D-103 Cancer terminator viruses: A strategy for targeting metastatic cancers

Abstract

Our laboratory pioneered subtraction hybridization and used this elegant and effective gene identification strategy to clone novel genes of physiological relevance. This methodology defined differentially regulated genes in an unbiased manner that are modified when metastatic human melanoma cells are pharmacologically induced to terminally differentiate and lose irreversibly oncogenic potential following treatment with IFN-band the protein kinase C activator mezerein. This approach, called DISH (differentiation induction subtraction hybridization), identified melanoma differentiation associated (mda) genes relevant to growth control, cancer development, tumor progression, and cancer cell survival. One intriguing gene identified using the DISH scheme was mda-7, which based on chromosomal location, secretory properties and structure has been classified as interleukin-24 (IL-24). mda-7/IL-24 is a novel member of the IL-10 gene family that promotes apoptosis and toxic autophagy in a broad-spectrum of human tumors, exerts potent “bystander” antitumor activity, inhibits tumor angiogenesis, stimulates the immune system and synergizes with conventional therapies (including chemotherapy, radiation, monoclonal antibodies and immunomodulators) to promote selective tumor destruction. mda-7/IL-24 displays profound anti-cancer activity in preclinical animal models (including nude, syngeneic and transgenic mice) and following intratumoral administration using a type 5 adenovirus in a Phase I/II clinical trial in patients with advanced cancers. To enhance the therapeutic efficacy of mda-7/IL-24, we generated a novel class of adenoviruses, called Cancer Terminator Viruses (CTVs), that selectively replicate in cancer cells and simultaneously produce mda-7/IL-24, Ad.5-CTV. A further iteration of this virus employs a chimera between Ad.5 and Ad.3, Ad.5/3, that employs Coxsackie-Adenovirus Receptors (CAR) as well as desmoglien and CD46 to infect cells, thereby increasing its infectivity in cancer cells with reduced CAR. Ad.5/3-CTV displays profound anti-cancer activity in pre-clinical animal models, including GBM, melanoma, and prostate, colorectal and breast cancer. A clinical trial is in preparation to test the effect of the Ad.5/3-CTV in patients with recurrent glioma. To facilitate the delivery of adenoviruses systemically, avoiding immune clearance and liver trapping, we have refined the ultrasound-targeted microbubble-destruction (UTMD) approach. This strategy has allowed us to deliver therapeutic viruses and proteins intravenously to internal target organs, such as the prostate, to evoke pre-clinical antitumor activity. To enhance further the therapeutic efficacy of the UTMD approach, we are employing microbubbles that contain targeting ligands on their surface permitting accumulation in the tumor vasculature, that is, decorated microbubbles. Employing the same cancer-selective promoter used in the original CTV, the rat progression elevated gene-3 promoter (PEG-Prom), we also developed genetic-based imaging approaches for metastases. These approaches use the PEG-Prom (or another cancer-selective promoter) to drive an imaging gene (eg, luciferase or HSV-Tk) linked to a delivery vehicle PEI. These nanoparticle vectors when combined with bioluminescence imaging and SPECT-CT permit non-invasive imaging of tumors and metastases in pre-clinical animal models. As a further iteration of our CTV we have used 2 cancer-selective and a non-selective promoter to generate first in class tripartite Ads that selectively replicate in cancer cells, produce an imaging agent in cancer cells (Lucirerase or HSV-Tk) and simultaneously produce the therapeutic immunogenic cytokine mda-7/IL-24, Ad.Tri-CTV. These “theranostic viruses” permit tumor and metastasis imaging and treatment through application of a single vector. Overall, the novel reagents and methodologies we have developed are providing paradigm shifts in how cancers will be detected and treated in the future.