Tumorspheres cultured from circulating epithelial tumor cells (CETCs) as diagnostic marker in patients with solid cancers.

11043 Background: Metastatic disease is a serious threat and the most common cause of cancer-associated death in patients with solid tumors. The presence of CETCs is closely related to tumor metastasis, but it is still unclear whether all CETCs are capable to proliferate and generate metastasis. Therefore we investigated their proliferative capacity by analyzing the frequency of tumorsphere formation with subsequent phenotypic characterization of the tumorspheres arising in patients with solid tumors. Methods: 37 patients with solid cancer and early metastatic disease and detectable CETCs were enrolled in the present study. 10 patients had breast, 10 colorectal, 10 prostate and 7 lung cancer. CETCs were determined using the maintrac method and the CETCs were cultured in suspension culture in the context of the other white blood cells allowing for epithelial sphere formation. Cell viability, stem cell marker expression and ALDH 1 activity was evaluated by fluorescence scanning microscope (Olympus Scan R). Results: Sphere formation was observed in 90 %, 90 %, 80 % and 85.7 % of patients with breast, colorectal, prostate and lung cancer, respectively. Among solid cancer patients the number of tumor spheres increased significantly with tumor progression, especially with development of distant metastasis. The selectivity for distant metastasis of the area under ROC curve for the number of tumorspheres was 0.72 (p < 0.02). Five or more tumorspheres grouped metastatic disease with a sensitivity and specificity of 88.2 % and 75 %, respectively. Analysis of surface marker expression profile of tumorspheres showed that tumorspheres cultured from CETCs had typical phenotype of cancer stem cells and tumorspheres in patients with breast cancer possessed a high enzymatic activity for ALDH 1 with the ALDEFLUOR assay. There was no sphere formation in 20 healthy donors. Conclusions: Here, we describe for the first time the identification of CETCs which are capable of forming tumorspheres with proliferative activity and stem cell characteristics. This may contribute to the design of tools for early detection of progression and treatment in solid cancer.