Detection of circulating tumour cells with the magnetic activated cell sorter

Simultaneously targeting cancer-associated fibroblasts and angiogenic vessel as a treatment for TNBC

Fibrotic tumor stroma plays an important role in facilitating triple-negative breast cancer (TNBC) progression and chemotherapeutic resistance. We previously reported a rationally designed protein (ProAgio) that targets integrin αvβ3 at a novel site. ProAgio induces apoptosis via the integrin. Cancer-associated fibroblasts (CAFs) and angiogenic endothelial cells (aECs) in TNBC tumor express high levels of integrin αvβ3. ProAgio effectively induces apoptosis in CAFs and aECs. The depletion of CAFs by ProAgio reduces intratumoral collagen and decreases growth factors released from CAFs in the tumor, resulting in decreased cancer cell proliferation and apoptotic resistance. ProAgio also eliminates leaky tumor angiogenic vessels, which consequently reduces tumor hypoxia and improves drug delivery. The depletion of CAFs and reduction in hypoxia by ProAgio decreases lysyl oxidase (LOX) secretion, which may play a role in the reduction of metastasis. ProAgio stand-alone or in combination with a chemotherapeutic agent provides survival benefit in TNBC murine models, highlighting the therapeutic potential of ProAgio as a treatment strategy.

Circulating Tumor Cells in Gastrointestinal Cancers: Current Status and Future Perspectives

Circulating tumor cells (CTCs), which are now defined as the "break away" cancer cells that derive from primary- or metastatic-tumor sites and present in the bloodstream, are considered to be the precursors of metastases. Considering the key role of CTCs in cancer progression, researchers are committed to analyze them in the past decades and many technologies have been proposed for achieving CTCs isolation and characterization with highly sensitivity and specificity until now. On this basis, clinicians gradually realize the clinical values of CTCs' detection through various clinical studies. As a "liquid biopsy," CTCs' detection and measurement can supply important information for predicting patient's survival, monitoring of response/resistance, assessment of minimal residual disease, evaluating distant metastasis, and sometimes, customizing therapy choices. Nowadays, eliminating CTCs of the blood circulation has been regarded as a promising method to prevent tumor metastasis. However, research on CTCs still faces many challenges. Herein, we present an overview to discuss the current concept of CTCs, summarize the available techniques for CTCs detection, and provide an update on the clinical significance of CTCs in gastrointestinal malignancies, especially focus on gastric and colorectal cancer.

Affinity Versus Label-Free Isolation of Circulating Tumor Cells: Who Wins?

The study of circulating tumor cells (CTCs) has been made possible by many technological advances in their isolation. Their isolation has seen many fronts, but each technology brings forth a new set of challenges to overcome. Microfluidics has been a key player in the capture of CTCs and their downstream analysis, with the aim of shedding light into their clinical application in cancer and metastasis. Researchers have taken diverging paths to isolate such cells from blood, ranging from affinity-based isolation targeting surface antigens expressed on CTCs, to label-free isolation taking advantage of the size differences between CTCs and other blood cells. For both major groups, many microfluidic technologies have reported high sensitivity and specificity for capturing CTCs. However, the question remains as to the superiority among these two isolation techniques, specifically to identify different CTC populations. This review highlights the key aspects of affinity and label-free microfluidic CTC technologies, and discusses which of these two would be the highest benefactor for the study of CTCs.

A combined micromagnetic-microfluidic device for rapid capture and culture of rare circulating tumor cells

Here we describe a combined microfluidic-micromagnetic cell separation device that has been developed to isolate, detect and culture circulating tumor cells (CTCs) from whole blood, and demonstrate its utility using blood from mammary cancer-bearing mice. The device was fabricated from polydimethylsiloxane and contains a microfluidic architecture with a main channel and redundant 'double collection' channel lined by two rows of dead-end side chambers for tumor cell collection. The microdevice design was optimized using computational simulation to determine dimensions, magnetic forces and flow rates for cell isolation using epithelial cell adhesion molecule (EpCAM) antibody-coated magnetic microbeads (2.8 μm diameter). Using this device, isolation efficiencies increased in a linear manner and reached efficiencies close to 90% when only 2 to 80 breast cancer cells were spiked into a small volume (1.0 mL) of blood taken from wild type mice. The high sensitivity visualization capabilities of the device also allowed detection of a single cell within one of its dead-end side chambers. When blood was removed from FVB C3(1)-SV40 T-antigen mammary tumor-bearing transgenic mice at different stages of tumor progression, cells isolated in the device using anti-EpCAM-beads and magnetically collected within the dead-end side chambers, also stained positive for pan-cytokeratin-FITC and DAPI, negative for CD45-PerCP, and expressed SV40 large T antigen, thus confirming their identity as CTCs. Using this isolation approach, we detected a time-dependent rise in the number of CTCs in blood of female transgenic mice, with a dramatic increase in the numbers of metastatic tumor cells appearing in the blood after 20 weeks when tumors transition to invasive carcinoma and exhibit increased growth of metastases in this model. Importantly, in contrast to previously described CTC isolation methods, breast tumor cells collected from a small volume of blood removed from a breast tumor-bearing animal remain viable and they can be easily removed from these devices and expanded in culture for additional analytical studies or potential drug sensitivity testing.

