Analysis of serum placental alkaline phosphatase activity in testicular cancer and cigarette smokers.

Serum PLAP/PLAP-like enzymes are elevated in testicular cancer patients and also in heavy smokers. Such elevations were measurable with anti-PLAP polyclonal and monoclonal antibodies, and an antigenic heterogeneity was demonstrated in the circulating enzymes. Thus polyclonal antibody revealed more of tumor PLAP-like antigen while a monoclonal antibody H7 detected PLAP of smokers better. PLAP of smokers and PLAP-like enzyme of cancer (seminoma) patients showed similar characteristics with respect to glycosylation pattern, charge and hydrophobicity. By these properties they were differentiated from PLAP of placenta.