All ETDs from UAB

Advisory Committee Chair

Joanne T Douglas

Advisory Committee Members

David T Curiel

Katri Selander

Gene P Siegal

Danny R Welch

Document Type

Dissertation

Date of Award

2008

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Most patients with advanced breast cancer develop osteolytic bone metastases, which have numerous complications. Because current therapies are not curative, new treatments are needed. Conditionally replicating adenoviruses (CRAds) are anti-cancer agents designed to infect and lyse tumor cells. For increased efficacy, CRAds have been armed with therapeutic transgenes. Osteoprotegerin (OPG), an inhibitor of osteoclastic bone resorption, represents a promising candidate with which to arm a CRAd intended to treat osteolytic bone metastases. We hypothesize that a CRAd armed with OPG will inhibit breast cancer bone metastasis and reduce tumor burden in the bone by directly lysing tumor cells and by inhibiting bone resorption through the action of OPG. We have constructed an armed CRAd (Ad5-Δ24-sOPG-Fc-RGD) by replacing viral E3B genes with a fusion of the ligand-binding domains of OPG and the Fc portion of human IgG1, for improved secretion. Conditional replication is conferred by a 24 base pair deletion within E1A (Δ24), which prevents the binding of E1A to cellular Rb and limits replication in normal cells. The incorporation of an RGD peptide sequence within the fiber knob confers transductional selectivity by directing infection to cells expressing αv integrins. A panel of control viruses has also been constructed. We first confirmed the expression of sOPG-Fc and the remaining E3 genes from our experimental viruses, and showed that expression from E3B inhibits neither the oncolytic potency nor the selectivity of replication of an RGD-modified CRAd. We demonii strated that infection of breast cancer cells by Ad-Δ24-sOPG-Fc-RGD both kills the infected cells by oncolysis and inhibits the formation of osteoclasts in an in vitro co-culture model. The efficacy of Ad-Δ24-sOPG-Fc-RGD was evaluated in a model of breast cancer bone metastasis in which athymic mice are injected intratibially with human breast cancer cells stably expressing luciferase, allowing the progression of osteolytic lesions to be monitored in live animals. The results of these studies demonstrated that our armed CRAd reduces tumor burden in the bone and inhibits osteoclast formation more effectively than an unarmed CRAd. We have therefore shown the enhanced therapeutic efficacy of the dual-action, armed CRAd in treating bone metastases of breast cancer.

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