Date of Award

2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Cell & Molecular Biology

First Advisor

Anil K. Rustgi

Abstract

MOLECULAR MECHANISMS OF ESOPHAGEAL SQUAMOUS CELL CARCINOMA

Apple Long

Anil K. Rustgi

Esophageal squamous cell cancer (ESCC) is the 6th leading cause of cancer related deaths amongst American men. Although rare, this disease has a high mortality rate with a 5-year survival of 17%. Incidentally TP53 mutation is the most common genetic alteration in ESCC, along with over expression of EGFR and CYCLIN D1. We have previously modeled the invasive features of ESCC, through an in vivo-like 3D organotypic culture system, utilizing primary epithelial cells that have been transformed by overexpression of mutant TP53 and EGFR. From this model, a RNA microarray was performed to determine critical genes that are upregulated at the front of invasion. WNT10A was found to be over 4-fold upregulated, along with a WNT-signaling gene signature in the invasive cells. We additionally found that increased WNT10A expression was associated with ESCC, compared to normal esophageal tissue and that increased WNT10A staining was associated with poor prognosis. Functionally, WNT10A was determined to induce increased proliferation, migration, invasion and stemness properties in transformed esophageal cancer cells. In addition to examining the oncogenic properties of WNT10A, we also focused on generating an in vivo model of mutant TP53 driven ESCC. We utilized a carcinogen, 4-nitroquinoline 1-oxide (4-NQO), as a challenge to induce genetic changes in the background of Tp53 mutation, specific to the oral squamous, esophagus and forestomach tissues. We found preliminarily that TP53 mutation, specifically the R172H mutant, can accelerate tumorigenesis as compared to loss of TP53 alone. Additionally, when RNA-seq was performed on the tumor derived TP53R172H/- and TP53-/- cells, we found an increase of genes associated with an epithelial to mesenchymal transition (EMT), in the TP53R172H/- cells. Mesenchymal genes such as Cdh2, Zeb1, Zeb2, Twist, and Snail were increased, while epithelial genes such as Cdh1, Epcam, and Krt4 were decreased. Altogether, we surmise that the TP53 mutant, R172H, can induce gain-of-function (GOF), oncogenic properties in order to promote tumorigenesis, potentially by inducing an EMT phenotype.

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