Low frequency epithelial cells in bone marrow aspirates from prostate carcinoma patients are cytogenetically aberrant

Liquid biopsy for monitoring of tumor dormancy and early detection of disease recurrence in solid tumors

Cancer is one of the three leading causes of death worldwide. Even after successful therapy and achieving remission, the risk of relapse often remains. In this context, dormant residual cancer cells in secondary organs such as the bone marrow constitute the cellular reservoir from which late tumor recurrences arise. This dilemma leads the term of minimal residual disease, which reflects the presence of tumor cells disseminated from the primary lesion to distant organs in patients who lack any clinical or radiological signs of metastasis or residual tumor cells left behind after therapy that eventually lead to local recurrence. Disseminated tumor cells have the ability to survive in a dormant state following treatment and linger unrecognized for more than a decade before emerging as recurrent disease. They are able to breakup their dormant state and to readopt their proliferation under certain circumstances, which can finally lead to distant relapse and cancer-associated death. In recent years, extensive molecular and genetic characterization of disseminated tumor cells and blood-based biomarker has contributed significantly to our understanding of the frequency and prevalence of tumor dormancy. In this article, we describe the clinical relevance of disseminated tumor cells and highlight how latest advances in different liquid biopsy approaches can be used to detect, characterize, and monitor minimal residual disease in breast cancer, prostate cancer, and melanoma patients.

Minimal residual disease in prostate cancer patients after primary treatment: theoretical considerations, evidence and possible use in clinical management

Minimal residual disease is that not detected by conventional imaging studies and clinically the patient remains disease free. However, with time these dormant cells will awaken and disease progression occurs, resulting in clinically and radiological detectable metastatic disease. This review addresses the concept of tumor cell dissemination from the primary tumor, the micrometastatic niche and tumor cell survival and finally the clinical utility of detecting and characterizing these tumor cells in order to guide management decisions in treating patients with prostate cancer.

Paired High-Content Analysis of Prostate Cancer Cells in Bone Marrow and Blood Characterizes Increased Androgen Receptor Expression in Tumor Cell Clusters

Purpose: Recent studies demonstrate that prostate cancer clones from different metastatic sites are dynamically represented in the blood of patients over time, suggesting that the paired evaluation of tumor cells in circulation and bone marrow, the primary target for prostate cancer metastasis, may provide complementary information.Experimental Design: We adapted our single-cell high-content liquid biopsy platform to bone marrow aspirates (BMA) to concurrently identify and characterize prostate cancer cells in patients' blood and bone and thus discern features associated to tumorigenicity and dynamics of metastatic progression.Results: The incidence of tumor cells in BMAs increased as the disease advanced: 0% in biochemically recurrent (n = 52), 26% in newly diagnosed metastatic hormone-naïve (n = 26), and 39% in metastatic castration-resistant prostate cancer (mCRPC; n = 63) patients, and their number was often higher than in paired blood. Tumor cell detection in metastatic patients' BMAs was concordant but 45% more sensitive than using traditional histopathologic interpretation of core bone marrow biopsies. Tumor cell clusters were more prevalent and bigger in BMAs than in blood, expressed higher levels of the androgen receptor protein per tumor cell, and were prognostic in mCRPC. Moreover, the patterns of genomic copy number variation in single tumor cells in paired blood and BMAs showed significant inter- and intrapatient heterogeneity.Conclusions: Paired analysis of single prostate cancer cells in blood and bone shows promise for clinical application and provides complementary information. The high prevalence and prognostic significance of tumor cell clusters, particularly in BMAs, suggest that these structures are key mediators of prostate cancer's metastatic progression. Clin Cancer Res; 23(7); 1722-32. ©2016 AACR.

Significance of apoptotic and non-apoptotic disseminated tumor cells in the bone marrow of patients with clinically localized prostate cancer

BACKGROUND

Disseminated tumor cells (DTC) can be detected in a high proportion of patients with localized solid malignancies. In prostate cancer (PC), determination of DTCs is critically discussed as there are conflicting results on their prognostic value. The aim of the present study was to evaluate the presence and prognostic role of DTCs in PC patients with a high risk of disease recurrence.

METHODS

248 patients with clinically localized PC undergoing radical prostatectomy with features of increased risk of recurrence (PSA ≥10 ng/ml or Gleason score ≥ 4 + 3 = 7 or pT ≥3) were included. All patients underwent intraoperative bone marrow (BM) aspiration biopsy. BM cells were evaluated by immunocytochemistry for cytokeratines and the apoptosis marker caspase-cleaved cytokeratin 18 (M30). Results of immunocytochemistry were correlated with clinical and pathological parameters and clinical outcome of the patients.

RESULTS

Of 248 patients, 47 (19.0%) had evidence of DTCs at time of radical prostatectomy. In 17 of these 47 patients (36.2%), DTCs expressed the apoptosis marker M30. We observed no correlation between the presence of DTCs and tumor stage, nodal stage, prostate-specific antigen, or Gleason score. After a median-follow-up of 58 months (23-76), no differences in rates of biochemical recurrence, development of metastases and cancer-specific death were observed between patients with and without DTCs while apoptosis markers had no role.

