[1552] Lewis B (LeB) Antigen Expression Is Lower in Breast Carcinoma and Is Associated with Hormone Receptor Status and Histological Type

K Simoes, IC Soares, A Wakamatsu, OK Okamoto, AA Jungbluth, VAF Alves, LJ Old. University of Sao Paulo School of Medicine, Sao Paulo, Brazil; Hospital de Clinical Luzia de Pinho Melo, UNIFESP, Sao Paulo, Brazil; Sao Paulo Federal University, Sao Paulo, Brazil; Ludwig Institute for Cancer Research, New York

Background: Characterization of cell surface expression of antigens such as LeB, is regarded a prerequisite for successful antibody-based cancer immunotherapy. Monoclonal antibody (mAb) 58-1066 was raised against LeB. To assess LeB expression profile in breast carcinoma and normal samples, further assessing it as a potential target for immunotherapy.
Design: Paraffin blocks from 106 high grade breast carcinoma specimens from the files of D. Pathology, Hospital das Clinicas, University of Sao Paulo, Brazil and 86 consecutive cases of carcinoma and non-neoplastic breast tissue from D. Pathology, Hospital de Clinicas Luzia de Pinho Melo, UNIFESP, Brazil. Immunohistochemistry was performed in Tissue Microarray samples: primary antibody: mAb58-1066; amplification system: Novolink, short polymer-base peroxidase method; semi-quantitation: estimation of percentage of membranous positive cells, classifying according to 10% increments as well as to intensity.
Results: Membranous immunostaining was seen in 80.6% and 22.3% of non-neoplastic and neoplastic samples, respectively. Non-neoplastic samples showed a higher amount of immunopositivite cells than carcinomas (means: 31.6% vs 4.5%, P<0.001). Intensity of membranous staining was higher in non-neoplastic samples ((0): 16.1% , (1): 29% , (2): 54.9%) versus carcinomas ((0): 77.7% , (1): 16.3% , (2): 6% ), p<0.001. LeB expression was higher in PR+ versus PR- breast carcinomas (24.8% vs 11.9%, p=0.001) and was more common in lobular versus ductal type (24.3% vs 19.3%, p=0.047). There was a trend for association of ER+ and higher LeB expression (22.3% vs 13%, p=0.077). HER-2 status (p=0,419), locorregional spread (pT, p=0,506 and pN, p=0,366) and histological grade (p=0,685) were not found related to LeB immuno-expression.
Conclusions: LeB membranous expression was seen in a subset of breast carcinomas, preferentially lobular and progesterone receptor positive lesions, with a borderline association with estrogen receptor status. Further studies should assess a possible therapeutic role of mAb 58-1066 in these subtypes of breast carcinomas. This study is supported by grants from ReceptaBiopharma and FINEP, Brazil.
Category: Pathobiology

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 219, Tuesday Afternoon