Blood-based reverse transcriptase polymerase chain reaction assays for prostatic specific antigen: long term follow-up confirms the potential utility of this assay in identifying patients more likely to have biochemical recurrence (rising PSA) following radical prostatectomy

Comparative Pathobiology of Canine and Human Prostate Cancer: State of the Art and Future Directions

First described in 1817, prostate cancer is considered a complex neoplastic entity, and one of the main causes of death in men in the western world. In dogs, prostatic carcinoma (PC) exhibits undifferentiated morphology with different phenotypes, is hormonally independent of aggressive character, and has high rates of metastasis to different organs. Although in humans, the risk factors for tumor development are known, in dogs, this scenario is still unclear, especially regarding castration. Therefore, with the advent of molecular biology, studies were and are carried out with the aim of identifying the main molecular mechanisms and signaling pathways involved in the carcinogenesis and progression of canine PC, aiming to identify potential biomarkers for diagnosis, prognosis, and targeted treatment. However, there are extensive gaps to be filled, especially when considering the dog as experimental model for the study of this neoplasm in humans. Thus, due to the complexity of the subject, the objective of this review is to present the main pathobiological aspects of canine PC from a comparative point of view to the same neoplasm in the human species, addressing the historical context and current understanding in the scientific field.

Individualization of Adjuvant Therapy After Radical Prostatectomy for Clinically Localized Prostate Cancer: Current Status and Future Directions

Radiation therapy indications in the postprostatectomy setting are evolving. Several retrospective series have identified a number of "high-risk" pathologic features associated with an elevated risk of disease recurrence after radical prostatectomy. More recently, several randomized phase III trials demonstrated superior biochemical relapse-free survival for adjuvant radiation therapy after prostatectomy for patients with these high-risk pathologic features, including positive margin status, extraprostatic extension, and/or seminal vesicle invasion. These series further suggested improvement in distant metastasis control and overall survival after 15 years. However, not all patients with high-risk features experience disease recurrence after surgery alone, and some subsets of patients experience suboptimal disease control and survival despite immediate postoperative radiotherapy. Furthermore, some patients without high-risk features will develop recurrence. The present review discusses the current data and potential future directions to improve individualization of therapy after prostatectomy.

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.

Circulating tumor cells: detection, molecular profiling and future prospects

Disseminated malignancy is responsible for the vast majority of cancer-related deaths. During this process, circulating tumor cells (CTC) are generated, spread from the primary tumor, colonize distant organs and lead to overt metastatic disease. CTC are essential for establishing metastasis; however, they are not sufficient as this process is highly inefficient and most will fail to grow in target sites. Several CTC die during migration while others remain dormant for several years and very few grow into macrometastases. CTC have been well documented in the bloodstream of cancer patients; however, the clinical relevance of this detection is still the subject of controversies and their biology is poorly understood. Indeed, available markers fail to distinguish between subgroups of CTC, and several current methods lack sensitivity, specificity or reproducibility in CTC characterization and detection. The advent of more precise technologies is renewing the interest in CTC biology. We will review herein recent findings on CTC biology, on the role of host-tumor interactions in CTC shedding and implantation, available methods of CTC detection and future perspectives for the molecular characterization of the CTC subset(s) responsible for the development of metastasis. Ultimately, understanding CTC biology and host-tumor 'complementarities' will help define metastasis-related biomarkers providing formidable and tailored novel therapeutic targets.

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.

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.

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.