CONCLUSIONS

In a single-centre cohort of patients with increased risk for disease recurrence, the presence of DTCs at the time of prostatectomy does not influence clinical outcome. For the first time in patients with PC, DTCs were evaluated for immunocytological features indicating apoptosis. Due to conflicting results of studies on DTCs, BM biopsies at time of radical prostatectomy cannot be recommended as a standard procedure in patients with clinically localized PC.

Combined genome and transcriptome analysis of single disseminated cancer cells from bone marrow of prostate cancer patients reveals unexpected transcriptomes

Bone is the most frequent site of metastasis in prostate cancer and patients with bone metastases are deemed incurable. Targeting prostate cancer cells that disseminated to the bone marrow before surgery and before metastatic outgrowth may therefore prevent lethal metastasis. This prompted us to directly analyze the transcriptome of disseminated cancer cells (DCC) isolated from patients with nonmetastatic (UICC stage M0) prostate cancer. We screened 105 bone marrow samples of patients with M0-stage prostate cancer and 18 bone marrow samples of patients without malignancy for the presence of EpCAM(+) single cells. In total, we isolated 270 cells from both groups by micromanipulation and globally amplified their mRNA. We used targeted transcriptional profiling to unambiguously identify DCCs for subsequent in-depth analysis. Transcriptomes of all cells were examined for the expression of EPCAM, KRT8, KRT18, KRT19, KRT14, KRT6a, KRT5, KLK3 (PSA), MAGEA2, MAGEA4, PTPRC (CD45), CD33, CD34, CD19, GYPC, SCL4A1 (band 3), and HBA2. Using these transcripts, we found it impossible to reliably identify true DCCs. We then applied combined genome and transcriptome analysis of single cells and found that EpCAM(+) cells from controls expressed transcripts thought to be epithelial-specific, whereas true DCCs may express hematopoietic transcripts. These results point to an unexpected transcriptome plasticity of epithelial cancer cells in bone marrow and question common transcriptional criteria to identify DCCs.

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 urokinase receptor (u-PAR)--a link between tumor cell dormancy and minimal residual disease in bone marrow?

Minimal residual disease (MRD) is hypothesized to be the major cause of tumor recurrence and metastasis even years and decades after primary cancer diagnosis and curative solid tumor resection. In these patients disseminated tumor cells reflecting MRD can be detected in the bone marrow years after treatment. It is to be assumed that genetic determinants and a complex interplay between the disseminated tumor cells and their microenvironment in the bone marrow are responsible for tumor cell dormancy and the final reactivation towards metastasis. The urokinase receptor (u-PAR), a critical regulator of invasion, intravasation, and metastasis, is found to be a key player in regulating the shift between single cell tumor dormancy and proliferation. This has mainly been attributed to a regulation by u-PAR of integrins, and the ability of the latter to propagate signals from fibronectin through the EGF-receptor, ERK, and p38 signaling. Interestingly, u-PAR is found in disseminated tumor cells in the bone marrow of solid cancer patients, and is associated with the expansion of these cells and clinical prognosis. Here we summarize and discuss findings on disseminated tumor cells in the bone marrow, MRD and the role of u-PAR in tumor biology, especially focusing on its specific role in providing a switch between tumor cell proliferation and dormancy. Finally, we discuss the hypothesis that u-PAR might be an essential molecule in bone marrow disseminated tumor cells for long-term survival during dormancy, and/or reactivation of their proliferation years after primary treatment.

Disseminated tumor cells in bone marrow following definitive radiotherapy for intermediate or high-risk prostate cancer

BACKGROUND

The purpose of this study was to explore the prevalence of disseminated tumor cells (DTCs) in bone marrow (BM) of clinically progression-free prostate cancer (PC) patients at least 2 years after curatively intended radiotherapy (RT) with or without adjuvant hormone treatment.

METHODS

All patients were T(1-3)N(0)M(0) with intermediate or high risk of progression. Median time from RT to BM sampling was 5 years (2-8). A standardized immunocytochemical method applying the anticytokeratin antibodies AE1/AE3 was used for DTCs detection in 130 patients. Morphological characterization of immunostained cells was performed to exclude false positive cells. The post-treatment BM was explored in relation to pre-treatment risk factors, treatment strategy and serum levels of Testosterone and PSA at the time of BM sampling. Longitudinal changes in BM status were studied in a sub-group of 109 patients who also had donated BM prior to treatment.

RESULTS

Post-treatment BM-aspirates were positive for DTCs in 17% of cases without correlation to any of the tested variables. Out of 14 patients who had DTCs in BM prior to treatment, all but one had become post-treatment negative. Out of 95 patients with pre-treatment negative BM status, 18 (19%) had become post-treatment positive.

CONCLUSIONS

DTCs in BM were found in 17% of clinically progression-free PC patients following RT. The detection of these cells may provide PSA-independent prognostic information remaining to be explored by prolonged follow-up.

