Figure 4.

Breast epithelia emerge from arrest in response to changes in their local microenvironment (A-D) MCF10A. To alter the cell microenvironment, acini that had been cultured in 3D for 14-d were picked and re-plated in 2D planar culture. The acini, which initially contained SA-β-gal-staining positive cells, spread onto the plastic (A) and SA-β-gal staining declined as cells emerged onto the 2D substratum. Over a period of 4 d following re-plating, cells showed a progressive increase in nucleolar number (B); n > 250 for each time point), and increased their proliferative capacity, as judged by EdU incorporation (C); 24-h after replate: n = 303; 48-h n = 381; 72-h n = 212). These changes correlated with increased expression of the cell cycle regulators cyclin D1 and pRb (D). Note that primary murine MEC acini that expressed SA-β-gal similarly reverted from cell cycle arrest on changing their microenvironment (Janes et al. 2011). Scale bars, 50 μm.