Assessment of SOX2 performance as a marker for circulating cancer stem-like cells (CCSCs) identification in advanced breast cancer patients using CytoTrack system.

Abstract

Background: Recent studies have highlighted that one of the main drivers for metastatic formation and resistance to the therapy are circulating tumor cells (CTCs) and cancer stem-like cells (CSCs). Measuring the CTCs has emerged as a non-invasive procedure for selecting the patients with higher risk of progression/relapse. However, still there are no methods enabling the identification of stem-like phenotype of the CTCs.

Methods: The image-based method was used for the identification of the circulating cancer stem-like cells (CCSCs) in metastatic breast cancer patients. The method was optimized using the CSCs established in the mammosphere culture of MCF-7 cells. Next the protocol was implemented to identify the CCSCs in samples collected from 60 patients.

Results: The recovery ratio for CCSCs identification using the established method was ∼60%. The CCSCs were identified as rare events accruing only in 2 patients out of 60, who participated in the study. Interestingly, the CCSCs were found only in CTC clusters. The analysis of SOX2 expression in formalin-fixed, paraffin-embedded material, revealed that the SOX2 expression was present in primary tumor samples.

Conclusion: The CCSCs presence was found to be a very rare event. The obtained results suggest that the CCSCs are mainly present in CTC clusters and stem-like reprograming of the cancer cells might occur early, in the primary tumor.