Positive prostate-specific antigen circulating cells detected by reverse transcriptase-polymerase chain reaction does not imply the presence of prostatic micrometastases

Cytokeratin 19 Expression by Reverse Transcriptase-Polymerase Chain Reaction in the Peripheral Blood of Prostate Cancer Patients

Aims and background

Sensitive reverse transcriptase-polymerase chain reaction-based techniques for detection of epithelial antigen expression, such as cytokeratin 19, in the peripheral blood mononuclear fraction of prostate cancer patients may allow the detection of tumor progression at A molecular level.

Methods

We studied cytokeratin 19 expression by reverse transcriptase-polymerase chain reaction in peripheral blood mononuclear cell samples of 10 control men and serially in 44 patients with prostate cancer every three months for 18 months.

Results

None of the 10 normal control men expressed cytokeratin 19 in their peripheral blood mononuclear fraction. In the patients, cytokeratin 19 positivity at entry was not associated with age, Gleason score, clinical stage, prostate-specific antigen or alkaline phosphatase. Interestingly, having at least one positive cytokeratin 19 result during follow-up correlated significantly with time to prostate-specific antigen progression (P = 0.049), especially in the subgroup of metastatic patients (P = 0.032).

Conclusions

We conclude that cytokeratin 19 expression by reverse transcriptase-polymerase chain reaction in the peripheral blood mononuclear cell fraction of prostate cancer patients correlates with time to prostate-specific antigen progression. Further studies are needed to confirm these findings.

Her2/neu Expression by Reverse Transcriptase-Polymerase Chain Reaction in the Peripheral Blood of Prostate Cancer Patients

Background/Aims

Evaluation of Her2/neu expression in the peripheral blood mononuclear cell fraction of prostate cancer patients by RT-PCR may afford an opportunity for the detection of circulating tumor cells and thus serve as a marker of micrometastatic disease.

Methods

We studied Her2/neu expression by reverse transcriptase-polymerase chain reaction in peripheral blood mononuclear cell fraction samples of 21 controls and serially in 43 patients with prostate cancer.

Results

None of the 21 controls expressed Her2/neu whereas 23.25% (95% CI, 11.75–38.63) of the patients were positive at entry into the study, and 65.11% (95% CI, 49.07–78.99) of them had at least one positive result during the follow-up period. Her2/neu positivity at study entry did not correlate significantly with PSA level, Gleason score, clinical stage or time to PSA progression. When we analyzed only patients with advanced disease, we observed a trend towards a shorter time to PSA progression in patients with at least one positive Her2/neu result during the follow-up (log-rank test, P = 0.08).

Conclusions

We conclude that Her2/neu expression in the peripheral blood mononuclear cell fraction of prostate cancer patients is frequent and therefore this assay may potentially be useful to detect the presence of micrometastatic disease in men with prostate cancer and for monitoring patients enrolled in trastuzumab-based therapeutic protocols.

Circulating Prostate Cells Found in Men with Benign Prostate Disease Are P504S Negative: Clinical Implications

Introduction. Developments in immunological and quantitative real-time PCR-based analysis have enabled the detection, enumeration, and characterization of circulating tumor cells (CTCs). It is assumed that the detection of CTCs is associated with cancer, based on the finding that CTCs can be detected in all major cancer and not in healthy subjects or those with benign disease. Methods and Patients. Consecutive men, with suspicion of prostate cancer, had blood samples taken before prostate biopsy; mononuclear cells were obtained using differential gel centrifugation and CPCs detecting using anti-PSA immunocytochemistry. Positive samples underwent further classification with anti-P504S. Results. 329 men underwent prostate biopsy; of these men 83 underwent a second biopsy and 44 a third one. Of those with a biopsy negative for cancer, 19/226 (8.4%) had CPCs PSA (+) P504S (−) detected at first biopsy, 6/74 (8.1%) at second biopsy, and 5/33 (15.2%) at third biopsy. Men with cancer-positive biopsies did not have PSA (+) P504S (−) CPCs detected. These benign cells were associated with chronic prostatitis. Conclusions. Patients with chronic prostatitis may have circulating prostate cells detected in blood, which do not express the enzyme P504S and should be thought of as benign in nature.

