Determination of free type and complex type prostate-specific antigen (PSA): differences in immunorecognition by Delfia PSA, ACS-PSA and Eiken PA kits

PSAの免疫認識の点からモノクローナル抗体・モノクローナル抗体の組み合わせ, モノクローナル抗体・ポリクローナル抗体の組み合わせ, ポリクローナル抗体・ポリクローナル抗体の組み合わせとし, Delfia法, ACS法, Eiken法をこれらの代表的キットとして検討した.PSAの血中存在様式であるfree PSAとACT-PSAの免疫認識にキット間で大きな違いがあること, free PSAとACT-PSAの比率が僅か3症例であるが症例間で大きく異なることが示された.前立腺癌の診断及びモニター上血中PSAを, total PSA値のみならずfree PSAとACT-PSAの存在様式別にも表現しておくことが重要である可能性を示唆した
To study immunorecognition of free type and complex type prostate-specific antigen (PSA) by current commercial PSA assays, sera from 3 patients with stage D2 prostate cancer were separated by Sephacryl S-200 chromatography and determined by Delfia PSA, ACS-PSA and Eiken PA kits. Two antibodies used in the 3 kits are 2 monoclonal, 1 monoclonal and 1 polyclonal and 2 polyclonal antibodies, respectively. Following chromatography, two PSA peaks were obtained in all patients. One was about 100 kDa and the other about 30 kDa. The former was considered to be the complex type PSA (complex with alpha-1 antichymotrypsin) and the latter to be free type PSA. As to free type PSA, the ACS-PSA kit and Eiken PA kit quantitated PSA values approximately 5.1 and 2.5 times higher than the Delfia PSA kit. For complex type PSA, the quantity determined by ACS-PSA kit was approximately 1.3 times higher than that determined by the Delfia PSA kit, while the quantity determined by the Eiken PA kit was about one third of that determined by Delfia PSA kit. The ratio of complex type PSA to total PSA (free type PSA + complex type PSA) was 74.8 +/- 14.9% (mean +/- SD) when determined by Delfia PSA kit, 59.3 +/- 18.4% by ACS-PSA kit and 52.9 +/- 13.8% by Eiken PA kit. The range of this ratio determined by ACS-PSA kit was from 47.3% to 80.5% in the 3 patients. These findings suggest that there are qualitative differences in immunorecognition of free type PSA and complex type PSA among current commercial PSA assays and that there are quantitative differences in the ratio of the 2 forms of PSA in serum among prostatic cancer patients. The measurement and follow-up of both free type and complex type PSA might be important for diagnosis and monitoring of prostate cancer.