Clinically relevant microfluidic magnetophoretic isolation of rare-cell populations for diagnostic and therapeutic monitoring applications

Cells of biomedical interest are, despite their functional significance, often present in very small numbers. Therefore the analysis and isolation of previously inaccessible rare cells, such as peripheral hematopoietic stem cells, endothelial progenitor cells, or circulating tumor cells, require efficient, sensitive, and specific procedures that do not compromise the viability of the cells. The current study builds on previous work on a rationally designed microfluidic magnetophoretic cell separation platform capable of throughputs of 240 μL min(-1). Proof-of-concept was first conducted using MCF-7 (1-1000 total cells) as the target rare cell spiked into high concentrations of Raji B-lymphocyte nontarget cells (~10(6) total cells). These experiments lead to the establishment of a magnet-based separation for the isolation of 50 MCF-7 cells directly from whole blood. Results show an efficiency of collection greater than 85%, with a purity of over 90%. Next, resident endothelial progenitor cells and hematopoietic stem cells are directly isolated from whole human blood in a rapid and efficient fashion (>96%). Both cell populations could be simultaneously isolated and, via immunofluorescent staining, individually identified and enumerated. Overall, the presented device illustrates a viable separation platform for high purity, efficient, and rapid collection of rare cell populations directly from whole blood samples.

Computational design optimization for microfluidic magnetophoresis

Current macro- and microfluidic approaches for the isolation of mammalian cells are limited in both efficiency and purity. In order to design a robust platform for the enumeration of a target cell population, high collection efficiencies are required. Additionally, the ability to isolate pure populations with minimal biological perturbation and efficient off-chip recovery will enable subcellular analyses of these cells for applications in personalized medicine. Here, a rational design approach for a simple and efficient device that isolates target cell populations via magnetic tagging is presented. In this work, two magnetophoretic microfluidic device designs are described, with optimized dimensions and operating conditions determined from a force balance equation that considers two dominant and opposing driving forces exerted on a magnetic-particle-tagged cell, namely, magnetic and viscous drag. Quantitative design criteria for an electromagnetic field displacement-based approach are presented, wherein target cells labeled with commercial magnetic microparticles flowing in a central sample stream are shifted laterally into a collection stream. Furthermore, the final device design is constrained to fit on standard rectangular glass coverslip (60 (L)×24 (W)×0.15 (H) mm(3)) to accommodate small sample volume and point-of-care design considerations. The anticipated performance of the device is examined via a parametric analysis of several key variables within the model. It is observed that minimal currents (<500 mA) are required to generate magnetic fields sufficient to separate cells from the sample streams flowing at rate as high as 7 ml∕h, comparable to the performance of current state-of-the-art magnet-activated cell sorting systems currently used in clinical settings. Experimental validation of the presented model illustrates that a device designed according to the derived rational optimization can effectively isolate (∼100%) a magnetic-particle-tagged cell population from a homogeneous suspension even in a low abundance. Overall, this design analysis provides a rational basis to select the operating conditions, including chamber and wire geometry, flow rates, and applied currents, for a magnetic-microfluidic cell separation device.

The clinical significance of circulating tumor cells in the peripheral blood

Tumors launch malignant cells into the circulation continuously. In early stages, the immune surveillance system eliminates these cells from the circulation, but at later times they may persist longer and be detected. The first recorded evidence of the presence of circulating tumor cells in the peripheral blood of cancer patients was documented in 1869. Now, modern molecular biologic and cell sorting techniques make their detection and characterization more practicable. This review will consider the methods currently available for their detection and characterization, and the clinical implications of their presence in various malignant conditions.

Differential interaction of magnetic nanoparticles with tumor cells and peripheral blood cells

PURPOSE

The separation of tumor cells from healthy cells is a vital problem in oncology and hematology, especially from peripheral blood. Magnetic assisted cell sorting (MACS) is a possibility to fulfill these needs.

METHODS

Tumor cell lines and leukocytes from peripheral blood were incubated with carboxymethyl dextran-coated magnetic nanoparticles under various conditions and separated by MACS.

RESULTS

We studied the interaction of magnetic nanoparticles devoid of antibodies with healthy and tumor cells. The magnetic nanoparticles interact with tumor cells and leukocytes and are located predominantly within the cell cytoplasm. Incubation of cell culture cells with magnetic nanoparticles led to a labeling of these cells without reduced biological properties for at least 14 days. The interaction of the magnetic nanoparticles with cells depends on several factors. The ionic strength (osmolality) of the solvent plays an important role. We could show that an increase in osmolality led to a dramatic reduction of labeled leukocytes. Tumor cells, however, are mildly affected. This could be detected not only in pure cultures of tumor cells or leukocytes but also in mixed cell populations.

