KS1/4 antigen (Ag), defined by the KS1/4 antibody (KS1/4), is expressed in many epithelial-derived carcinomas and normal epithelial cell surfaces. The cDNA encoding KS1/4 has been isolated and contains an open reading frame of 314 amino acids including a putative signal sequence. KS1/4 Ag migrates as three glycosylated polypeptides with molecular masses of 35, 40 and 42 kDa. The 40 and 42 kDa species are similar proteins and appear to differ only by their degree of N-linked glycosylation. The 35 kDa species results from proteolytic cleavages of the larger molecular weight proteins. KS1/4 was first described as a monoclonal antibody which recognized a lung adenocarcinoma associated antigen. In oncolytic drug targeting studies, KS1/4 suppressed the growth of human lung tumor xenografts in athymic nude mice. Subsequent studies showed that KS1/4 reacts with a variety of tumor tissues including colon, breast, ovarian, and pancreas. It also recognizes normal epithelium including colon, stomach, small intestine, liver, kidney, lung, pancreas, skin and ovary. These results suggest that KS1/4 Ag represents an epithelial cell/epithelial-derived carcinoma marker. KS1/4 recognizes a 40 - 42 kDa antigen expressed on the cell surfaces of a variety of epithelial tumors and normal epithelial cell types. KS1/4 also recognizes a 35 kDa proteolytic fragment. UCLA-P3 cells derived from a human adenocarcinoma of the lung were used as immunogen.
The antibody was conjugated to BD Horizon™ BV421 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max at 421-nm, BD Horizon BV421 can be excited by the violet laser and detected in the standard Pacific Blue™ filter set (eg, 450/50-nm filter). BD Horizon BV421 conjugates are very bright, often exhibiting a 10 fold improvement in brightness compared to Pacific Blue conjugates.