Correlation between CD8+ T cells specific for prostate-specific antigen and level of disease in patients with prostate cancer

Modest work has been performed to improve the sensitivity of residual disease detection or investigate the contribution that the immune system makes in controlling metastatic tumor growth, in particular, the frequency and biological actions of peptide-specific CD8+ T lymphocytes in limiting metastatic disease and/or maintaining remission. Fifty-three peripheral blood samples from 32 prostate cancer (PC) patients were investigated for the presence of circulating prostate-specific antigen (PSA)-expressing cells (CPECs) using a highly sensitive and specific assay combining immunomagnetic epithelial cell enrichment with nested RT-PCR of PSA mRNA. Using HLA-A2 tetramer complexes, frequency of CD8+ T cells specific for PSA-derived peptides was determined. Additionally, serum concentrations of PSA and testosterone were measured. CPECs were detected in 26% of peripheral blood samples from PC patients. CD8+ T cells specific for PSA-derived peptides were detected at low frequency in HLA-A2-positive PC patients. The correlation between these PSA-specific CD8+ T cells and residual prostate tumor cells and clinical measures was investigated. Our data suggest that frequency of PSA-specific CD8+ T cells is correlated to CPECs, but not to serum PSA level.

Circulating tumor cells: the 'leukemic phase' of solid cancers

It is well known that malignant cells circulate in the bloodstream of patients with solid tumors. However, the biological significance of circulating tumor cells (CTCs) and the clinical relevance of their detection are still debated. Besides technical issues regarding CTC-detection methods, discontinuous shedding of CTCs from established cancer deposits, genomic instability and metastatic inefficiency might underlie the conflicting results currently available. Nevertheless, technological advances and recent clinical findings are prompting researchers to dissect CTC biology further. Here, we review these recent findings, and discuss the prospects for the identification and molecular characterization of the CTC subset that is responsible for metastasis development. This would provide a formidable tool for prognosis evaluation, anticancer-drug development and, ultimately, cancer-therapy personalization.

Prognostic Significance of Baseline Reverse Transcriptase-PCR for Prostate-Specific Antigen in Men with Hormone-Refractory Prostate Cancer Treated with Chemotherapy

PURPOSE

Methods accurately categorizing the diverse biology of prostate cancer are needed. A positive baseline reverse transcriptase-PCR for prostate-specific antigen (RT-PCR PSA) in the androgen-independent setting is an independent prognostic marker of survival. The objectives of the current study were to examine the prognostic implication of baseline RT-PCR PSA positivity during treatment with an active chemotherapeutic agent and explore whether an RT-PCR PSA "response" provides prognostic information.

MATERIALS AND METHODS

In a combined analysis of a phase I and a randomized phase II trial of BMS-247550 (an epothilone B analogue), 104 patients with hormone-refractory prostate cancer had whole blood samples collected at baseline, then with each cycle of therapy. RT-PCR PSA was assessed and related to time to progression (TTP).

RESULTS

From 100 evaluable patients, 368 samples were received, of which 90.8% were evaluable for RT-PCR PSA status. Baseline RT-PCR PSA status was significantly associated with TTP (hazard ratio, 2.22; 95% confidence interval, 1.40-3.52). Twenty-six of 38 patients positive at first assessment had at least one follow-up RT-PCR PSA that was negative ("response"). In univariate analysis, RT-PCR PSA response was not significantly associated with TTP, but in multivariate analysis, RT-PCR PSA response was of borderline statistical significance in predicting TTP (hazard ratio, 0.41; 95% confidence interval, 0.16-1.01).

CONCLUSION

These results provide further confirmation that baseline RT-PCR PSA is a statistically significant predictor of TTP in hormone-refractory prostate cancer. Moreover, this is the first report to suggest that RT-PCR PSA response during chemotherapy treatment may predict TTP.

Molecular monitoring of organ recipients from cancer-affected donors by detection of circulating tumor cells

We have initiated regular molecular monitoring based on nested RT-PCR detection of circulating tumor cells for monitoring recipients of organs from cancer-affected donors in Italy (in the context of a "Donation Safety and Donated Organ Quality" project organized by the Centro Nazionale Trapianti). Five patients are being monitored. For two patients who each received a kidney from a single donor with prostate adenocarcinoma, RT-PCR was performed using PSA mRNA. For three recipients of organs (two livers and one kidney) from donors with renal cell carcinoma, RT-PCR was performed using cytokeratine 18 and 19 mRNA. Blood samples from five healthy subjects were used as negative controls. After a median monitoring time of 26 months (range 8 to 32), none of the regular 3-month assays has tested positive. This pilot study suggests that detection of circulating tumor cells by nested RT-PCR may provide a feasible molecular monitoring, which might assist decision making regarding other forms of clinical surveillance.

