a possible role of mAb3S193 for treatment of subsets of metastatic prostatic adenocarcinoma.
Category: Genitourinary (including renal tumors)

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 103, Wednesday Afternoon