Date of Graduation

5-2018

Document Type

Thesis (MS)

Program Affiliation

Biomedical Sciences

Degree Name

Masters of Science (MS)

Advisor/Committee Chair

Faye M. Johnson, M.D., Ph.D.

Committee Member

Don L. Gibbons, M.D., Ph.D.

Committee Member

Joya Chandra, Ph.D.

Committee Member

Subrata Sen, Ph.D.

Committee Member

Pierre D. McCrea, Ph.D.

Abstract

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide. Outcomes are poor for patients with recurrent, advanced or metastatic NSCLC. Polo-like kinase 1 (PLK1), involved in the regulation of mitotic processes and the response to DNA damage, is overexpressed in NSCLC. Inhibiting PLK1 may be an effective treatment for NSCLC patients as it is involved in the mechanisms of resistance to several chemotherapy drugs. PLK1 inhibition or knock-down has various effects in cancer cells, including mitotic arrest, apoptosis, and senescence. Predictive biomarkers have not been identified to select those patients who are likely to respond to PLK1 inhibitors although a small subset of NSCLC patients respond well to single agent therapy.

Our lab found that mesenchymal NSCLC cell lines were more sensitive to PLK1 inhibitors than the epithelial cell lines in vitro. The induction of an epithelial phenotype using miR-200 expression increased resistance to PLK1 inhibition, whereas the induction of a mesenchymal phenotype using ZEB1 expression or TGF-β increased PLK1 inhibition–induced apoptosis. To elucidate the mechanisms of resistance to PLK1 inhibition, our lab compared gene and protein expression in sensitive and resistant NSCLC cell lines and we identified β-Catenin, SMAD4 and PDK1 to be differentially regulated between epithelial and mesenchymal NSCLC cell lines after PLK1 inhibition. We tested the role of β-Catenin, SMAD4 and PDK1 in PLK1 inhibition induced apoptosis in NSCLC.

Here, we demonstrate that mesenchymal NSCLC tumors are more sensitive to PLK1 inhibition compared to epithelial NSCLC in vivo in patient derived-xenograft (PDX) models as well as orthotopic mouse models in which the EMT properties are manipulable by modulating the miR200/ZEB1 axis. To facilitate analysis of these in vivo studies, we developed a novel semi-automated method of metastatic lung tumor burden calculation from computed tomography images by the calculation of the mass of the thoracic cavity. This method takes into account the aggregate tumor metastases in the thoracic cavity which significantly accounts for tumor burden in lung adenocarcinoma and provides details about the dynamic processes that occur in vivo over time.

Keywords

PLK1, lung cancer, patient-derived xenograft, PDX, orthotopic, EMT, epithelial to mesenchymal transition

Available for download on Saturday, May 04, 2019

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