(489v) Are Circulating Tumor Cells Present in the Peripheral Blood of Cancer Patients Cancer Stem Cells?

During the last decade, a significant number of studies have been reported on the presence of circulating tumor cells, CTC's, in the peripheral blood and bone marrow of cancer patients. In addition, a significant number of studies have been reported on the use of PCR technology to detect these CTC and DTC's. While the presence of CTC and DTC, as well as positive results using PCR technology have been reported on a number of different types of cancer, the two most highly studied cancers are Breast and Melanoma cancer (Patel et al. 2008; Cristofanilli et al. 2004; Muller et al. 2005; Mocellin et al. 2006). A majority of these studies have used a positive selection technology to separate and identify the CTC based on the surface expression of an epithelial marker (such as EpCAM); however we are only aware of one study (our own) in which a purely negative enrichment technology was used (Yang et al. 2009.

In this presentation we will demonstrate that circulating tumor cells in the blood and patients with Squamous Cell Carcinoma of the Head and Neck and Breast Cancer not only can contain a significant number of CTC, but, through confocal imaging that these cells express cell surface markers that are reported to be Cancer Stem Cells and that these CTC express mesenchymal characteristics. We are the first to report this because our magnetic enrichment technology (currently being commercialized) is a purely negative enrichment approach: we only target for removal ?normal cells?; thereby allowing the CTC to be recovered in system effluent. This methodology does not require assumption with respect to specific markers on the surface of CTC which thereby limits what one ?finds?. This biasing by using positive selection has been recently proven to limit the types of CTC that one can isolate (Sieuwerts et al. 2009).