Combining Regulatory Angiogenic Gene Therapy and Virotherapy for the Treatment of Breast Cancer

This thesis describes the design of a virotherapy strategy capable of destroying both breast cancer vasculature and tumour cells, using an oncolytic adenovirus expressing angiogenesis-regulating proteins. Five oncolytic adenoviruses were compared to identify the best virotherapy agent for breast cancer, including measurement of cytotoxicity in vitro, and replication, intra-tumoural spread and anticancer efficacy in vivo. The viruses tested were Ad-dI922-947 (targets G1-8 checkpoint defects); Ad-Onyx-015 and Ad-Onyx-017 (target p53/mRNA nuclear export defects); Ad-vKH1 (targets Wnt pathway defects) and AdEHE2F (targets estrogen receptor/G1-8 checkpoint/hypoxia signalling defects). AdEHE2F demonstrated optimal oncolytic activity and selectivity against breast cancer, accordingly this virus was engineered to express potent regulatory angiogenic proteins, namely soluble Flt1 and soluble Delta like-4 (0114). sFlt1 is the soluble extra-cellular domain of VEGFR1 and binds to and sequesters VEGFA, thereby preventing VEGFR2 stimulation which is crucial to trigger angiogenesis. sOll4 is the soluble extracellular domain of 0114 and has been previously shown to block 01l4/Notch signalling. 01l4/Notch signalling increases a chaotic and non-functional angiogenesis which ultimately delays tumour growth. Importantly, VEGF and 0114 are the only angiogenesis genes reported to be haploinsufficient in vascular development and both have been shown to have a good anti-tumour effect. sFlt1 and sOll4 genes were substituted for the viral genes E3 6.7K1gp19K of AdEHE2F, thereby using endogenous adenoviral machinery to drive production. The activities of AdEHE2F viruses expressing either sFlt1 or sOll4 were compared in vitro and in vivo. sFlt1 (expressed from AdEHE2F) inhibited endothelial cell proliferation and sprouting whereas sOll4 increased proliferation and branching in vitro. In vivo AdEHE2F expressing sFlt1 or sOll4 both showed superior anticancer activity compared to parental AdEHE2F, indicating at least additive efficacy between virotherapy and regulatory angiogenic approaches.EThOS - Electronic Theses Online ServiceGBUnited Kingdo