Showing papers by "Klaus Pantel published in 2008"

Review: Biological relevance of disseminated tumor cells in cancer patients.

Abstract: The prognosis of cancer patients is largely determined by the occurrence of distant metastases. In patients with primary tumors, this relapse is mainly due to clinically occult micrometastasis present in secondary organs at primary diagnosis but not detectable even with high resolution imaging procedures. Sensitive and specific immunocytochemical and molecular assays enable the detection and characterization of disseminated tumor cells (DTC) at the single cell level in bone marrow (BM) as the common homing site of DTC and circulating tumor cells (CTC) in peripheral blood. Because of the high variability of results in DTC and CTC detection, there is an urgent need for standardized methods. In this review, we will focus on BM and present currently available methods for the detection and characterization of DTC. Furthermore, we will discuss data on the biology of DTC and the clinical relevance of DTC detection. While the prognostic impact of DTC in BM has clearly been shown for primary breast cancer patients, less is known about the clinical relevance of DTC in patients with other carcinomas. Current findings suggest that DTC are capable to survive chemotherapy and persist in a dormant nonproliferating state over years. To what extent these DTC have stem cell properties is subject of ongoing investigations. Further characterization is required to understand the biology of DTC and to identify new targets for improved risk prevention and tailoring of therapy. Our review will focus on breast, colon, lung, and prostate cancer as the main tumor entities in Europe and the United States.

Circulating Tumor Cells and Bone Marrow Micrometastasis

Abstract: Sensitive immunocytochemical and molecular assays allow the detection of single circulating tumor cells (CTC) in the peripheral blood and disseminated tumor cells (DTC) in the bone marrow as a common and easily accessible homing organ for cells released by epithelial tumors of various origins. The results obtained thus far have provided direct evidence that tumor cell dissemination starts already early during tumor development and progression. Tumor cells are frequently detected in the blood and bone marrow of cancer patients without clinical or even histopathologic signs of metastasis. The detection of DTC and CTC yields important prognostic information and might help to tailor systemic therapies to the individual needs of a cancer patient. In the present review, we provide a critical review of (a) the current methods used for detection of CTC/DTC and (b) data on the molecular characterization of CTC/DTC with a particular emphasis on tumor dormancy, cancer stem cell theory, and novel targets for biological therapies; and we pinpoint to (c) critical issues that need to be addressed to establish CTC/DTC measurements in clinical practice.

Detection and monitoring of cell-free DNA in blood of patients with colorectal cancer.

Abstract: Cell-free tumor-specific and normal DNA are released into the blood circulation by cellular necrosis and apoptosis. We examined whether circulating DNA in blood of patients with colorectal cancer could be used as an additional marker for diagnosis and response to therapy. The concentration of circulating cell-free DNA in the blood of 55 patients with advanced colorectal cancer and 20 healthy donors was measured. One to four follow-up serum samples from 14 patients were also available. Patients with colorectal cancer had a wide range of DNA concentrations in their blood. The calculated values were between 22 and 3922 ng/mL DNA, with a mean and median value of 1157 ng/mL and 868 ng/mL, respectively. In contrast, the average concentration of cell-free DNA in the serum of healthy donors was significantly lower (5-16 ng/mL). During therapy the levels of serum DNA were not constant, but fluctuated, regardless of the chemotherapy used. High DNA levels of >1000 ng/mL of blood significantly correlated with a shorter survival (P= 0.02). Quantitative analysis demonstrates that elevated DNA levels can be detected in blood of patients with colorectal cancer and may be a useful tool in combination with other tumor markers for detection of colorectal cancer.

Cancer micrometastasis and tumour dormancy.

Abstract: Many epithelial cancers carry a poor prognosis even after curative resection of early stage tumours. Tumour progression in these cancer patients has been attributed to the existence and persistence of disseminated tumour cells (DTC) in various body compartments as a sign of minimal residual disease. Bone marrow (BM) has been shown to be a common homing organ and reservoir for DTC. A significant correlation between the presence of DTC in BM and metastatic relapse has been reported in various tumour types. However, only a portion of patients with DTC in BM at primary surgery relapse. Thus far, little is known about the conditions required for the persistence of dormancy or the escape from the dormant phase into the active phase of metastasis formation. Thereby, this peculiar stage of conceivably balanced tumour cell division and death may last for decades in cancer patients. Most likely, the ability of a dormant DTC to "be activated" is a complex process involving (i) somatic aberrations in the tumour cells, (ii) the interaction of the DTC with the new microenvironment at the secondary site, and (iii) hereditary components of the host (i.e., cancer patient). In this review, we will summarize the key findings of research on micrometastatic cancer cells and discuss these findings in the context of the concept of tumour dormancy.

