Molecular staging of prostate cancer with the use of an enhanced reverse transcriptase-PCR assay

Biomarkers for Treatment Response in Advanced Prostate Cancer

Simple Summary

Prostate cancer is a leading cause of cancer-related death among males. Many treatments are available to manage the disease, but despite this, ultimately advanced prostate cancer is incurable and fatal. In order to improve survival and minimize side effects from these various treatments, the treatments need to be given in an optimal sequence or combination. This optimal use of therapies must be individualized, and biomarkers can be used for these decisions. Biomarkers can be useful in predicting whether a patient will respond to a treatment option and may help avoid use of therapies that are not expected to be effective. Many biomarkers are already in clinical use while many others are currently being investigated and may become part of clinical practice in future. In this review, we discuss both established and novel biomarkers with a role in management of advanced prostate cancer.

Abstract

Multiple treatment options with different mechanisms of action are currently available for the management of metastatic prostate cancer. However, the optimal use of these therapies—specifically, the sequencing of therapies—is not well defined. In order to obtain the best clinical outcomes, patients need to be treated with the therapies that are most likely to provide benefit and avoid toxic therapies that are unlikely to be effective. Ideally, predictive biomarkers that allow for the selection of the therapies most likely to be of benefit would be employed for each treatment decision. In practice, biomarkers including tumor molecular sequencing, circulating tumor DNA, circulating tumor cell enumeration and androgen receptor characteristics, and tumor cell surface expression (PSMA), all may have a role in therapy selection. In this review, we define the established prognostic and predictive biomarkers for therapy in advanced prostate cancer and explore emerging biomarkers.

Circulating Tumor Cells as a Predictor of Treatment Response in Clinically Localized Prostate Cancer

PURPOSE

Using nonenrichment-based, potentially more sensitive Epic Sciences circulating tumor cell (CTC) platform, we sought to detect and characterize CTCs in untreated, high-risk localized prostate cancer and to evaluate their clinical implication.

METHODS

Between 2012 and 2015, blood samples were prospectively collected from patients with National Comprehensive Cancer Network high-risk localized prostate cancer undergoing either radiotherapy (XRT) plus androgen deprivation therapy or radical prostatectomy (RP) with curative intent. Samples were analyzed with the Epic Sciences platform with 4^J,6-diamidino-2-phenylindole, CD45, cytokeratin (CK), and androgen receptor (AR) N-terminal staining. CTC counts were correlated with biochemical recurrence (BCR).

RESULTS

A diversity of CTC subtypes, including CK-positive, CK-negative, AR-positive, and CTC clusters, were observed in 73.3% (33 of 45) of patients with evaluable data. The median follow-up was 14.2 months (range, 0.5 to 43.7 months). BCR occurred more frequently in the RP group than XRT (15 of 26 v one of 19), with most patients in the XRT group continuing to receive androgen deprivation therapy. A higher proportion of metastatic events were observed in the RP group (five of 26 v one of 19). In the RP group, BCR and development of metastases were associated with a higher total number of CTCs, AR-positive CTCs, and CTC phenotypic heterogeneity. One patient who developed BCR and metastases quickly after RP had diverse phenotypical CTC subtypes, and single-cell genomic analyses of all detectable CTCs confirmed common prostate cancer copy number alterations and PTEN loss.

CONCLUSION

CTCs can be identified in most patients with high-risk localized prostate cancer before definitive therapy using the Epic Sciences platform. If confirmed in a larger cohort with longer follow-up, phenotypic and genomic characterization of CTCs pretherapy may provide an additional means of risk stratifying patients with newly diagnosed high-risk disease and potentially help identify patients who could require multimodal therapy.

Preliminary Clinical Evaluation of free/total PSA Ratio by the IMMULITE® system

The role of free (F) and complexed serum PSA is now under investigation. In the present study, we evaluated the clinical significance of F-PSA and F/Total (T) PSA ratio in a preliminary series of samples from 88 patients with prostate cancer (PC), 113 with benign prostatic disease (BPD), and 98 with non-prostatic disease (NP). We used the F-PSA and third generation T-PSA (DPC, Los Angeles, USA) chemiluminescent enzyme immunometric assays with the IMMULITE automated system. At the 10 ng/ml cutoff for T-PSA levels, we obtained a sensitivity of 83% with a specificity of 100% in NP and 80% in BPD. The addition of the FIT ratio –rather than F-PSA levels – was useful to better discriminate PC and BPD in the cases erroneously classified by T-PSA alone: 44/68 samples (65%) were correctly diagnosed. Moreover, the FIT ratio was particularly effective in the critical T-PSA range between 4.1-9.9 ng/ml; 26/40 cases (65%) were correctly evaluated. In conclusion, the FIT ratio seems to be an interesting auxiliary test to T-PSA, to be reserved for selected cases where additional diagnostic information is necessary.

Strategies for Isolation and Molecular Profiling of Circulating Tumor Cells

Cancer is the leading cause of death by disease worldwide, and metastasis is responsible for more than 90% of the mortality of cancer patients. Metastasis occurs when tumor cells leave the primary tumor, travel through the blood stream as circulating tumor cells (CTCs), and then colonize secondary tumors at sites distant from the primary tumor. The capture, identification, and analysis of CTCs offer both scientific and clinical benefits. On the scientific side, the analysis of CTCs could help elucidate possible genetic alterations and signaling pathway aberrations during cancer progression, which could then be used to find new methods to stop cancer progression. On the clinical side, non-invasive testing of a patient's blood for CTCs can be used for patient diagnosis and prognosis, as well as subsequent monitoring of treatment efficacy in routine clinical practice. Additionally, investigation of CTCs early in the progression of cancer may reveal targets for initial cancer detection and for anti-cancer treatment. This chapter will evaluate strategies and devices used for the isolation and identification of CTCs directly from clinical samples of blood. Recent progress in the understanding of the significance of both single CTCs and circulating tumor microemboli will be discussed. Also, advancements in the use of CTC-based liquid biopsy in clinical diagnosis and the potential of CTC-based molecular characterization for use in clinical applications will be summarized.

KLK3, PCA3, and TMPRSS2-ERG expression in the peripheral blood mononuclear cell fraction from castration-resistant prostate cancer patients and response to docetaxel treatment

BACKGROUND

To monitor systemic disease activity, the potential of circulating tumor cells (CTCs) bears great promise. As surrogate for CTCs we measured KLK3, PCA3, and TMPRSS2-ERG messenger RNA (mRNA) in the peripheral blood mononuclear cell (PBMC) fraction from a castration-resistant prostate cancer (CRPC) patient cohort and three control groups. Moreover, biomarker response to docetaxel treatment was evaluated in the patient group.

METHODS

Blood samples from 20 CRPC patients were analyzed at four different time points (prior to docetaxel treatment, at 9 weeks, 27 weeks, and 2 months after treatment). Blood was drawn once from three control groups (10 age-matched men, 10 men under 35 years of age, 12 women). All samples were analyzed for KLK3, PCA3, and TMPRSS2-ERG mRNA by using a quantitative nucleic acid amplification assay with gene-specific primers in the complementary DNA synthesis.