The Use of Real-Time Reverse Transcription-PCR for Prostate-Specific Antigen mRNA to Discriminate between Blood Samples from Healthy Volunteers and from Patients with Metastatic Prostate Cancer

PURPOSE

A clinical role for nonquantitative reverse transcription-PCR (RT-PCR) using prostate-specific antigen in blood samples from patients with prostate cancer remains undefined. Assay variation and detection of prostate-specific antigen mRNA illegitimate transcription may explain inconsistent results between studies. Defining levels of prostate-specific antigen mRNA expression in blood samples from healthy volunteers and patients with prostate cancer would allow cutoffs to be established to distinguish the two groups.

EXPERIMENTAL DESIGN

Quantitative real-time RT-PCR for prostate-specific antigen mRNA was established and levels of prostate-specific antigen mRNA measured in bloods samples from healthy volunteers (n=21) and patients with localized (n=27) and metastatic (n=40) prostate cancer.

RESULTS

Levels of prostate-specific antigen mRNA were significantly higher in blood samples from patients with metastatic prostate cancer than in blood samples from patients with localized prostate cancer (P <0.001) or in blood samples from healthy volunteers (P <0.01); levels between patients with localized prostate cancer and healthy volunteers were no different. Assay sensitivity to detect patients with metastatic prostate cancer was 68% with specificity of 95%. In patients with newly diagnosed metastatic prostate cancer, monitoring response to hormonal therapy was possible with this assay. No correlation between levels of prostate-specific antigen mRNA and serum prostate-specific antigen protein levels was found, suggesting that prostate-specific antigen mRNA and serum prostate-specific antigen protein levels reflect different features of prostate cancer, i.e., circulating tumor cells and total tumor bulk, respectively.

CONCLUSIONS

Quantitative RT-PCR discriminates patients with metastatic prostate cancer from healthy volunteers and patients with localized prostate cancer but cannot discriminate patients with localized prostate cancer from healthy volunteers. A role for quantitative RT-PCR has been identified in the assessment and monitoring of patients with metastatic prostate cancer.

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.

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.

Quantitative real-time rt-PCR for detection of circulating prostate-specific antigen mRNA using sequence-specific oligonucleotide hybridization probes in prostate cancer patients

OBJECTIVE

A great number of studies have failed thus far to demonstrate that the presence of PSA-expressing tumor cells in the blood of prostate cancer (PC) patients is a highly sensitive prognostic marker, particularly after radical prostatectomy (RPX). These studies have only relied on qualitative or semiquantitative detection techniques, however. We report our initial experience in testing real-time RT-PCR for the detection of PSA mRNA using a quantitative online PCR system, the LightCycler(TM), and sequence-specific oligonucleotide hybridization probes.

METHODS

Blood samples were obtained before and after surgery from 129 patients undergoing RPX for localized PC and from 19 patients undergoing transurethral resection of the prostate for benign prostatic hyperplasia (BPH). Quantitative RT-PCR for the detection PSA mRNA was performed using the LightCycler system with RNA Amplification Kit Hybridization Probes and sequence-specific oligonucleotide hybridization probes.

RESULTS

PSA mRNA was detected by the LightCycler in 28 patients (39%) with pT2 tumors, in 22 patients (38%) with >pT2 tumors, but in only 3 patients (16%) with BPH. The mean values of the LNCaP cell equivalents were higher in >pT2 patients than in pT2 patients (37 x 10(3) and 104 x 10(3)) or BPH patients (7.1 x 10(3) and 4.8 x 10(3)) both preoperatively (333 x 10(3)/ml blood) and postoperatively (545 x 10(3)).

