DD3PCA3 RNA Analysis in Urine – A New Perspective for Detecting Prostate Cancer
Introduction
Early detection of prostate cancer is today mainly based on measurement of serum prostate specific antigen (tPSA) and, to a lesser extent, on digital rectal examination, with an aggressive biopsy policy with any sign of abnormality [1]. By lowering the threshold cut-off where biopsies are performed the sensitivity of tPSA as a biochemical marker may exceed to 90%, but the positive predictive value in the “grey zone “of 2.5–10 ng/ml drops to <25% [2]. As a result 4 out of 5 patients biopsied because of tPSA values in this range will show no cancer at biopsy. The use of tPSA derivatives, tPSA correlations to prostate volume and changes over time and sophisticated statistical models improve specificity somewhat but still do not solve the specificity problem [3]. More prostate cancer specific biomarkers are needed.
Better understanding of the molecular mechanisms of prostate cancer oncogenesis and improved analytical techniques like differential display analysis have identified prostate cancer specific genes such as PSMA, PCGEM-1, PSCA, PDEF, Prostase, NKX3.1 and DD3PCA3 [4]. The DD3PCA3 gene (“differential display code 3”) is localized at chromosome 9q21–22 and was found to be 10–100 fold overexpressed in 53 of 56 human prostate cancer samples in a Northern blot analysis whereas it was not expressed in adjacent non-malignant prostatic tissues [5]. Using the more sensitive reverse transcription polymerase chain reaction no DD3PCA3 transcripts were demonstrated in a wide range of normal human tissues and other human malignant tumors, rendering it the most prostate cancer specific gene identified so far [6]. The current understanding is that the DD3PCA3 gene expresses a non coding messenger RNA in epithelial prostate cells and functions as a polyadenylated RNA transcript, but no cytoplasmic protein results from its transcription [7].
With quantitative RT-PCR using dual time-resolved fluorescence from mRNA of DD3PCA3 prostate cancer samples cells have been shown to have a median 66 fold up-regulation as compared to normal prostate tissues [5]. Transcriptional activity showed no correlation to grade and significant overexpression was already demonstrable in prostate tissues containing <10% prostate cancer cells in a background of predominately non-malignant cells [4]. This permits the detection of prostate cancer cells shedded into urine. Utilizing the DD3PCA3 quantitative RT-PCR TRF hybridization assay Hessels et al. [4] evaluated urines of 108 men with a serum tPSA levels 3–10 ng/ml after digital rectal massage. With the DD3PC3/PSA mRNA ratio and transrectal ultrasound guided biopsy as a reference parameter an area under the curve of the Receiver Operating Characteristic Curve (ROC Curve) of 71% was obtained. With a cut-off value of 200 × 10−3, this reflects a sensitivity of 67% and specificity of 83%—a dramatic improvement as compared to serum tPSA [4].
Quantitative RT-PCR techniques require highly specialized laboratories and can not reasonably be utilized for routine clinical use. Recently a nucleic acid sequence based amplification assay (NASBA) for qualitative simultaneous detection of DD3PCA3 mRNA and PSAmRNA as a housekeeping gene in urine was introduced (uPM3™ DiagnoCure, Quebec, Canada) [8], [9]. We studied its usefulness prospectively in patients coming to prostate biopsy because of an abnormal tPSA and/or suspicious findings at DRE.
Section snippets
Materials and methods
201 patients with an elevated serum tPSA level and/or abnormal digital rectal examination referred to our department for prostate biopsy were included in this prospective study between June 2002 and December 2003. Approval was obtained from the Institutional Ethics Committee and written informed consent from each patient. Patients who had had any transurethral manipulation, radiotherapy, were on hormonal therapy, had an indwelling catheter or acute urinary infection before biopsy were excluded
Results
Urine samples from 201 patients were analyzed for DD3PCA3 RNA expression in the study period. 74/201 (37%) of patients were positive for prostate cancer on biopsy. 158/201 (79%) collected urine samples were found positive for PSAmRNA expression and thus were identified as evaluable samples which contain sufficient prostate cells to perform DD3PCA3 analysis (79% adequacy rate). There was no apparent difference in clinical parameters and the type of cancers detected among the overall group and
Discussion
Novel approaches in molecular technology seem to overcome hurdles in detecting prostate cancer cells in urinary samples and therefore prostate cancer diagnosis from urine is coming into the realm of clinical practice [13], [14]. Analysis of urinary sediments to detect prostate cancer cells after prostate massage was performed for GSTP1 hypermethylation and showed a specificity of 98% and a sensitivity of 73% in 92 patients [15], [16]. Telomerase activity is known to be expressed in at least 90%
Conclusions
The uPM3™ assay offers a new minimally invasive early detection tool for prostate cancer. In this prospective clinical study, it outperformed standard serum PSA at 4 and 2.5 ng/ml cut-offs in terms of specificity and PPV and had an overall accuracy of 78%.
Editorial Comment
Jack Schalken (Nijmegen, Netherlands)
Summary: Test for the more accurate diagnosis of prostate cancer, using state-of-the-art molecular technology is now validated in independent study.
With the rapidly
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2021, Biomedicine and PharmacotherapyCitation Excerpt :Growing evidences have confirmed that lncRNA PCA3 (prostate cancer antigen 3) can be overexpressed by 60- to 100-fold in more than 90% of prostates and is undetectable in other tumor types [72–74]. Urinary PCA3 as a diagnostic biomarker has shown superior diagnostic efficacy to serum prostate specific antigen (PSA) and digital rectal examination, with a sensitivity of 58–82% and a specificity of 56–76% [75]. Nowadays, urine PCA3 is widely used in prostate cancer detection and has been approved by the US Food and Drug Administration (FDA) [76].
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