RESULTS

At baseline, mRNA for KLK3 was detected in 17 (89%, 95% CI 76-100%), PCA3 in 10 (53%, 95% CI 30-75%), and TMPRSS2-ERG in seven of 19 evaluable patients (37%, 95% CI 15-59%). In contrast, the blood samples from all 32 healthy volunteers were reproducible negative for all markers. In response to docetaxel treatment, KLK3 levels decreased in 80% (95% CI 60-100%), PCA3 in 89% (95% CI 68-100%), and TMPRSS2-ERG in 86% (95% CI 60-100%) of patients.

CONCLUSIONS

The feasibility of a highly sensitive modified nucleic acid amplification assay to assess KLK3, PCA3, and TMPRSS2-ERG mRNA in the PBMC fraction from CRPC patients was demonstrated. Moreover, response of these markers to systemic treatment was shown.

Clinical use of novel urine and blood based prostate cancer biomarkers: a review

In the era of upcoming techniques for molecular profiling, breakthroughs led to new discoveries in the field of prostate cancer (PCa) biomarkers. Since the early 1990s a tremendous increase in PCa incidence is seen, dedicated to the introduction of prostate specific antigen (PSA) testing. However, due to its lack of specificity many men undergo unnecessary biopsies, resulting in a rising incidence of clinically insignificant PCa. To overcome this drawback, cancer specific biomarkers are needed to identify patients who are at high risk of harbouring PCa and to distinguish patients with aggressive disease from patients with insignificant cancer. The most non-invasive, easy to obtain substrate for biomarker measurement is urine. The most promising markers to date are PCA3 and TMPRSS2-ERG. Both markers demonstrate to have a higher specificity and diagnostic accuracy for PCa outcome compared to serum PSA. This might better predict the presence of PCa and therefore reduce the number of unnecessary biopsies. Combining both markers in a panel might result in an even higher diagnostic accuracy, given the heterogeneity of the disease. In PCa management, circulating tumour cells (CTCs) detected in the blood seem a promising tool to predict treatment response and survival benefit. Although results appear to be encouraging, the biggest challenge about new markers in PCa is to validate them in large clinical trials and subsequently implement these markers into clinical practice. In this review we discuss the clinical usefulness of novel, non-invasive tests in PCa management.

Quantitative RT-PCR analysis of PSA and prostate-specific membrane antigen mRNA to detect circulating tumor cells improves recurrence-free survival nomogram prediction after radical prostatectomy

BACKGROUND

Circulating tumor cell (CTC) analysis is a potential new biomarker in prostate cancer. We hypothesize that quantitative detection of CTCs in patients pre- and post-radical prostatectomy (RP) using quantitative TaqMan® fluorogenic RT-PCR will improve the accuracy of the Kattan nomogram to predict the probability of recurrence-free survival (RFS) post-RP.

METHODS

Ninty-two patients who underwent RP between 2004 and 2009 had venous blood samples taken pre- (Day - 1) and post-operatively (Day + 7). We performed quantitative Taqman® RT-PCR to detect circulating prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) mRNA. We calculated both the logarithmic ratio of Day + 7/Day - 1 for PSA (PSAr) and PSMA (PSMAr) expression (log(Day+7/Day-1) ) and the Kattan nomogram predicted probability of disease recurrence for each patient. We then analyzed how the AUC-ROC analysis for the Kattan nomogram prediction alone (K) compared to the addition of the PSAr and PSMAr in predicting 5-year RFS.

RESULTS

The mean age (years), PSA (ng/ml), and follow-up (mo) was 65.1, 9.13, and 72, respectively. The AUCs for K, PSAr + K, and PSMAr + K were 0.752 (95%CI 0.620-0.860), 0.830 (95%CI 0.740-0.911), and 0.837 (95%CI 0.613-0.923), respectively (P = 0.03). The Kattan 5-year PSA RFS was 75%. The actual 5-year PSA RFS survival rate was 77%.

CONCLUSIONS

Data from modern quantitative RT-PCR to detect circulating prostate-derived PSA and PSM mRNA pre- and post-RP improves the accuracy of the Kattan nomogram to predict biochemical recurrence.

Detection of α-Methylacyl-Coenzyme-A Racemase Transcripts in Blood and Urine Samples of Prostate Cancer Patients

BACKGROUND

Alpha-methylacyl-coenzyme-A racemase (AMACR) has been shown to be a highly specific marker for prostate cancer cells, even in the earliest stages of malignant progression. It is expressed at much higher levels than prostate-specific antigen (PSA) in malignant tissues, and is not expressed at appreciable levels in normal prostatic epithelium. In this study, we demonstrate the quantitative detection of AMACR transcripts in peripheral blood of prostate cancer patients using real-time RT-PCR. In addition, we have undertaken a pilot study to demonstrate the potential application of this technique for the detection of prostate tumor cells in urine samples from patients with prostate cancer.

METHODS

A real-time RT-PCR assay was developed for detection of the expression of AMACR in prostate cancer patients. Blood samples from 163 patients were tested at various stages of disease progression, with or without therapy. Blood specimens from patients with benign prostate disorders and other types of cancer were also evaluated.

RESULTS

In 28 of 58 samples from patients with known metastatic disease who were undergoing treatment, an AMACR expression signal above the cut-off value was detected, consistent with the presence of circulating tumor cells. In 39 of 88 patients with presumptive organ-confined disease, there was evidence of low levels of circulating tumor cells. Comparison of AMACR RT-PCR with known serum PSA values indicated that a combination of these parameters significantly increased the sensitivity for detection of progressive disease. In a pilot study analyzing urine samples from seven prostate cancer patients, elevated AMACR expression levels were detected in the urine sediments of four of six stage-T1 prostate cancer patients and in the one patient with stage-T2 prostate cancer.

CONCLUSION

The data presented in this study indicates that AMACR real-time RT-PCR may aid in the detection and staging of prostate cancer.

Prostate specific membrane antigen mRNA in blood as a potential predictor of biochemical recurrence after radical prostatectomy

We investigated whether the detection of prostate specific membrane antigen (PSMA) in blood preoperatively has predictive value for biochemical recurrence (BCR) after radical prostatectomy in patients with prostate cancer. All 134 patients scheduled to receive radical prostatectomy for prostate cancer were prospectively enrolled. The authors used nested reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect PSMA mRNA-bearing cells in peripheral blood, and analyzed the ability of PSMA mRNA positivity to predict BCR after surgery. PSMA-mRNA was detected in 24 (17.9%) patients by RT-PCR. Over a median follow-up of 20 months (range, 3 to 46 months), BCR developed in 15 patients (11.2%) and median time to BCR was 7 months (range, 3 to 25 months). Kaplan-Meier analysis revealed a significant difference between those positive or negative for PSMA in terms of recurrence-free actuarial probability (log rank P=0.0039). Multivariate analysis showed that positivity for PSMA mRNA (HR: 3.697, 95% CI 1.285-10.634, P=0.015) and a biopsy Gleason score of >or=7 (HR: 4.500, 95% CI 1.419-14.274, P=0.011) were independent preoperative predictors of BCR. The presence of PSMA mRNA in peripheral blood can be used to predict BCR after radical prostatectomy.