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.

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.

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.

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.

Numeric definition of the clinical performance of the nested reverse transcription-PCR for detection of hematogenous epithelial cells and correction for specific mRNA of non-target cell origin as evaluated for prostate cancer cells

BACKGROUND

Inappropriate quality management of reverse transcription-PCR (RT-PCR) assays for the detection of blood-borne prostate cancer (PCa) cells hampers clinical conclusions. Improvement of the RT-PCR methodology for prostate-specific antigen (PSA) mRNA should focus on an appropriate numeric definition of the performance of the assay and correction for PSA mRNA that is not associated with PCa cells.

METHODS AND RESULTS

Repeated (RT-)PCR tests for PSA mRNA in single blood specimens from PCa patients and PCa-free controls, performed by four international institutions, showed a large percentage (approximately equal to 50%) of divergent test results. The best estimates of the mean, lambda (SD), of the expected Poisson frequency distributions of the number of positive tests among five replicate assays of samples from PCa-free individuals were 1.0 (0.2) for 2 x 35 PCR cycles and 0.2 (0.1) for 2 x 25 PCR cycles. Assessment of the numeric value of the mean can be considered as a new indicator of the performance of a RT-PCR assay for PSA mRNA under clinical conditions. Moreover, it determines the required number of positive test repetitions to differentiate between true and false positives for circulating prostate cells. At a predefined diagnostic specificity of > or = 98%, repeated PCRs with lambda of either 1.0 or 0.2 require, respectively, more than three or more than one positive tests to support the conclusion that PSA mRNA-containing cells are present.

CONCLUSIONS

Repeated nested PCR tests for PSA and appropriate handling of the data allow numeric quantification of the performance of the assay and differentiation between analytical false and true positives at a predefined accuracy. This new approach may contribute to introduction of PSA RT-PCR assays in clinical practice.

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.

Detection of tumor specific gene expression in bone marrow and peripheral blood from patients with small cell lung carcinoma

BACKGROUND

Small cell lung carcinoma (SCLC) has the propensity to grow rapidly and metastasize extensively. Detection of micro-dissemination of SCLC may have clinical relevance. For its detection, tumor-specific gene expressions were examined in peripheral blood and bone marrow aspirate from patients with SCLC.

METHODS

Expression of prepro-gastrin-releasing peptide (preproGRP), neuromedin B receptor (NMB-R) and gastrin-releasing peptide receptor (GRP-R) were examined by reverse transcriptase polymerase chain reaction (RT-PCR) in peripheral blood and bone marrow aspirate from 40 untreated patients with SCLC. Control samples consisted of peripheral blood samples from 5 patients with nonsmall cell lung cancer (NSCLC) and 20 healthy volunteers.

RESULTS

Positive rates of preproGRP, NMB-R, and GRP-R in bone marrow aspirate of patients with SCLC were 23% (9/40), 8% (3/40), and 10% (4/40), respectively. Those rates in peripheral blood were 11% (4/38), 5% (2/38), and 29% (11/38), respectively. Although GRP-R expression was detected in patients with NSCLC and in healthy volunteers, preproGRP and NMB-R expressions were not detected in patients with NSCLC and in healthy volunteers. All three gene expressions in bone marrow were more frequently observed in patients with bone marrow metastasis, accessed by biopsy, than in patients without. PreproGRP gene expression in bone marrow was also more frequent in patients with bone metastasis, accessed by bone scintigram, than in patients without, and was related to poorer survival.

CONCLUSIONS

Micro-dissemination of SCLC was detectable by RT-PCR of preproGRP and NMB-R, both specific for SCLC. These gene expressions in bone marrow may be related to disease extent and prognosis.

