Figure 1.

Basement membrane (BM) mechanics counteract tumour extracellular matrix (ECM)-induced invasion. (A) 3D reconstructed confocal images showing a local basement membrane (BM) disruption and cell invasion event (left acinus) on a 12 kPa PDMS silicone rubber substrate. Left: Local BM disruption foci (asterisks) and collective cell transmigration are present at the cell–BM–substrate interface. Right: Massive cell dissemination and a collapsed, cell-free BM hull (red), indicating the late invasion phase. (B) Experimental conditions to resemble the shift from physiological to malignant breast tissue states by altering BM development and substrate compliance. (C) MCF10A breast acini-derived BMs with progressive developmental stages. Micrographs are illustrating ld-BM and hd-BM structures with representative increasing deposition of BM-specific marker proteins type IV collagen and laminin-332. (D) Cumulative events of BM transmigration onset over time and (E) fraction of invasive acini after 65 h and different BM states and substrate compliance levels. (F) Cumulative BM transmigration onset, (G) fraction of invasive acini after 65 h and (H) and individual invasion times for EGF-pretreated acini, comparing again different BM states and substrate compliance levels. (I) Cumulative BM transmigration after type IV collagenase and EGF pretreatment and (J) corresponding individual times of invasion for hd-BM acini soft substrate. (K) Cumulative BM transmigration, (L) fraction of invasive acini after 65 h and (M) corresponding times of invasion for individual acini after pretreatment with MMP inhibitor marimastat, again for different BM states, substrate compliance levels and ±EGF. n: sample size of at least three independent experiments (see Table S1 for exact invasive fraction values and mean invasion timepoints). Scatter plots (H,J,M): bars: mean with 95% confidence interval (CI). Scale bars: 50 µm; n.s.: p ≥ 0.05; ****: p < 0.0001).