CONCLUSION

This observation gives us the opportunity to selectively label and separate tumor cells but not leukocytes from the peripheral blood.

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.

Evaluation of multiparameter flow cytometry for the detection of breast cancer tumor cells in blood samples

We comparatively evaluated different cytokeratin (CK) reagents analyzed by flow cytometry (FCM) for the identification of the best combination of DNA/CK staining for detecting minimal numbers of breast cancer cells in peripheral blood (PB). In 59 primary breast cancer tumors, we comparatively analyzed the reactivity for up to 6 different anti-CK reagents using multiparameter FCM: anti-CK7, anti-CK20, anti-pan-CK, anti-CK8/CK18, anti-CK8, and anti-CK18. Afterward, dilutional experiments of Michigan Cancer Foundation (MCF)7 breast cancer cells in PB were performed, and the sensitivity of a DNA/CK18 staining was evaluated. Our results showed that anti-CK18 reagents were those providing the brightest and more sensitive staining for primary breast cancer tumor cells by FCM. Dilutional experiments of MCF cells in PB showed that the DNA/anti-CK18 double staining was highly specific for the identification of epithelial cells; its sensitivity ranged between 10(-6) and 10(-7) (detection of 1 tumor cell among 10(6) to 10(7) nucleated blood cells). Combined assessment of DNA cell contents and reactivity for CK18 by FCM is a sensitive method for the specific identification of breast cancer cells in PB.

Free colorectal cancer cells on the peritoneal surface: correlation with pathologic variables and survival

BACKGROUND

Clinicopathologic staging of colorectal cancer remains the best predictor of survival. Prognostication for an individual with colorectal cancer remains elusive. This study was designed to investigate the incidence of free surface colorectal cancer cells detected by cytology during elective open curative resection, to correlate their presence with particular clinicopathologic variables and determine whether their presence was predictive of cancer-specific survival.

METHODS

Over a six-year period in one institution, all elective colon and intraperitoneal rectal cancer specimens were assessed during primary resection for the presence of free colorectal cancer cells by means of a simple and tested specimen imprint cytology methodology. Clinicopathologic variables were assessed prospectively and blinded to cytology results. All patients were followed up routinely until death and if the patient was not seen within the last six months, information was obtained from the New South Wales Registry of Births, Deaths and Marriages in Australia.

RESULTS

Overall, 26 of 281 (9.25 percent) colorectal cancers had positive cytology for cancer cells on the peritoneal surface of the bowel. Poorly differentiated tumors were significantly associated with positive cytology. Tumor penetration, presence of vascular or neural invasion, mucinous characteristics, lymph node status, and operative procedure performed were not statistically significant predictors of positive cytology. Overall, 43 of the 281 patients (15.3 percent) died during the mean follow-up period of 49.2 months from cancer-related deaths. Of these patients, 8 had positive cytology and 35 had negative cytology results. Cancer-specific survival assessed with the log-rank test was significantly associated with positive cytology in univariate (P = 0.008) and multivariate analysis (P < 0.001).

CONCLUSION

In this study, the presence of free surface colorectal cancer cells has been shown to be predictive of survival and is independent of direct peritoneal invasion and lymph node status. Thus, further assessment of this simple prognostic variable is warranted and selection of patients with positive cytology for possible adjuvant therapies may be beneficial.

Selection, proliferation and differentiation of bone marrow-derived liver stem cells with a culture system containing cholestatic serum in vitro

AIM: To explore the feasibility of direct separation, selective proliferation and differentiation of the bone marrow-derived liver stem cells (BDLSC) from bone marrow cells with a culture system containing cholestatic serum in vitro.

METHODS: Whole bone marrow cells of rats cultured in routine medium were replaced with conditioning selection media containing 20 mL/L, 50 mL/L, 70 mL/L, and 100 mL/L cholestatic sera, respectively, after they attached to the plates. The optimal concentration of cholestatic serum was determined according to the outcome of the selected cultures. Then the selected BDLSC were induced to proliferate and differentiate with the addition of hepatocyte growth factor (HGF). The morphology and phenotypic markers of BDLSC were characterized using immunohistochemistry, RT-PCR and electron microscopy. The metabolic functions of differentiated cells were also determined by glycogen staining and urea assay.

