Detection and clinical implications of early systemic tumor cell dissemination in breast cancer.

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 using ultrasensitive immunocytochemical and molecular assays able to detect even single metastatic cells. Analyses of bone marrow (BM) samples show that disseminated cells are present in 20-40% of primary breast cancer patients without any clinical or histopathological signs of metastasis. The common homing of circulating breast cancer cells in BM is indicative for systemic tumor cell spread and predictive for growth of overt metastases in relevant organ sites such as bone, lung, or liver. Recent clinical studies involving more than 3000 breast cancer patients demonstrated that the presence of tumor cells in BM at primary diagnosis is an independent prognostic factor for unfavorable clinical outcome. To date, sampling of BM, however, is not a routine procedure in clinical management of breast cancer patients. Therefore, several research groups have developed sensitive assays for detection of circulating tumor cells in peripheral blood. Studies evaluating the clinical relevance of these blood assays are ongoing. Here, we will review the existing tumor cell assays and discuss their current clinical relevance and perspectives for the clinical management of breast cancer patients.     

Current status in human breast cancer micrometastasis

PURPOSE OF REVIEW: Current research and clinical developments on hematogeneous micrometastasis in breast cancer patients are summarized. RECENT FINDINGS: Distant metastasis is the leading cause of cancer-related death in breast cancer and bone marrow is a common homing organ for blood-borne disseminated tumor cells derived from primary breast carcinomas. Sensitive immunocytochemical or molecular assays now allow the detection of single disseminated tumor cells in bone marrow or the peripheral blood at a frequency of 10 and these cells are detected in 10-60% of breast cancer patients without clinical or even histopathologic signs of metastasis. Recently, evidence has emerged that the detection of disseminated tumor cells and circulating tumor cells may provide important prognostic information, and in particular might help to monitor efficacy of therapy. Moreover, the characterization of disseminated tumor cells/circulating tumor cells has shed new light on the complex process underlying early tumor cell dissemination and metastatic progression in cancer patients. SUMMARY: Research on disseminated tumor cells/circulating tumor cells will help to identify novel targets for biological therapies aimed at preventing metastatic relapse and to monitor the efficacy of these therapies. In particular, understanding tumor dormancy and identifying metastatic stem cells might result in the development of new concepts for antimetastatic therapies.     

Recent translational research: circulating tumor cells in breast cancer patients

In breast cancer patients, hematogenous tumor cell dissemination can be detected, even at the single cell level, by applying immunocytochemical and molecular assays. Various methods for the detection of circulating tumor cells in the peripheral blood have been described. Results from recently reported studies suggest that circulating tumor cell levels may serve as a prognostic marker and for the early assessment of therapeutic response in patients with metastatic breast cancer. However, in early-stage breast cancer, the impact of circulating tumor cells is less well established than the presence of disseminated tumor cells in bone marrow; several clinical studies have demonstrated that cells of the latter type are an independent prognostic factor at primary diagnosis. In this article we briefly summarize recent studies examining the presence of circulating tumor cells in the blood and discuss further clinical applications.     

Disseminated tumor cells in breast cancer: detection, characterization and clinical relevance

Hematogenous distant metastasis is the leading cause of cancer-related death in breast cancer and other solid tumors. By applying sensitive immunocytochemical or molecular assays, disseminated tumor cells (DTCs) in bone marrow can be detected in 20-40% of breast cancer patients without any clinical or even histopathological signs of metastasis. The detection of DTCs provides prognostic information and might help to identify patients who need adjuvant therapy, and to monitor the efficacy of adjuvant therapy. Within the last few years, various efforts have led to an increased sensitivity in the detection of DTC. This review will summarize the most important methods for DTC detection in bone marrow and for circulating tumor cells in the blood of breast cancer patients, the clinical relevance of DTCs and, finally, provide an outlook on clinical implications.     

Significance of micrometastasis in bone marrow and blood of operable breast cancer patients: research tool or clinical application?

Approximately 25% of breast cancer patients without lymph node metastases develop systemic relapse. A growing body of data supports the notion that hematogenous dissemination of breast cancer cells occurs independently of lymphatic spread of disease; however, current clinical practice does not involve routine analysis of circulating or disseminated cells. Recent studies have documented that both circulating tumor cells (CTCs) within the blood and disseminated tumor cells (DTCs) in bone marrow can be identified using a variety of techniques. It is now clear that the presence of DTCs correlates with subsequent development of clinically evident bone metastases, and a worse outcome from breast cancer. While there are data identifying prognostic significance of CTCs in patients with metastatic breast cancer, there are few data regarding CTCs in operable patients. Factors such as presence of a cancer stem cell phenotype and/or certain microenvironmental conditions are involved in the establishment of distant metastases from a primary breast cancer, emphasizing the need for further studies within this area. The purpose of this report is to review the data regarding CTCs and DTCs in patients with operable breast cancer.     