Detection of circulating cells expressing chromogranin A gene transcripts in patients with lung neuroendocrine carcinoma

High grade lung neuroendocrine carcinomas, like small and large cell neuroendocrine carcinomas, pose therapeutic problems. Most initially respond to chemotherapeutic agents, but early relapses are frequent and are resistant to the presently available treatments. Our study reports for the first time the development and evaluation of a test for detecting the presence of circulating tumour cells by measuring chromogranin A gene transcripts with reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blotting. The test is specific and sensitive (detection of 10 cancer cells/ml blood), and only minimally invasive. Positivity is statistically correlated to high grade neuroendocrine carcinomas and to a poor prognosis with a 3-fold higher lethal risk. The test now needs to be assessed for its usefulness as a tool in the initial staging procedures and follow-up by comparison with the recent immunoradiometric assay (RIA) for detection of chromogranin A in the serum.

Characterization of KLK4 expression and detection of KLK4-specific antibody in prostate cancer patient sera

The ability to identify prostate tumor or prostate tissue specific genes that are expressed at high levels and use their protein products as targets could greatly aid in the diagnosis and treatment of prostate cancer. Using a polymerase chain reaction (PCR)-based subtraction technique, we have recovered the recently described KLK4 (prostase) gene from human prostate cDNA. In this study, KLK4 gene expression in human prostate tumors was further characterized using cDNA quantitative PCR and immunohistochemistry, demonstrating that the gene is specifically expressed at both the mRNA and protein levels in normal human prostate tissue, and in both primary and metastatic prostate tumor samples. Quantitative mRNA analysis also demonstrated low level expression including adrenal gland, salivary gland and thyroid. Finally, it was demonstrated that prostate cancer patient sera contain antibodies that bind specifically to recombinant KLK4 protein. This antibody has been used to detect KLK4-specific peptides in epitope mapping experiments. The relatively specific expression profile and elevated level of KLK4 mRNA and protein in both tumor and normal prostate tissues, in addition to detectable KLK4-specific antibody in cancer patient sera, supports additional efforts to determine if KLK4 can play a role in the diagnosis of prostate cancer, the monitoring of residual disease, or act as a target for immunotherapy.

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%.

Molecular Markers in Prostate Cancer: The Role in Preoperative Staging

Radical prostatectomy as a primary treatment for clinically localized prostate cancer has increased dramatically over the past decade due to prostate-specific antigen (PSA) screening and the awareness of the increased incidence of localized disease. Despite the stage migration to increase clinically localized disease, there are still vast numbers of men who harbor occult extraprostatic extension and develop recurrence after surgery. The study of molecular markers in the blood or tissue of surgical patients prior to treatment, called " molecular staging, " is the focus of this review. The reverse transcriptase- polymerase chain reaction (RT-PCR) test for PSA gene expression in peripheral blood or bone marrow has received considerable attention since its first report in 1992. The test detects messenger RNA species for prostate-specific/abundant genes such as PSA and prostate-specific membrane antigen. These messenger RNAs were not detected in normal blood or bone marrow, but were detected in some prostate cancer patients presumably due to circulating prostatic epithelial cells. These prostate epithelial cells are thought to be occult metastases cells, and early studies correlated a positive RT-PCR test with surgical pathology adverse features such as positive margins. Despite the many studies over the past few years, there have been inconsistent results, and the most recent studies have not been able to confirm clinical utility. Bone marrow RT-PCR has been more promising; however, it is still a research tool that needs further study. The study of molecular markers in tissue material, ie, prostate biopsy samples prior to radical prostatectomy, is problematic due to the sampling error inherent in a multifocal heterogeneous tumor such as prostate cancer. The tumor suppressor proteins p53 and p27, Bcl-2 oncoprotein, Ki-67 proliferation index protein, E-cadherin, and microvessel density have been assessed in preradical prostatectomy needle biopsy. Results have been conflicting, and none are yet accepted as a clinically useful marker. Current and future work is focusing on analysis of multiple gene expressions or proteins simultaneously via gene chip or proteomics technology. While these expression profiles might be of value in whole prostate surgical specimens where tissues are well characterized, it is unclear how this new technology will be applied to the needle biopsy samples. Although molecular staging of radical prostatectomy patients has been under study for a decade, all assays remain research tools. Still, this area holds great promise for improving the accuracy of staging and providing a more accurate prognosis of individual men with clinically localized prostate cancer.

