Sansone et al. investigated the interaction of IL-6 and mammary stem/progenitor cells, as elevated serum levels of IL-6 have been associated with poor outcome in breast cancer patients, with results supporting the role of IL-6 in promoting malignant features in Notch-3-expressing progenitor/stem cells from human ductal breast carcinoma and normal mammary gland. This evidence concerns the gene IL6 and breast cancer.