Date of Graduation
Doctor of Philosophy (PhD)
Don L. Gibbons
Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the United States, due in part to the robust affinity of lung cancer cells to metastasize. Understanding the processes that contribute to metastasis provides promise for the discovery of novel therapeutic targets. Epithelial-tomesenchymal transition (EMT) is a proposed model for the initiation of metastasis. During EMT cell adhesion and polarity is reduced, allowing epithelial cancer cells to dissociate from the primary tumor and invade distant organs. The transcription factor zinc finger E-box-binding homeobox 1 (ZEB1) has been reported to uniquely correlate with NSCLC disease progression and to confer therapy resistance in multiple tumor types. Additionally, depletion of ZEB1 has been found to reverse therapy resistance, hence uncovering regulators of ZEB1 provides promise for innovative therapeutic strategies that may improve lung cancer patient outcome. Recent publications demonstrate that ZEB1 undergoes post-translational modification, suggesting a method for regulating ZEB1 function; however, the extent to which ZEB1 is modified as well as the purpose of ZEB1 modification has not been fully elucidated. Here, we apply two independent screens- BioID and an Epigenome shRNA dropout screen- to define ZEB1 interactors that regulate post-translational modification and are critical to metastatic NSCLC. These screens revealed an interaction amongst ZEB1 and the histone deacetylase (HDAC)-containing nucleosome and deacetylase remodeling complex (NuRD). Through treatment with class I HDAC inhibitors Trichostatin A, we identified that ZEB1 homodimerizes and determine that acetylation at lysine residue 811 regulates this association. Furthermore, we identify the NuRD complex as a novel ZEB1 co-repressor and the Rab22 GTPase activating protein TBC1D2b as a ZEB1/NuRD complex target. We find that TBC1D2b suppresses E-cadherin internalization, thus hindering cancer cell invasion and metastasis. Ultimately, this project provides a novel regulatory node for ZEB1 function and insight to the role of EMT in endocytosis.
Lung cancer, Metastasis, Epithelial-Mesenchymal Transition