Reliability of PCR-based detection of occult tumour cells: lessons from real-time RT-PCR

For the molecular detection of rare tumour cells in clinical samples, real-time reverse transcription-polymerase chain reaction (RT-PCR) offers two important advantages over conventional RT-PCR assays: the results are quantitative and, perhaps more importantly, it facilitates exact sensitivity controls on a per sample basis as well as exact comparison of different assay protocols. We report here on quantitative results obtained with different protocols for RNA isolation and cDNA synthesis for amplification of beta2-microglobulin transcripts using the light cycler system. Furthermore, housekeeping gene-specific PCRs were compared with PCRs specific for an artificial transcript (internal standard) detected simultaneously at a level comparable to the wild-type sequence. Artificial tyrosinase transcripts derived from a vector construct stably transfected into a human lymphoma cell line were used as a model to test the usefulness of artificial internal standards as an alternative to housekeeping genes. The highest RNA yields were obtained using a combination of phenol-chloroform extraction and the High Pure RNA Isolation Kit. Analysing beta2-microglobulin transcript-specific RT-PCRs, the highest sensitivity was obtained for cDNAs generated with Omniscript reverse transcriptase and oligo-p(dT)15 primer. Regarding patient blood samples, RT-PCRs specific for beta2-microglobulin, porphobilinogen deaminase and artificial tyrosinase transcripts provided quantitative data for all, for 18 out of 21, and for 10 out of 21 samples, respectively. Quantification of beta2-microglobulin transcripts by the light cycler system defined the protocol revealing the highest cDNA quality. Comparisons of quantitative data from RT-PCRs specific for beta2-microglobulin, porphobilinogen deaminase and artificial tyrosinase transcripts enabled us to determine a close range for crossing points within which sufficient cDNA quality can be guaranteed, even for the detection of rare transcripts. PCRs specific for the artificial internal standard are ideally suited for cDNA quality assessment on a per sample basis.

The role of imaging studies and molecular markers for selecting candidates for radical prostatectomy

For the typical patient who has newly diagnosed prostate cancer, clinically organ-confined disease of moderate grade, and a PSA less than 10 ng/mL, the current role of imaging studies and molecular biomarkers is limited. Bone scans are not necessary for newly diagnosed men with a PSA less than 10 ng/mL in the absence of bone pain. Similarly, abdominal and pelvic CT scanning rarely provides any useful diagnostic or staging information when the PSA is less the 20 ng/mL and is indicated rarely. Endorectal coil MR imaging adds staging information for patients with a PSA between 10 and 20 ng/mL, a Gleason score of 7 or less, and 50% or more positive biopsies on a sextant sampling. Indium 111 capromab pendetide scanning (ProstaScint) is FDA-approved to evaluate newly diagnosed patients at high risk for metastases. These patients have a Gleason score of 7 or greater and a PSA greater than 20 ng/mL, a Gleason score of 8 to 10 regardless of the PSA value, or clinical stage T3 disease and a Gleason score of 6 or greater. RT-PCR testing of blood or bone marrow for prostate-specific or prostate cancer-specific gene expression, or "molecular staging," is a promising technique whose current use is still investigational. Much useful information may be gained by careful study of prostate needle biopsy material. Aside from current Gleason grading and the number or percentage of cores involved with cancer, no molecular biomarker is approved for clinical use. p27, p53, bcl-2, Ki-67 (MIB-1), and the assessment of neovascularity hold promise, but prospective multicenter studies are needed. In the long-term, multiple gene expression profiling of biopsy material using gene chips may revolutionize the care of patients with prostate cancer and those who elect radical prostatectomy.