Molecular assays for the detection of prostate tumor derived nucleic acids in peripheral blood

BACKGROUND

Prostate cancer is the second leading cause of cancer mortality in American men. Although serum PSA testing is widely used for early detection, more specific prognostic tests are needed to guide treatment decisions. Recently, the enumeration of circulating prostate epithelial cells has been shown to correlate with disease recurrence and metastasis following definitive treatment. The purpose of our study was to investigate an immunomagnetic fractionation procedure to enrich circulating prostate tumor cells (CTCs) from peripheral blood specimens, and to apply amplified molecular assays for the detection of prostate-specific markers (PSA, PCA3 and TMPRSS2:ERG gene fusion mRNAs).

RESULTS

As few as five prostate cancer cells were detected per 5 mL of whole blood in model system experiments using anti-EpCAM magnetic particles alone or in combination with anti-PSMA magnetic particles. In our experiments, anti-EpCAM magnetic particles alone exhibited equivalent or better analytical performance with patient samples compared to a combination of anti-EpCAM + anti-PSMA magnetic particles. Up to 39% of men with advanced prostate cancer tested positive with one or more of the molecular assays tested, whereas control samples from men with benign prostate hyperplasia gave consistently negative results as expected. Interestingly, for the vast majority of men who tested positive for PSA mRNA following CTC enrichment, their matched plasma samples also tested positive, although CTC enrichment gave higher overall mRNA copy numbers.

CONCLUSION

CTCs were successfully enriched and detected in men with advanced prostate cancer using an immunomagnetic enrichment procedure coupled with amplified molecular assays for PSA, PCA3, and TMPRSS2:ERG gene fusion mRNAs. Our results indicate that men who test positive following CTC enrichment also exhibit higher detectable levels of non-cellular, circulating prostate-specific mRNAs.

Circulating and disseminated tumor cells in the management of breast cancer

Despite the advances in early detection and treatment of cancer, patients continue to die of the disease even when they seek care at an early stage. For patients with breast cancer, it is now possible to detect circulating tumor cells (CTCs) in the bloodstream and disseminated tumor cells (DTCs) in the bone marrow by using immunocytochemical and molecular methods. CTCs and DTCs have been found to share similar genotypic and phenotypic characteristics with so-called breast cancer stem cells, a finding that could potentially explain the eventual relapse of disease in a patient previously considered to have been cured by primary therapy. In some studies, the presence of CTCs or DTCs at the time of diagnosis of breast cancer is an independent adverse prognostic variable. However, before CTC/DTC testing can achieve standard-of-care status, there must be improvement in the sensitivity, precision, and reproducibility of the detection methods.

Circulating prostate tumor cells detected by reverse transcription-PCR in men with localized or castration-refractory prostate cancer: concordance with CellSearch assay and association with bone metastases and with survival

BACKGROUND

Reverse transcription-PCR (RT-PCR) assays have been used for analysis of circulating tumor cells (CTCs), but their clinical value has yet to be established. We assessed men with localized prostate cancer or castration-refractory prostate cancer (CRPC) for CTCs via real-time RT-PCR assays for KLK3 [kallikrein-related peptidase 3; i.e., prostate-specific antigen (PSA)] and KLK2 mRNAs. We also assessed the association of CTCs with disease characteristics and survival.

METHODS

KLK3, KLK2, and PSCA (prostate stem cell antigen) mRNAs were measured by standardized, quantitative real-time RT-PCR assays in blood samples from 180 localized-disease patients, 76 metastatic CRPC patients, and 19 healthy volunteers. CRPC samples were also tested for CTCs by an immunomagnetic separation system (CellSearch; Veridex) approved for clinical use.

RESULTS

All healthy volunteers were negative for KLK mRNAs. Results of tests for KLK3 or KLK2 mRNAs were positive (> or =80 mRNAs/mL blood) in 37 patients (49%) with CRPC but in only 15 patients (8%) with localized cancer. RT-PCR and CellSearch CTC results were strongly concordant (80%-85%) and correlated (Kendall tau, 0.60-0.68). Among CRPC patients, KLK mRNAs and CellSearch CTCs were closely associated with clinical evidence of bone metastases and with survival but were only modestly correlated with serum PSA concentrations. PSCA mRNA was detected in only 7 CRPC patients (10%) and was associated with a positive KLK mRNA status.

CONCLUSIONS

Real-time RT-PCR assays of KLK mRNAs are highly concordant with CellSearch CTC results in patients with CRPC. KLK2/3-expressing CTCs are common in men with CRPC and bone metastases but are rare in patients with metastases diagnosed only in soft tissues and patients with localized cancer.

Detection of circulating tumor cells in prostate cancer patients: methodological pitfalls and clinical relevance

Disseminated malignancy is the major cause of prostate cancer-related mortality. Circulating tumor cells (CTCs) are essential for the establishment of metastasis. Various contemporary and molecular methods using prostate-specific biomarkers have been applied to detect extraprostatic disease that is undetectable by conventional imaging techniques, assessing the risk for disease recurrence after therapy of curative intent. However, the clinical relevance of CTC detection is still controversial. We review current literature regarding molecular methods used for the detection of CTCs in the peripheral blood and bone marrow biopsies of patients with prostate cancer, and we discuss the methodological pitfalls that influence the clinical significance of molecular staging.

Identification of enhancer of zeste homolog 2 expression in peripheral circulating tumor cells in metastatic prostate cancer patients: a preliminary study

PURPOSE

Enhancer of zeste homolog 2 (EZH2), a kind of transcriptional repressor, is reportedly over-expressed in metastatic prostate cancer. In this study, we analyzed EZH2 mRNA in circulating tumor cells (CTCs) in peripheral blood as a biomarker in patients with metastatic prostate cancer.

PATIENTS AND METHODS

Ber-EP4 coated immunomagnetic beads were used to harvest CTCs, and mRNA was isolated by oligo- dT conjugated immunomagnetic beads. Reverse transcriptase- polymerase chain reaction for EZH2 mRNA was performed and the expression density was measured. The sensitivity of this test for detection of EZH2 mRNA was determined by serial dilutions of a human prostate cancer cell line. Blood samples were collected from 20 patients each with metastatic or localized prostate cancer and 10 healthy volunteers.

RESULTS

Sensitivity experiments showed that the test was highly sensitive as it could detect 10 tumor cells per 5 mL. EZH2 mRNA expression was obtained from peripheral blood samples of patients and control subjects. EZH2 mRNA expression density in the metastatic prostate cancer group was significantly higher than in the control (p=0.023) and localized prostate cancer groups (p=0.019). There was no difference between the control and localized prostate cancer groups (p > 0.05).

