Detection of human pancreatic adenocarcinomas by histochemical staining with monoclonal antibody AR1-28

Hybridoma AR1-28 [Chin and Miller, Cancer Res 45:1723-1729, 1985] was produced using splenocytes from BALB/c mice which had been immunized with human pancreatic adenocarcinoma cell line RWP-1 [Dexter et al, Cancer Res 42:2705-2714, 1982]. This antibody cross reacted with the RWP-2 cell line. AR1-28, an IgG1 antibody, stained the membranes of five (RWP-1, RWP-2, BxPC-3, HPAF-2, and T3M4) out of ten human pancreatic tumor cell lines by immunofluorescence techniques. Electron microscopy on RWP-2 cells, stained by indirect immunoperoxidase, confirmed a membrane location for the AR1-28 antigen. Twenty-three of the 27 clinical specimens (83%) of formalin-fixed, paraffin-embedded pancreatic cancers tested were positive. Varying intensities of staining were observed and were related to the degree of differentiation achieved by the tumor: poorly differentiated tumors showing the least staining while well-differentiated tumors showed the greatest intensity of staining in a predominantly apical location. Immunoblotting showed that AR1-28 reacts with a 200,000-dalton antigen present in extracts of RWP-1 and RWP-2 cells. This monoclonal antibody may be useful in the classification of pancreatic tumor cells.