STAT3 and breast cancer: Further, in order to confirm the role of STAT3 signaling in TAM derived IL-6 mediated CSC enrichment in breast cancer, 4T1 cells were pre-treated with Stattic, a specific inhibitor of STAT3, followed by treatment with CM of activated RAW264.7 cells or recombinant IL-6 (50 ng/ml) and Sca-1 expression and ALDH1 activity was examined by flow cytometry.