Date of Award
Doctor of Philosophy (PhD)
Amplification or mutations in members of the epidermal growth factor receptor family, such as HER2, have been identified in several human diseases. In particular, mutations in the intracellular kinase domain have been identified in breast, colon, and lung cancers. The Cancer Genome Atlas has identified HER2 mutations or gene amplification in seven percent of colon cancer patients. These mutations are well known to promote enhanced cell growth and transformation of colon cancer cell lines. Previous studies have found HER2 mutations to confer anchorage independent growth and activation of downstream signaling pathways such as MAPK. Although HER2 mutations have been extensively characterized using cell line overexpression models, the role of HER2 alterations on tumorigenesis, particularly in the gastrointestinal tract, has not been studied. In this thesis, the role of an activating HER2 mutation, V777L, was examined using small intestinal organoids, a three-dimensional culture model. Additionally, we also sought to explore the cooperative role of both HER2 and APC mutations. Using this model, we showed distinct morphological changes in intestinal organoids upon expression of either
HER2 or APC alone, or in combination. Furthermore, in vivo expression of HER2V777L driven by the Lgr5-Cre recombinase showed increased intestinal hyperplasia throughout the small intestine and the loss of distinct intestinal cell populations. This work is the first characterization of an activating HER2 mutation in the intestine using a transgenic mouse model and a three-dimensional culture model. Lastly, we show that in vitro expression of oncogenic mutations such as KRAS in HER2 mutated colon cancer cell lines confers reduced sensitivity to a HER2-targeted therapeutic, neratinib, which further illustrates the impact of multiple oncogenic mutations on cell growth. Taken together, we illustrate the role of HER2 and co-occurring mutations on the intestinal epithelium as well as the effect of HER2 and KRAS co-occurring mutations on colon cancer cell line inhibitor sensitivity and downstream signaling pathways.
Chair and Committee
Matt Ciorba, Jim Janetka, Linda Pike, Sheila Stewart,
Murray, Elisa, "Modeling HER2 Mutations in Colorectal Cancer using a HER2 Transgenic Mouse Model and Gastrointestinal Organoids" (2020). Arts & Sciences Electronic Theses and Dissertations. 2332.