Global Gene Expression Profiling of Circulating Tumor Cells

Abstract

Metastases from primary tumors are responsible for most cancer deaths. It has been shown that circulating tumor cells (CTCs) can be detected in the peripheral blood of patients with a variety of metastatic cancers and that the presence of these cells is associated with poor clinical outcomes. Characterization of CTCs in metastatic cancer patients could provide additional information to augment management of the disease. Here, we describe a novel approach for the identification of molecular markers to detect and characterize CTCs in peripheral blood. Using an integrated platform to immunomagnetically isolate and immunofluorescently detect CTCs, we obtained blood containing z100 CTCs from one metastatic colorectal, one metastatic prostate, and one metastatic breast cancer patient. Using the RNA extracted from the CTC-enriched portion of the sample and comparing it with the RNA extracted from the corresponding CTCdepleted portion, for the first time, global gene expression profiles from CTCs were generated and a list of cancerspecific, CTC-specific genes was obtained. Subsequently, samples immunomagnetically enriched for CTCs from 74 metastatic cancer patients and 50 normal donors were used to confirm by quantitative real-time reverse transcription-PCR CTC-specific expression of selected genes and to show that gene expression profiles for CTCs may be used to distinguish normal donors from advanced cancer patients as well as to differentiate among the three different metastatic cancers. Genes such as AGR2, S100A14, S100A16, FABP1, and others were found useful for detection of CTCs in peripheral blood of advanced cancer patients. (Cancer Res 2005; 65(12): 4993-7)

The pro-metastatic protein anterior gradient-2 predicts poor prognosis in tamoxifen-treated breast cancers

“…Furthermore, AGR2 predicts poor prognosis in prostate cancers (Zhang et al, 2007). Finally, expression of genes including AGR2 and others could detect circulating tumour cells in peripheral blood of advanced cancer patients (Smirnov et al, 2005).…”

Isolating highly enriched populations of circulating epithelial cells and other rare cells from blood using a magnetic sweeper device

“…Applications range from characterization of circulating epithelial cells (CEpCs) in the peripheral blood of cancer patients for disease prognosis and personalized treatment (1)(2)(3)(4)(5)(6)(7); circulating fetal cells in maternal blood for prenatal diagnosis (8)(9)(10); and antigen-specific lymphocytes for immune monitoring (11). The deconvolution of profiling data to extract the relevant biology of rare cells from the mixture of blood leukocytes is challenging, and in most cases impractical (12,13). Efficient enrichment of these cells of interest is critical before characterization; otherwise, leukocyte contamination would overwhelm any subsequent molecular analyses of rare cells.…”

Molecular characterization of circulating tumor cells in large quantities of contaminating leukocytes by a multiplex real-time PCR

“…Next, only candidate genes are selected by comparing the corresponding depleted and enriched fractions for minimal expression in the CTCdepleted fraction and significant expression in the CTCenriched fraction [21]. Also less sophisticated methods such as only selecting markers with high expression in tissue samples from primary tumors and a median 1,000-fold lower expression in normal blood [7] have been used.…”