Significance of micrometastasis in bone marrow and blood of operable breast cancer patients: research tool or clinical application?

Approximately 25% of breast cancer patients without lymph node metastases develop systemic relapse. A growing body of data supports the notion that hematogenous dissemination of breast cancer cells occurs independently of lymphatic spread of disease; however, current clinical practice does not involve routine analysis of circulating or disseminated cells. Recent studies have documented that both circulating tumor cells (CTCs) within the blood and disseminated tumor cells (DTCs) in bone marrow can be identified using a variety of techniques. It is now clear that the presence of DTCs correlates with subsequent development of clinically evident bone metastases, and a worse outcome from breast cancer. While there are data identifying prognostic significance of CTCs in patients with metastatic breast cancer, there are few data regarding CTCs in operable patients. Factors such as presence of a cancer stem cell phenotype and/or certain microenvironmental conditions are involved in the establishment of distant metastases from a primary breast cancer, emphasizing the need for further studies within this area. The purpose of this report is to review the data regarding CTCs and DTCs in patients with operable breast cancer.     

Clinical relevance and biology of circulating tumor cells

Most breast cancer patients die due to metastases, and the early onset of this multistep process is usually missed by current tumor staging modalities. Therefore, ultrasensitive techniques have been developed to enable the enrichment, detection, isolation and characterization of disseminated tumor cells in bone marrow and circulating tumor cells in the peripheral blood of cancer patients. There is increasing evidence that the presence of these cells is associated with an unfavorable prognosis related to metastatic progression in the bone and other organs. This review focuses on investigations regarding the biology and clinical relevance of circulating tumor cells in breast cancer.     

Role of circulating tumor cells and disseminated tumor cells in primary breast cancer

Metastasis remains a main cause of death in patients with breast cancer regardless of improvements in treatment. Prospective clinical studies of this minimal residual disease have shown disseminated tumor cells (DTCs) in bone marrow and circulating tumor cells (CTCs) in peripheral blood, neither of which can be detected by conventional imaging, to be prognostic and predictive markers for responsive treatment in patients with metastatic breast cancer. However, the guideline from the American Society of Clinical Oncology does not recommend measuring CTCs for clinical decisions because of a lack of evidence for an established, sound methodology and with proven clinical relevance. The Southwest Oncology Group trial S0500 to validate the clinical relevance of CTCs for treatment decisions in patients with metastatic breast cancer is ongoing. In patients with primary breast cancer, the low detection rate of CTCs has been overcome by recent advances in technology. Although generally DTCs were more detectable than CTCs and the association between presence of DTCs and poor prognosis has been shown, the invasiveness of sample collection of DTCs from bone marrow is generally hard for patients to accept. In this review, we concentrate on the question of whether we need to consider CTCs and DTCs in the management of primary breast cancer on the basis of the evidence of the clinical relevance of CTCs and DTCs. The promising role of the molecular characterization of CTCs, which does have the potential for being a predictor for tumor behavior and development, is suggested as a new targeting strategy.     

Clinical Relevance of Micrometastatic Disease in Patients with Solid Tumors

Distant metastases are the main cause of cancer-related death. The onset of the metastatic process can now be assessed in cancer patients by the use of sensitive immunocytochemical and molecular methods which allow the identification of single disseminated carcinoma cells or small tumor cell clusters in regional lymph nodes, peripheral blood, or distant organs. Among the distant organs, bone marrow is a common homing organ for disseminated cancer cells derived from various primary sites, and the presence of these cells predicts the occurrence of overt metastases in bone and other organs. The bone marrow is, therefore, a very useful indicator organ for the presence of disseminated cancer cells. The current assays for detection of micrometastatic tumor cells may be used to improve tumor staging with potential consequences for adjuvant therapy. Another promising clinical application is monitoring the response to adjuvant therapies, which, at present, can only be assessed retrospectively after an extended period of clinical follow-up. Moreover, tools recently established in several laboratories allow further insights into the phenotype and genotype of micrometastases. The available data indicate that micrometastatic cells represent a selected population of cancer cells that express a considerable degree of heterogeneity with regard to chromosomal aberrations and phenotypic properties. Identification of the molecular determinants of micrometastatic cells may help to design new strategies to detect and eliminate minimal residual cancer. The present review summarizes the current state of research on micrometastatic disease in patients with solid tumors.     