RESULTS: Bone marrow cells formed fibroblast-like but not hepatocyte-like colonies in the presence of 20 mL/L cholestatic serum. In 70 mL/L cholestatic serum, BDLSC colonies could be selected but could not maintain good growth status. In 100 mL/L cholestatic serum, all of the bone marrow cells were unable to survive. A 50 mL/L cholestatic serum was the optimal concentration for the selection of BDLSC at which BDLSC could survive while the other populations of the bone marrow cells could not. The selected BDLSC proliferated and differentiated after HGF was added. Hepatocyte-like colony-forming units (H-CFU) then were formed. H-CFU expressed markers of embryonic hepatocytes (AFP, albumin and cytokeratin 8/18), biliary cells (cytokeratin 19), hepatocyte functional proteins (transthyretin and cytochrome P450-2b1), and hepatocyte nuclear factors (HNF-1α and HNF-3β). They also had glycogen storage and urea synthesis functions, two of the critical features of hepatocytes.

CONCLUSION: The selected medium containing cholestatic serum can select BDLSC from whole bone marrow cells. It will be a new way to provide a readily available alternate source of cells for clinical hepatocyte therapy.

Carcinoembryonic antigen mRNA in the mesenteric vein is not a predictor of hepatic metastasis in patients with resectable colorectal cancer: a long-term study

PURPOSE

The clinical value of carcinoembryonic antigen messenger ribonucleic acid in the draining venous blood has been controversial because of short observation period. The authors prospectively investigated the clinical significance of detection of carcinoembryonic antigen messenger ribonucleic acid in the draining venous blood to predict hepatic metastases in patients with resectable colorectal cancer.

METHODS

Drainage venous blood from 80 patients who underwent curative resections for colorectal cancer were obtained immediately before surgery to determine the presence of cancer cells by means of reverse transcription polymerase chain reaction.

RESULTS

After an average follow-up period of 52.1 months, 7 of the 35 patients (20 percent) with positive carcinoembryonic antigen messenger ribonucleic acid had hepatic metastases, whereas 2 of the 45 patients (4.5 percent) with negative carcinoembryonic antigen messenger ribonucleic acid had hepatic metastases. The cumulative probability of hepatic metastatic recurrence rate differed significantly between two patient groups with positive or negative carcinoembryonic antigen messenger ribonucleic acid expression in the drainage vein (log-rank, 4.900; P = 0.0269). However, 28 of the 35 patients (80 percent) with positive carcinoembryonic antigen messenger ribonucleic acid did not have hepatic metastases. Additionally, Cox proportional hazards models identified the presence of lymph node metastases as the only independent predictor of hepatic metastatic recurrence.

CONCLUSIONS

This study failed to demonstrate the high predictive value of carcinoembryonic antigen messenger ribonucleic acid detection in the draining venous blood for the development of hepatic metastases. However, the authors demonstrated that the presence of cancer cells in the draining venous blood was the essential and initial step to the development of hepatic metastasis.

Characterization of antibody binding to three cancer-related antigens using flow cytometry and cell tracking velocimetry

Proper antibody labeling is a fundamental step in the positive selection/isolation of rare cancer cells using immunomagnetic cell separation technology. Using either a two-step or single-step labeling protocol, we examined a combination of six different antibodies specific for three different antigens (epithelial specific antigen, epithelial membrane antigen, and HER-2/Neu) on two different breast cancer cell lines (HCC1954 and MCF-7). When a two-step labeling protocol was used (i.e., anti-surface marker-fluoroscein-isothiocyanate [FITC] [primary Ab], anti-FITC magnetic colloid [secondary Ab]) saturation of the primary antibody was determined using fluorescence intensity measurements from flow cytometry (FCM). The saturation of the secondary antibody (or saturation of a single-step labeling) was determined using magnetophoretic mobility measurements from cell tracking velocimetry (CTV). When the maximum magnetophoretic mobility was the primary objective, our results demonstrate that the quantities necessary for antibody saturation with respect to fluorescence intensity were generally higher than those recommended by the manufacturer. The results demonstrate that magnetophoretic mobility varies depending on the types of cell lines, primary antibodies, and concentration of secondary magnetic colloid-conjugated antibody. It is concluded that saturation studies are a vital preparatory step in any separation method involving antibody labeling, especially those that require the specificity of rare cell detection.

Prognostic value of postoperative detection of blood circulating tumor cells in patients with colorectal cancer operated on for cure

OBJECTIVE

To assess whether postoperative detection of circulating tumor cells in peripheral blood influenced the prognosis of patients with colorectal cancer after radical surgery.

SUMMARY BACKGROUND DATA

In a previous study, the authors demonstrated that baseline detection of blood circulating tumor cells does not have prognostic significance in patients with colorectal cancer. However, surgical procedures may increase tumor cell detachment and mobilization.

METHODS

Sixty-six patients with histologically confirmed colorectal cancer operated on for cure were included in this study. Circulating tumor cells were detected by means of reverse transcriptase-polymerase chain reaction targeting to carcinoembryonic antigen messenger RNA in peripheral blood samples obtained 24 hours after surgery. Endpoints of the study were tumor recurrence, overall survival, and cancer-related survival. Univariate (Kaplan-Meier method) and multivariate (Cox regression model) analyses were performed.