Molecular characterization of minimal residual cancer cells in patients with solid tumors

The failure to reduce the mortality of patients with solid tumors is mainly a result of the early dissemination of cancer cells to secondary sites, which is usually missed by conventional diagnostic procedures used for tumor staging. PCR was shown to be superior to conventional techniques in detecting circulating tumor cells and micrometastases allowing the identification of one tumor cell in up to 10(7) normal cells in various sources such as blood, bone marrow, lymph nodes, urine or stool. The methods used are based on the detection of either genomic alterations in oncogenes and tumor suppressor genes or on the mRNA expression of tissue-specific and tumor-associated genes. The additional implementation of techniques for cancer cell purification had a significant impact on analytical sensitivity and specificity of MRCC detection. For patients with e.g. melanoma, breast, colorectal or prostate cancer it was demonstrated that the presence of disseminated cancer cells defines a subgroup of patients with reduced time to recurrence. The possibility to use easily accessible body fluids as a source for MRCC detection enables longitudinal observations of the disease. In this review we discuss the potential of molecular characterization of MRCC as a tool to improve prognostication, therapy selection and drug targeting as well as therapy monitoring.

Immunomagnetic cell enrichment detects more disseminated cancer cells than immunocytochemistry in vitro

PURPOSE

We describe a method to improve tumor cell detection compared to currently available immunocytochemical methods by using immunomagnetic cell enrichment.

MATERIALS AND METHODS

Two different methods of immunomagnetic cell enrichment using antibody coated magnetic beads were tested and compared with unenriched immunocytochemistry. One method was positive selection of epithelial cells from mononuclear cells with the antiepithelial antibody BER-EP4 and the other was depletion of mononuclear cells with the antileukocyte antibody CD45. Mononuclear cells were isolated from peripheral blood by density centrifugation and various numbers of tumor cells were added. The 5 different cell lines from urological malignancies used in the study were DU-145, RT-4, CAKI-2, KTCTL-2 and KTCTL-30. Following incubation of cell suspensions with the beads, cell separation was performed in a magnetic field. After centrifugation on glass slides immunocytochemical staining for cytokeratin was performed. A total of 112 experiments were completed and negative controls were obtained.

RESULTS

The number of tumor cells detected by positive selection and depletion was significantly higher than by immunocytochemistry (p <0.001). The median enrichment factor and tumor cell recovery rate for positive selection and depletion were 15.3 and 61.2%, and 13.0 and 57.3%, respectively (not significant). With less than 1 tumor cell suspended in 106 mononuclear cells, the probability of tumor cell detection was 23% for immunocytochemistry alone and 93.3% for both enrichment methods (p <0.01). No false-positive results were observed.

CONCLUSIONS

Compared to immunocytochemistry, immunomagnetic cell enrichment significantly improves the sensitivity of detection of epithelial cells added to mononuclear cells. Both methods of enrichment were equally effective and may be important for clinical practice in the future.

Pitfalls in the detection of disseminated non-hematological tumor cells

There is not yet a consensus on the reliability of the methods that should be used for the detection of rare disseminated tumor cells from non-hematological malignancies. In this review, we will discuss the advantage and drawbacks of the classical approach of immunocytochemistry and the molecular detection by reverse transcriptase polymerase chain reaction (RT-PCR). The interpretation of the biological significance of circulating tumor cells and the pitfalls of the detection techniques are the main causes of discrepancy between the conclusions of different tumor-cell detection (TCD) studies.

RT-PCR-based detection of occult disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. An overview

Despite recent progress in early detection and local curative therapy, patients with primary epithelial cancer quite frequently relapse with incurable metastasis. Early disseminated tumor cells that may be seminal for distant failure and are undetectable by current diagnostic methods have been identified by immunocytochemical techniques in bone marrow of cancer patients using monoclonal antibodies against cytokeratins. Recently, promising new molecular approaches, namely, reverse transcriptase--polymerase chain reaction (RT-PCR) assays, have been suggested as a potential technique for the detection of minimal residual tumor burden by targeting mRNA transcribed from epithelial genes in bone marrow, peripheral blood, or lymph nodes. Several studies using RT-PCR thus far indicate a highly sensitive and specific staging tool, although the prognostic value is still controversial. However, limitations may arise from ectopic expression of marker mRNA in hematopoietic cells and deficient expression in circulating tumor cells. The present review focuses on the relevant literature and demonstrates the range of current applications of RT-PCR-based assays for detecting disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. We will both summarize technical evaluations of published molecular approaches and discuss the widely disparate results on PCR findings in clinical studies.

