Abstract

Detection and Expression Profiling of Tumor Initiating Cells (TIC) Among the Peripherally Circulating Epithelial Tumor Cells from Patients with Breast Cancer

Katharina Pachmann, Professor, University of Jena

The detection of tumor cells circulating in the peripheral blood of patients with breast cancer is a sign that cells have been able to leave the primary tumor and survive in the circulation. However, in order to form metastases they require additional properties such as the ability to adhere, self renew and grow. Here we present data that a variable fraction among the circulating tumor cells detected by the maintrac® approach express mRNA of the stem cell gene nanog and of the adhesion molecule vimentin and are capable of forming tumor spheres a property ascribed to TIC.  Between 10 to 50 circulating epithelial antigen positive cells detected by the maintrac® approach were selected randomly from each of 20 patients with breast cancer before and after surgery and isolated using automated capillary aspiration and deposited individually onto slides for expression profiling. In addition, the circulating tumor cells were cultured without isolation among the white blood cells from five patients with breast cancer in different stages of disease using culture methods favoring growth of epithelial cells. Although no EpCAM mRNA positive cells expressing stem cell genes or the adhesion molecule vimentin were detected before surgery, 10 to 20% of the cells were found to be positive for mRNA of these genes after surgery. Most surprisingly, it was possible to grow tumor spheres (Fig 1) from these circulating cells without previous isolation in all patients in a fraction comprising between 1‰ of the epithelial antigen positive cells in patients with newly diagnosed tumor up to 10% in a patient with advanced breast cancer.  We show here, that among the peripherally circulating tumor cells a variable fraction is able to express stem cell and adhesion properties and can be grown into tumor spheres, a property ascribed to cells capable of initiating tumors and metastases.