CONCLUSION

Real-time RT-PCR with the LightCycler appears to be a promising method for the preoperative detection of circulating LNCaP tumor cells in PC as reflected by PSA mRNA. Considering the low detection rates in BPH patients, the method may also be suitable for patient monitoring after RPX and could thus play an important role in deciding on early radiotherapy or even hormone ablation therapy. Additional long-term follow-up will have to show whether patients with high expression of PSA mRNA actually have an increased risk or recurrence and whether the method is suitable as well to detect progression.

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 significance of reverse transcriptase polymerase chain reaction for prostate-specific antigen in metastatic prostate cancer: a nested study within CALGB 9583

PURPOSE

To determine whether reverse transcriptase polymerase chain reaction (RT-PCR) to detect circulating prostate-specific antigen (PSA)-positive cells is a prognostic factor for survival in hormone refractory prostate cancer and to validate the prognostic importance of this test in relation to other known prognostic factors.

PATIENTS AND METHODS

A single centralized laboratory received and analyzed whole blood for RT-PCR for PSA for a subset of patients enrolled on two Cancer and Leukemia Group B (CALGB) randomized trials (CALGB 9583 and CALGB 9480). Using 9583, a prognostic model was developed and an independent data set (CALGB 9480) was used to validate the fitted model.

RESULTS

Of 162 patients in 9583, 91 (56%) patients were negative for RT-PCR for PSA and 71 (44%) patients were positive. The median survival time was 21 months (95% confidence interval [CI], 18 to 27 months) for RT-PCR-negative patients compared with 11 months (95% CI, 8 to 15 months) for RT-PCR-positive patients (P < or =.001). In multivariable analysis, the hazard ratio (HR) for death was 1.7 (95% CI, 1.2 to 2.4; P =.006) for positive RT-PCR patients compared with negative RT-PCR patients. A fitted model that incorporated RT-PCR for PSA and other factors was used to classify patients from 9480 into one of two risk groups: low or high. We observed good agreement between the observed and predicted survival probabilities for the two risk groups.

CONCLUSION

RT-PCR to detect PSA-positive circulating cells is confirmed to be a significant prognostic factor of survival in patients with hormone refractory prostate cancer. This model could be used to stratify patients in randomized phase III trials.

Can the reverse transcriptase-polymerase chain reaction for prostate specific antigen and prostate specific membrane antigen improve staging and predict biochemical recurrence?

OBJECTIVE

To evaluate the perioperative gene-specific primed nested reverse transcription-polymerase chain reaction (RT-PCR) for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) for staging patients undergoing radical prostatectomy and predicting biochemical recurrence.

PATIENTS AND METHODS

In 80 consecutive patients undergoing radical prostatectomy for prostate cancer, blood samples were drawn before, during and 1 and 7 days after removing the prostate. After buffy coat and mRNA extraction, gene-specific primed nested RT-PCR was performed for PSA, PSMA and glyceraldehyde-3-phosphate dehydrogenase mRNA, and Southern blot analysis of the PCR reaction.

RESULTS

The sensitivity of gene-specific RT-PCR to detect tumour cells was comparable with random primed RT-PCR. In the 80 patients the stage distribution was pT1 in two (2.5%), pT2 in 30 (37.5%) and > or = pT3 in 48 (60%); the nodal status was pN0 in 57 (71%), pN1 in 11 (14%) and pN2 in 12 (15%). The gene-specific RT-PCR reaction for PSA and PSMA was positive in no patients with pT1, 11 (37%) with pT2 and 23 (48%) with stage > or = pT3 disease. The result for PSA was positive in 12 (52%) and for PSMA in 11 (48%) of those with positive nodal status. Neither gene-specific RT-PCR for PSA or PSMA was able to predict organ-confined disease (P > 0.5). After a median (range) follow-up of 37 (11-67) months a biochemical recurrence was predicted in 65% of patients by preoperative RT-PCR for both PSA and PSMA, with a sensitivity, specificity, positive and negative predictive value of 58%, 80%, 87% and 47%, respectively; the assay after surgery predicted a recurrence in 73%, with respective values of 68%, 84%, 84% and 57%.

