Identification of novel regulators of colorectal adenocarcinoma and head and neck squamous cell carcinoma

Abstract

Cancer is the second leading cause of death in the United States. It is important to identify novel drivers of cancer in order to understand these diseases so we can improve patient prognosis. This dissertation focuses on two types of cancer, colorectal adenocarcinoma (CRC) and head and neck squamous cell carcinoma (HNSCC), and the discovery of novel regulators in each using different methods.

In CRC, publically available data from The Cancer Genome Atlas (TCGA) was utilized. A bioinformatics analysis was used to connect protein expression data to clinical outcome, thus identifying proteins that are associated with poor prognosis in CRC. This analysis identified both known and novel regulators of CRC. Two of these molecules were further studied: insulin-like growth factor binding protein 2 (IGFBP2) and GATA3. These initial findings were validated by follow-up experiments. High levels of IGFBP2, a known but understudied molecule in CRC progression, were associated with poor prognosis. Using a tissue microarray (TMA) stained with IGFBP2, I found that IGFBP2-high staining patients had significantly decreased survival and recurrence-free survival. Low levels of GATA3, a transcription factor never associated with CRC, were associated with poor prognosis. With in vitro experiments using GATA3-manipulated cell lines, I showed that GATA3 overexpression decreases three-dimensional colony growth and invasiveness but not intrinsic proliferation rates.

Cortactin is overexpressed through the 11q13 amplicon in 30-40% of HNSCC cases and controls a number of actin-based cellular phenotypes important for tumor progression. I found the cortactin SH3 domain was critical for Golgi morphology and in vivo tumor growth. Shank2, a cortactin SH3 binding protein that is also overexpressed through the 11q13 amplicon, has never been studied in any type of cancer. Using Shank2-manipulated cells, I found Shank2-knockdown decreased invasion, and preliminary evidence suggested a decrease in MMP secretion and invadopodia activity.

Identification and characterization of these novel regulators, IGFBP2, GATA3, and Shank2, gives us mechanistic insight into the progression of CRC and HNSCC.