Monoclonal antibodies to an ectopically expressed alkaline phosphatase in a human malignant cell line.

The D98/AH-2 cell line (a subline of HeLa) expresses a form of alkaline phosphatase (ALP) which closely resembles the adult and fetal intestinal forms of ALP. To characterize this ectopic form of ALP, four monoclonal antibodies were raised against D98/AH-2 ALP, and their binding with ALPs from D98/AH-2 cells, placenta, fetal intestine (meconium), adult intestine, and liver was compared using an electrophoretic titration procedure. The ALPs were either untreated or treated with neuraminidase. All four monoclonal antibodies bound desialated D98/AH-2 ALP most strongly. Adult intestinal ALP, which does not contain sialic acid residues, reacted much more strongly than either sialated or desialated fetal intestinal ALP. Two of the four monoclonal antibodies reacted very weakly or not at all with placental ALP, but two others reacted more strongly with placental ALP than with fetal intestinal ALP. None of the antibodies reacted with liver ALP. From these results, it appears that D98/AH-2 ALP may be a modified form of adult intestinal ALP.