Co-culture with HMF supports MCF10A viability. (a) Direct co-culture of both MCF10A and HMF within the gel, white arrows indicate CK18− clusters, i.e. HMF, (b) MCF10A within the gel with HMF indirect co-culture, (c) schematic illustrating the set-up of each co-culture variant, (d) indirect co-culture of the three breast epithelial cell lines MCF10A, DCIS.com and MCF7 (6 mg/mL peptide gels). Each cell type was seeded at 5 × 105 cells/mL, shown at day 7. Scale bar 50 μm for CK18 stain in panel (d), otherwise all scale bars are 100 μm.