RESULTS

After a median follow-up of 36 months, 15 patients (23%) had tumor relapse and 14 had died (21%), 8 of them from a cancer-related cause. Cox regression analysis identified lymph node metastases and gender as independent predictors of tumor recurrence and cancer-related survival, whereas overall survival was dependent on the degree of differentiation of the primary tumor. More importantly, the presence of circulating tumor cells after surgery had no prognostic influence on tumor recurrence, overall survival, or cancer-related survival.

CONCLUSIONS

Postoperative detection of blood circulating tumor cells had no prognostic significance in patients with colorectal cancer operated on for cure.

Immunomagnetic enrichment and detection of isolated tumor cells in bone marrow of patients with epithelial malignancies

The detection of isolated tumor cells (ITC) in the bone marrow of patients with epithelial malignancies is an independant prognostic factor for several entities as breast cancer, colorectal cancer or non-small lung cancer. However, with conventional immunocytology using Ficoll density gradient and APAAP staining, only a small proportion of the bone marrow samples can be scanned for cytokeratin-positive (CK+) cells. To improve detection rates, we evaluated the enrichment of ITC by magnetic activated cell sorting (MACS) compared to regularly stained cytospins. Recovery experiments with a CK+ breast cancer cell line (SKBR3) were performed to calculate the MACS enrichment rate. Bone marrow was obtained by aspiration from 20 patients with carcinomas of epithelial origin and from 17 controls. ITC were enriched and stained with magnetically labeled CAM 5.2 antibodies directed to cytokeratin 7 and 8. MACS of SKBR3 seeded in peripheral blood revealed average recovery rates of 62% and 48% and average enrichment factors of 104-fold and 8139-fold of the CK+ cells after one and after two separations, respectively. After immunomagnetic enrichment, CK+ cells were detected in 16 of 20 (80%) cancer patients, whereas only 7 (35%) patients showed CK+ cells without magnetic enrichment (P = 0.002). Ten of twelve (83%) patients with metastatic disease (stage M1) and six of eight (75%) patients without any overt metastases (M0) had CK+ cells in their bone marrow. None of the negative controls showed any CK+ cells. Enrichment with magnetically labeled anti cytokeratin antibodies increases the detection rate of epithelial cells in bone marrow of cancer patients compared to immunocytology.

Comparison of two density gradient centrifugation systems for the enrichment of disseminated tumor cells in blood

BACKGROUND

The detection of disseminated tumor cells in peripheral blood is limited by the presence of very few tumor cells within a large number of blood cells. Therefore, tumor cell detection calls for enrichment systems with effective depletion of blood cells and high tumor cell recovery.

METHODS

We compared the new density gradient centrifugation method OncoQuick with the standard method of Ficoll. The enriched cell fractions were quantified. Tumor cell spiking experiments examined the recovery of tumor cells as detected by immunocytochemistry and cytokeratin-20 reverse transcriptase-polymerase chain reaction (RT-PCR). Clinical application of OncoQuick was evaluated in 37 peripheral blood samples of patients with gastrointestinal carcinomas.

RESULTS

The depletion of mononuclear cells (MNCs) in the enriched cell fraction after OncoQuick centrifugation was 632-fold, with an average cell number of 9.5 x 10(4), compared with Ficoll, with a depletion factor of 3.8 and a mean number of 1.6 x 10(7) MNCs. The mean tumor cell recovery rates were 87% for OncoQuick and 84% for Ficoll. The increased depletion of MNCs with OncoQuick centrifugation further simplified immunocytochemical evaluation by reducing the number of cytospins and increasing the tumor cell density. Due to the reduced number of co-enriched MNCs by OncoQuick, the blood volume, which could be analyzed in one RT-PCR reaction, was increased up to 30 ml. Examination of peripheral blood samples from 37 patients with gastrointestinal tumors showed a cytokeratin-20 detection rate of 30% and a significant correlation with the presence of distant metastases (P < 0.02).

CONCLUSIONS

OncoQuick significantly reduced the co-enriched number of MNCs, with a high tumor cell recovery rate. Processing blood from tumor patients with OncoQuick increased the chance of detecting circulating tumor cells.

Immunomagnetic enrichment and detection of micrometastases in colorectal cancer: correlation with established clinical parameters

PURPOSE

Micrometastatic disease in bone marrow is of prognostic significance in colorectal cancer patients. However, detection rates of standard immunocytology are relatively low. We used magnetic activated cell sorting (MACS), a highly sensitive method, to increase detection rates and correlated the presence of cytokeratin (CK)-expressing cells with clinical parameters.

PATIENTS AND METHODS

Bone marrow was obtained from 51 consecutive patients with newly diagnosed colorectal adenocarcinoma who underwent primary surgery and 18 control subjects. International Union Against Cancer (UICC) stage I disease was diagnosed in 11 patients, stage II disease was diagnosed in 14 patients, stage III disease was diagnosed in 12 patients, and stage IV disease was diagnosed in 14 patients. CK-positive cells were enriched and stained with magnetically labeled CAM 5.2 antibodies directed to CK 7 and 8.