CONCLUSION

EZH2 mRNA expression in circulating epithelial cells represents a promising marker for detecting early metastasis in prostate cancer. However, more specific and sensitive techniques for detection of CTCs are needed to avoid mononuclear cell contamination.

Reverse transcriptase-polymerase chain reaction and immunohistochemical studies for detection of prostate stem cell antigen expression in prostate cancer: potential value in molecular staging of prostate cancer

OBJECTIVES

To determine whether detection of prostate stem cell antigen (PSCA) expression has potential for molecular staging in prostate cancer (PCa), we examined the relationship between established prognostic factors, biochemical recurrence (BCR) and PSCA expression.

METHODS

This study was comprised of 66 patients who underwent radical prostatectomy for the treatment of PCa. We employed reverse transcriptase-polymerase chain reaction (RT-PCR) to detect PSCA mRNA-bearing cells in peripheral blood, and used immunohistochemical (IHC) techniques to identify PSCA protein expression in microarrayed tissue.

RESULTS

PSCA-mRNA was detected in the peripheral blood of nine (13.6%) patients by RT-PCR. Whereas 3.2% of patients with low-grade disease were PSCA positive, 22.9% of patients with high-grade disease were PSCA positive (P = 0.030). There was also a significant relationship of RT-PCR PSCA positivity to whether or not the tumor was confined to the prostate. Whereas only 6.8% of patients with prostate-confined disease were RT-PCR PSCA positive, 27.3% of extraprostatic diseases were RT-PCR PSCA positive (P = 0.022). IHC studies of tumor tissue microarrays demonstrated that PSCA expression intensity was related to both extraprostatic extension (P = 0.014) and positive surgical margin (P = 0.053). Whereas 23.8% of prostate-confined diseases were high intensity, 54.5% of extraprostatic diseases were high intensity. BCR developed in seven patients (10.6%) during the follow-up period (median, 16.2 months; range, 9-25 months). Prognostic factors increasing the risk of BCR included: seminal vesicle invasion (P = 0.004), extraprostatic disease (P = 0.019), lymphovascular emboli (P = 0.036) and RT-PCR PSCA positivity (P = 0.004) in univariate analysis.

CONCLUSIONS

We were able to detect PSCA mRNA-bearing cells in peripheral blood by RT-PCR, and also identify PSCA protein expression in tumors by IHC analysis of tissue microarrays. RT-PCR PSCA positivity in peripheral blood may be a potential modality for molecular staging of PCa.

The detection and isolation of viable prostate-specific antigen positive epithelial cells by enrichment: a comparison to standard prostate-specific antigen reverse transcriptase polymerase chain reaction and its clinical relevance in prostate cancer

PURPOSE

To isolate prostate epithelial cells from the peripheral blood and bone marrow, and compare prostate-specific antigen (PSA) reverse transcriptase polymerase chain reaction (RT-PCR) performed on unenriched or epithelial enriched peripheral blood and bone marrow samples.

PATIENTS AND METHODS

Peripheral blood samples from 371 patients with prostate cancer and 141 controls, and bone marrow samples from 292 patients with prostate cancer and 43 controls were obtained. One aliquot was assessed with PSA RT-PCR. Another was enriched for epithelial cells with paramagnetic immune microbeads and assessed for: (1) PSA immunohistochemistry, (2) PSA RT-PCR, and (3) immunofluorescent detection of epithelial cells.

RESULTS

In the bone marrow (P < 0.01), but not the peripheral blood (P = 0.62), we observed significantly higher detection rates of disseminated PSA expressing epithelial cells after enrichment. The presence of epithelial cells with or without evidence of PSA production was uncommon among controls both in peripheral blood (1% and 0%) and bone marrow (11% and 0%). In patients with active prostate cancer, 46% to 74% had epithelial cells in peripheral blood, and 20% to 64% had PSA expressing epithelial cells. In bone marrow, 55% to 92% had epithelial cells, and 43% to 83% had PSA expressing epithelial cells. Particularly in bone marrow, circulating cells were frequently detected in men without evidence of disease after prostatectomy. With limited follow-up, the detection of epithelial cells or PSA expressing epithelial cells in peripheral blood or bone marrow before radical prostatectomy does not define a population of patients that will have biochemical failure.

CONCLUSIONS

Immunomagnetic enrichment frequently detects epithelial, presumably malignant, cells in the peripheral blood and, especially, the bone marrow of patients with prostate cancer. Viable cells can be acquired for gene expression and phenotyping studies.

High detection rate of circulating tumor cells in blood of patients with prostate cancer using telomerase activity

BACKGROUND

Circulating tumor cells (CTCs) cannot be readily detected with currently available methods in the majority of patients with prostate cancer. Telomerase activation, one of the major immortalization events, is found in most cases of prostate cancer. We attempted to develop a method using telomerase activity to isolate CTCs in patients with prostate cancer.

PATIENTS AND METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using Ficoll-Hypaque. Immunomagnetic beads coated with an epithelial cell-specific antigen antibody (BerEP4) were used to harvest epithelial cells from PBMCs. Telomerase activity was detected in harvested epithelial cells using the telomerase-PCR-enzyme-linked immunosorbent assay method.

RESULTS

Blood samples from 107 patients with prostate cancer were studied. CTCs were detected in 19 of 24 (79%) patients with advanced prostate cancer. In contrast, CTCs were not detected in blood samples from 22 healthy male volunteers. CTCs were even identified in patients with an undetectable (<0.1 ng/ml) serum prostate-specific antigen (PSA). CTCs were detected in 55 of 70 (79%) patients with localized prostate cancer before radical prostatectomy (n = 30) or brachytherapy (n = 40). CTCs were also detected in 3 of 13 patients (23%) with an undetectable serum PSA measured at least 1 year after radical prostatectomy, which is consistent with the expected relapse rate in this setting.

CONCLUSION

CTCs can be detected using telomerase activity in a large majority and a wide variety of patients with prostate cancer, including those with localized disease.

Molecular markers for prostate cancer

Serum PSA testing has been used for over 20 years as an aid in the diagnosis and management of prostate cancer. Although highly sensitive, it suffers from a lack of specificity, showing elevated serum levels in a variety of other conditions including prostatitis, benign prostate hyperplasia, and non-cancerous neoplasia. During this period, numerous serum protein analytes have been investigated as alternative and/or supplemental tests for PSA, however in general these analytes have likewise suffered from a lack of specificity, often showing serum elevations in other clinical presentations. More recently, molecular assays targeting prostate disease at the DNA or RNA level have been investigated for potential diagnostic and prognostic utility. With the aid of modern genomics technologies, a variety of molecular biomarkers have been discovered that show potential for specific correlation with prostate cancer. Much of this discovery has been retrospective, using microdissected tissue from prostatectomy. The goal of current research is to apply genomic assays to noninvasive specimens such as blood and urine. Progress in this area is the subject of this review.

