Expression of Lewis carbohydrate antigens in metastatic lesions from human prostatic carcinoma.

BACKGROUND

Monoclonal antibodies B1 and B3 react with Lewis(y) and related carbohydrate antigens, which are abundant in many solid tumors. These antibodies, when conjugated to a toxin, have been used to target a variety of cancers. Treatment options for advanced prostate cancer are very limited, and there is a need to develop new therapies. In this study, we have asked whether antibodies B1 and B3 react with metastatic lesions from human prostatic carcinoma.

METHODS

Indirect streptavidin-biotin peroxidase immunohistochemistry was performed on formalin-fixed specimens from prostate cancer metastases. A total of 6 lymph node metastatic samples from patients who did not receive endocrine treatment and specimens of 14 distant metastases from patients who failed hormonal therapy were obtained.

RESULTS

Of the samples, 6 lymph node and 11 distant metastases stained for B1. In the case of B3 staining, 6 lymph node and 10 distant metastatic lesions were positive. In about half of these metastatic samples, more than 40% of cells were immunoreactive with either antibody. Two metastatic samples stained neither for B1 nor for B3 antibody. In general, B1 staining intensity was stronger in samples in which more than 40% of cells were positive.

CONCLUSIONS

Our results suggest that B1 and B3 immunoconjugates could be applied to target a substantial percentage of prostate cancer metastases.