All ETDs from UAB

Advisory Committee Chair

Harald Sontheimer

Advisory Committee Members

Michael Brenner

L Burt Nabors

Michelle Olsen

Linda Wadiche

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

The most common malignant primary brain tumor, gliomas usually derive from glial cells including oligodendrocytes and astrocytes. These tumors are characterized by high rates of proliferation and aberrant migration which make them notoriously difficult to treat using standard treatment paradigms such as chemotherapy and radiation. In order for glioma cells to migrate into the surrounding brain tissue, they must undergo rapid and dynamic volume changes. Previous work published by the Sontheimer laboratory and others indicates glioma utilize the flux of ions across the cell membrane to aid in volume changes associate with cell migration. In this dissertation, I show the Sodium-Potassium-Chloride Cotransporter Isoform-1 (NKCC1) plays an important role in glioma biology, providing the ionic gradients required for volume regulation. Emphasizing its role in migration and invasion, I demonstrate that NKCC1 contributes to glioma cell migration using pharmacological or genetic inhibition of NKCC1. In addition, a genetic knockdown of NKCC1 abolishes Regulatory Volume Increase (RVI) in human glioma cells, suggesting that RVI in gliomas is solely dependent on NKCC1. Furthermore, NKCC1 inhibition reduced the invasion distance of glioma cells implanted into the brains of immunocompromised mice. Volume changes must be tightly coordinated to support successful cell invasion. One known regulator of NKCC1 in other cells is With-No-Lysine kinase 3 (WNK3). Here, I show that WNK3 is expressed in glioma cell lines and appears to have increased expression in patient biopsies of gliomas. I show hitherto unrecognized protein-protein interaction occurring between WNK3 and NKCC1 under hyperosmotic conditions. WNK3 inhibition through genetic knockdown reduces glioma cell migration and abolishes the cells' ability to undergo RVI to a similar extent as a loss of NKCC1. This data suggests that WNK3 is the exclusive regulator of NKCC1 in glioma cells and that targeting NKCC1 and its regulation would provide innovative approaches to treating malignant gliomas.

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