Free PSA forms in prostatic tissue and sera of prostate cancer patients: analysis by 2-DE and western blotting of immunopurified samples

OBJECTIVE: The isoform pattern of free prostate-specific antigen (fPSA) from sera of patients with prostate cancer (PCa) and no evidence of prostate cancer (NPCa), cancerous and non-cancerous tissues and seminal plasma, have been compared, above all regarding the degree of sialylation, with the aim to show a better discrimination of PCa and NPCa. DESIGN AND METHODS: The samples have been immunopurified and analyzed by two dimensional gel electrophoresis and western blotting. It was investigated which patterns were obtained when looking for the fPSA and the (-5/-7)proPSA (precursor form) before and after desialylation. RESULTS: The fPSA sialylation and the proPSA pattern in cancerous and non-cancerous prostate tissues were similar to each other and only slightly different from PCa and NPCa sera. The different fPSA isoforms observed could not be due solely to differences in the degree of sialylation, because different fPSA and (-5/-7)proPSA precursor isoforms were still present after complete desialylation. CONCLUSIONS: Although slight differences in the fPSA and (-5/-7) proPSA glycosylation and isoform pattern were observed, they were not large enough to be considered to improve PCa diagnosis.