Defense Date

2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biochemistry

First Advisor

Dr. Paul Dent

Abstract

The impact of Ad.mda-7 on the survival of renal cell carcinoma lines (RCC), primary renal epithelial cells, glioblastoma multiforme lines (GBM), and primary rodent astrocytes is unknown. The present studies examine whether the GST fusion protein, GST-MDA-7, and the adenovirus, Ad.mda-7, altered the growth and survival of the A498 and UOK121N RCC lines or radiosensitized GBM, respectively. Due to previous findings that the RCC lines, but not primary renal epithelial cells, were resistant to type 5 adenoviral infection, we used purified GST-MDA-7 protein to show that GST-MDA-7, but not GST, caused a dose-dependent reduction in A498 and UOK121N proliferation but not that of primary renal epithelial cells. Free radical species, generated by clinically relevant concentrations of arsenic trioxide, synergized with subnanomolar concentrations of GST-MDA-7 to inhibit the proliferation, viability, and long-term survival of RCC. We also found that MDA-7 (IL-24), when expressed via a recombinant replication defective adenovirus, Ad.mda-7, exerted anti-proliferative effects on GBM cells, an effect found to be enhanced in a greater than additive fashion when combined with ionizing radiation. These findings argue that MDA-7, in combination with agents that generate free radicals, such as arsenic trioxide and ionizing radiation, may have potential in the treatment of RCC and GBM. Geldanamycins are currently being used in a number of clinical trials in different tumor cell types, such as hepatocellular carcinoma (HCC), targeting the inhibition of the heat shock protein and molecular chaperone Hsp90. Previous studies have demonstrated that geldanamycins have dose limiting toxicity in vivo due to their actions in promoting normal liver dysfunction. These studies show that the geldanamycin derivative, 17-allylamino-17-demethoxygeldanamycin (17-AAG), interacts with the secondary bile acid, deoxycholic acid (DCA), to kill primary rat hepatocytes and HuH7 human hepatoma cells. An effect abolished by the addition of the ROS-quenchers, NAC and Trolox. Collectively, these findings argue that geldanamycins may not be a viable therapy for HCC treatment and that 17-AAG toxicity in primary hepatocytes may be, at least upon initial drug exposure, due to ROS generation and mechanisms independent of Hsp9O inhibition and the down-regulation of "classical" Hsp90 client proteins.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

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