CONCLUSIONS

Gene-specific primed nested RT-PCR for PSA and PSMA is a sensitive and simple assay; it might add substantial information for tumour staging in individual patients. RT-PCR before surgery allows the prediction of recurrence in 65% of cases and after surgery in 73%.

Predictive factor analysis as the basis for the clinical utility of percent positive prostate biopsies in patients with intermediate-risk prostate cancer

OBJECTIVES

To define the clinical reason for the further refinement of stratification of prostate-specific antigen (PSA) outcome using percent positive prostate biopsies in intermediate-risk patients.

METHODS

A chi-square metric was used to compare the distribution of pretreatment clinical and post-treatment pathologic factors for patients with intermediate-risk prostate cancer with 50% or less versus greater than 50% positive prostate biopsies. The PSA outcome stratified by the percent positive biopsies was calculated according to the Kaplan-Meier actuarial method. Comparisons of actuarial PSA failure-free survival were performed using the log-rank test.

RESULTS

The group with greater than 50% positive biopsies for prostate cancer had a significantly higher proportion of patients with pretreatment PSA values greater than 10 to 20 ng/mL (P = 0.01), biopsy Gleason score 4+3 (P = 0.05), and 1992 American Joint Committee on Cancer clinical category T2b (P = 0.01) than did the group with less than 50% positive biopsies. The group with greater than 50% positive biopsies also had a significantly higher proportion of patients with prostatectomy Gleason score 4+3 or higher (P = 0.001), pathologic Stage T3b (P <0.0001), and rate of positive surgical margins (P = 0.002) than did the group of patients with less than 50% positive biopsies.

CONCLUSIONS

The results of this study provide an explanation on the basis of the pretreatment and post-treatment predictive factors for the difference in PSA outcome for intermediate-risk patients when stratified by the percent positive biopsies.

Increased expression of PSA mRNA during brachytherapy in peripheral blood of patients with prostate cancer

OBJECTIVES

To determine the extent of iatrogenic tumor cell dissemination during brachytherapy by assessing prostate-specific antigen (PSA) mRNA expression in circulating prostate tumor cells using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. The instrumentation used in the radioisotope seed placement of the prostate causes trauma to blood vessels and provides a vascular access for tumor cells that can lead to potential iatrogenic dissemination and systemic failure.

METHODS

Twenty-five patients treated for brachytherapy were recruited in the study. Controls included 4 normal men and 1 woman; case controls included 4 patients who underwent prostate biopsy for prostate cancer diagnosis. Peripheral blood (10 mL) was collected before, during, and after the brachytherapy procedure. Total RNA was isolated from mononuclear cells and phosphorus-32 RT-PCR was performed to analyze the mRNA expression of PSA and G6PDH genes.

RESULTS

Of 25 patients, 23 were negative for PSA mRNA expression and 2 were positive for PSA mRNA expression before brachytherapy. Of the 23 patients who were negative for PSA mRNA expression before treatment, 15 patients (65%) turned positive during or after brachytherapy and the remaining 8 patients remained negative throughout the treatment. Eight of the 25 patients developed rising serum PSA levels. Of these 8 patients, 1 (12.5%) did not have PSA mRNA expression in the peripheral blood before, during, or after brachytherapy; the remaining 7 patients who developed rising serum PSA levels had PSA mRNA expression after brachytherapy (P = 0.03).

CONCLUSIONS

These findings strongly suggest that iatrogenic shedding of prostate cells occurs as a result of brachytherapy and raises the concern that these cells liberated at the time of brachytherapy increase the risk of metastatic deposits and results in systemic failure, as measured by serum PSA levels.

Preoperative combined nested reverse transcriptase polymerase chain reaction for prostate-specific antigen and prostate-specific membrane antigen does not correlate with pathologic stage or biochemical failure in patients with localized prostate cancer undergoing radical prostatectomy

PURPOSE

We report a prospective study examining the ability of preoperative nested reverse transcriptase polymerase chain reaction (RT-PCR) for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) to predict pathologic stage and biochemical recurrence in patients with clinically localized prostate cancer treated with radical prostatectomy.

