230. A Novel Gammaretroviral Shuttle Vector Insertional Mutagenesis Screen To Identify Breast Cancer Metastasis Genes

Abstract

Retroviral insertional mutagenesis screens have been used to efficiently identify genes involved in a wide variety of cancers. Identifying causal driver genes in malignant disease is crucial to develop improved targeted therapies. Here, we have utilized a replication-incompetent gammaretroviral vector to perform a mutagenesis screen to identify genes involved in breast cancer metastasis progression. MDA-MB-231 cells that were mutagenized with a gammaretroviral vector were xenotransplanted into the mammary fat pad of immunodeficient mice, and the primary tumors and metastases allowed to develop. Metastatic tumors were collected and analyzed for proviral integration sites using a shuttle vector rescue approach that allows for rapid rescue of plasmids in E. coli that contain long terminal repeat-chromosomal junctions. In our approach, clones with vector proviruses that dysregulate nearby metastatic driver genes have a selective advantage to form metastatic tumors. The vector provirus acts as a molecular tag to identify candidate dysregulated metastasis driver genes. Using this approach, we identified several candidate breast cancer metastasis genes including WWTR1 (TAZ), a known and recently validated breast cancer metastasis gene. Identifying genes that drive the metastatic process can identify targets for improved therapy.