Genomic alterations indicate tumor origin and varied metastatic potential of disseminated cells from prostate cancer patients

Disseminated epithelial cells can be isolated from the bone marrow of a far greater fraction of prostate-cancer patients than the fraction of patients who progress to metastatic disease. To provide a better understanding of these cells, we have characterized their genomic alterations. We first present an array comparative genomic hybridization method capable of detecting genomic changes in the small number of disseminated cells (10-20) that can typically be obtained from bone marrow aspirates of prostate-cancer patients. We show multiple regions of copy-number change, including alterations common in prostate cancer, such as 8p loss, 8q gain, and gain encompassing the androgen-receptor gene on Xq, in the disseminated cell pools from 11 metastatic patients. We found fewer and less striking genomic alterations in the 48 pools of disseminated cells from patients with organ-confined disease. However, we identify changes shared by these samples with their corresponding primary tumors and prostate-cancer alterations reported in the literature, evidence that these cells, like those in advanced disease, are disseminated tumor cells (DTC). We also show that DTCs from patients with advanced and localized disease share several abnormalities, including losses containing cell-adhesion genes and alterations reported to associate with progressive disease. These shared alterations might confer the capability to disseminate or establish secondary disease. Overall, the spectrum of genomic deviations is evidence for metastatic capacity in advanced-disease DTCs and for variation in that capacity in DTCs from localized disease. Our analysis lays the foundation for elucidation of the relationship between DTC genomic alterations and progressive prostate cancer.

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Recent advances in the detection of bone marrow micrometastases: A promising area for research or just another false hope? A review of the literature

The presence of early disseminated tumor cells (DTC), otherwise termed micrometastases or minimal residual disease, in the bone marrow (BM), or other secondary compartments, such as the blood and the lymph nodes, is the main reason for recurrence of patients with early stage epithelial cancers after "curative" resection of the primary tumor. There is increasing evidence, that the detection of DTC in BM aspirates may provide additional and independent prognostic information and aid in the stratification of these patients for adjuvant clinical treatment. However, the clinical relevance of micrometastases has not yet been firmly established. In addition, the molecular events and interactions that prevail in early metastatic disease and determine the formation or not of overt metastases remain poorly understood. The methods currently used for the detection of micrometastatic cells include extremely sensitive immunocytochemical and molecular assays, often in conjunction with enrichment techniques for the purification of tumor cells and additional increase of their sensitivity. Nevertheless, the specificity of these methods is mostly inadequate. After the impressive advances of molecular cytogenetics, a highly accurate and global assessment of the genetic status of tumors is now possible. Therefore, the greatest challenge of our time is the application of these novel technologies for the clarification of the key molecular events that initiate metastatic spread. This will further enable us to identify the highly specific and sensitive diagnostic and prognostic markers as well as the therapeutic targets which are so urgently needed.

A European interlaboratory testing of three well-known procedures for immunocytochemical detection of epithelial cells in bone marrow. Results from analysis of normal bone marrow

BACKGROUND

This investigation intended to study the unspecific background to be expected in normal bone marrow (BM), comparing three well recognized protocols for immunocytochemical detection of disseminated carcinoma cells. The interlaboratory variation in screening and evaluation of stained cells was analyzed and different screening methods were compared.

METHODS

BM mononuclear cells (BM MNC) from 48 normal BMs were immunostained in parallel by three participating laboratories. The protocols, based on three different anti-cytokeratin antibodies, have all been in common use for detection of disseminated carcinoma cells: the A45-B/B3 protocol (Hamburg), the CK2 protocol (Augsburg) and the AE1AE3 protocol (Oslo). For all protocols, the immunostained cells were visualized by the same alkaline-phosphatase (AP) detection system (APAAP) followed by detection of the cells by manual screening and by two different automated screening systems (ACIS from Chromavision and MDS1 from Applied Imaging). Detected AP-visualized cells were morphologically classified into unambiguous hematopoietic (Uhc) and questionable cells (Qc, potentially interpreted as tumor cells).

RESULTS

Seven of 48 BMs (15%) harbored > or = 1 AP-visualized cell(s) among 1 x 10(6) BM MNC, both for the A45-B/B3- and for the AE1AE3 protocol, while for CK2 a higher proportion of BMs (21 BMs; 44%) harbored AP-visualized cells (P < 0.01, McNemar's test). The number of Qc was, for all protocols, 1 log lower than the total number of AP-visualized cells. On average, the frequency of Qc was 0.04, 0.08, and 0.02 per 10(6) BM MNC with A45-B/B3, CK2 and AE1AE3, respectively, and the number of Qc-positive BMs 1, 4, and 1. The MDS1 screening sensitivity was similar to manual screening, while ACIS detected fewer cells (P < 0.001, McNemar's test).

CONCLUSIONS

All protocols resulted in AP-visualization of occasional hematopoietic cells. However, morphological classification brings the specificity to a satisfactory high level. Approximately 10% of AP-visualized cells were categorized "questionable". The CK2 protocol turned out less specific than the A45-B/B3 and AE1AE3 protocols.

Telomerase activity in disseminated prostate cancer cells

OBJECTIVE

To analyse telomerase activity in disseminated prostate cancer cells isolated from bone marrow aspirates taken from men with localized prostate cancer before radical prostatectomy (RP).

