Sox6 over-expression maintains luminal differentiation in mammary epithelial cells in vitro. A) qPCR analysis of Krt14, Krt18, Esr1 and Sox6 expression levels (mean levels from three independent experiments ± 95% confidence intervals) in cells transduced with virus expressing GFP only (light grey bars) or expressing both Sox6 and GFP (dark grey bars) compared to non-infected cells (open bars). B) Immunofluorescence staining for keratin 14 (upper two rows) and keratin 18 (lower two rows) expression in primary mouse mammary epithelial cells transduced with lentivirus expressing GFP only or Sox6 and GFP. Bars = 30 μm. Arrows indicate keratin positive cells in the Sox6 transduced cultures. These are common in the K18 stained cells but rare and only weakly stained in the K14 stained cells [see Additional file 20].