[Development and characterization of a monoclonal antibody which recognizes a new prostate-organ specific antigen]

Development and characterization of monoclonal antibodies which recognizes a new prostate-organ specific antigen.

For development of monoclonal antibodies, hybrid cells were prepared by fusion of spleen cells of BALB/c mice immunized with the homogenates of surgically resected prostatic tissue and P 3 x Ag 8 U 1 (P 3 U 1) murine myeloma cells. Supernatants of hybrid clones were primarily screened using an ELISA on human prostatic cancer cell line PC-3 and human bladder cancer cell line T-24. In the secondary screening, they were tested on normal tissues by immunohistochemical staining. To characterize the antigens, biochemical analyses were performed using seminal plasma as an antigen by western blotting and gel filtration, and the reactivity of antibodies were compared with that of antibodies against prostatic acid phosphatase (PAP), prostate-specific antigen (PSA) and gamma-seminoprotein (gamma-Sm).

A monoclonal antibody termed KP-9 was obtained and it only reacted with PC-3 and prostate tissues, but did not react with other cell lines and normal tissues. Immunohistochemical staining of prostate tissue revealed that KP-9 stained grandular epithelium and grandular exudate of normal and malignant prostatic tissues, and especially, strongly stained the apical site of grandular epithelium. Western blotting and gel filtration of seminal plasma suggested that the molecular weight of the KP-9 antigen was more than 300,000 and was different from PAP, PSA and gamma-Sm.

We have developed a monoclonal antibody, KP-9 which specifically reacts with prostatic cancer as well as benign prostatic tissues. The antigen recognized by KP-9 appeared to be a new prostate-organ specific antigen and may be a useful marker for prostatic cancer such as PAP, PSA and gamma-Sm.