Specific immunoassays for placental alkaline phosphatase as a tumor marker.
Human placental (hPLAP) and germ cell (PLAP-like) alkaline phosphatases are polymorphic and heat-stable enzymes. This study was designed to develop specific immunoassays for quantifying hPLAP and PLAP-like enzyme activity (EA) in sera of cancer patients, pregnant women, or smokers. Polyclonal sheep anti-hPLAP antibodies were purified by affinity chromatography with whole hPLAP protein (ICA-PLAP assay) or a synthetic peptide (aa 57-71) of hPLAP (ICA-PEP assay); the working range was 0.1-11 U/L and cutoff value was 0.2 U/L EA for nonsmokers. The intra- and interassay coefficients of variation were 3.7%-6.5% (ICA-PLAP assay) and 9.0%-9.9% (ICA-PEP assay). An insignificant cross-reactivity was noted for high levels of unheated intestinal alkaline phosphatase in ICA-PEP assay. A positive correlation between the regression of tumor size and EA was noted in a child with embryonal carcinoma. It can be concluded that ICA-PEP assay is more specific than ICA-PLAP, which is still useful to detect other PLAP/PLAP-like phenotypes.
Stinghen
Sérvio T
ST
Centro de Genética Molecular e Pesquisa do Câncer em Crianças (CEGEMPAC), Curitiba, PR, CEP 80030-110, Brazil.
Moura
Juliana F
JF
Zancanella
Patrícia
P
Rodrigues
Giovanna A
GA
Pianovski
Mara A
MA
Lalli
Enzo
E
Arnold
Dodie L
DL
Minozzo
João C
JC
Callefe
Luis G
LG
Ribeiro
Raul C
RC
Figueiredo
Bonald C
BC