PATIENTS AND METHODS

Disseminated epithelial prostate cancer cells were isolated from bone marrow aspirates from 69 men with localized prostate cancer before RP, by magnetic column-chromatography enrichment, followed by isolation of fluorescently labelled epithelial cells by micropipetting. We used pools of 10 non-epithelial bone marrow cells after tumour cell enrichment as control samples. These pure cell pools were tested for the presence of telomerase activity.

RESULTS

In all, 49 of the patient samples contained disseminated prostate cancer cells. Homogeneous pools of 10 cells were obtained from 35 of these; 49% of the 35 specimens showed telomerase activity, whereas all five control samples did not. Telomerase activity in the 35 samples was not significantly associated with Gleason score, preoperative prostate-specific antigen level, tumour stage, or surgical margin status. Follow-up is continuing to assess an association with disease recurrence.

CONCLUSION

This work shows the feasibility of isolating disseminated cancer cells for analysing individual or pooled cells. Compared to tissue staining, where telomerase is detected in 80-90% of samples, we found lower rates of telomerase activity in the disseminated tumour cells (49%). Telomerase-negative cells might provide information about cell dormancy, as telomerase is a marker of cell proliferation in immortal and cancer cells. Telomerase-positive cells might predict early disease recurrence, but a longer follow-up is needed to test this possibility.

Methods for isolating circulating epithelial cells and criteria for their classification as carcinoma cells

Novel assay methods developed for the isolation and characterization of circulating tumor cells (CTC) of epithelial origin offer the potential of markers for the non-invasive gathering of clinical information relevant to the diagnosis, evolution and treatment of carcinoma. Of the numerous techniques currently used to analyze CTC, slide-based assays are perhaps the most common. While traditional combined immunocytochemical/brightfield microscopy systems continue to be the most frequently employed, fluorescence-based analysis is gaining in importance. This is partly because fluorescence microscopy analysis of slide-mounted CTC can provide simultaneously cytogenetic as well as morphologic and multiple phenotypic information. In particular, fluorescence microscopy analysis of slide-mounted CTC can accurately determine genetic changes at the chromosomal level in patients with recurrent disease. More importantly, by identifying genetic aberrations in CTC, it becomes possible to choose those patients most likely to benefit from a given treatment. The potential of this technique has already been demonstrated by employing fluorescence in situ hybridization (FISH) methods to measure expression of the HER2/neu gene in tissue from patients with breast carcinoma for the specific purpose of identifying those patients most likely to respond to Trastuzumab targeted therapy. Here, we review the major methodologies used in the preparation and analysis of the slide-based assays.

Circulating tumor cells in breast cancer: correlation to bone marrow micrometastases, heterogeneous response to systemic therapy and low proliferative activity

PURPOSE

The incidence and biological characteristics of circulating tumor cells in the blood of patients with breast cancer were examined and subgroups were evaluated in the context of systemic treatment and the presence of disseminated tumor cells in bone marrow.

EXPERIMENTAL DESIGN

Circulating tumor cells were isolated from the peripheral blood of patients with breast cancer using a gradient system designed for the enrichment of circulating tumor cells (OncoQuick). Circulating tumor cells were identified with the anti-cytokeratin antibody, A45-B/B3. In subsets of patients, expression of the proliferation-associated Ki-67 antigen in circulating tumor cells and the concomitant presence of micrometastases in bone marrow were examined.

RESULTS

In patients with primary breast cancer (stage M(0)), circulating tumor cells were detected in 5 of 60 patients (8.3%) after surgery and before initiation of adjuvant chemotherapy; a positive correlation to the presence of disseminated tumor cells in bone marrow was observed (P = 0.030, n = 53). During the course of adjuvant chemotherapy, repeated analysis of 20 M(0) patients revealed the occurrence of circulating tumor cells in 7 of 16 patients that were initially negative. Patients with metastatic disease (stage M(1)) showed circulating tumor cells in 25 of 63 cases (39.7%, P < 0.0001 as compared with M(0) patients), and a positive finding was correlated with elevated concentrations of the serum tumor marker CA15.3 (P = 0.0093). Performing repeated analysis in a subgroup of 25 M(1) patients, circulating tumor cells were found more frequently in patients with progressive disease than in patients with stable disease or remission (87.5% versus 43.8% of patients with circulating tumor cells, respectively; P = 0.047). Independent of the disease-stage, none of the 47 patients examined for the proliferative status of their circulating tumor cells showed coexpression of Ki-67.

CONCLUSIONS

Circulating tumor cells seem to be nonproliferating cells that persist during chemotherapy. Circulating tumor cell detection is linked to disease progression and elevated tumor marker concentrations in patients with metastatic breast cancer.

Detection of Micrometastatic Disease in Bone Marrow: Is It Ready for Prime Time?