RESULTS

CK-positive cells were found in 33 (65%) patients and were absent in 18 (35%). Four of 11 (36%) patients with UICC stage I disease, nine of 14 (64%) with stage II diease, eight of 12 (67%) with stage III disease, and 12 of 14 (86%) with stage IV disease were CK-positive. Epithelial cells were more frequently found in pT3/4 (72%) than in pT1/2 (36%) tumors (P =.026), but there was no difference for lymph node status. CK-positive patients had a higher chance for elevated carcinoembryonic antigen (85% v 15%, P = NS) and CA 19-9 levels (92% v 8%, P =.019). There were no significant differences in CA 72-4, sex, age, tumor grading, or tumor localization regarding the presence of CK-positive cells. All control subjects were CK-negative.

CONCLUSION

In searching for micrometastases in colorectal cancer patients, we have achieved high detection rates by using MACS. The presence of these cells correlated significantly with tumor stage, tumor extension, and the tumor marker CA 19-9.

Lack of prognostic influence of circulating tumor cells in peripheral blood of patients with colorectal cancer

BACKGROUND AND AIMS

Circulating tumor cells in peripheral blood may be detected using high-sensitivity molecular techniques in several types of solid neoplasms, but their significance in colorectal cancer is controversial. The aim of this study was to assess the prognostic value of carcinoembryonic antigen (CEA) messenger RNA (mRNA) detection in peripheral blood samples from patients with colorectal cancer.

METHODS

Peripheral vein blood samples from 95 consecutive patients with histologically confirmed colorectal carcinoma were obtained immediately before surgery to determine the presence of circulating tumor cells by use of a reverse-transcription polymerase chain reaction targeting CEA mRNA. Endpoints of the study were disease-free and overall survival. Results are referred to the whole series and, more importantly, to the 68 patients who underwent surgery for cure.

RESULTS

After a median follow-up of 42 months, 19 of 68 patients (28%) operated on for cure had tumor relapse. In addition, 50 of 68 patients (73%) were alive. The probability of disease-free and overall survival was dependent on lymph node metastases and degree of differentiation, but not on the presence of circulating tumor cells (disease-free survival: relative risk, 1.00; 95% confidence interval [CI], 0.39-2.22, P = 0.99; overall survival: relative risk, 0.91, 95% CI, 0.34-2.43; P = 0.84). Similar results were obtained when all 95 patients with colorectal cancer were analyzed (disease-free survival: relative risk, 1.11; 95% CI, 0.63-1.95; P = 0.71; overall survival: relative risk, 1.21; 95% CI, 0.63-2.30, P = 0.55).

CONCLUSIONS

Preoperative detection of blood circulating tumor cells by means of reverse-transcription polymerase chain reaction of CEA does not have prognostic significance in patients with colorectal cancer.

Immunomagnetic tumor cell selection--implications for the detection of disseminated cancer cells

BACKGROUND

The optimal method for the detection of disseminated epithelial cancer cells has not yet been found. The standard method, using immunocytochemistry, offers a sensitivity of up to 10(-6). Molecular methods such as cytokeratin-19 RT-PCR are about 10 times as sensitive, but they are hampered by interference such as illegitimate gene expression.

STUDY DESIGN AND METHODS

Immunomagnetic bead selection of epithelial cancer cells using conjugates directed against the human epithelial antigen (HEA) followed by immunocytochemistry testing was investigated in this trial.

RESULTS

No cytokeratin-positive cells could be enriched from 56 control samples. In 104 clinical samples of bone marrow aspirations, PBPC collections, and venous blood obtained from breast cancer patients, the cytokeratin-positive rate increased significantly, from 29.9 percent before selection to 54.8 percent after enrichment. Even the yield of detected cancer cells was significantly higher after selection. Up to 2.5 x 10(8) MNCs were easily processed. However, the mean cancer cell recovery after HEA enrichment was only 24.4 percent. Subsequently, selected epithelial cells were successfully immunophenotyped by use of a double-stain technique detecting cytokeratin-positive cells and the urokinase-like plasminogen activator receptor.

CONCLUSION

HEA bead selection in combination with the standard immunocytochemistry method is a powerful and specific tool for the detection of disseminated cancer cells without false-positive results. Furthermore, it delivers enough cells for subsequent investigations such as characterization studies.

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.