PATIENTS AND METHODS

One hundred forty-one patients were entered onto the study. Preoperative evaluation included clinical T stage, serum PSA, biopsy Gleason score, and serum RT-PCR for PSA/PSM. Univariate and multivariate logistic regression models, Kaplan-Meier estimates, and Cox proportional hazards modeling were used to identify predictors of pathologic stage and biochemical failure.

RESULTS

Seventy-three patients (51.8%) were RT-PCR positive for PSA, PSM, or both. In the multivariate logistic regression model, only initial PSA was an independent predictor of pathologic stage as defined by organ-confined disease (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.00 to 1.13; P =.026) or organ-/specimen-confined disease (OR, 1.09; 95% CI, 1.02 to 1.16; P =.009). Overall Kaplan-Meier biochemical relapse-free survival (bRFS) was 85% at 59 months. Multivariate analysis of predictors for bRFS with the Cox proportional hazards model indicated that only initial PSA (OR, 1.05; 95% CI, 1.02 to 1.09; P =.004) and biopsy Gleason score (OR, 3.57; 95% CI, 1.37 to 9.58; P =.009) were independent predictors of biochemical failure. RT-PCR status did not predict pathologic stage or biochemical failure. Repeat analysis excluding 27 patients who received preoperative androgen-deprivation therapy did not change the results.

CONCLUSION

Combined nested RT-PCR for PSA and PSM is not an independent predictor of pathologic stage or biochemical failure in patients with localized prostate cancer undergoing radical prostatectomy. This assay has no clinical utility in this patient population.

Presence of circulating prostate cancer cells in African American males adversely affects survival

African-Americans (AAM) with prostate cancer are more likely to relapse than Caucasian-Americans (CAM) despite controlling for known prognostic factors. One explanation may be that micrometastatic disease in AAM behaves more aggressively than in CAM. We tested this hypothesis by comparing the reverse transcriptase polymerase chain reaction amplification of the Prostatic Specific Antigen-mRNA (RTPCR PSA-mRNA) results from peripheral blood samples of AAM and CAM with respect to disease outcome. We evaluated the peripheral blood of 246 consecutive patients at the time of radical prostatectomy. The RTPCR PSA-mRNA test for determination of circulating prostate cancer cells was performed. The results were stratified by races and correlated with standard clinico-pathological variables and disease free survival. 27% and 23% of AAM and CAM patients were RTPCR PSA-mRNA positive, respectively. The RTPCR PSA-mRNA status correlated with the pathologic stage in CAM but not in AAM, (p = 0.05). There was no association with Gleason score, PSA level, or clinical stage with the RTPCR PSA-mRNA status in either group. AAM with organ-confined prostate cancer were marginally more likely to have circulating prostate cells than similarly staged CAM (24% vs. 17%). In AAM but not CAM who had prostate cancer, the RTPCR PSA-mRNA status correlated with and was an independent predictor of disease-free survival. Our data suggests that, though the likelihood of having circulating prostate cells is the same in AAM and CAM, the presence of circulating prostate cells in AAM is predictive of a worse outcome. This may partially explain the worse prognosis in AAM vs. CAM with clinically localized prostate cancer.

Detection of prostate-specific antigen RNA before and after radical retropubic prostatectomy and transurethral resection of the prostate using "Light-Cycler"-based quantitative real-time polymerase chain reaction

OBJECTIVES

To report our initial experience gained in establishing real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection of prostate-specific antigen (PSA) mRNA using the quantitative online PCR system LightCycler. Many studies have thus far failed to provide the desired proof that the detection of circulating PSA-expressing tumor cells with RT-PCR in the blood samples of patients with prostate cancer (PCa) is a highly sensitive prognostic and course marker. One of the possible reasons is the lack of reliable quantification methods.

