Fig. 1

Human mammary epithelial cells develop multilayered morphology under postconfluent conditions. A Timeline. Characteristic microscopy for each of the named stages at right. Scale bars are 100 μm. B Postconfluent cultures yield dome-like structures (red arrowheads) and tubelike structures (blue arrows). Scale bar is 250 μm. C Postconfluent cultures grown on low-stiffness substrates yield lucent spheroids (red arrowheads), dark spheroids (red arrows), and cable-like structures (blue arrowheads). The surrounding regions are sometimes cleared of cells. Scale bar is 250 μm. D Collagenase treatment causes postconfluent cultures to condense into branching structures reminiscent of mammary organoids. Scale bars are 1 cm. E In intimate contact with plastic, these branching structures show i) focal attachment, ii), enlargement of attached regions, and iii) cellular proliferation. Scale bar is 250 μm