Fig. 4. Only laminin-1 and not laminin-5 and -10/11 can correctly polarize acini in collagen gels. Luminal epithelial cells without myoepithelial (LEP alone) had no correctly polarized acini. Addition of 10% rBM or pure laminin-1 reversed polarity to the same degree as normal-derived myoepithelial cells (MEP). Neither affinity purified laminin-5 nor laminin-10/11 possessed the ability to revert acinus polarity.