Date of Award

6-3-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Microbiology, Molecular Biology and Biochemistry

First Advisor

Wei Qiu

Abstract

Hepatocellular carcinoma (HCC) is a deadly cancer, and there is a pressing need to identify novel therapeutic targets. Our lab characterized focal adhesion kinase (FAK) as a driver of HCC, where FAK is required to induce HCC in mouse models. In HCC, 16% of patients harbor an amplification of the PTK2 gene, and these patients have decreased survival. Because of its role in tumor promotion, FAK has been investigated as a therapeutic target, however these therapies show little clinical efficacy. We hypothesize that selectively treating patients with high levels of FAK will significantly benefit from FAK-targeting therapeutics, however there are currently no known biomarkers for FAK. We used a proteolysis-targeting chimera (FP) to degrade FAK in vitro and showed significant growth inhibition following treatment. RNA-seq of FP-treated cells showed connective tissue growth factor (CTGF) was significantly downregulated. CTGF is secreted from cells and can be detected in serum, making it a suitable biomarker candidate. We confirmed the downregulation of CTGF following FP treatment at the mRNA, intracellular protein level, and secreted protein level. Overexpression of FAK led to an increase in intracellular and secreted CTGF protein levels. To assess CTGF alone in HCC, we used an shRNA knockdown and found that shCTGF significantly inhibited cell growth in vitro and in vivo. RNA-seq of shCTGF cells showed an increase in SKP2 and a decrease in p27. Furthermore, we showed that HIF1 mediates the regulation of CTGF by FAK. Using immunohistochemistry of HCC patient tumor samples, we saw a strong correlation between FAK and CTGF protein. Using the DEN/CCl4 murine model, FAK knockout attenuated tumor formation, and in wild type mice, an increase in serum CTGF levels was seen as tumors progressed. Finally, serum collected from patients at high risk for developing HCC suggest CTGF can be used as a marker for tumor formation for tumors with high FAK expression. Overall, FAK promotes the expression and secretion of CTGF, which promotes HCC. FAK is a promising therapeutic target in HCC, and identification of CTGF as a downstream target of FAK suggests CTGF as a treatment-indicating biomarker for FAK in HCC patients.

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Available for download on Wednesday, August 18, 2027

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