Minimal residual disease (MRD), or isolated tumor cells (ITCs) in bone marrow, may be the source of potentially fatal overt distant metastases in solid tumors even years after primary treatment. MRD can be detected by immunohistochemical methods using antibodies directed against cytokeratins or cell-surface markers or molecular, polymerase chain reaction-based techniques. Among solid tumors, the clinical relevance of MRD has been most extensively studied in breast cancer patients. Recently, the highest level of evidence for the prognostic impact of MRD in primary breast cancer was reached by a pooled analysis comprising more than 4,000 patients, showing poor outcome in patients with MRD at primary therapy. Yet the clinical application of MRD detection is hampered by the lack of a standardized detection assay. Moreover, clinical trial results demonstrating the benefit of a therapeutic intervention determined by bone marrow status are still absent. Recent results suggest that, in addition to its prognostic impact, MRD can be used for therapy monitoring or as a potential therapeutic target after phenotyping of the tumor cells. Persistent MRD after primary treatment may lead to an indication for extended adjuvant therapy. However, until clinically relevant data regarding successful therapy of MRD are available, treatment interventions on the basis of MRD should only be performed within clinical trials.

BM micrometastases and circulating tumor cells in breast cancer patients: where have we been, where are we now and where does the future lie?

Over the past 15 years early tumor cell dissemination has been detected in patients with breast cancer using sensitive immunocytochemical and molecular assays based on the use of MAb and PCR, respectively. Clinical studies involving more than 4,000 breast cancer patients have now demonstrated that the presence of disseminated tumor cells in BM identified with immuncytochemical assays at primary diagnosis is a strong and independent prognostic factor. The published studies for the detection of disseminated tumor cells in BM fulfill the highest level of evidence as prognostic markers in primary breast cancer. In addition, various assays for the detection of circulating tumor cells in the peripheral blood have been developed recently and some studies suggest a potential clinical relevance of this parameter as a prognostic and predictive factor. Comparative analyzes indicate that the prognostic information derived from BM and blood screening seems to be complementary and not redundant. Advanced methods for molecular characterization of single tumor cells and the surrounding environment have been developed lately, and this approach allows new insights into the metastatic cascade and characterization of targets for therapeutic approaches. Taken together, these findings provide the basis for the implementation of disseminated tumor cells in BM or blood as markers for stratification and assessment of therapies in prospective clinical trials. The valuable information derived from these trials should help to improve future treatment of breast cancer patients.

Bone marrow micrometastases and circulating tumor cells: current aspects and future perspectives

Early tumor cell dissemination at the single-cell level can be revealed in patients with breast cancer by using sensitive immunocytochemical and molecular assays. Recent clinical studies involving more than 4000 breast cancer patients demonstrated that the presence of disseminated tumor cells in bone marrow at primary diagnosis is an independent prognostic factor. In addition, various assays for the detection of circulating tumor cells in the peripheral blood have recently been developed and some studies also suggest a potential clinical relevance of this measure. These findings provide the basis for the potential use of disseminated tumor cells in bone marrow or blood as markers for the early assessment of therapeutic response in prospective clinical trials.

Evaluation of bone marrow in breast cancer patients: prediction of clinical outcome and response to therapy

Blood-borne distant metastasis is the leading cause of cancer-related death in breast cancer. The onset of this fundamental process can now be assessed in cancer patients by using ultrasensitive immunocytochemical and molecular assays able to detect even single metastatic cells. To date, clinical studies with large study populations, validated immunoassays, and adequate follow-up time provide evidence for the independent prognostic value of the presence of disseminated tumor cells in the bone marrow. At present, bone marrow evaluation may therefore be considered a diagnostic tool for improved risk assessment with regard to distant relapse and death, especially among potentially curable breast cancer patients. Except for promising pilot studies, no data are available to support the immediate use of bone marrow evaluation for treatment monitoring in order to enable the prediction of response to adjuvant therapy.

Relevance of disseminated tumour cells in blood and bone marrow of patients with solid epithelial tumours in perspective

Currently-used systems to predict prognosis in patients with solid epithelial tumours after surgical resection of the tumour do not give any guarantees for the individual patient. In this respect the clinical relevance of the presence of disseminated tumour cells in blood and bone marrow has been frequently studied. Because of growing awareness that information on merely the presence of disseminated tumour cells is not sufficient for prognostic and therapeutic purposes, attention for characterization of disseminated tumour cells has increased. Numerous reviews have already been published on the detection and clinical relevance of disseminated tumour cells. Therefore, this paper will mainly focus on the biological significance of these cells and discusses the (in)efficiency of the metastatic process, the genotypic and phenotypic characteristics of disseminated tumour cells, and their structure of appearance. Despite the fact that information gained on the several individual aspects is substantial, it did not render any solid solutions for individual patient management yet. Hence, a combined approach of several aspects of disseminated tumour cells together with characteristics and behaviour of the primary tumour is needed to substantially improve our knowledge on the role of disseminated tumour cells in the complex process of tumour metastasis.

