In the present study, we have used a SOX2-enhancer-GFP-reporter system, as it proved to be a good model during our screening of various stemness-related transcriptional factors, to identify and purify sub-population(s) of MCF7 and MDA-MB-231 breast cancer cells, with low and high levels of SOX2-transcriptional activity, by flow cytometry analysis. Here, SOX2 is linked to breast cancer.