Circulating biomarkers for prostate cancer

Due to its significant applicability for early detection, risk prediction and follow-up evaluation, prostate specific antigen (PSA) has revolutionized our ability to treat prostate cancer patients. With the prevalent use of PSA for early detection during the last two decades, disease characteristics have been altered towards early detected, localized tumors with a high chance of cure following local therapy. This advantage faces the risk of overdetection and overtreatment. In addition, PSA lacks both, sensitivity and specificity to accurately detect patients at risk of prostate cancer. Therefore, novel biomarkers are urgently needed to improve identification of men at risk of having the disease and to predict the natural behaviour of the tumor. Recent advances in the evaluation of high-throughput technologies have led to the discovery of novel candidate markers for prostate cancer. This article will briefly discuss current PSA-based strategies and review several novel biomarkers for prostate cancer, detectable in blood.

Evaluation and significance of circulating epithelial cells in patients with hormone-refractory prostate cancer

OBJECTIVE

To determine the feasibility of using flow cytometry fluorescence-activated cell sorting (FACS) analysis for detecting circulating epithelial cells (CECs) in patients with hormone-refractory prostate cancer (HRPC), and to determine whether CECs can be used to predict survival in these patients.

PATIENTS AND METHODS

Several prognostic models that include routinely used clinical and laboratory variables for predicting survival in men with HRPC have been reported; the presence of CECs measured by reverse transcriptase-polymerase chain reaction for prostate-specific antigen (PSA) in patients with HRPC is an independent prognostic factor for survival. CECs detected by FACS analysis correlate with advanced stage and poor survival outcome. A retrospective study was conducted to assess the presence of CECs by FACS analysis in metastatic HRPC patients initiating systemic chemotherapy with a taxane-based regimen. The association between clinical variables previously described and the presence of CECs along with the effect of the magnitude of CECs on survival was calculated, in 41 patients with HRPC, all of whom had peripheral blood collected for FACS analysis.

RESULTS

Except for four patients, all those with metastatic HRPC had detectable CECs. Among these patients, the number of CECs/mL was correlated with age, serum PSA level and serum alkaline phosphatase (ALP). Higher serum levels of PSA and ALP predicted a poor survival outcome. Similarly, patients with < or =1.8 CECs/mL had a significantly longer survival than those with more CECs/mL (P = 0.02). With a median follow-up of 15.4 months, the median overall survival for all patients was 18.4 months.

CONCLUSIONS

The presence of more CECs in patients with metastatic HRPC was associated with a poorer survival outcome; levels of > or =1.8 CECs/mL were associated with a shorter survival in patients with metastatic HRPC.

Role of lymphadenectomy in clinically organ-confined prostate cancer

There has been considerable debate about the utility of pelvic lymph node dissection (PLND) when performing a radical prostatectomy. Reported practices vary from those who always perform an extended PLND to those who employ a predictive nomogram in their decision making to those who are increasingly not performing a PLND in low-risk disease. A Medline search was used to identify relevant manuscripts dealing with the role of lymphadenectomy in clinically organ-confined prostate cancer. A greater number of lymph nodes (LN) removed and examined at prostatectomy for prostate cancer appears to increase the likelihood of finding LN metastases and increase prostate cancer-specific survival even in patients who have histologically uninvolved LN. This survival benefit may result from more accurate staging and possible removal of occult metastases. The need for and extent of PLND in prostate cancer, especially in low-risk disease, however, is unlikely.

Analysis of peripheral blood for prostate cells after autologous transfusion given during radical prostatectomy

OBJECTIVES

To determine if cells expressing prostate-specific antigen (PSA) can be detected in blood collected by a cell-saver during radical prostatectomy (RP) or in the peripheral blood after intraoperative autotransfusion (IAT).

PATIENTS AND METHODS

In all, 112 men with clinical T1c-T2 prostate cancer undergoing RP were prospectively assessed. A cell-saver system was used in each to collect blood from the surgical field after prostate manipulation. IAT was given based on clinical indications. Standardized peripheral blood samples were collected from patients before RP, in the recovery room afterward, and at 3-5 weeks after surgery. A reverse-transcriptase-polymerase chain reaction assay for PSA mRNA was used to detect prostate cells in cell-saver and peripheral blood samples. Patients were followed after surgery with PSA measurements to assess biochemical failure.

RESULTS

PSA-expressing cells were detected in 88% of cell-saver reservoir and 13% of preoperative blood samples. No PSA-expressing prostate cells were detected in any peripheral blood samples collected 3-5 weeks after surgery. Analysis of data with 40 months of follow-up showed IAT was not an independent predictor of biochemical failure in multivariate analysis.

CONCLUSIONS

Although IAT blood contains PSA-expressing cells, none could be detected 3-5 weeks after surgery. IAT during RP was not associated with a greater risk of biochemical failure.

Significance of the Percentage of Prostate Needle Biopsy Cores with Cancer as a Predictor of Disease Extension in Radical Prostatectomy Specimens in Japanese Men

OBJECTIVES

To evaluate the significance of the percent of positive biopsy cores (PPBC) with cancer, which has been shown to be one of the most useful predictors of prostate cancer extension in patients undergoing radical prostatectomy.

MATERIALS AND METHODS

This study included 120 patients who underwent radical prostatectomy for prostate cancer without any neoadjuvant therapies. All of these patients were diagnosed by random prostate biopsy targeting 8 cores; that is, standard sextant cores and 2 additional cores from the bilateral anterior lateral horns. We evaluated the appropriate cut-off points of PPBC for predicting disease extension according to the number of biopsy cores. Based on these criteria, multivariate analysis was then performed to determine whether PPBC could be an independent factor differentiating organ-confined disease from extraprostatic disease.

RESULTS

The most suitable PPBC cut-off value using findings targeting 8 cores for predicting disease extension was 37.5%. If PPBC was calculated based on the outcome of standard sextant cores alone, it is most appropriate to use 33.3% as the cut-off point. Multivariate analysis showed that PPBC calculated based on the standard sextant cores and percent of cancer in the biopsy set could be used as independent factors predicting disease extension irrespective of other biopsy-associated factors.

CONCLUSIONS

For predicting disease extension, it may be useful to calculate PPBC based on the outcomes of standard sextant biopsy cores alone even if additional cores were taken, and that PPBC calculated in such a way may be the strongest preoperative predictor of prostate cancer extension in Japanese men scheduled for radical prostatectomy.

Quantitative real-time reverse transcription: polymerase chain reaction of prostate-specific antigen (PSA) for detection of circulating prostatic cells in patients with clinically localized prostate cancer

OBJECTIVE

To evaluate the clinical utility of using the real-time reverse transcriptase-polymerase chain reaction (RT-PCR) to quantify prostate-specific antigen (PSA) mRNA in peripheral blood samples from patients with prostate cancer as a predictor of extraprostatic extension of the disease and to assess any correlations with known predictive markers of this condition.