METHODS

Blood samples before and after surgery were obtained from 87 patients who underwent radical prostatectomy for locally confined PCa and 27 patients who underwent transurethral resection of the prostate for benign prostatic hyperplasia. Eight days postoperatively, additional blood samples were obtained from the patients with PCa. Quantitative no-nested RT-PCR for PSA mRNA (291 bp) was performed using the LightCycler system applying the SYBR Green protocol. The number of circulating LNCaP tumor cell-equivalents per sample was estimated from the mean amplification value measured in a given number of LNCaP cells.

RESULTS

PSA mRNA was detected preoperatively in 19 patients with Stage pT2 tumor (40%) and in 28 patients with tumor greater than Stage pT2 (72%), but in only 2 patients with benign prostatic hyperplasia (8%; analysis of variance, P <0.001). Significant quantitative differences were observed among Stage pT2 disease (1034 LNCaP tumor cell-equivalents/mL), greater than Stage pT2 disease (7830 cells/mL), and benign prostatic hyperplasia (58 cells/mL; analysis of variance for all groups, P <0.001). The correlation between the detection of PSA expression by RT-PCR and the Gleason score and serum PSA value was statistically significant.

CONCLUSIONS

Our results show that the initial experience with the LightCycler system for PSA-assisted detection of circulating PSA mRNA in PCa by RT-PCR may be a promising preoperative prognostic marker for organ-confined or locally advanced PCa. Long-term follow-up of these patients with PCa must demonstrate the clinical value of molecular diagnostics with quantitative RT-PCR systems.

Frequency of PSA-mRNA-bearing cells in the peripheral blood of patients after prostate biopsy

Transrectal ultrasound (TRUS) guided prostate biopsy is standard diagnostic procedure for prostate cancer (PCa). However, possibility of dissemination of cancer cells by biopsy is not negligible. To investigate this possibility, we examined prostate specific antigen (PSA)-bearing cells in peripheral blood of the 108 patients before and after prostate biopsy. Peripheral blood samples were obtained from 108 patients with elevated serum PSA (sPSA) levels, who had undergone sextant prostate biopsy using TRUS. The presence of PSA-mRNA bearing cells was examined using the nested RT-PCR method enabling detection of one LNCaP cell diluted in 1 ml of whole blood. Among 108 patients, 62 and 46 were diagnosed with benign prostatic hyperplasia (BPH) and PCa, respectively. PSA-mRNA was detected in 3 PCa cases but in no BPH patients before and after biopsy, and in 16 BPH (25.8%) and in 21 PCa (45.7%) patients only after biopsy (P< 0.01). The patients with positive mRNA before biopsy had higher sPSA (P< 0.001), and those after biopsy had higher sPSA and PSA density (PSAD) levels (P< 0.05). Positive PSA-mRNA cases had more cancer involved biopsy cores than the negative PSA-mRNA cases (P< 0.001). Although further investigations are needed, the present findings suggest that prostate biopsy might scatter prostate cells in the blood stream especially in cases with high sPSA and, thus, might contribute to tumour spreading in the cases of prostate cancer.

Technical aspects of minimal residual disease detection in carcinoma patients

The burden of occult malignant cells which remains after a course of treatment that has resulted in clinical remission is referred to as minimal residual disease (MRD). MRD is increasingly considered as a determinant of local or systemic recurrence in cancer patients. During the last 20 years, methods for the detection of rare cancer cells have evolved from mere cytomorphological investigations to a variety of immunological and molecular assays. Since surgical therapy remains the best treatment option for cancer patients with resectable tumors, the first question to address is whether the removal of the tumor was complete or some cancer cells remained from the tumor at the primary site. Several tumor-associated DNA alterations have been identified to solve this diagnostic problem. Assays detecting tumor-associated DNA alterations have been applied to resection margins and body fluids such as bronchoalveolar lavage, sputum, urine, pancreatic juice, colonic lavage, and stool. Due to the higher sensitivity of immunocytochemical and reverse-transcriptase polymerase chain reaction (RT-PCR)-based assays, the second question to be addressed is whether systemic hematogenous or lymphatic spread of cancer cells occurred. Disseminated cancer cells have been detected in bone marrow aspirates, peripheral blood, and lymph node biopsies, and cancer cell dissemination is regarded as a relevant and independent prognostic factor. Thus, sensitive techniques for the detection of MRD are likely to guide indications for surgical or adjuvant therapy protocols in clinical oncology. However, since many of the assays for the detection of MRD are complex, and results are influenced by a variety of technical aspects, the majority of diagnostic applications have not yet been sufficiently standardized. Consequently, quality control and reproducibility of minimal disease detection assays remain unsolved problems. Therefore, well controlled collaborative studies are urgently required to evaluate indications and diagnostic standards for these assays. This review summarizes technical aspects and their implications for the clinical application of presently available assays for MRD detection in carcinoma patients.

