Prof. Dr. Aladár Szalay
We have previously shown that bacteria injected intravenously into live animals entered and replicated in solid tumors and metastases. The tumor-specific amplification process was visualized in real time using luciferase-catalyzed luminescence and green fluorescent protein fluorescence, which revealed the locations of the tumors and metastases. Escherichia coli and three attenuated pathogens (Vibrio cholerae, Salmonella typhimurium, and Listeria monocytogenes) all entered tumors and replicated. Similarly, the cytosolic vaccinia virus also showed tumor-specific replication, as visualized by real-time imaging. These findings indicate that neither auxotrophic mutations, nor vaccinia virus deficient for the thymidine kinase gene, nor anaerobic growth conditions were required for tumor specificity and intratumoral replication. We observed localization of tumors by light-emitting microorganisms in immunocompetent and in immunocompromised rodents with syngeneic and allogeneic tumors. Based on their 'tumor-finding' nature, bacteria and viruses may be designed to carry multiple genes for detection and treatment of cancer.
A new recombinant VV, GLV-1h68, as a simultaneous diagnostic and therapeutic agent, was constructed by inserting three expression cassettes (encoding Renilla luciferase-green fluorescent protein (RUC-GFP) fusion, β-galactosidase, and β-glucuronidase) into the F14.5L, thymidine kinase (TK), and hemagglutinin (HA) loci of the viral genome, respectively. Intravenous (i.v.) injections of GLV-1h68 (1x107 pfu/mouse) into nude mice with established (500 mm3) subcutaneous (s.c.) GI-101A human breast tumors were used to evaluate its toxicity, tumor targeting specificity and oncolytic efficacy. GLV-1h68 demonstrated an enhanced tumor targeting specificity and much reduced toxicity compared to its parental LIVP strains. The tumors colonized by GLV-1h68 exhibited growth, inhibition, and regression phases followed by tumor eradication within 130 days in 95% of the mice tested. Tumor regression in live animals was monitored in real time based on decreasing light emission, hence demonstrating the concept of a combined oncolytic virus-mediated tumor diagnosis and therapy system. Transcriptional profiling of regressing tumors based on a mouse-specific platform revealed gene expression signatures consistent with immune defense activation, inclusive of interferon stimulated genes (STAT-1 and IRF-7), cytokines, chemokines and innate immune effector function. These findings suggest that immune activation may combine with viral oncolysis to induce tumor eradication in this model, providing a novel perspective for the design of oncolytic viral therapies for human cancers.
Ongoing research in our laboratories involve extensive interactions. Members of Genelux Corporation in San Diego, USA, and Bernried, Bavaria, are engaged with us in the elucidation of cell biological and molecular events, which lead to tumor colonization, induction of apoptotic or necrotic events within tumors, resulting in tumor eradication in tumor xenograft models. Members of our laboratory are interacting with the oncolytic virus program at Memorial Sloan-Kettering Cancer Center in New York in the area of tumor therapy and imaging, with the National Institute of Health in the field of innate immunity and with the German Cancer Center in Heidelberg in the area of colonization of spontaneous tumors. In Würzburg, we have our graduate students and postdoctoral fellows take advantage of the enormous wealth of knowledge at our University and work together regarding MR imaging of colonized tumors with members of the Department of Physics.