Fig. 5: Mechanical stretching normal myoepithelial cells induces integrin β6 expression.

a Cartoon depicting duct sizes for a normal duct, and a DCIS duct without and with integrin β6 expression (not to scale). b Representative images of integrin β6 by immunohistochemical staining in human breast tissue samples featuring adjacent normal ducts (40 μm), and an integrin β6-negative and β6–positive DCIS duct. Scale bar, (top) 200 μm and (bottom) 100 μm. c Box and whiskers plot showing DCIS duct sizes with (n = 656) or without (n = 713) integrin β6 expression. Box plot represents the median (central line) and interquartile range (IQR; box), and whiskers represent the maximum and minimum. **P = 0.0312 (two-tailed t-test). d–f Representative images of integrin β6 (green) and fibronectin (FN, magenta) by immunofluorescent staining in unstretched (Unstr) or stretched (Str) myoepithelial cell line; N-1089 (d) and primary normal myoepithelial cells; N-1989 (e) and N-1492 (f). Nuclei were counterstained with DAPI (blue). Scale bar, 20 μm. Images are representative of three experiments. g–i Immunoblots of integrin β6 and fibronectin (FN) in unstretched or stretched myoepithelial cells generated as in (d–f). HSC70 serves as loading control. Images are representative of three experiments. j–l Bar graphs showing qRT-PCR analysis for ITGB6 using RNA isolated from unstretched or stretched myoepithelial cell line; N-1089 (j) and primary normal myoepithelial cells; N-1989 (k) and N-1492 (l) (error bars, +s.e.m). n = 3 biological replicates, 3 technical replicates; ****P < 0.0001 (j, k) and ***P = 0.0001 (l) (two-tailed t-test). m–o, Bar graphs showing qRT-PCR analysis for FN1 using RNA isolated from unstretched or stretched myoepithelial cells generated as in (j–l) (error bars, +s.e.m). n = 3 biological replicates, 3 technical replicates; ****P < 0.0001 (two-tailed t-test).