B. Galvan et Tk. Christopoulos, QUANTITATIVE REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION FOR PROSTATE-SPECIFIC ANTIGEN MESSENGER-RNA, Clinical biochemistry, 30(5), 1997, pp. 391-397
Objective: To develop a quantitative reverse transcriptase-polymerase
chain reaction assay for monitoring the prostate-specific antigen (PSA
) mRNA. Methods: PSA mRNA is amplified, in parallel, with the mRNA of
beta-actin, a housekeeping gene. The ratio of the amplification produc
ts obtained reflects the relative amount of PSA mRNA with respect to a
ctin mRNA. During PCR, digoxigenin-dUTP is incorporated in the amplifi
ed sequences. The PCR products are analyzed separately by time-resolve
d immunofluorometric hybridization assays, using specific probes immob
ilized in microtiter wells. The hybrids are reacted with alkaline phos
phatase-labeled anti-digoxigenin antibody. The phosphate ester of fluo
rosalicylate is used as a substrate. The fluorosalicylate produced for
ms a fluorescent complex with Tb3+-EDTA which is measured by time-reso
lved fluorometry. Results: The hybridization assays for both PSA and a
ctin amplification products show linearity in the range of 1.4-110 pmo
l/L. The exponential phase of PCR amplification extends up to 200,000
and 100,000 PSA and actin cDNA molecules, respectively. We prepared mi
xtures containing various numbers of LNCaP cells in one million cells
that do not express PSA and used them as samples in the proposed assay
. The ratio of the fluorescence values obtained after analysis of PSA
and actin amplification products is linearly related to the number of
LNCaP cells in the range of 20 to 3000 cells. Reproducibility studies
demonstrate %CVs for the fluorescence ratios of 14.7, 11.8, and 12.2 w
hen samples containing 150, 300 and 1600 LNCaP cells were analyzed (n
= 4). Conclusions: A quantitative analytical methodology is provided f
or monitoring PSA mRNA. The assay is expected to be beneficial in the
study of prostate cancer spread.