Characterization Of TM9SF2 And WAC As Novel Colorectal Cancer Driver Genes

Abstract

The studies performed in this dissertation focused on the characterization of two candidate cancer genes, TM9SF2 and WAC, and their role in colorectal cancer (CRC). Interest in these two genes stems from their discovery as frequently mutated genes in a mouse-based CRC mutagenesis screen. The first chapter will discuss CRC and provide an historical overview of the methods used to discover novel CRC driver genes. The chapter will also cover modern strategies to identify exciting new CRC driver genes before it ends with a thorough overview of the transposon based forward mutagenesis screen used for CRC gene discovery. The second chapter describes my work demonstrating that the transmembrane protein TM9SF2 is a novel CRC oncogene. Here, we have shown that TM9SF2 is a significant driver gene in murine CRC tumors and, with multiple approaches, that TM9SF2 is overexpressed in approximately one-third of human CRC samples. We provide functional data demonstrating that shRNA-mediated reduction of TM9SF2 or complete knockout by CRISPR/Cas9 drastically reduces tumor fitness in human CRC cell lines. Finally, we provide evidence that high TM9SF2 expression is correlated with poor patient prognosis. The third chapter focuses on the WAC gene and its potential tumor suppressor activity in CRC. We have shown that WAC is frequently mutated in murine CRC mutagenesis screens and that reduction in WAC expression reduces cell growth. This chapter also discusses our finding that loss of WAC is detrimental to mouse embryonic development. The final chapter in this dissertation provides a discussion of the significance of these findings and how these results will impact the CRC research community.