Disseminated tumor cells in bone marrow and circulating tumor cells in blood of breast cancer patients: current state of detection and characterization.

Abstract: Despite the progress resulting from early detection and improved adjuvant therapy, the prognosis of breast cancer patients is still limited by the occurrence of distant metastases largely due to clinically occult micrometastases that remain undetected at primary diagnosis even by high-resolution imaging approaches. Recent research efforts have concentrated on the identification of additional parameters allowing individual risk assessment and stratification of patients for targeted therapies, since traditional prognostic factors are not sufficient to predict metastatic relapse and treatment decisions are still mainly based on statistical risk parameters. Highly sensitive and specific immunocytochemical and molecular assays now enable the detection and characterization of disseminated and circulating tumor cells (DTCs and CTCs, respectively) at the single cell level in bone marrow (BM) and peripheral blood, providing insights into the first crucial steps of the metastatic cascade. However, because of the still high variability of results in DTC/CTC detection, the necessity of standardized approaches will be discussed. A large number of studies showed that the presence of DTCs in BM has prognostic impact for primary breast cancer patients. DTCs are likely to escape from chemotherapy by maintaining a dormant nonproliferating state. There is also evidence for a stem cell-like phenotype of DTCs, probably contributing to the opportunity to escape from dormancy control and to start expansion to manifest metastases. Blood would also be an ideal source for the detection and monitoring of CTCs because of an easy noninvasive sampling procedure enabling repeated analyses. While prognostic significance of CTCs could be reliably demonstrated for metastatic breast cancer, studies to analyze the impact of CTCs in primary breast cancer patients and the potential to replace or supplement BM analysis are still ongoing. Furthermore, molecular characterization of CTCs might contribute to improving targeted and more individualized cancer therapies.

Micrometastatic spread in breast cancer: detection, molecular characterization and clinical relevance

Abstract: Immunocytochemical or molecular assays allow the detection of single disseminated tumor cells (DTCs) in the bone marrow (BM) or the peripheral blood in 10% to 60% of breast cancer patients without signs of metastasis. Results from recently reported studies suggest that circulating tumor cell (CTC) levels may serve as a prognostic marker and be used for early assessment of therapeutic response in patients with metastatic breast cancer. In early stage breast cancer, however, the impact of CTCs is less well established than that of DTCs in BM, where several clinical studies demonstrated that such cells are an independent prognostic factor at primary diagnosis. The characterization of DTCs/CTCs has already shed new light on the complex process underlying early tumor cell dissemination and metastatic progression in cancer patients. Characterization of DTCs should help to identify novel targets for biological therapies aimed to prevent metastatic relapse. In addition, understanding tumor 'dormancy' and identifying metastatic stem cells might result in the development of new therapeutic concepts.

Genome-wide microarray gene expression, array-CGH analysis, and telomerase activity in advanced ovarian endometriosis: a high degree of differentiation rather than malignant potential.

Abstract: The aim of the present study was to investigate whether endometriosis and cancer share common molecular characteristics. Tissue samples were collected prospectively during diagnostic laparoscopy of patients with primary infertility. Using high-density oligonucleotide microarrays, (Affymetrix Gene Chip HG-U133 Set) the genome-wide gene expression profile of advanced ovarian endometriosis was analyzed compared with matched normal endometrium. Expression of TERT, the gene encoding the telomerase reverse transcriptase subunit, and telomerase activity were analyzed in eutopic and ectopic endometrium. Genome-wide, high-resolution array-CGH was used to screen for genomic aberrations in endometriosis. Expression microarray data were validated quantitatively with RT-PCR. The genes RARRES1 and RARRES2 (retinoic acid receptor responder 1 and 2) were found to be up-regulated in endometriosis, suggesting a high degree of differentiation. Consistently, down-regulated genes included those involved in the cell cycle, cell metabolism and homeostasis. Expression of TERT and telomerase activity were present in eutopic but absent in ectopic endometrium. Array-CGH revealed a normal genomic pattern without gross amplifications and deletions. In conclusion, these data suggest that advanced ovarian endometriosis represents a highly differentiated tissue with minimal or no malignant potential.

