Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) for the measurement of prostate-specific antigen mRNA in the peripheral blood of patients with prostate carcinoma using the TaqMan (TM) detection system

Circulating prostate cells can be detected in peripheral blood of patients with clinically localized or advanced prostate carcinoma. Traditionally, ne sted reverse transcriptase-polymerase chain reaction (RT-PCR) is used for t his as a sensitive, but qualitative only, detection system. We developed a quantitative real-time RT-PCR method for measuring prostate-specific antige n (PSA) mRNA in peripheral blood of prostate cancer patients. A quantitativ e assay was developed using an external standard reference curve generated with RNA from the human prostate cell line LNCaP. Basal blood samples were collected from 44 patients without evidence of distant metastases and from 30 healthy controls. In 29 patients surgically treated with radical prostat ectomy, the measurement of PSA mRNA was performed in blood samples collecte d before, at the end and 6 days after surgery. In 14 patients treated with radiotherapy, the measurements were repeated at 3-month intervals to evalua te time-related changes during therapy. The measurements were also performe d for one year at 3-month intervals in one patient treated with anti-androg en therapy. We found detectable PSA mRNA in 14/44 (32%) basal blood samples. A wide ran ge of values were observed in these patients, ranging from 0.5 to 1724 pg o f total LNCaP RNA/ml blood. In patients undergoing radical prostatectomy, c irculating PSA mRNA was detectable in eight patients in basal samples, and in seven of them also in blood specimens collected at the end of surgery, s howing an increase in only two patients. In blood samples collected 6 days later, PSA mRNA was dramatically reduced in all patients, but still present in seven of them. In four patients, whose basal samples were negative, PSA mRNA was detectable in samples collected at the end of surgery and three o f them were negative after 6 days. In patients who did not receive surgical treatment, a rapid decrease in PSA mRNA was demonstrated in five patients treated with radiotherapy and in one patient undergoing androgen deprivatio n. No detectable PSA mRNA was found in healthy controls. The levels of PSA mRNA in peripheral blood from patients with prostate carc inoma can be easily measured by this sensitive, quantitative and reliable p rocedure. This assay is a promising tool for the detection and follow-up of these patients.