To evaluate GCSH expression in vivo as well as in vitro, paraffin-embedded normal breast and breast cancer tissue (Fig. 1A,B) as well as three commercially available breast cancer cell lines (MCF-7, MDA-MB-231 and BT-20; Fig. 1C) in comparison with non-tumorigenic controls were immunolabeled with a monoclonal, full length GCSH-specific antibody. This evidence concerns the gene GCSH and breast carcinoma.