Identification of Loss of Heterozygosity on Circulating Free DNA in Peripheral Blood of Prostate Cancer Patients: Potential and Technical Improvements

Abstract: Background: Accurate identification of loss of heterozygosity (LOH) on circulating free DNA is often restricted by technical limitations such as poor quality and quantity of tumor-specific DNA and contamination by normal DNA. However, plasma DNA may harbor tumor-specific genetic alterations and could therefore be an interesting target for noninvasive examinations of tumor DNA. Methods: By PCR-based fluorescence microsatellite analysis using 12 polymorphic markers, we investigated LOH on cell-free DNA in blood plasma from 59 patients with localized prostate cancer (PCa) and 12 with metastatic disease (MPCa). In addition, plasma DNA from 21 PCa patients was fractionated into high- and low-molecular-weight DNA by 2 different column systems. To avoid appearance of artificial allelic loss and stabilize the amplification, TMAC (tetramethylammonium chloride) was added to each PCR. Results: Overall incidences of LOH at all markers analyzed were 10% in PCa and 12% in MPCa samples. Highest frequencies were found at markers D11S898 (28%) in PCa and D6S1631 (27%) in MPCa. Statistical evaluation showed significant associations between LOH and increasing Gleason scores for the marker combinations D6S1631\*D8S286\*D9S171 ( P = 0.03) and D8S286*D9S171 ( P = 0.05). Fractionation of plasma DNA resulted in a higher overall LOH frequency in the low-molecular-weight DNA fraction (23%) compared with the high-molecular-weight DNA (7%). Conclusions: LOH analysis of circulating DNA can provide tumor-specific genetic information on PCa patients. Fractionation of plasma DNA and addition of TMAC improved LOH detection and general assay performance.

Microsatellite analysis of allelic imbalance in tumour and blood from patients with prostate cancer.

Abstract: OBJECTIVE To investigate whether a high frequency of allelic imbalance (AI) is associated with clinicopathological variables of patients with prostate cancer. PATIENTS AND METHODS We analysed loss of heterozygosity (LOH) and microsatellite (MS) instability (MSI) on circulating plasma DNA in a polymerase chain reaction (PCR)-based MS study of 230 patients with prostate cancer and 43 with benign prostatic hyperplasia (BPH) using a panel of 13 polymorphic MS markers. RESULTS The overall incidence of AI was significantly higher in primary tumours (34%) than in blood plasma samples from patients with prostate cancer (11%). Although LOH (2.0%) and MSI (1.5%) were also found in BPH plasma samples, their frequencies were low. AI identified in plasma samples from patients with prostate cancer could be retrieved in 63% of the paired tumour samples. The highest concordance of AI and retention of heterozygosity between tumour and plasma samples was 83% at the marker D8S360. There were high frequencies of LOH at the markers THRB, D7S522 and D8S137 in both types of specimens. The markers D11S898 and D11S1313 on the chromosome arm 11q showed frequent MSI. The comparison with established risk factors showed significant associations of an increase in prostate volume with AI at the combined markers D6S474/D7S522 in tumour tissues and at D7S522 in plasma samples (P < 0.04). In the primary tumours there was a further correlation of LOH at D11S1313 with increasing tPSA value (P = 0.005). The combination of total prostate-specific antigen (PSA) and % free PSA was associated with LOH at THRB in plasma samples. CONCLUSIONS Plasma-based MS analysis may have clinical value for the molecular staging of prostate cancer.

A Comparative Study of Tissue Inhibitor of Metalloproteinases-1 Levels in Plasma and Tumour Tissue from Patients with Primary Breast Cancer and in Plasma from Patients with Metastatic Breast Cancer

Abstract: Objective: Tissue inhibitor of metalloproteinases-1 (TIMP-1) has been investigated as a potential tumour marker in breast cancer. Here we investigated the correlation between TIMP-1 in tumour tissue and plasma to evaluate whether TIMP-1 in plasma is actually a surrogate marker for TIMP-1 in primary tumours. Furthermore, we assessed whether increased TIMP-1 levels in plasma could be indicative of tumour progression in patients with advanced breast cancer. Methods: Tumour tissue and preoperatively collected plasma samples from 96 primary breast cancer patients were included together with plasma samples from 46 patients with advanced disease. TIMP-1 levels were measured by ELISA. Results: TIMP-1 levels in plasma (median 81.5 ng/ml, range 41.9–174.9) and tumour tissue (median 25.4 ng/mg of total protein, range 0–110.2) from primary breast cancer patients were not correlated (r = 0.05, p = 0.6). Plasma levels of TIMP-1 in primary breast cancer patients were significantly lower than levels in patients with advanced disease (median 108.7 ng/ml, range 59.7–560.7; p Conclusions: Our findings suggest that TIMP-1 release into the blood might be controlled by an active mechanism. They also point to plasma TIMP-1 as a potential marker for predicting tumour progression and for monitoring tumour burden in metastatic breast cancer patients.