A major obstacle in the successful treatment of cancer is the occurrence of metastasis. The presence of CETCs is closely related to tumor recurrence, but the mechanisms through which CETCs promote metastasis are still unclear. The aim of this study was to determine the proliferative capacity of CETCs by analyzing the frequency of mammosphere formation with subsequent phenotypic characterization of the spheres arising in breast cancer patients.
CETCs were cultured under condition favoring growth of mammospheres from 38 patients with breast cancer, including a subpopulation of 13 patients with metastatic disease. Cell viability, stem cell marker expression and ALDH 1 activity was evaluated by fluorescence scanning microscope (Olympus Scan®R).
Sphere formation was observed in 74 % of patients with breast cancer. Patients with distant metastasis had higher numbers of mammospheres (median 13,0 vs 1,0; p≤0,001) compared to patients without metastasis. In multivariate analysis, a high number of mammospheres was associated with the presence of metastasis. The mammospheres area under the ROC curve was 0,99. Six or more spheres classified metastatic disease with a sensitivity and specificity of 96 % and 100 %, respectively. These results suggest that above cut-off six in the number of mammospheres is statistically highly indicator for disease progression. Analysis of surface marker expression profile of mammospheres showed that spheres cultured from CETCs had typical phenotype of cancer stem cells with a high enzymatic activity for ALDH 1 with the ALDEFLUOR assay. There was no sphere formation in a control group with 50 healthy donors.
This study demonstrates that a small fraction of CETCs has proliferative activity.
Identifying the CETC subset with cancer stem cells properties may provide more clinically useful prognostic information and may be a new indicator for the presence of metastases.
Citation Format: Monika Pizon, Dorothea Zimon, Ulrich Pachmann, Katharina Pachmann. Mammospheres derived from circulating epithelial tumor cells are an indicator for presence of metastasis in patient with breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-06-06.