Date of Award

1-1-2018

Embargo Period

5-1-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

Paula Traktman

Second Advisor

Steven Rosenzweig

Third Advisor

Alan Diehl

Fourth Advisor

Carol Williams

Fifth Advisor

Amy Hudson

Abstract

Vaccinia-related kinase 1 (VRK1) is a pro-proliferative nuclear serine/threonine kinase. Mice engrafted with VRK1-depleted MDA-MB-231 cells develop fewer distal metastases than mice engrafted with control cells, suggesting a potential role for VRK1 in cell migration, invasion, and/or colonization. In work described herein, we investigated the impact of VRK1 overexpression on human mammary epithelial cells. We demonstrated that VRK1 overexpression in MCF10A cells (normal mammary epithelial cells) diminishes cell invasion and impairs both single-cell and sheet migration, as well as the migration-associated processes of cell spreading and cytoskeletal rearrangement. Interestingly, VRK1-overexpressing cells show reduced accumulation of the mesenchymal marker vimentin and increased accumulation of the epithelial cell-cell adhesion markers E-cadherin, and claudin-1. 3XF-VRK1 overexpression is also associated with reduced levels of the transcriptional repressors snail, slug, and twist, which regulate E-cadherin and claudin-1 expression. Because these data indicate that VRK1 overexpression augments the epithelial properties of MCF10A cells, we further studied the impact of VRK1 in more relevant 3D matrigel cultures. VRK1 overexpression clearly accelerates the initial stages of cell proliferation, leading to the formation of larger acini with somewhat misshapen morphology. However, the subsequent proliferative arrest that accompanies acinus maturation remains unperturbed. Our findings suggest that VRK1, by regulating the transcription repressors snail, slug, and twist1, can promote the mesenchymal-to-epithelial transition (MET) associated with cancer cell colonization. We also determined that the MET phenotype induced by VRK1 overexpression is reversible by TGFβ treatment. Immunohistochemical analysis of human tumor tissue microarrays (TMAs) revealed that VRK1 protein levels are higher in lymph node metastases than in patient-matched primary mammary tumors. Using public databases, we determined that VRK1 is among the top 10% of overexpressed transcripts in multiple subtypes of invasive breast cancer, and that high levels of VRK1 expression are correlated with a reduced rate of relapse-free survival. Taken together, we demonstrate that VRK1 can induce a partial MET that may account for the association of VRK1 overexpression with breast cancer progression and reduced patient survival.

Rights

All rights reserved. Copyright is held by the author.

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