Molecular detection of cancer cells in bone marrow and peripheral blood of patients with operable breast cancer. Comparison of CK19, MUC1 and CEA using RT-PCR

We have compared three different RT-PCR procedures to measure cytokeratin 19 (CK19), carcinoembryonic antigen (CEA) and mucin MUC1 gene expression in order to determine their diagnostic value in detecting tumour cells in bone marrow aspirates of patients with operable breast cancer. In an experimental model, the best sensitivity was observed for CK19 and MUC1 RT-PCR assays, although only the CEA and CK19 assays showed good specificity. The study of 42 patients showed that a 'CK19 positive/CEA positive' RT-PCR assay in bone marrow correlated positively with a positive axillary lymph node status (N(0) versus N(1-3), P<0.05). Both assays were also positive in 17% of node negative patients. RT-PCR assays were more sensitive in bone marrow than in peripheral blood. Our results suggest that CK19 and CEA RT-PCR assays are powerful methods for detecting disseminated breast cancer cells. A larger study with long-term follow-up is required in order to clarify their clinical usefulness.     

Detection, characterization and tumorigenicity of disseminated tumor cells in human bone marrow

Monoclonal antibodies have been used to detect tumor cells in bone marrow of patients with neuroblastoma, breast cancer, small cell lung cancer, prostatic cancer and gastrointestinal carcinoma. By comparative analysis immunocytology proved to be more sensitive than conventional cytology and histology and had the additional advantage of specificity. A positive correlation exists between the presence of tumor cells in bone marrow and the extent of the primary tumor. The proliferative potential of the micrometastatic cells was assessed by characterization of EGF and transferrin receptors, tumorigenicity was shown by xenotransplantation experiments in nu/nu mice in a few instances. First follow-up studies indicate that the presence of disseminated tumor cells in bone marrow can be taken as predicting the subsequent development of overt metastasis.     

Optimisation of the RT-PCR detection of immunomagnetically enriched carcinoma cells

Background  

Immunomagnetic enrichment followed by RT-PCR (immunobead RT-PCR) is an efficient methodology to identify disseminated carcinoma cells in the blood and bone marrow. The RT-PCR assays must be both specific for the tumor cells and sufficiently sensitive to enable detection of single tumor cells. We have developed a method to test RT-PCR assays for any cancer. This has been investigated using a panel of RT-PCR markers suitable for the detection of breast cancer cells.     

Minimal residual disease and circulating tumor cells in breast cancer

Tumor cell dissemination in bone marrow or other organs is thought to represent an important step in the metastatic process. The detection of bone marrow disseminated tumor cells is associated with worse outcome in early breast cancer. Moreover, the detection of peripheral blood circulating tumor cells is an adverse prognostic factor in metastatic breast cancer, and emerging data suggest that this is also true for early disease. Beyond enumeration, the characterization of these cells has the potential to improve risk assessment, treatment selection and monitoring, and the development of novel therapeutic agents, and to advance our understanding of the biology of metastasis.     

UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 6 (ppGalNAc-T6) mRNA as a potential new marker for detection of bone marrow-disseminated breast cancer cells

The evaluation of disseminated epithelial tumor cells in patients with early stages of breast cancer has generated considerable interest because of its potential association with poor clinical outcome. Considering that O-glycosylation pathways are frequently altered in breast cancer, we performed this work to evaluate the potential usefulness of UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts) (a family of glycosyltransferases which catalyze the first key step of mucin-type O-glycosylation) to detect disseminated cells in bone marrow samples from patients with operable breast cancer. Using RT-PCR assays, we studied the gene expression of 9 enzymes (ppGalNAc-T1-T9). Among the ppGalNAc-Ts expressed by breast tumors (-T1, -T2, -T3, -T6 and -T7), the best specificity (negative results on all PBMN cell samples from healthy donors) was shown for ppGalNAc-T6. Thus, we selected this enzyme as a target gene for further evaluation. ppGalNAc-T6 mRNA was found in 22/25 (88%) breast cancer samples, in all 3 human breast cancer cell lines evaluated (MCF-7, ZR75-1 and T47D), in 1/30 (3%) PBMN cells and 0/19 bone marrow samples obtained from patients without cancer. Using this method, 22/61 (36%) patients with breast cancer, who underwent curative surgery, showed positive ppGalNAc-T6 mRNA in bone marrow aspirates obtained prior to surgery, including 11/34 patients with stage-I or -II, without histopathological lymph node involvement. In a preliminary follow-up evaluation, 19/61 patients experienced recurrence of the disease. ppGalNAc-T6 was positive in 11/19 (57.9%) of these patients. Interestingly, in the group of patients without lymph node involvement, disease recurrence was observed in 54.5% of patients who showed ppGalNAc-T6 mRNA-positive bone marrow aspirates and only in 4.3% of patients when ppGalNAc-T6 was negative (p = 0.014). These results indicate that ppGalNAc-T6 mRNA could be a specific marker applicable to the molecular diagnosis of breast cancer cells dissemination.     

