Graduation Date

Fall 12-14-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Biochemistry & Molecular Biology

First Advisor

Justin L. Mott

Abstract

How are cholangiocarcinoma cells different from non-malignant cholangiocytes?

All of the hallmarks of cancer apply- those reported in this dissertation include cell proliferation, migration, apoptosis, and evasion of growth suppression. My studies began with testing how apoptosis might be regulated through embelin, a small molecule reported to sensitize cells to apoptosis by blocking XIAP. My data however revealed that embelin reduced the proliferative capacity in cholangiocarcinoma cells, but did not increase cell death. Malignant cells exhibit dysregulation of microRNA processing and expression. Hence, my studies seeking ways that cholangiocarcinoma eludes apoptosis transitioned to the oncomiR miR-106b, which is overexpressed in cholangiocarcinoma. I observed that miR-106b protected cholangiocarcinoma cells from apoptosis. Genome-wide screening identified the landscape of miR-106b-targeted genes in a cholangiocarcinoma cell line, some with roles in tumor biology. MiR-106b targets included members of the Krüppel-like factor (KLF) family of transcription factors.

The function of KLF2 in biliary epithelia or cholangiocarcinoma is unknown. I describe in part how the cholangiocyte senses the environment through the primary cilium and translates this to regulation of KLF2, a flow-responsive regulatory protein and tumor suppressor in several cancers. I observed lower expression of KLF2 in malignant cholangiocarcinoma cells and tumors compared to normal, and its enforced expression inhibited proliferation and migration while reducing sensitivity to apoptosis. In the normal bile duct epithelium, environmental cues are detected by the cholangiocyte primary cilium, a sensory organelle that functions as a signaling nexus for the cell. Cholangiocarcinoma cells are highly proliferative despite extracellular signals to remain quiescent. Cholangiocarcinoma cells often lose their cilia, resulting in altered communication and unchecked cell growth. I identified a cholangiocyte signaling axis in which the primary cilium maintains quiescence through enhanced KLF2 expression. I present the first finding of a ciliary-dependent KLF2 flow response in cholangiocytes. Overall, this dissertation sought deeper understanding of biochemical and molecular features of cholangiocarcinoma and added to our understanding of microRNAs and mechanosensory pathways.

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Available for download on Saturday, December 07, 2019

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