Explorations of the cell signaling behind keratinocyte motility, cancer drug resistance, adipocyte differentiation, and other cellular processes


The regulation of cellular motility and proliferation in epithelial tissues is crucial for wound healing and maintenance of the epithelial sheet, but dysregulation of these processes can lead to the development of cancer. We used live-cell microscopy to characterize an autocrine/ paracrine signaling loop involving matrix metalloproteinase TACE, extracellular ligand TGF-α, growth factor receptor EGFR, and the ERK/MAPK signal transduction pathway. Activation of this signaling loop in HaCaT keratinocytes leads to increased motility and cell cycle flux, for which TACE is specifically required. Intercellular junctions and the actin cytoskeleton are also known to regulate epithelial cell motility. We observed that depleting α-catenin, an essential component of adherens junctions, activates the TACE/TGF-α/EGFR/ERK signaling loop and leads to increased motility and proliferation in HaCaT keratinocytes. I am using motility analysis tools developed during this study to build upon our previous findings and further our understanding of the cooperation between intercellular junctions and the actin cytoskeleton in regulating cellular motility. Specifically, I have used chemical inhibitors to determine that the disruption of tight junctions or the inhibition of actin branching negates the increase in motility we observed in HaCaT keratinocytes upon depletion of α-catenin. Resistance to programmed cell death is one of the recognized hallmarks of cancer, and it also contributes to the development of resistance to anti-tumor therapeutics. CLPTM1L is a transmembrane protein that has been shown to activate anti-apoptotic signaling, and changes to its gene locus have been identified as risk factors in many different types of cancer. I observed that expression of CLPTM1L increases in HCT116 colon cancer cells upon treatment with histone deacetylase inhibitor largazole and that depletion of CLPTM1L makes largazole more effective at killing these cancer cells at lower doses. A luciferase reporter-based screen for upregulators of CLPTM1L promoter activity among a library of 100 FDA-approved cancer drugs indicates that many small molecules, especially microtubule poisons, lead to increased CLPTM1L expression in immortalized skin epithelial cells. While much about the behavior and regulation of CLPTM1L remains unknown, these findings indicate that it could contribute to resistance to many commonly used cancer drugs.

Doctoral dissertation, University of Colorado Boulder
Graycen Wheeler
Graycen Wheeler
Water reporter | Report for America corps member

Graycen is a journalist, a biochemist, a tabletop RPG enthusiast and several other things.