METHODS

Immediately before radical prostatectomy, peripheral blood samples were taken from 42 men with clinically localized prostate cancer and analysed for PSA and 18S ribosomal (endogenous control) genes using real-time RT-PCR (with gene expression assays and the comparative CT-cycle threshold-method for quantifying). A total of 30 healthy male blood donors aged <50 y was taken as a control group. The relationships between PSA mRNA values, pathological and clinical features were analysed. PSA mRNA value, PSA level and biopsy Gleason score were then compared as predictors of extraprostatic extension.

RESULTS

PSA gene expression was 3.73 times significantly higher in patients with clinically localized prostate cancer than in healthy men (P<0.05). There was no relationship between PSA real-time RT-PCR values and pathological stage pT2 or pT3 (P=0.5), and no association between PSA mRNA value and serum PSA level (P=0.9) or the Gleason score of the preoperative biopsy (P=0.9).

CONCLUSION

There was no significant advantage in using the real-time RT-PCR assay of PSA mRNA before surgery to stage prostate cancer and to discriminate between organ-confined and extraprostatic extension.

Detection of Circulating Prostate Cancer Cells Using Real Time Rt – Pcr: Our Experience

PCR (Polymerase Chain Reaction) has revolutionized molecular genetics and continues to be applied to many fields of medicine and biology. We used nested real time RT – PCR to detect circulating prostate cells in patients affected by prostate cancer, in order to evaluate a possible clinical role of this technique. We present our initial experience.

[Prostate cancer: Diagnosis and staging]

The discovery and the use of serum prostate specific antigen (PSA) has considerably improved the diagnosis of prostate cancer during the past 20 years. Before PSA era, early diagnosis was only based on the digital rectal examination (DRE) of which the Limitations have been evidenced; over half of the tumours diagnosed by such means had already spread out of the prostate and were incurable. Assessment of serum PSA has allowed the diagnosis to be made at an earlier stage of the disease, curable by current treatments. Whichever the diagnostic tools, transrectal ultrasound (TRUS) prostatic biopsies remain necessary for diagnosis ascertainment, taking into account the low specificity of PSA assessment. The feasibility of a diagnosis at an early and curable stage of the disease has logically resulted in screening procedures aimed at reducing the high mortality related to prostate cancer. The numerous publications on prostate cancer screening provide precise information on the accuracy of available diagnostic means (PSA, DRE, TRUS, combined PSA and DRE), on the characteristics of screened tumours (stage and differentiation), and also on the population of men likely to benefit from the screening (age at beginning and end of the screening, frequency of PSA testing, identification of the men with ethnic and/or genetic predisposition). In those early diagnosed prostate cancers, the assessment of loco-regional cancer extension (extracapsular and/or, microscopic nodal involvement), remains unsatisfactory because no imaging technique (ultrasonography, CT scan, MRI,...) allows visualising the tumour itself or microscopic metastases. Nevertheless, the combination of multiple parameters such as DRE data, PSA level, biopsy data and tumour differentiation helps approaching with an increasing precision (nomograms) the true pathologic stage of the disease. Such advances allow distinguishing, among the very heterogeneous group of prostate cancers, tumours that differ from one to another in terms of disease stage, progression and prognosis, which is helpful for the determination of an adapted therapeutic strategy.

Prognostic Value of Combined “Triple”-Reverse Transcription-PCR Analysis for Prostate-Specific Antigen, Human Kallikrein 2, and Prostate-Specific Membrane Antigen mRNA in Peripheral Blood and Lymph Nodes of Prostate Cancer Patients

PURPOSE

We present the largest study of both peripheral blood and lymph node samples examining the utility of reverse transcription-polymerase chain reaction (RT-PCR) for established molecular markers as a diagnostic tool in the molecular staging of prostate cancer patients undergoing radical prostatectomy.

EXPERIMENTAL DESIGN

Peripheral blood from 358 patients was obtained before radical prostatectomy. Corresponding obturatory lymph node samples were collected from 153 of these patients. Nested RT-PCR for prostate-specific antigen (PSA), human kallikrein 2 (hK2), and prostate-specific membrane antigen (PSMA) were performed on cDNA from peripheral blood. The lymph node cDNA was analyzed for PSA und hK2 expression.

RESULTS

RT-PCR in peripheral blood was positive in 124 (34.6%) of 358 samples for PSA, 215 (60.1%) of 358 for PSMA, and 97 (27.1%) of 358 for hK2. Comparison of positive RT-PCR rates of pT(2) and pT(3) tumors in corresponding peripheral blood for PSA, PSMA, and hK2 were 31.9 and 40.0%, 58.8 and 62.5%, and 26.9 and 27.5%, respectively. Histopathologically, cancer-free lymph node samples were positive in RT-PCR for PSA and hK2 in 70 (49.6%) of 141 and 89 (63.2%) of 141 of cases. All histologically positive lymph node samples (n = 12, pN+) were positive for PSA RT-PCR. PSA RT-PCR alone, as well as combined PSA/PSMA RT-PCR evaluation, in peripheral blood showed a significant association with grading. PSA RT-PCR lymph node-negative samples were significantly less likely positive in their corresponding peripheral blood RT-PCR sample.

CONCLUSIONS

Although the preoperative PSA RT-PCR in peripheral blood correlated with the grading of prostate cancer, no combination of RT-PCR results using "triple" markers (PSA, hK2, PSMA) in peripheral blood and/or lymph nodes yielded additional preoperative staging information.

Intraoperative dissemination of tumour cells in patients with Ewing tumours detected by RT-PCR

Using reverse transcriptase polymerase chain reaction (RT-PCR) we evaluated the occurrence of tumour-cell ribonucleic acid (RNA) in the blood during surgery in patients with Ewing tumours. The patients received irradiation and chemotherapy according to the protocol of the European Intergroup Cooperative Ewing Sarcoma Study (EICESS) 92. Blood samples were taken from 15 patients. Intra-operative dissemination was found during 2/8 resections but showed no relation to patient survival. At second-look biopsy, detection of tumour-cell RNA was associated with relapse and metastases in 3/4 patients. The results suggest that pre-operative treatment did not completely prevent dissemination of tumour cells during surgery of Ewing tumours.