The Systemic Progression of Human Cancer: A Focus on the Individual Disseminated Cancer Cell—The Unit of Selection

The metastatic progression of solid tumors is discussed controversially. Because metastasis is usually lethal, it appears as an end point of successive cellular changes. This has led to the prevailing interpretation that genetic changes, in addition to those present in the most advanced clone of the primary tumor, are required to initiate invasion, dissemination, and growth at anatomically distant sites. It has become possible to detect and analyze single disseminated cancer cells at ectopic sites long before metastasis can be diagnosed by standard clinical techniques. Because the finding of single disseminated cancer cells correlates with the subsequent development of distant metastasis, these cells have been identified as the precursors of metastasis. Their direct molecular-genetic characterization, however, shows that dissemination occurs very early in the process of accumulation of genetic changes and suggests that metastases may seldom be derived from the dominant clone of the primary tumor. In contrast, it appears that cancer cell evolution explores a multitude of variant cells from which systemic cancer can develop independently. This review integrates data derived by different approaches into a model of systemic cancer progression.

Patterns of aneusomy for three chromosomes in individual cells from breast cancer tumors

Multi-color fluorescence in situ hybridization (FISH) can determine the changes in the copy numbers of several chromosomes simultaneously and can therefore be used to identify aneusomic patterns in individual cells. Aneusomic patterns may be useful for determining the malignant nature of rare epithelial cells in the blood of cancer patients. Touch preparations from 74 primary breast tumors were evaluated for aneusomy of chromosomes 1, 8 and 17 by tri-color-FISH. In the first part of the analysis, percentages of aneusomy for individual chromosomes and their combinations were determined. In the second part of the analysis, aneusomic patterns for these three chromosomes were analyzed in individual tumor cells and compared to aneusomic patterns observed in leukocytes and in individual cells from benign and normal breast tissue to determine aneusomic patterns indicative of malignancy. Ninety-two percentage of the primary breast carcinomas showed aneusomy for one or more enumerator probes. Comparison with benign breast tissue identified six aneusomic patterns in individual carcinoma cells indicative for malignancy by statistical analysis and not observed in leukocytes. Hence, certain patterns of aneusomy in individual cells involving chromosomes 1, 8 and 17 are indicative of malignancy in individual breast tumor cells and may be useful for determining malignancy of rare epithelial cells in the blood of breast cancer patients.

Multicolor-FICTION: expanding the possibilities of combined morphologic, immunophenotypic, and genetic single cell analyses

Phenotypic and genotypic analyses of cells are increasingly essential for understanding pathogenetic mechanisms as well as for diagnosing and classifying malignancies and other diseases. We report a novel multicolor approach based on the FICTION (fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms) technique, which enables the simultaneous detection of morphological, immunophenotypic, and genetic characteristics of single cells. As prerequisite, multicolor interphase fluorescence in situ hybridization assays for B-cell non-Hodgkin's lymphoma and anaplastic large-cell lymphoma have been developed. These assays allow the simultaneous detection of the most frequent primary chromosomal aberrations in these neoplasms, such as t(8;14), t(11;14), t(14;18), and t(3;14), and the various rearrangements of the ALK gene, respectively. To establish the multicolor FICTION technique, these assays were combined with the immunophenotypic detection of lineage- or tumor-specific antigens, namely CD20 and ALK, respectively. For evaluation of multicolor FICTION experiments, image acquisition was performed by automatic sequential capturing of multiple focal planes. Thus, three-dimensional information was obtained. The multicolor FICTION assays were applied to well-characterized lymphoma samples, proving the performance, validity, and diagnostic power of the technique. Future multicolor FICTION applications include the detection of preneoplastic lesions, early stage and minimal residual diseases, or micrometastases.

Molecular determinants of occult metastatic tumor cells in bone marrow

The success of mammographic screening for breast cancer is that it involves increasingly more patients with small primary tumors formerly thought to have an overall excellent prognosis. Yet, only approximately two thirds of these patients actually have this favorable prognosis, while the remaining third develops metastatic disease. Thus, there is emerging evidence that epithelial tumor cells can disseminate into secondary organs at an earlier stage of primary tumor development than appreciated by current risk classifications. Bone marrow is one of the most prominent secondary organs screened for the presence of disseminated tumor cells. The current data suggest that bone marrow micrometastases represent a selected population of dormant and heterogeneous cancer cells. The analysis of micrometastatic cells opens a new avenue by which to assess the molecular determinants of both early tumor cell dissemination and subsequent outgrowth into overt metastases. Moreover, identifying therapeutic target structures (e.g., HER2/neu), monitoring the elimination of bone marrow micrometastases, and assessing treatment-resistant tumor cell clones might help to understand the current limitations of adjuvant systemic therapy. This review summarizes the current knowledge of the biological characteristics of micrometastatic cancer cells in bone marrow of breast cancer patients.

Characterization of disseminated tumor cells

The most prominent secondary organs screened for the presence of occult disseminated tumor cells are regional lymph nodes and bone marrow. The current data suggest that micrometastatic cells represent a selected population of dormant cancer cells, which still express a considerable degree of heterogeneity. The analysis of micrometastatic cells will open a new avenue to assess the molecular determinants of both early tumor cell dissemination and subsequent outgrowth into overt metastases. Moreover, identifying therapeutic target structures (e.g., HER2), monitoring the elimination of bone marrow micrometastases, and assessing treatment-resistant tumor cell clones may help in understanding the current limitations of adjuvant systemic therapy. This review summarizes the current knowledge on the biological characteristics of micrometastatic cancer cells in bone marrow and lymph nodes of cancer patients.

