Fig. 1

Correlation of increasing matrix stiffness with protrusion formation of MCF10A acini. 3D cultures of MCF10A cells on the indicated Matrigel/Collagen I mixtures (100:0, 75:25, 50:50, 25:75, 0:100) were analysed by microscopy. A Phalloidin (green), Laminin V (red) and nuclei (DAPI, blue) staining of acinar structures at day 4 after seeding on matrices with increasing Collagen I percentages. Arrowheads indicate protrusions. The corresponding increase of Young's elastic modulus of the matrix is depicted below. B Diameters of individual acini (diamonds) measured at day 4, day 8 and day 14. Black horizontal lines indicate mean diameter and SEM (whiskers) of three biologically independent replicates. C Quantification of protrusion formation at day 4, day 8 and day 14. At least 11 acini were assessed each day, the percentage of protrusion-positive acini calculated, and the entire experiment repeated 3 times. D Calculated roundness index of individual acini (diamonds). Statistical significance compared to acini formed on pure Matrigel was determined using a one-way ANOVA and the means for each time point. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001. Error bars, SEM (n = 3). Scale bars, 50 μm