CAFs promote breast cancer cell proliferation. a Cell viability assay in MCF-7, BT-474, SK-BR-3 and MDA-MB-231 cells treated with NAF and CAFs CM for 2 or 4 days. Three independent experiments were performed in triplicate. Data are presented as the mean ± s.d. b ELISA results of IL-6 from breast cancer supernatant cocultured with NAF1 (red), CAF40 (green) or CAF74 (blue). The experiments were performed at least three times independently with similar results. Columns, mean of triplicate experiments; bars, s.d. c Quantification of CD126+ breast cancer cells by flow cytometry. d Examination of the cell cycle by flow cytometry analysis in SK-BR-3 cells. e Colony formation was increased in SK-BR-3 cocultured with CAF40- and CAF74-CM compared to NAF1-CM. The dotted area of the stained cell colonies was quantified by Image-Pro Plus software (Media Cybernetics, USA) and normalized to the results. Columns, mean of triplicate experiments; bars, s.d.