Detection of tumor cells in blood using CD45 magnetic cell separation followed by nested mutant allele-specific amplification of p53 and K-ras genes in patients with colorectal cancer

A new method for detecting circulating tumor cells that is based on magnetic-activated cell separation (MACS) and nested mutant allele-specific amplification (nested MASA) was evaluated in patients with colorectal cancer using the p53 and K-ras genes as genetic markers. By negative selection with anti-CD45 monoclonal antibody-conjugated supermagnetic microbeads, the proportion of tumor cells was enriched 9-fold. By the combination of MACS and nested MASA, 10 tumor cells in 10(7) normal peripheral blood mononuclear cells could be detected without false-positives. Using this method, we examined blood taken from the tumor drainage veins of 23 patients with colorectal cancer. Eighty-seven percent (20/23) of primary tumor tissues showed p53 and/or K-ras gene mutations. Forty-five percent (9/20) of patients with p53 and/or K-ras mutations in the primary tumor showed the same mutated genes in the blood samples. There was a significant association between the presence of p53 and K-ras gene mutation in the blood and tumor size, depth of invasion, and venous invasion. Blood gene mutation was detected in 80% (4/5) of samples from patients with synchronous liver metastases. Sixty percent (3/5) of patients with mutant genes in the blood developed asynchronous liver metastases after surgery. The overall survival of patients with p53 and/or K-ras gene mutation-positive findings in blood was significantly shorter than that of patients testing negative on Kaplan-Meier analysis. Our results suggest that the method may be useful for reliable detection of tumor cells circulating in the blood and may help to identify patients at high risk for relapse.

Circulating tumorous cells in patients with hepatocellular carcinoma. Clinical impact and future directions

The circulation of liver-derived cells in patients with hepatocellular carcinoma (HCC) has been demonstrated by reverse transcriptase-polymerase chain reaction (RT-PCR) analyses. Contrasting results have been reported until now about the clinical impact of these assays, mainly due to technical differences. The use of RT-PCR approaches is now clearly, not suitable for recognition of circulating tumorous cells (CTC) when the test is performed after invasive medical or surgical procedures. Furthermore, the RT-PCR approach is incapable of analyzing the expression of invasion-related genes in CTC. Recently, new assays have been proposed to isolate CTC. They allow immunomorphological and molecular characterization of individual tumor cells. Based on these new results, new therapeutic approaches of metastases should be developed in the near future.

Abdominal insufflation does not cause hematogenous spread of colon cancer

BACKGROUND AND PURPOSE

Previous investigators have suggested that port-site recurrences are possibly a result of abdominal insufflation, forcing viable cancer cells into the circulation to metastasize and thrive in areas of trauma. Using a syngeneic animal cancer model, we tested the hypothesis that pneumoperitoneum increases the incidence of wound metastasis by a blood-borne mechanism.

METHODS

Male BD IX rats (N = 150) were injected intraperitoneally with 2 x 10(5) viable syngeneic 1,2-dimethylhydralazine-induced colon cancer cells (DHD-K12). Animals were divided into three groups: A (abdominal insufflation with 3-cm incision on the back into muscle remote from the peritoneum); B (3-cm back incision alone); and C (control group with 3-cm midline abdominal incision). Three weeks after surgery, the animals were euthanized and autopsied.

RESULTS

In the two groups with back wounds, the incidence of cancer growth at the incision was zero, as demonstrated grossly and by histologic sample (A: 0/47, B: 0/43). In contrast, the autopsied control group had a 42% incidence of metastasis to the wound (25/59). There seemed to be no difference in the distribution of intra-abdominal disease between those rats that underwent insufflation and those that did not.

CONCLUSION

It is unlikely that pneumoperitoneum promotes hematogenous wound implantation of free intraperitoneal cancer cells.

Isolation by size of epithelial tumor cells : a new method for the immunomorphological and molecular characterization of circulatingtumor cells

We have developed a new assay, ISET (isolation by size of epithelial tumor cells), which allows the counting and the immunomorphological and molecular characterization of circulating tumor cells in patients with carcinoma, using peripheral blood sample volumes as small as 1 ml. Using this assay, epithelial tumor cells can be isolated individually by filtration because of their larger size when compared to peripheral blood leukocytes. ISET parameters were defined using peripheral blood spiked with tumor cell lines (HepG2, Hep3B, MCF-7, HeLa, and LNCaP). ISET can detect a single, micropipetted tumor cell, added to 1 ml of blood. We also demonstrate that fluorescence in situ hybridization can be used to perform chromosomal analyses on tumor cells collected using ISET. Polymerase chain reaction-based genetic analyses can be applied to ISET-isolated cells, and, as an example, we demonstrate homozygous p53 deletion in single Hep3B cells after filtration and laser microdissection. Finally, we provide evidence for the in vivo feasibility of ISET in patients with hepatocellular carcinoma undergoing tumor resection. ISET, but not reverse transcriptase-polymerase chain reaction, allowed analysis of cell morphology, counting of tumor cells, and demonstration of tumor microemboli spread into peripheral blood during surgery. Overall, ISET constitutes a novel approach that should open new perpectives in molecular medicine.

