Polarized mammary structures are resistant to apoptosis induction. S1 acini within 3D lrBM were treated with E-cadherin blocking antibody to perturb polarity. T4–2 structures within 3D lrBM were treated with beta-1 integrin inhibitory antibody to restore polarity. A Confocal microscopy of beta-catenin and laminin-5. S1 and reverted T4–2 acini have junctionally organized beta-catenin and basally secreted laminin-5, in contrast to disrupted S1 and disorganized T4–2 colonies. B Apoptotic index of the cell cultures in (A), either untreated (basal), or treated with etoposide, Fas-R, or TNF-α. (Reproduced with modification by permission Cancer Cell from Weaver et al, 2002.)