GSTP1 CpG island hypermethylation as a molecular biomarker for prostate cancer

Somatic hypermethylation of CpG island sequences at GSTP1, the gene encoding the pi-class glutathione S-transferase, appears to be characteristic of human prostatic carcinogenesis. To consider the potential utility of this epigenetic alteration as a biomarker for prostate cancer, we present here a comprehensive review of the literature describing somatic GSTP1 changes in DNA from prostate cells and tissues. GSTP1 CpG island hypermethylation has been detected in prostate cancer DNA using a variety of assay techniques, including (i) Southern blot analysis (SB), after treatment with (5-m)C-sensitive restriction endonucleases, (ii) the polymerase chain reaction, following treatment with (5-m)C-sensitive restriction endonucleases (RE-PCR), (iii) bisulfite genomic sequencing (BGS), and (iv) bisulfite modification followed by the polymerase chain reaction, using primers selective for target sequences containing (5-m)C (MSP). In the majority of the case series so far reported, GSTP1 CpG island hypermethylation was present in DNA from at least 90% of prostate cancer cases. When analyses have been carefully conducted, GSTP1 CpG island hypermethylation has not been found in DNA from normal prostate tissues, or from benign prostatic hyperplasia (BPH) tissues, though GSTP1 CpG island hypermethylation changes have been detected in DNA from candidate prostate cancer precursor lesions proliferative inflammatory atrophy (PIA) and prostatic intraepithelial neoplasia (PIN). Using PCR methods, GSTP1 CpG island hypermethylation has also been detected in urine, ejaculate, and plasma from men with prostate cancer. GSTP1 CpG island hypermethylation, a somatic epigenetic alteration, appears poised to serve as a molecular biomarker useful for prostate cancer screening, detection, and diagnosis.

Detection of HER-2/neu-positive circulating epithelial cells in prostate cancer patients

HER-2/neu may play a role in prostate carcinogenesis. The aim of this study was to use the expression of HER-2/neu as a molecular marker for the detection of circulating tumour cells (CTCs) in the blood of patients with prostate cancer (PC). Blood samples were collected from 42 patients with PC and nine healthy volunteers. Immunomagnetic beads were used to harvest epithelial cells from peripheral blood mononuclear cells. Total RNA was extracted and reverse transcribed before analysis by real-time PCR with HER-2/neu-specific primers. CTCs were HER-2/neu positive in six out of 11 (54%) patients with metastatic disease and in three out of 31 (9.6%) patients with localised PC (P=0.004). In blood samples from nine healthy volunteers, we detected no expression of HER-2/neu. The present method appears to be minimally invasive, highly sensitive and a specific approach for detecting CTCs in PC. Furthermore, it may help better target HER-2/neu in advanced PC.

[Conditions for the development of a program of reverse transcriptase-polymerase chain reaction for molecular staging of prostatic cancer]

OBJECTIVE

To determine accurately the conditions for the development of tests using RT-PCR for PSA in patients with prostate cancer.

METHOD

Gen amplification of PSA in cultures of the human prostate tumoral cell line LNCaP with RT-PCR under hot-start conditions, and verification through enzyme restriction digestion of the PCR product. Also, calculation of the PCR test limit of detection through serial dilutions of LNCaP cells in peripheral blood mononucleate cells.

RESULTS

A highly specific, easy to perform, reproducible RT-PCR protocol has been developed. The lowest limit of detection reached was 1 PSA synthesising cell per 10(6) peripheral blood mononucleate cells.

CONCLUSIONS

RT-PCR is a highly sensitive technique that allows detection of small numbers of PSA producing cells in peripheral blood. This experience allows to establish with precision the conditions for the development of RT-PCR tests for PSA.

Quantitative PSA RT-PCR for preoperative staging of prostate cancer

BACKGROUND

The clinical value of detecting prostate specific antigen (PSA) mRNA in the peripheral blood mononuclear cell fraction of patients (pts) by standard RT-PCR assays with localized prostate cancer remains controversial. We used a quantitative RT-PCR assay to measure the PSA mRNA copy number in addition to the qualitative PSA RT-PCR and correlated the results with clinical parameters.

METHODS

Total RNA was extracted from the peripheral blood mononuclear cell fraction of 115 prostate cancer pts prior to radical retropubic prostatectomy (RP) who received 3 months of neoadjuvant androgen deprivation. For quantitative RT-PCR, a PSA-like internal standard (IS) was added to each sample prior to reverse transcription and the PCR products for PSA and IS were selectively detected with fluorescent europium chelates after hybridization. Corresponding qualitative PSA-RT-PCR was performed for all samples.

RESULTS

The median PSA copy number was 126 (range: 0-37988). There were no significant correlations established between qualitative or quantitative RT-PCR results and given clinical parameters. Corresponding quantitative and qualitative RT-PCR results were significantly associated (P = 0.01).

CONCLUSIONS

We were unable to show any additional value of quantitative as well as qualitative PSA RT-PCR for preoperative staging of prostate cancer so far. Nevertheless, the long-term follow up of the patients has to be awaited.

Prognostic value of circulating prostate cells in patients with a rising PSA after radical prostatectomy

BACKGROUND

To predict poor outcome in patients with a biochemical recurrence (rising PSA) after radical prostatectomy (RP), urologists rely primarily on Gleason score, PSA doubling time, and time from surgery to biochemical (i.e., PSA) recurrence. In the present study, we assess the value of RT-PCR detection circulating prostate cells in blood of patients with a rising PSA.

METHODS

RNA from blood samples was obtained from 55 patients with a rising PSA and from 45 patients without evidence of biochemical failure (PSA < 0.1 ng/ml). Both groups were matched for age, Gleason score, pT stage, and interval between radical prostatectomy and PCR testing.

RESULTS

PSA positive cells were detected in 1/45 (2%) patients without a PSA recurrence and 19/55 (34%) patients with a PSA recurrence. In the rising PSA group, mean PSA doubling time was significantly shorter in patients with positive RT-PCR (5 months) than in patients with negative RT-PCR (16 months; P = 0.001). An earlier onset of recurrence was also detected in patients with a positive RT-PCR (31 months for positive RT-PCR vs. 50 months for negative RT-PCR) but this result did not achieve statistical significance (P = 0.102). Salvage radiation therapy was administered in 15 patients. Three of the five patients with a positive RT-PCR progressed during radiotherapy whereas 7 of the 10 patients with a negative RT-PCR obtained a complete response and none have progressed.

CONCLUSIONS

These preliminary results suggest that RT-PCR detection of prostate cells in blood of patients after RP correlates with rapidly progressing biochemical failure after RP.

Measurement of thyroglobulin mRNA in peripheral blood as an adjunctive test for monitoring thyroid cancer

AIMS

Monitoring treated patients with thyroid cancer for recurrent or metastatic disease is currently based upon the serial measurement of circulating plasma thyroglobulin (Tg) concentrations. However, the clinical usefulness of Tg immunoassays is limited by poor sensitivity and interference from anti-Tg antibodies. This study investigated whether the detection of Tg mRNA in peripheral blood, using reverse transcriptase polymerase chain reaction (RT-PCR), is of value in the biochemical surveillance of patients with thyroid cancer.

METHODS

RNA was extracted from peripheral blood of five normal controls, six patients with abnormal thyroid function tests, and 28 patients who had undergone thyroidectomy for well differentiated thyroid cancer. From each, an 87 bp product from base pair 262 to 348 in the cDNA sequence of the thyroglobulin gene was amplified by RT-PCR.

RESULTS

Tg mRNA was detected in normal individuals and patients with thyroid cancer. In the group of patients studied, identification of metastatic thyroid tissue by radioiodine scanning correlated better with Tg mRNA assay results than with serum Tg concentrations (accuracy 84% v 75%). No interference from circulating Tg antibodies was apparent. In patients studied prospectively over a 12 month period, there was a significant correlation between detectable Tg mRNA in peripheral blood and the presence or absence of metastatic disease, as demonstrated by radioiodine scanning.

