Breast epithelial morphogenesis: The role of annexins and primary cilia

Models of three dimensional (3D) mammary acinar morphogenesis are extensively used to study oncogenic transformation of breast epithelial cells. Using these models, factors and mechanisms that lead to aberrant 3D acinar morphology can be identified and studied. Furthermore the role of these factors and mechanisms in breast cancer initiation can be elucidated. By proteomics analysis of a panel of isogenic clones derived from human mammary epithelial cells, our laboratory has identified a number of protein changes that characterize aberrant 3D acinar morphology. These changes include deregulation of members of the Annexin superfamily (specifically Annexin A2 (ANXA2) downregulation and Annexin A8 (ANXA8) upregulation) and proteins associated with primary cilia formation and function. Both Annexins and primary cilia play important roles in cellular processes relevant for mammary acinar morphogenesis and can be affected in cancer. Based on these preliminary data, we hypothesize that deregulation of members of the Annexin superfamily can affect 3D mammary epithelial cell morphogenesis and that aberrant 3D acinar morphogenesis is characterized by primary cilia defects. The overall objective of this master dissertation is to study the effect of ANXA2 and ANXA8 on 3D acinar architecture and assess the morphological changes and distribution of primary cilia in normal and aberrant 3D mammary acinar development. In this thesis, we show that both ANXA2 knock down and ectopic expression of ANXA8 in human mammary epithelial cells are sufficient to impair 3D acinar morphogenesis. Furthermore, by using a method to detect primary cilia during 3D acinar development, we found that primary cilia mainly arise in mature mammary acini, where they protrude into the lumen. In contrast, in aberrant 3D acini, the primary cilia are shorter and show no polarization as it is in breast cancer cells. This study suggests that Annexin deregulation and primary cilia defects are implicated in breast cancer initiation and/or progression.