Regulation of Cell- Generated Forces during Phenotypic Reversion by a Novel Laminin Chain in 3D Culture of Human Breast Tumor Cells

Abstract

Laminins are heterotrimeric extracellular glycoproteins found in, but not confined to, basement membranes (BMs). They are important components in formation of the molecular networks of BMs as well as in cell & tissue polarity, differentiation and morphogenesis. They are secreted by cells and serve to initiate the template required for multicellular assembly. Mass spectroscopy of the isolated membrane fractions revealed a differential expression of an unexpected laminin chain where human malignant breast cells have a higher expression than that of non malignant cells in 3D lrECM. We thus asked the question what is the role of this endogenously produced laminin for 3D acinar morphogenesis. Recently, we reported that non-malignant cells in a 3D laminin-rich gel generate a centripetal force resulting in coherent angular motion (CAMo) to establish acini. On the other hand, malignant cells are randomly motile but regain the ability to rotate during ‘phenotypic reversion'. We show that there is a differential deposition of this laminin in the BM in malignant tissues from human patient biopsies. Modulation of expression via shRNA reveals that malignant cells regain the ability to generate centripetal forces and thus re-enter the acinar morphogenetic program. We determine that the cells' ability to perform CAMo is in part due to both the expression and localization of this particular laminin chain. These data show the intimate dynamic reciprocity between the cells and the ECM to establish polarity and form tissue architecture