Blood levels of a pteridine-binding alpha 1-acid glycoprotein in cancer patients.
A variant of alpha 1-acid glycoprotein was found previously in blood of malignant cases. It had been characterized as a pteridine-binding alpha 1-acid glycoprotein (P-AGPM). P-AGPM as well as the corresponding fraction of control origin were selectively enriched in the supernatant (Fraction b), obtained after digitonin extraction and subsequent alcohol and trichloroacetic acid fractionation of whole blood. In Fraction b, alpha 1-acid glycoprotein from control subjects + P-AGPM comprised 90 to 95% of total protein; it was quantitated by colorimetric determination of the protein-bound tyrosine and calibrated with the isolated compound. During a screening of malignant and nonmalignant cases, P-AGPM proved to be an acute-phase reactant to some extent. Marked increases during extended cancer and especially during leukemias corroborated the view that P-AGPM may be identical with abnormal orosomucoid. Longitudinal sections during leukemias suggested that the biopterin of leukemic cells may be metabolically related to the pteridine moiety of P-AGPM. Biopterin determinations by means of Crithidia assay in the blood of 136 cases of solid tumors showed that, due to its high rate of renal clearance, blood biopterin is not a reliable and persistent marker for proliferative activity, unless it is contained in the immature blood cells themselves, as is the case during leukemias.
D001708:Biopterins / Q000097:blood; D002352:Carrier Proteins / Q000032:analysis*; D006801:Humans; D007938:Leukemia / Q000097:blood; D009369:Neoplasms / Q000097:blood*; D009961:Orosomucoid / Q000032:analysis* / Q000378:metabolism; D011621:Pteridines / Q000378:metabolism*
D002352:Carrier Proteins; D009961:Orosomucoid; D011621:Pteridines; D001708:Biopterins