CONCLUSIONS

These results suggest that detection of Tg mRNA in blood is a more sensitive marker for metastatic thyroid disease than Tg immunoassay, and appears to be unaffected by the presence of circulating anti-Tg antibodies.

Biochemical staging of prostate cancer

PSA continues to be one of the most effective and widely used cancer screening tools available. Its popularity in prostate cancer screening, however, has eroded its usefulness in the staging of this disease. As more men are screened every year on a routine basis with DRE and PSA, the average PSA at diagnosis has drifted down to well below 10 ng/mL in many centers, including ours. This trend is likely to accelerate, as a PSA cut off for prompting biopsy of the prostate of 2.5 ng/mL gains more widespread acceptance. The recent realization that, at these levels, serum PSA is more reflective of the presence of BPH than of the extent of cancer and, therefore, does not provide additional staging information, has renewed the search for new biochemical markers that are capable of predicting prostate cancer stage and prognosis. Because of the heterogeneity of this disease, it is unlikely that a single biochemical marker that is capable of accurately staging all prostate cancer patients will be found. For this reason, nomograms that are capable of integrating various parameters to predict stage and prognosis will remain indispensable. As new biochemical markers that provide independent predictive information about stage or prognosis are identified, they can be incorporated into currently available nomograms. Of the biochemical markers discussed in this article, IL-6sR and TGF-beta1 are the most promising. By incorporating them into a preoperative nomogram designed to predict PSA recurrence, we found that they improved the ability to predict biochemical recurrence by a statistically and clinically significant margin. The ability to stage prostate cancer and predict response to therapy has improved dramatically over the last 3 decades. Nevertheless, there is still a need for new biochemical markers that will improve the ability to predict an individual patient's stage and response to therapy. Incorporating these new markers into nomograms will enhance the ability to provide optimal care for each prostate cancer patient.

RT-PCR for PSA as a prognostic factor for patients with clinically localized prostate cancer treated with radiotherapy

OBJECTIVES

To study prospectively the prognostic significance of the reverse transcriptase-polymerase chain reaction (RT-PCR) assay for patients with prostate cancer treated definitively with external beam radiotherapy. The RT-PCR assay for prostate-specific antigen (PSA) has been used to detect circulating prostate cancer cells in the serum of patients with prostate cancer.

METHODS

In prospective fashion, serum RT-PCR testing was performed before and/or after definitive therapy, with the results scored as positive or negative. The results were analyzed for 161 patients, and the RT-PCR result was correlated with the treatment outcome.

RESULTS

The median follow-up was 29 months. The pretreatment RT-PCR result was not predictive of biochemical relapse-free survival (bRFS) or clinical disease-free survival (DFS). Of 25 patients with T3-T4 tumors, those with a negative pretreatment RT-PCR result had better bRFS and a trend was noted toward better DFS compared with those with a positive result. Among patients with Gleason score 8 to 10 tumor who underwent pretreatment testing (n = 19), those with a negative RT-PCR result had better bRFS and DFS compared with those with a positive result. A trend toward better bRFS was seen for patients with negative versus positive post-treatment RT-PCR results. The DFS was better for patients with negative versus positive post-treatment RT-PCR results.

CONCLUSIONS

RT-PCR, when obtained before radiotherapy, may be predictive of outcome for patients with more advanced stages or higher Gleason scores. Post-treatment testing predicted for clinical relapse. Additional study is needed before RT-PCR is used regularly in clinical practice.

Determination of prostate specific antigen mRNA in peripheral blood by reverse transcriptase polymerase chain reaction and a simple chemiluminometric hybridization assay in a high-throughput format

In recent years, the mRNA for prostate-specific antigen (PSA) has been investigated as a potential marker for molecular staging of prostate cancer. We report a simple, rapid, and sensitive assay protocol for the quantification of PSA mRNA in peripheral blood by using reverse transcriptase polymerase chain reaction (RT-PCR) and a chemiluminometric hybridization assay. A recombinant RNA internal standard (IS) that has the same size and primer binding sites as the PSA mRNA is included in the RT-PCR mixture. Total RNA from the sample is coextracted with a constant amount of IS RNA and subjected to RT-PCR. Amplified sequences are labeled with biotin during PCR by using a biotinylated upstream primer. The products are heat-denatured and hybridized with oligonucleotide-specific probes (for PSA and IS) that are immobilized in microtiter wells. Immobilization of oligonucleotide probes is achieved by adsorption of their conjugates with bovine serum albumin. The hybrids are measured using alkaline phosphatase-labeled streptavidin and a dioxetane chemiluminogenic substrate. The ratio of the luminescence values obtained for the PSA mRNA and the RNA IS is a linear function of the initial amount of PSA mRNA present in the sample prior to RT-PCR amplification. The linear range extended from 50 to 500,000 PSA mRNA copies, and the overall reproducibility of the assay, including RT-PCR and hybridization, ranged from 11.5 to 14.2%. Samples containing total RNA from PSA-expressing LNCaP cells give luminescence ratios that are linearly related to the number of cells in the range of 0.04-400 cells. The method was applied to PSA mRNA determination in peripheral blood of healthy individuals, patients with benign prostate hyperplasia, patients with prostate cancer, and patients with other types of localized cancer.

Detection and isolation of prostate cancer cells from peripheral blood and bone marrow

OBJECTIVES

To detect and isolate disseminated prostate cancer cells because significant effort has been directed toward defining the characteristics of the primary tumor that predict progression, but little progress has been made on evaluating the disseminated prostate cancer cell. Prostate-specific antigen (PSA) reverse transcriptase-polymerase chain reaction results in the bone marrow (BM) and peripheral blood (PB) of men with prostate cancer suggest many have disseminated cancer cells.

METHODS

Disseminated epithelial cells were isolated from the BM and PB using Miltenyi antibody-coated paramagnetic microparticle technology. In the two-step selection process, anti-CD45 and anti-CD61 were used for negative selection, and anti-human epithelial antigen was used for positive selection. Cells were then stained for Ber-EP4 (a distinct epitope of the human epithelial antigen) and PSA. PSA reverse transcriptase-polymerase chain reaction was performed on an enriched aliquot.

RESULTS

The normal controls were negative. Before prostatectomy, PSA-expressing epithelial cells were detected in 54% of BM and 24% of PB samples. At a median of 4 months after prostatectomy, PSA-expressing cells were detected in 33% of BM and 9% of PB specimens from men without evidence of disease. In men more than 5 years after prostatectomy, PSA-expressing cells were detected in the BM of 4 (29%) of 14, 2 of whom subsequently developed evidence of disease recurrence.

CONCLUSIONS

The findings suggest that dissemination of cells is an early event in prostate cancer that is insufficient for the development of metastases. Isolation will allow interrogation of the phenotype and genotype of the cells.