Detection of circulating melanoma cells by immunomagnetic cell sorting

We developed a cellular approach to the identification of circulating melanoma cells in peripheral blood using immunomagnetic cell sorting. One hundred seventy-eight blood samples from 129 melanoma patients and 30 samples from healthy persons and nonmelanoma patients were examined. After density gradient centrifugation the interphase was incubated with the mAb 9.2.27. Positive cells were labeled with magnetic microbeads and enriched by immunomagnetic cell sorting. Cells were stained using an alkaline phosphatase-antialkaline phosphatase assay and examined by light microscopy. In spiking experiments, melanoma cells seeded at a concentration of one melanoma cell per ml whole blood could be detected reliably with the assay. Circulating melanoma cells were not found in 30 controls examined, nor were 9.2.27-positive cells found in 41 patients with primary malignant melanoma. In patients with regional lymph node metastases and in patients with disseminated disease, circulating 9.2.27-positive cells could be detected in 3 out of 22 patients (13.6%) and 10 out of 66 patients (15.2%) examined. We present a sensitive and specific immunocytological approach to detect circulating melanoma cells in peripheral blood. The method is not suitable for early detection of metastases but is a valuable tool for further investigating biological characteristics of circulating melanoma cells.

Expression of mucins and cytokeratins in ovarian cancer cell lines

The expression pattern of the epithelial cell markers MUC1 (CA15-3, EMA), CA125 (OC125), human epithelial antigen HEA (Ber-EP4) and cytokeratins (Ck7, Ck8, Ck7/8, Ck8/18/19) was studied in seven human ovarian cancer cell lines. We analyzed the cell lines by immunofluorescence to determine the surface as well as cytoplasmic expression. Furthermore, we evaluated the mRNA expression of MUC1, Ck18 and Ck19 by reverse transcriptase-polymerase chain reaction (RT-PCR). All cell lines were positive for MUC1. However, expression patterns and staining intensity depended on the different epitope-specific antibodies. CA125, a typical serum marker for ovarian carcinomas, was positive only in two cell lines. HEA was strongly positive in three cell lines, whereas the others expressed the antigen only weakly in the cytoplasm. Ck7 was not expressed in three of the seven cell lines. Ck7/8 was detectable in all cell lines and was strongly expressed in four of them. MUC1 mRNA was expressed by all cell lines as detected by RT-PCR. These findings permit selection of a suitable marker for the detection of disseminated ovarian cancer cells.

Detection of colonic cells in peripheral blood of colorectal cancer patients by means of reverse transcriptase and polymerase chain reaction

Circulating tumour cells play a central role in the metastatic process, but little is known about the relationship between this cellular subpopulation and the development of secondary disease. This study was aimed at assessing the presence of colonic cells in peripheral blood of patients with colorectal cancer in different evolutionary stages, by means of reverse transcriptase polymerase chain reaction (RT-PCR) targeted to carcinoembryonic antigen (CEA) mRNA. In vitro sensitivity was established in a recovery experiment by preparing serial colorectal cancer cell dilutions. Thereafter, 95 colorectal cancer patients and a control group including healthy subjects (n=11), patients with other gastrointestinal neoplasms (n=11) or inflammatory bowel disease (n=9) were analysed. Specific cDNA primers for CEA transcripts were used to apply RT-PCR to peripheral blood samples. Tumour cells were detected down to five cells per 10 ml blood, thus indicating a sensitivity limit of approximately one tumour cell per 10(7) white blood cells. CEA mRNA expression was detected in 39 out of 95 colorectal cancer patients (41.1%), there being a significant correlation with the presence of distant metastases at inclusion. None of the healthy volunteers and only 1 of 11 patients (9.1%) with other gastrointestinal neoplasms had detectable CEA mRNA in peripheral blood. By contrast, CEA mRNA was detected in five of the nine patients (55.6%) with inflammatory bowel disease. These results confirm that it is feasible to amplify CEA mRNA in the peripheral blood, its presence being almost certainly derived from circulating malignant cells in colorectal cancer patients. However, CEA mRNA detectable in blood of patients with inflammatory bowel disease suggests the presence of circulating non-neoplastic colonic epithelial cells.

The exfoliation of free malignant cells in the peritoneal cavity during resection of colorectal cancer

The presence of free malignant cells in the peritoneal cavity following potentially curative resection of colorectal cancer may be responsible for some cases of local recurrence. Twenty-six patients (age 58-88 years, male:female 12:14) undergoing colorectal cancer surgery were studied to determine frequency of occurrence of tumour cells in the peritoneal cavity using an immuno-magnetic cell separation technique. Peritoneal washings were collected after opening the peritoneal cavity and also prior to closure. A murine monoclonal antibody specific for epithelial cells was added to the peritoneal washings followed by magnetic labelled goat-antimouse antibody. The labelled tumour cells were retrieved by passing through the magnetic activated cell sorter (MACS). Tumour cells were detected in peritoneal washings from 11 patients (preresection only n = 0, post-resection only n = 6, and both n = 5). Five of these 11 patients had potentially curative surgery. This study supports the use of MACS in detecting free malignant cells in the peritoneal cavity.