Date of Award

5-2022

Document Type

Dissertation

Degree Name

Ph.D.

Department

Basic Medical Sciences

Committee Chair

Dr. Steve Lim, Ph.D.

Abstract

Focal adhesion kinase (FAK) is a ubiquitous expressed protein tyrosine kinase. In growing cells, FAK localizes to the plasma membrane where it interacts with several components of the focal adhesion complex and coordinates integrin signaling. Early studies using genetic mouse models revealed that deletion or catalytic inactivation of FAK resulted in early embryonic lethality with vascular, cell proliferation, and cell survival defects. As a result, FAK was coined as a vital mediator of cell migration, proliferation, and cell survival and multiple small molecule FAK inhibitors (FAK-I) had been designed to inactivate FAK catalytic functions in multiple pathologies, particularly in cancer. FAK-I had demonstrated efficacy in alleviating tumor growth and metastasis, and some are currently in clinical developmental phases. Inactive FAK is nuclear localized and still retains important scaffold functions that we scarcely know about. More importantly, little is known about the impact of inactive nuclear-localized FAK in solid tumors or in the tumor microenvironment (TME, the immediate surrounding of tumors cells). In this dissertation, I sought to dissect the role of nuclear FAK localization in cancer progression by focusing in two cell types of the TME: tumor (chapter II) and endothelial cells (chapter III) FAK-I prompted FAK nuclear localization in B16F10 melanoma cells. Nuclear FAK was able to bind and ubiquitinate DNA methyltransferase xx 3A (DNMT3A), thus reducing DNMT3A protein stability. Loss of DNMT3A reduced global DNA methylation which increased the expression of the tumor suppressor gene, suppressor of cytokine signaling 3 (SOCS3). Tetracycline inducible (Tet-on) SOCS3 expression reduced B16F10 melanoma proliferation and viability. Stable knockdown of DNMT3A, increased SOCS3 expression. FAK-I also blocked B16F10 melanoma ear tumor growth, reduced DNMT3A expression and increased SOCS3 in vivo. Further, genetic, and pharmacological inhibition of FAK blocked vascular endothelial growth factor (VEGF)/ fibroblast growth factor (FGF)-induced Matrigel plug angiogenesis in vivo. FAK-I reduced HB-EGF protein and mRNA expression in various mouse, human EC lines and human infantile hemangioma cell lines, resulting in reduced EC proliferation. FAK-I also reduced HB-EGF mRNA expression in vivo anagenesis model. Mechanistically, FAK-I reduced nuclear localization, tyrosine phosphorylation and protein stability of the transcriptional coactivator, yes associated protein 1 (YAP) which reduced HB-EGF expression. Taken together, the information gathered in this dissertation suggests that nuclear-localized FAK negatively regulates cancer progression by increasing the expression of tumor suppressor genes in tumor cells and blocking the expression of angiogenic factors in endothelial cells.

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