Prostate-specific Antigen Expression in Neoplastic Human Myeloid Cell Lines

Abstract

Prostate-specific antigen (PSA) is a 33-kDa serine protease produced by prostatic epithelial cells under the influence of the androgen receptor (1) . Although PSA previously was thought to be a prostatic tissue-specific protein not expressed in any other tissue in men or women, at present it is considered to be present in many nonprostatic tissues and fluids (2)(3) . PSA expression in both physiological and pathological conditions is not organ- or sex-specific; however, it is steroid hormone-mediated (4) . In fact, several cell lines (from breast, ovary, prostate, and lung cancer) showed specific PSA production modulated by steroid hormones (3)(5)(6) . Recently, nested PCR has shown PSA messenger RNA in a variety of non-prostate cells, including hematological cell lines (7)(8) , nondiseased peripheral blood (9)(10) , and bone marrow specimens (11)(12) . The finding of PSA expression within cells that are outside of the prostate is of great clinical utility in establishing the nonspecificity of PSA as an indicator of micrometastatic malignant disease (13)(14)(15) . To establish the presence of PSA immunoreactivity in nondiseased human peripheral blood unfractionated leukocytes (PBLs) and in leukemic cell lines, we undertook the present study on PSA content and immunoreactivity in blood samples from 10 healthy female and male volunteers, ages 25–42 years (mean, 33 ± 4 years). After collection, the blood samples were enriched in unfractionated mononuclear cells by centrifugation at 500 g for 20 min at 4 °C on Ficoll-Hypaque (Pharmacia). Erythrocyte-depleted blood samples were prepared and counted after treatment with a lysing solution (Coulter Electronics). Sera from PSA-negative healthy control females were used as the negative …