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 Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.