ABILITY OF BIOELECTRIC SIGNALS TO INSTRUCT REGENERATION AND CANCER-ASSOCIATED BEHAVIORS.
Abstract: In many ways cancer is regeneration gone awry. Both processes involve many of the same behaviors and molecular pathways. However, regeneration occurs with impeccable coordination while in cancer many control mechanisms are lost leading to vastly different outcomes. Discovering the key factors responsible for the bifurcation between a path of regulated healing or unrestricted growth will ... read moreprovide valuable insight into new clinical strategies to both cure cancer and to improve healing after injury or disease. The determining factor is often thought to be mutations in DNA, however only a small percentage of cells carrying cancer causing mutations ever go on to form a tumor suggesting additional factors are at play. One mechanism with an early involvement in both regeneration and cancer is bioelectric signaling; changes in ion flows and the electric potential across a cell membrane. The purpose of this work was to explore this understudied signaling mechanism, specifically investigating whether changes in the electric membrane potential (Vmem) are sufficient to instruct regeneration and cancer-associated behaviors. Ostoegenic differentiation of human adult mesenchymal stem cells (hMSC) was used as a model of healthy regeneration. I utilized expression of specific ion channels, culture in different extracellular ion concentrations and inhibition or activation of ion channels with pharmacological agents to modulate Vmem of hMSC during differentiation. None of the conditions tested increased differentiation as determined by quantitative analysis of osteogenic markers. Differences in membrane potential have also been reported between healthy and cancerous cells. In order to test whether Vmem plays an instructive role in cancer, similar methods were used to modulate the Vmem of two breast epithelial cell lines. One of the cell lines was highly metastatic and thus modeled the highly diseased state and the other was a spontaneously immortalized non-tumorigenic cell line with a lower threshold of transformation than primary healthy cells, providing a model to investigate disease onset. While some of the treatments did lead to changes in cancer-related behaviors, overall the effects did not correlate with membrane potential suggesting they were enacted by Vmem-independent mechanisms. Together, these results are not supportive of an instructive role for Vmem, but instead suggest Vmem is a critical part of the cell machinery that is beneficial to most cell behaviors.
Thesis (Ph.D.)--Tufts University, 2016.
Submitted to the Dept. of Cell, Molecular & Developmental Biology.
Advisors: David Kaplan, and Grace Gill.
Committee: Jim Schwob, Mark Ewen, and Mike Levin.
Keywords: Cellular biology, Biophysics, and Biomedical engineering.read less