Primary systemic therapy does not eradicate disseminated tumor cells in breast cancer patients

Introduction The presence of disseminated tumor cells in the bone marrow of breast cancer patients has proven to be an independent prognostic factor. The aim of this study was to investigate the status of tumor cell dissemination after primary systemic therapy in relation to therapy response. Methods Bone marrow aspirates were obtained from 120 patients after completion of primary systemic therapy. Disseminated tumor cells were detected by immunocytochemistry using the APAAP method. Bone marrow status was correlated with clinicopathological factors as well as tumor response to primary systemic therapy. Results Sixty out of 120 patients had disseminated tumor cells in their bone marrow aspirates (50%). Response rates were 18% for pathologic complete remission, 52% for partial remission, 28% for no change and 3% for progression. Despite complete remission, 36% of these patients were bone marrow positive. In the partial remission group, the positivity rate was 48%. About 61% of patients with stable disease had disseminated tumor cells in their bone marrow. A trend to higher positivity rates was observed in the poor responder group compared to responders (61% vs. 38%, P = 0.1). Conclusion Primary systemic therapy does not completely eradicate disseminated tumor cells in the bone marrow of breast cancer patients. The biological role of persistent disseminated tumor cells needs to be further investigated to optimize current and future therapeutic strategies.     

乳腺癌患者骨髓GalNAcT mRNA的检测及其临床意义

目的：研究乳腺癌患者骨髓β1，4-N-乙酰半乳糖胺转移酶（GalNAcT）mRNA的表达，探讨其作为乳腺癌骨髓微转移检测指标对临床的应用价值。方法：对40例乳腺癌患者的骨髓及外周血采用巢式RT—PCR方法检测GalNAcT mRNA表达，同时以免疫组化的方法检测骨髓标本中细胞角蛋白（cytokeratin，CK）的表达。结果：40例患者骨髓中GalNAcT mRNA阳性表达17例（42．5％），外周血阳性表达7例（17．5％）；10例血液系统良性疾病患者骨髓和15例健康志愿者外周血中GaINAcT mRNA均为阴性。免疫组化结果显示：40例乳腺癌骨髓中有11例（27．5％）CK阳性，其GalNAcT mRNA都阳性；有6例（15．0％）CK阴性而GalNAcT mRNA阳性。结论：RT—PCR和免疫组化都是检测乳腺癌患者骨髓微转移的可靠的方法，但前者的敏感性高于后者。GalNAcT mRNA可作为一种新的肿瘤标志物来检测乳腺癌患者骨髓微转移。     

Cyclooxygenase-2 expression in primary breast cancers predicts dissemination of cancer cells to the bone marrow

Purpose Cyclooxygenase-2 (COX2) plays a role in breast cancer progression at various stages starting from pre-malignant phenotype to clinical metastasis. Breast cancer metastasizes commonly to the bone and preclinical studies suggest an involvement of COX2 in this process. Detection of disseminated tumor cells in the bone marrow of patients at the time of surgery correlates with the subsequent development of clinical bone metastasis. Therefore, to investigate whether COX2 is important for breast cancer metastasis in humans, we analyzed COX2 protein expression by immunostaining of primary tumors from 112 operable stages I, II, or III patients and determined its correlation with bone marrow micrometastasis (BMM). Methods We detected COX2 protein in primary tumors by immunostaining with a monoclonal antibody, and tumor cells present in the bone marrow by immunostaining for epithelial cytokeratins and by morphological criteria. Results COX2 expression in primary breast cancer correlated with BMM in a highly statistically significant manner (P = 0.006). Our statistical analyses of correlations of the COX2 positivity in primary tumor with other clinically relevant indicators revealed that COX2 positivity correlates with high nuclear grade (P = 0.0004). Furthermore, we were able to detect COX2 protein in BMM by immunostaining. Conclusions These studies indicate that COX2 produced in primary breast cancer cells may be vital to the initial development of BMM that may subsequently lead to osteolytic bone metastases in patients with breast cancer, and that COX2 inhibitors may be useful in halting this process.