Prognostic potential of a PSA complex in sera of prostate cancer patients with α2‐macroglobulin deficiency

Abstract

We previously reported on a number of cases of metastatic prostate cancer (PCa) in which serum alpha2-macroglobulin (alpha2M) levels were markedly decreased to less than 20 mg/dl (alpha2M deficiency). In order to elucidate the relative proportions of free and a prostate-specific antigen (PSA) complex in PCa patients with alpha2M deficiency, we have assessed serum alpha2M and total PSA levels, and ratios of free PSA to total PSA (F/T ratios) at each stage of PCa. Moreover, the PSA reactivity profile was determined on fractionated serum specimens of PCa patients using high-performance liquid chromatography (HPLC) using a TSKG-3000 SWXL column. Measurement of alpha2M concentration was performed by laser-nephelometry. PSA levels were determined by enzyme immunoassay, free PSA by radioimmunoassay. In those PCa patients with alpha2M deficiency, serum alpha2M and F/T ratios were lower, whereas PSA levels were higher when compared with those PCa patients without alpha2M deficiency (P<0.05). PSA elution profiles on HPLC columns revealed two major peaks. The proportion of PSA-antichymotrypsin (PSA-ACT) increased, whereas the proportion of free PSA decreased in PCa patients with alpha2M deficiency as compared with those PCa patients without alpha2M deficiency. F/T ratios were significantly lower in PCa patients with alpha2M deficiency than in those PCa patients without alpha2M deficiency. PSA-ACT and F/T ratio may be useful for monitoring bone metastasis in PCa.