Recent advances in technologies for the detection of occult metastatic cells in bone marrow of breast cancer patients

Approximately half of breast cancer patients with stage I-III disease will suffer metastatic disease despite resection with tumour-free margins. In 30-40% of these patients, individual carcinoma cells can already be detected at the time of primary therapy in cytological bone marrow preparations using immunocytochemistry. Numerous prospective clinical studies have shown that the presence of occult metastatic cells in bone marrow is prognostically relevant to patient survival. Only a few studies failed to do so, thus stimulating a critical discussion on the methodology and clinical value of bone marrow analysis. The potential for obtaining improved prognostic information on patient outcome, for monitoring tumour cell eradication during adjuvant and palliative systemic therapy, and for specifically targeting tumour biological therapies are intriguing clinical opportunities that may be afforded by bone marrow analysis. Standardized and robust methodology is a prerequisite for clinical application of these techniques, however.

Clinical relevance of occult metastatic cells in the bone marrow of patients with different stages of breast cancer

Data are emerging about the prognostic relevance of occult metastatic cells in the bone marrow of patients with various solid tumors. Discrepancies among different studies on the prognostic relevance of isolated tumor cells may be caused by tumor cell heterogeneity and the use of different immunoassays. There is increasing evidence that validated anticytokeratin antibodies (e.g., A45-B/B3) represent the present standard for the detection of isolated tumor cells. This immunocytochemical assay allows the identification of patients with occult tumor cell dissemination that cannot be identified by conventional screening methods in tumor staging. According to recent studies, these patients are at higher risk for subsequent development of distant metastases and might therefore benefit from early systemic therapy. At advanced stages of the disease, the micrometastatic tumor load after adjuvant therapy, or at the time of emerging recurrences, appears to reflect the tumor's ability to progress. Therapeutic monitoring and cell-cycle independent antibody-based therapy are among possible implications of this new, promising diagnostic tool. The present review also focuses on state of the art, reliable detection methods of occult metastatic cells in the bone marrow of breast cancer patients and on the prognostic relevance of these cells at different stages of the disease.

Prognostic significance of an increased number of micrometastatic tumor cells in the bone marrow of patients with first recurrence of breast carcinoma

BACKGROUND

Using cytokeratin (CK) as a histogenetic marker of epithelial tumor cells in the bone marrow of patients with primary breast carcinoma, a subgroup of patients with decreased survival can be identified. This study was designed to evaluate the frequency and prognostic relevance of such cells in patients with recurrent breast carcinoma.

METHODS

Bone marrow aspirates from 65 patients were analyzed immunocytochemically for the presence of CK positive cells. A quantitative immunoassay with monoclonal anti-CK antibody A45-B/B3 was used and 2 x 10(6) bone marrow cells per patient were evaluated. For prognostic evaluation the authors calculated a cutoff value of micrometastatic tumor cells by analogy to classification and regression tree (CART) analysis. Patients were monitored prospectively for a median of 37 months (range, 11-63 months).

RESULTS

Bone marrow micrometastases were present in 5 of 32 patients (16%) with locoregional recurrence and in 24 of 33 patients (73%) with distant recurrence. The bone marrow status yielded no prognostic indication for patients with locoregional recurrence. In contrast, a cutoff value of 2.5 tumor cells per 1 million bone marrow cells analyzed (2.5 x 10(-6) tumor cells) correlated with a significantly different prognosis for women with distant disease. Patients with metastatic disease and a micrometastatic tumor load of > 2.5 x 10(-6) tumor cells survived for a mean of 6 months (95% confidence interval [95% CI], 2.0-9.1) compared with 17 months (95% CI, 11.6-22.0) for patients with < or = 2.5 x 10(-6) tumor cells (P < 0.0001). Multivariate analysis, allowing for hormone receptor status, disease free interval prior to recurrence, manifestation site of metastases, age, and micrometastases in bone marrow, revealed that bone marrow involvement was an independent risk factor, with a hazard ratio of 7.4 (95% CI, 1.6-13.3) for disease-related death.

CONCLUSIONS

An increased number of micrometastases identified in the bone marrow of patients with metastatic breast carcinoma represents an independent prognostic factor that may influence future therapeutic strategies for patients with metastatic breast carcinoma.

Cytokeratin-positive cells in the bone marrow and survival of patients with stage I, II, or III breast cancer

BACKGROUND

Cytokeratins are specific markers of epithelial cancer cells in bone marrow. We assessed the influence of cytokeratin-positive micrometastases in the bone marrow on the prognosis of women with breast cancer.

METHODS

We obtained bone marrow aspirates from both upper iliac crests of 552 patients with stage I, II, or III breast cancer who underwent complete resection of the tumor and 191 patients with nonmalignant disease. The specimens were stained with the monoclonal antibody A45-B/B3, which binds to an antigen on cytokeratins. The median follow-up was 38 months (range, 10 to 70). The primary end point was survival.

