Prostate-specific Antigen Messenger RNA Is Expressed in Non-Prostate Cells: Implications for Detection of Micrometastases

Prostate specific antigen (PSA) is generally believed to be expressed only by prostate epithelium. If this were true of PSA RNA, then detecting PSA RNA in cells outside of the prostate would indicate metastasis. PCR can detect rare prostate cancer cells. To enhance sensitivity, we developed “nested primer” PCR to detect PSA RNA. With this method, PSA RNA is present in several non-prostate cell lines, including BG-1 (ovarian), SK-MES-1 (lung), and HL-60 (myeloid leukemia), and some normal blood. A low level of PSA RNA detectable by nested primer PCR is present in some cells of non-prostate origin and may interfere with sensitive methods to detect micrometastases. Transcripts of other genes thought to be organ specific may have similar limitations.