Date of Graduation
5-2013
Document Type
Dissertation (PhD)
Program Affiliation
Experimental Therapeutics
Degree Name
Doctor of Philosophy (PhD)
Advisor/Committee Chair
David J. McConkey, Ph.D.
Committee Member
Kevin A. Morano, Ph.D.
Committee Member
Mary Ann Smith, Ph.D.
Committee Member
Varsha Gandhi, Ph.D.
Committee Member
Joya Chandra, Ph.D.
Abstract
The mechanisms underlying cellular response to proteasome inhibitors have not been clearly elucidated in solid tumor models. Evidence suggests that the ability of a cell to manage the amount of proteotoxic stress following proteasome inhibition dictates survival. In this study using the FDA-approved proteasome inhibitor bortezomib (Velcade®) in solid tumor cells, we demonstrated that perhaps the most critical response to proteasome inhibition is repression of global protein synthesis by phosphorylation of the eukaryotic initiation factor 2-α subunit (eIF2α). In a panel of 10 distinct human pancreatic cancer cells, we showed marked heterogeneity in the ability of cancer cells to induce eIF2α phosphorylation upon stress (eIF2α-P); lack of inducible eIF2α-P led to excessive accumulation of aggregated proteins, reactive oxygen species, and ultimately cell death. In addition, we examined complementary cytoprotective mechanisms involving the activation of the heat shock response (HSR), and found that induction of heat shock protein 70 kDa (Hsp72) protected against proteasome inhibitor-induced cell death in human bladder cancer cells. Finally, investigation of a novel histone deacetylase 6 (HDAC6)-selective inhibitor suggested that the cytoprotective role of the cytoplasmic histone deacetylase 6 (HDAC6) in response to proteasome inhibition may have been previously overestimated.
Keywords
proteasome, bortezomib, pancreatic cancer, bladder cancer, eIF2alpha, HRI, Hsp70, HDAC6, proteotoxicity
Included in
Cancer Biology Commons, Cell Biology Commons, Molecular Biology Commons, Neoplasms Commons