RESULTS

Cytokeratin-positive cells were detected in the bone marrow specimens of 2 of the 191 control patients with nonmalignant conditions (1 percent) and 199 of the 552 patients with breast cancer (36 percent). The presence of occult metastatic cells in bone marrow was unrelated to the presence or absence of lymph-node metastasis (P=0.13). After four years of follow-up, the presence of micrometastases in bone marrow was associated with the occurrence of clinically overt distant metastasis and death from cancer-related causes (P<0.001), but not with locoregional relapse (P=0.77). Of 199 patients with occult metastatic cells, 49 died of cancer, whereas of 353 patients without such cells, 22 died of cancer-related causes (P<0.001). Among the 301 women without lymph-node metastases, 14 of the 100 with bone marrow micrometastases died of cancer-related causes, as did 2 of the 201 without bone marrow micrometastases (P<0.001). The presence of occult metastatic cells in bone marrow, as compared with their absence, was an independent prognostic indicator of the risk of death from cancer (relative risk, 4.17; 95 percent confidence interval, 2.51 to 6.94; P<0.001), after adjustment for the use of systemic adjuvant chemotherapy.

CONCLUSIONS

The presence of occult cytokeratin-positive metastatic cells in bone marrow increases the risk of relapse in patients with stage I, II, or III breast cancer.

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.

Lack of effect of adjuvant chemotherapy on the elimination of single dormant tumor cells in bone marrow of high-risk breast cancer patients

PURPOSE

There is an urgent need for markers that can predict the efficacy of adjuvant chemotherapy in patients with solid tumors. This study was designed to evaluate whether monitoring of micrometastases in bone marrow can predict the response to systemic chemotherapy in breast cancer.

PATIENTS AND METHODS

Bone marrow aspirates of 59 newly diagnosed breast cancer patients with either inflammatory (n = 23) or advanced (> four nodes involved) disease (n = 36) were examined immunocytochemically with the monoclonal anticytokeratin (CK) antibody A45-B/B3 (murine immunoglobulin G(1); Micromet, Munich, Germany) before and after chemotherapy with taxanes and anthracyclines.

RESULTS

Of 59 patients, 29 (49.2%) and 26 (44.1%) presented with CK-positive tumor cells in bone marrow before and after chemotherapy, respectively. After chemotherapy, less than half of the previously CK-positive patients (14 of 29 patients; 48.3%) had a CK-negative bone marrow finding, and 11 (36. 7%) of 30 previously CK-negative patients were CK-positive. At a median follow-up of 19 months (range, 6 to 39 months), Kaplan-Meier analysis of 55 assessable patients revealed a significantly reduced overall survival (P =.011; log-rank test) if CK-positive cells were detected after chemotherapy. In multivariate analysis, the presence of CK-positive tumor cells in bone marrow after chemotherapy was an independent predictor for reduced overall survival (relative risk = 5.0; P =.016).

CONCLUSION

The cytotoxic agents currently used for chemotherapy in high-risk breast cancer patients do not completely eliminate CK-positive tumor cells in bone marrow. The presence of these tumor cells after chemotherapy is associated with poor prognosis. Thus, bone marrow monitoring might help predict the response to systemic chemotherapy.

Sensitive fluorescent in situ hybridisation method for the characterisation of breast cancer cells in bone marrow aspirates

AIM

The presence of malignant cells in the blood and bone marrow of patients with cancer at the time of surgery may be indicative of early relapse. In addition to their numbers, the phenotypes of the micrometastatic cells might be essential in determining whether overt metastases will develop. This study aimed to establish a sensitive method for the detection and characterisation of malignant cells present in bone marrow.

METHODS

In spiking experiments, SKBR3 cells were mixed with mononuclear cells in known proportions to mimic bone marrow samples with micrometastatic cells. Tumour cells were extracted using SAM-M450 Dynabeads coupled to the MOC-31 anti-epithelial antibody, and were further analysed for amplification of erbB2 and int2 by fluorescent in situ hybridisation (FISH). erbB2 and int2 copy numbers were also determined in 15 primary breast cancers, and bone marrow samples from patients with amplification were analysed for micrometastatic cells by immunomagnetic enrichment and FISH.

RESULTS

In model experiments, cells with amplification could be detected in bead selected fractions when ratios of tumour cells (SKBR3) to mononuclear cells were as low as 10:10(7). Among the tumour samples, eight showed increased copy numbers of erbB2 and/or int2, and three of these patients had detectable numbers of tumour cells in their bone marrow: 4000, 540, and 26 tumour cells/10(7) mononuclear cells, respectively. The patient with 540 tumour cells/10(7) mononuclear cells showed high level amplification of erbB2 and suffered from a particularly aggressive disease, whereas the patient with 4000 tumour cells/10(7) mononuclear cells had favourable disease progression.

CONCLUSION

These results demonstrate the feasibility and advantage of combining immunomagnetic selection and FISH characterisation of cancer cells in bone marrow samples. It is possible that molecular characterisation of such cells could provide prognostically valuable information.