Total cath-D expression was determined in 159 whole cytosols from primary BC biopsies (HR+/HER2+ (n = 38); HR-/HER2+ (n = 38); HR+/HER2- (n = 42); HR-/HER- (n = 41)) by sandwich ELISA with the immobilized anti-human cath-D D7E3 antibody and the anti-human cath-D M1G8 antibody coupled to HRP. The gene discussed is ERBB2; the disease is breast cancer.