Molecular detection and characterization of circulating tumor cells and micrometastases in prostatic, urothelial, and renal cell carcinomas

The detection and molecular characterization of circulating tumor cells (CTCs) and micrometastases in urinary tract and prostatic tumors may have important prognostic and therapeutic implications. In the last decade, numerous groups have attempted the detection of occult tumor cells in renal, prostatic, and urothelial carcinomas using the highly sensitive reverse-transcriptase polymerase chain reaction (RT-PCR). In prostatic carcinoma (PC), tissue-specific transcripts were detected with high specificity in the blood of patients with localized and advanced disease. PCR assays for PC detection were shown to be strong predictors of poorer outcome in some reports, while a lack of prognostic significance was found in other studies. There was a vast difference in the PCR positivity rates between various groups studying PC. This discrepancy could be due to variations in PCR methodology. In urothelial and renal cell carcinoma, the amount of research on the subject is still too limited. Currently, these assays for occult tumor cells are promising but are not yet ready to use in PC and urinary tract tumors. Because of the many limitations of PCR (e.g., false positives), many groups are developing new approaches for the detection of occult tumor cells. The most attractive technique involves immunomagnetic isolation of intact CTC and micrometastases prior to downstream analysis. The tumor-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry, and in situ hybridization. This will lead to better quantification and molecular characterization of these tumor cells.

Blood and serum substances for markers of prostate cancer

Serummarkers for prostate carcinoma are widely applied for the purpose of early detection of cancer and the differentiation between benign and malignant disease, for the pre-treatment staging of detected prostatic cancers, and for the monitoring of prostate cancer after curative or palliative therapies. This review illustrates the limitations of current markers for prostatic disease in blood en serum. It gives an overview of what is known about PSA and its isoforms, hK2, PSMA, and PSCA, and discusses, based on this information, in what direction current research is developing in order to improve these markers.

Molecular detection and characterisation of circulating tumour cells and micrometastases in solid tumours

The detection and molecular characterisation of circulating tumour cells (CTC) and micrometastases may have important prognostic and therapeutic implications. Because their numbers are very small, these tumour cells are not easily detected using conventional methods. In the last decade, numerous groups have attempted to detect occult tumour cells in solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). These assays were in the vast majority directed against tissue-specific markers. PCR was shown to be superior to conventional techniques in detecting occult tumour cells allowing the identification of one malignant cell mixed with 1-10 million normal cells. In some tumours like melanoma and prostatic carcinoma, tissue-specific transcripts were detected with high specificity in the blood of patients with localised and advanced disease. In some reports, PCR was shown to be a strong predictor of poorer outcome. However, due to the many limitations of PCR (e.g false-positives), many groups are developing new approaches for the detection of occult tumour cells. The most attractive technique involves immunomagnetic isolation of CTC and micrometastases prior to downstream analysis. The tumour-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry and in situ hybridisation. This will lead to better quantification and molecular characterisation of these tumour cells. In conclusion, the molecular detection and characterisation of occult tumour cells offer a great opportunity for better stratifying patients with solid tumours and for developing new prognostic markers and targeted therapies.