Detection of circulating breast cancer cells by reverse transcriptase polymerase chain reaction (RT-PCR)

Gene expression of cytokeratin 19 and its molecular detection in human breast cancer cell lines

Cytokeratins have been identified as useful tools in oncology diagnostics. In this study, cytokeratin19 (CK19) expression was studied in three human breast cancer cell lines, SKBR3, BT549, and BT474 using RT-PCR. CK19 was expressed in tumor cell of different origin, showing higher expression in invasive breast cancer with ER(+) (BT474) than invasive breast cancer with ER(-) (BT549) and breast adenocarcinoma with ER(-) (SKBR3). Two primer sets were used to evaluate CK19 expression. Primer set I (hCK19/1) and primer set II (hCK19/2) were used to amplify the CK19 human gene at a 215bp and 384bp, respectively, whereas PBMC and RAW264.7 (mouse macrophage) no detectable PCR products were obtained. The sensitivity for detection was determined by two methods, i.e., cDNA dilution (the dilution of cDNA from RNA of breast cancer cells) and cell dilution (the dilution of breast cancer cells in PBMC). hCK19/2 was more sensitive than hCK19/1. In cDNA dilution, the lower limits of primer set II for detection were 400, 40 and 40 cells for SKBR3, BT549 and BT474 cells, respectively. While in cell dilution all of the 3 breast cancer cells could be detected at 1 cancer cell in 10(4), 10(6) and 10(5) PBMC, respectively. The data supported the possibility that CK19 could be detected and be the marker for breast cancer in patient blood.

DETECTION OF DISSEMINATED TUMOR CELLS IN PERIPHERAL BLOOD

Metastases are the major cause of cancer-related deaths in patients with solid epithelial malignancies, such as breast, colorectal and prostate carcinomas. Hematogenous spreading of tumor cells from a primary tumor can be considered as a crucial step in the metastasis cascade leading eventually to the formation of clinically manifest metastases. Consequently, as shown in recent studies, the detection of disseminated tumor cells in peripheral blood might be of clinical relevance with respect to individual patient prognosis and staging or monitoring of therapy. However, the rarity of disseminated tumor cells in peripheral blood renders the application of sensitive techniques mandatory for their detection. The emergence of highly sophisticated reverse transciptase-polymerase chain reaction (RT-PCR) assays, combining a preanalytical enrichment step with the assessment of multiple molecular tumor markers expressed in disseminated tumor cells, provides a powerful tool in detecting disseminated tumor cells with high sensitivity and specificity. This review will discuss currently used tumor markers as well as experimental means to enhance the sensitivity and specificity of RT-PCR assays to detect disseminated tumor cells in the peripheral blood of patients with breast, colorectal, and prostate cancers, and their clinical relevance assessed in recent studies.

American Society of Clinical Oncology 2007 update of recommendations for the use of tumor markers in breast cancer

PURPOSE

To update the recommendations for the use of tumor marker tests in the prevention, screening, treatment, and surveillance of breast cancer.

METHODS

For the 2007 update, an Update Committee composed of members from the full Panel was formed to complete the review and analysis of data published since 1999. Computerized literature searches of MEDLINE and the Cochrane Collaboration Library were performed. The Update Committee's literature review focused attention on available systematic reviews and meta-analyses of published tumor marker studies. In general, significant health outcomes (overall survival, disease-free survival, quality of life, lesser toxicity, and cost-effectiveness) were used for making recommendations. Recommendations and

CONCLUSIONS

Thirteen categories of breast tumor markers were considered, six of which were new for the guideline. The following categories showed evidence of clinical utility and were recommended for use in practice: CA 15-3, CA 27.29, carcinoembryonic antigen, estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, urokinase plasminogen activator, plasminogen activator inhibitor 1, and certain multiparameter gene expression assays. Not all applications for these markers were supported, however. The following categories demonstrated insufficient evidence to support routine use in clinical practice: DNA/ploidy by flow cytometry, p53, cathepsin D, cyclin E, proteomics, certain multiparameter assays, detection of bone marrow micrometastases, and circulating tumor cells.

Real-time RT-PCR correlates with immunocytochemistry for the detection of disseminated epithelial cells in bone marrow aspirates of patients with breast cancer