Detection of extraprostatic prostate cells utilizing reverse transcription-polymerase chain reaction

This article reviews the utility of reverse transcription-polymerase chain reaction (RT-PCR) in prostate cancer. RT-PCR aims to detect occult micrometastases in non-prostatic sites. Due to its exquisite analytical sensitivity, RT-PCR is able to amplify and detect even low-level, prostate-specific messages present at these extraprostatic sites. In recent years, a fair amount of data on the clinical utility of the technique had been reported. The target tissues under investigation are peripheral blood, bone marrow aspirate, and lymph nodes. Favorite markers of choice are prostate-specific antigen (PSA), prostate-specific membrane antigen (PSMA), and human glandular kallikrein-2 (hK2). False positives among negative controls are low. For the most part, RT-PCR is inadequate in detecting tumor cells in the peripheral blood from patients who are known to have metastatic prostate cancer. All studies showed that RT-PCR could detect PSA, PSMA or hK2 mRNAs in the circulation of patients who have organ-confined or extraprostatic disease. Most studies showed that RT-PCR utilizing current markers could not be used as a prospective test to diagnose prostate cancer. However, a few studies also showed that the detection rate could be predictive and sensitive enough to differentiate patients with organ-confined disease from those with extraprostatic disease. Data from PSA- or PSMA-RT-PCR using lymph nodes as the tissue source is more encouraging. RT-PCR was able to detect PSA and/or PSMA positive samples that have not been detected by conventional pathology.

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

Reverse transcriptase polymerase chain reaction (RT-PCR) assay is a sensitive technique to detect circulating cells expressing prostate-specific antigen (PSA) in blood or bone marrow from patients with prostate cancer. When applied to prostate cancer patients at our institution, this technique identifies those patients with a greater likelihood of extra-prostatic disease. We evaluated RT-PCR PSA as a predictor of PSA recurrence and compared it with pre-operative (serum PSA, digital rectal examination, Gleason score on biopsy) and post-operative parameters (pathological findings). Three hundred nineteen men scheduled for radical prostatectomy had an enhanced RT-PCR PSA assay before surgery. The enhanced RT-PCR PSA protocol has been previously described. PSA recurrence was defined as any serum PSA value above 0.2 microgram/l. Forty-six patients had PSA recurrence. The mean follow-up was 25.4 months. Recurrence free survival was 53% for patients with positive RT-PCR PSA vs. 84% if RT-PCR PSA was negative. By using multivariate analyses, RT-PCR PSA status was not an independent predictor of PSA recurrence compared to pathological stage pT3, Gleason score on prostate specimen and serum PSA. If only pre-operative parameters were studied, serum PSA and RT-PCR PSA status were 2 independent pre-operative predictors of PSA recurrence compared with Gleason score on biopsy and digital rectal examination. Int. J. Cancer (Pred. Oncol.) 84:360-364, 1999.

Blinded evaluation of reverse transcriptase-polymerase chain reaction prostate-specific antigen peripheral blood assay for molecular staging of prostate cancer

OBJECTIVES

The reverse transcriptase-polymerase chain reaction (RT-PCR)-prostate-specific antigen (PSA) assay to detect presumed occult micrometastatic prostate cancer has been controversial, and this molecular staging has been thought to be clinically useful by some groups but not others.

METHODS

We used a sensitive nested RT-PCR assay with specific primers derived from the PSA sequence and a very stringent two-step PCR protocol with denaturing temperature of 94 degrees C annealing and extension temperature of 68 degrees C. This method enabled us to detect PSA-expressing LNCaP prostate cancer (PC) cells as low as one cell of 10 million lymphocytes (1/10(7)). Ninety-six patients with PC were studied, including 85 before radical prostatectomy (RP), and 22 controls, including healthy men and women and men with benign prostatic hyperplasia.

