In this thesis, we used genetically engineered mouse models and a variety of cell-culture based assays to identify genes and pathways that are involved in the development and treatment of invasive... Show moreIn this thesis, we used genetically engineered mouse models and a variety of cell-culture based assays to identify genes and pathways that are involved in the development and treatment of invasive lobular carcinoma (ILC). To identify novel genes and pathways involved in the development of ILCs we employed a Sleeping Beauty (SB)-based insertional mutagenesis screen in conditional Cdh1 knockout mice. We show that active transposon mutagenesis drives ILC formation and analysis of common insertion sites in SB-induced tumors identified a mutually exclusive group of four genes (MYH9, MYPT1/2 and ASPP2), three of which are frequently altered in human ILCs. We then went on to show that these hits not only drive ILC development but also do so through a shared mechanism. We identified that all four hits result in actomyosin relaxation which enables E-cadherin deficient mammary epithelial cells to invade into the mammary stroma and initiate tumor development. In addition, we show that mammary epithelial cells that lose E-cadherin expression can survive in the fibrous stroma directly surrounding the mammary ducts through interactions with components of the basement membrane. Lastly, we used active mobilization of transposons to identify resistance mechanisms to the FGFR inhibitor AZD4547. Show less
In this thesis, we used genetically engineered mouse models to identify genes and pathways that are involved in ILC formation and in the development of resistance to FGFR-targeted therapy. These... Show moreIn this thesis, we used genetically engineered mouse models to identify genes and pathways that are involved in ILC formation and in the development of resistance to FGFR-targeted therapy. These mice carry conditional alleles of Cdh1, which result in the inactivation of the cell-adhesion molecule E-cadherin when Cre-recombinase is expressed. As mice with mammary-specific inactivation of E-cadherin alone were not prone to develop mammary tumors, they were used to investigate the contribution of additional genetic mutations to the development of ILCs using different genetic approaches. Firstly, we used non-germline modeling to study the role of PI3K-AKT signaling in the development of ILCs by performing intraductal injections of high-titer lentiviruses. Secondly, we employed a Sleeping Beauty (SB)-based insertional mutagenesis screen in conditional Cdh1 knockout mice to identify novel genes and pathways involved in the development of ILCs. We show that active transposon mutagenesis drives ILC formation and analysis of common insertion sites in SB-induced tumors identified a mutually exclusive group of four genes, of which three are frequently aberrated in human ILCs. Lastly, we used active mobilization of transposons in transplanted mouse ILCs to identify genes involved in acquiring resistance to the FGFR inhibitor AZD4547. Show less