Real-time reverse transcriptase–polymerase chain reaction (RT–PCR) is a technique with the potential of improving the quantification of disseminated epithelial cells (DEC) in haematological tissues due to its exquisite sensitivity. This sensitivity may lead to false positivity. Immunocytochemistry (ICC) is regarded as the standard methodology to diagnose DEC. In this study, detection with ICC was compared with quantitative real-time RT–PCR for CK-19 and mammaglobin (hMAM) mRNA in bone marrow (BM) of patients with metastatic breast cancer (MBC). Bone marrow was aspirated from 14 control patients and from 29 patients with MBC. Mononuclear cells (MNC) were isolated. Immunostaining was carried out with the Epimet kit. Quantitative PCR was performed on the ABI Prism 7700. The CK-19 and hMAM mRNA quantities were normalised against β-Actin and calculated relative to a calibrator sample (relative gene expression). All controls were negative by ICC and for hMAM expression measured by RT–PCR, whereas the median RGE value for CK-19 was 0.57. For the MBC patients, the median RGE for hMAM was 0 and 10 out of 25 (40%) tested positive. Median RGE for CK-19 was 2.9 and 20 out of 25 (80%) tested positive. With ICC, the median value was 1 stained cell per sample, and 15 out of 24 (62%) samples were positive. A correlation was observed between CK-19 and hMAM expression (r=0.7; P=0.0003), and between hMAM expression and ICC (r=0.6; P=0.003). CK-19 expression and ICC (r=0.9; P<0.0001) showed the strongest correlation. Reverse transcriptase–polymerase chain reaction for CK-19 resulted in a higher number of positive BM samples of patients with MBC than ICC. Since an excellent correlation is observed between ICC and RT–PCR, and RT–PCR is probably more sensitive with the advantage of being less observer dependent and thus also more easy to automate, we consider our quantitative real-time RT–PCR method as validated for the detection of DEC in the bone marrow of breast cancer patients.

Dipeptidase 1: a candidate tumor-specific molecular marker in colorectal carcinoma

The aim of this study was to identify tumor-specific markers for the detection of rare disseminated colorectal tumor cells in peripheral venous blood and in intra-peritoneal saline lavage samples collected before and after resection of colorectal tumors. Using cDNA micro-array screening, we found dipeptidase 1 (DPEP1) to be highly expressed in colon tumors compared to matched normal mucosa. Relative reverse transcriptase (RT)-PCR showed that DPEP1 was over-expressed by >/=2 fold in colon tumor compared to normal colonic mucosal tissue in 56/68 (82%) patients. Using immunobead RT-PCR, a technique that first enriches for epithelial cells, we found DPEP1 positive cells in intra-peritoneal lavage and venous blood samples from 15/38 (39%) colorectal cancer cases. This is the first report of DPEP1 as a marker for disseminated colon tumor cells.

Breast cancer biomarkers and molecular medicine

The first part of this two-part review of established and emerging breast cancer biomarkers and molecular diagnostics considers breast cancer predisposition, screening tests for diagnosis, diagnosis using small specimens and metastatic lesions, micrometastatic disease and breast cancer prognosis assessment. Prognostic factors covered in this review include: cytogenetic markers, DNA ploidy and S phase determination, cell proliferation markers, cell cycle regulators and growth factor measurements including epithelial growth factor receptor, HER-2/neu and a variety of other relevant molecules controlling proliferation, differentiation and angiogenesis. The first section of part two will continue the consideration of breast cancer prognostic factors including oncogenes, tumor suppressor genes, cell adhesion molecules, invasion-associated proteins and proteases, hormone receptor proteins, drug resistance proteins, apoptosis regulators, transcription factors, telomerase, DNA repair and methylation and transcriptional profiling using high-density genomic microarrays. The second section of part two will consider the prediction of therapy response using the techniques of pharmacogenetics and pharmacogenomics.

Cell filtration-laser scanning cytometry for the characterisation of circulating breast cancer cells

BACKGROUND

Epithelial cells may be detected in the circulation of the majority of patients with metastatic breast cancer. Quantification of such presumptive cancer cells might allow for the monitoring of patients with early or late stage disease as an early index of relapse. Additionally, biomarker analysis may allow a more rational approach to therapeutics. We have developed a new method for the detection and characterisation of these cells.

METHODS

Blood was filtered through polycarbonate membranes containing cylindrical pores, 8 microm in diameter. All the red cells and a large majority of the white blood cells passed through the filter while the larger epithelial cells were trapped. Cells on the membrane were fixed in ethanol, stained with propidium iodide and anti-pan-cytokeratin-FITC (to identify epithelial cells). The filters were then examined by laser scanning cytometry (LSC), which allowed enumeration and localisation of cells.

RESULTS

With normal blood spiked with cells from breast carcinoma cell lines, 99.9% of the leukocytes passed through the membrane, while close to 100% of the epithelial cells were trapped, with a detection limit of less than one epithelial cell/ml of blood. All of 20 samples from patients with widespread metastatic disease contained cytokeratin-positive cells with the morphological characteristics of carcinoma cells, the number of cells ranging from 0.2 to 5.7/ml of blood.

CONCLUSIONS

Cell filtration-LSC is a viable technique for detecting and studying breast carcinoma cells in peripheral blood.

Polymerase chain reaction in the staging of solid tumors

Polymerasechain reaction (PCR) is a molecular biology technique that holds great promise as a way to perform molecular staging of cancer by detecting very early metastatic disease. Significant data suggest that PCR analysis may play an important role in the management of colorectal cancer in the future. However, for PCR staging of breast cancer, progress awaits identification of gene markers that have sufficient sensitivity and specificity. Within the next few years, the results of the Sunbelt Melanoma Trial and other ongoing studies will determine whether PCR evaluation of sentinel lymph nodes and peripheral blood cells has prognostic relevance in melanoma. The future of cancer management will likely revolve around the molecular staging of tumors, and PCR is but one method that may better define subgroups of patients that are appropriate candidates forvarious anticancer therapies.