RESULTS

In 85 patients undergoing RP, a minimum of two independent RT-PCR-PSA assays detected circulating prostate cells preoperatively in 27 patients (31.8%). Of 12 patients with locally advanced or advanced stage cancer, RT-PCR-PSA was positive in 5 (41.7%); of the 22 controls, no patient was RT-PCR-PSA positive. In 10 randomly selected cases, the RT-PCR product was confirmed as PSA by DNA sequencing. Of the 27 patients undergoing RP who were RT-PCR positive, 11 (40.7%) had non-organ-confined disease (pT3a or greater), and of the 58 patients who were RT-PCR negative, 32 (55.2%) had non-organ-confined disease. Patients with RT-PCR positive results also had lower margin positivity (9 of 27, 33.3%) than did patients with RT-PCR negative results (21 of 58, 36.2%). Finally, at a mean follow-up of 25.7 months, 5 (18.5%) of 27 RT-PCR positive patients had recurrence (PSA) compared with 14 (24.1%) of 58 RT-PCR negative patients.

CONCLUSIONS

On the basis of this blinded study, RT-PCR for PSA-expressing cells in 85 patients before RP is not related to clinical stage, age, race, grade, Gleason sum, serum PSA or prostatic acid phosphatase, tumor volume, or tumor multifocality. RT-PCR positivity did not predict pathologic stage or early PSA recurrence. A standardized RT-PCR assay needs to be developed to account for interlaboratory discrepancies.

Prostate-specific antigen and new related markers for prostate cancer

Although prostate-specific antigen (PSA), or human kallikrein 3, is the most valuable tool available for the diagnosis and management of prostate cancer, as currently used it is insufficiently sensitive and specific for early detection or staging of the malignancy. Many new concepts have been introduced in order to optimize the clinical use of PSA measurements, but each one has its own drawbacks. The molecular forms of PSA, especially the free PSA, seem to be useful for the detection of prostate cancer in men with PSA concentrations falling in the 4-10 microg/l range. New molecular techniques, such as reverse transcriptase polymerase chain reaction for the detection of minimal amounts of PSA messenger RNA and prostate-specific membrane antigen, offer new promise for the prognosis and possibly staging of prostate cancer. On the other hand, human kallikrein 2, a serine protease closely related to PSA that is also expressed predominantly in the prostate, may be a new adjuvant marker for prostate cancer. As for its biological functions, PSA can no longer be regarded as a specific prostate molecule associated mainly with semen liquefaction when it has a possible role as a prognostic indicator in female breast cancer. The biological role of PSA in normal tissues and tumors may be much more complex than previously thought and requires further investigation.

Quantification of prostate-specific antigen mRNA by coamplification with a recombinant RNA internal standard and microtiterwell-based hybridization

We report a quantitative analytical methodology for prostate-specific antigen (PSA) mRNA, which is based on the coamplification of the target with a recombinant RNA internal standard (IS) using reverse transcriptase-polymerase chain reaction. PSA mRNA and the RNA IS contain the same primer recognition sites and generate amplification products that have identical sizes but differ in a 24-bp sequence located in the center of the molecule. Amplified sequences are labeled with biotin using a biotinylated upstream primer. The products are captured on streptavidin-coated microtiter wells and hybridized to specific probes labeled with the hapten digoxigenin. The hybrids are determined using alkaline phosphatase-labeled anti-digoxigenin antibody and time-resolved fluorometry. The ratio of the fluorescence values obtained for the PSA mRNA and the RNA IS is a linear function of the amount of PSA mRNA present in the sample. Samples containing total RNA from PSA-expressing cells (LNCaP cells) in addition to 1 μg of RNA from healthy cells give fluorescence ratios related linearly to the number of cells in the range of 4 to 3000 cells.