All ETDs from UAB

Advisory Committee Chair

Maurizio Grimaldi

Advisory Committee Members

Michael Brenner

Candace Floyd

Lori L McMahon

Harald Sontheimer

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Malignant gliomas, including glioblastomas, are the main primary adult brain tumor. Even with current therapies, the median survival time for patients diagnosed with glioblastomas is only about 12 months. Therefore, it is imperative to identify pathways that can induce glioma cell death. This dissertation provides evidence defining how Endoplasmic Reticulum Stress Response (ERSR) induction promotes cell death selectively in malignant glioma cells (MGCs). I present data showing a correlation between ER Ca2+ storage abnormalities, ER ribosome-translocon expression and activity, ERSR intensity and cell death in MGCs. These data show ERSR induction with thapsigargin (THAP) results in a larger loss of ER Ca2+, an enhancement of ERSR, ER-associated caspases (4/12) and caspase 3 activation and death in MGCs to a much higher degree than in primary astrocytes. MGCs have been reported to have enhanced levels of protein synthesis. I confirm that increased expression of the translocon, a part of the ribosomal complex responsible for ER protein translocation, is a phenomenon associated with ER Ca2+ loss. Pharmacologically inhibiting translocon Ca2+ permeability prevented the THAP-induced ER Ca2+ loss, ERSR deployment, and MGCs death. Conversely, stimulating translocon Ca2+ permeability caused ER Ca2+ loss, ERSR deployment, and MGCs death. Based on these findings, we set out to identify novel small molecules that could mimic THAP actions. We engineered a high throughput assay and queried a library of 1200 FDA approved drugs for agents able to activate ERSR. Spiperone (SPIP), a small molecule identified in our screening, causes ERSR induction and marked cytotoxicity in MGCs. Post screening validation indicates that SPIP induced GRP78 expression and activated ER associated caspases and caspase 3 in MGCs. SPIP also causes ER Ca2+ release from the THAP sensitive store in MGCs. In silico molecular docking analysis indicates that SPIP could bind to SERCA at the cyclopiazonic acid binding site but not to the inositol 1, 4, 5 triphosphate receptor. Future plans include in vivo studies to determine the effect of SPIP on tumor regression. In conclusion, these findings reveal a weakness of MGCs that could be exploited to identify and develop novel therapeutic strategies to treat incurable glial malignancies.

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