Shigella Mediated Depletion of Macrophages in a Murine Breast Cancer Model Is Associated with Tumor Regression

A tumor promoting role of macrophages has been described for a transgenic murine breast cancer model. In this model tumor-associated macrophages (TAMs) represent a major component of the leukocytic infiltrate and are associated with tumor progression. Shigella flexneri is a bacterial pathogen known to specificly induce apotosis in macrophages. To evaluate whether Shigella-induced removal of macrophages may be sufficient for achieving tumor regression we have developed an attenuated strain of S. flexneri (M90TΔaroA) and infected tumor bearing mice. Two mouse models were employed, xenotransplantation of a murine breast cancer cell line and spontanous breast cancer development in MMTV-HER2 transgenic mice. Quantitative analysis of bacterial tumor targeting demonstrated that attenuated, invasive Shigella flexneri primarily infected TAMs after systemic administration. A single i.v. injection of invasive M90TΔaroA resulted in caspase-1 dependent apoptosis of TAMs followed by a 74% reduction in tumors of transgenic MMTV-HER-2 mice 7 days post infection. TAM depletion was sustained and associated with complete tumor regression

Specific antibody-receptor interactions trigger InlAB-independent uptake of listeria monocytogenes into tumor cell lines

<p>Abstract</p> <p>Background</p> <p>Specific cell targeting is an important, yet unsolved problem in bacteria-based therapeutic applications, like tumor or gene therapy. Here, we describe the construction of a novel, internalin A and B (InlAB)-deficient <it>Listeria monocytogenes </it>strain (Lm-spa⁺), which expresses protein A of <it>Staphylococcus aureus </it>(SPA) and anchors SPA in the correct orientation on the bacterial cell surface.</p> <p>Results</p> <p>This listerial strain efficiently binds antibodies allowing specific interaction of the bacterium with the target recognized by the antibody. Binding of Trastuzumab (Herceptin^®) or Cetuximab (Erbitux^®) to Lm-spa⁺, two clinically approved monoclonal antibodies directed against HER2/neu and EGFR/HER1, respectively, triggers InlAB-independent internalization into non-phagocytic cancer cell lines overexpressing the respective receptors. Internalization, subsequent escape into the host cell cytosol and intracellular replication of these bacteria are as efficient as of the corresponding InlAB-positive, SPA-negative parental strain. This specific antibody/receptor-mediated internalization of Lm-spa⁺is shown in the murine 4T1 tumor cell line, the isogenic 4T1-HER2 cell line as well as the human cancer cell lines SK-BR-3 and SK-OV-3. Importantly, this targeting approach is applicable in a xenograft mouse tumor model after crosslinking the antibody to SPA on the listerial cell surface.</p> <p>Conclusions</p> <p>Binding of receptor-specific antibodies to SPA-expressing <it>L. monocytogenes </it>may represent a promising approach to target <it>L. monocytogenes </it>to host cells expressing specific receptors triggering internalization.</p

Regression of Human Prostate Tumors and Metastases in Nude Mice following Treatment with the Recombinant Oncolytic Vaccinia Virus GLV-1h68

Virotherapy using oncolytic vaccinia virus strains is one of the most promising new strategies for cancer therapy. In the current study, we analyzed the therapeutic efficacy of the oncolytic vaccinia virus GLV-1h68 against two human prostate cancer cell lines DU-145 and PC-3 in cell culture and in tumor xenograft models. By viral proliferation assays and cell survival tests, we demonstrated that GLV-1h68 was able to infect, replicate in, and lyse these prostate cancer cells in culture. In DU-145 and PC-3 tumor xenograft models, a single intravenous injection with GLV-1h68 resulted in a significant reduction of primary tumor size. In addition, the GLV-1h68-infection led to strong inflammatory and oncolytic effects resulting in drastic reduction of regional lymph nodes with PC-3 metastases. Our data documented that the GLV-1h68 virus has a great potential for treatment of human prostate carcinoma

Significant Growth Inhibition of Canine Mammary Carcinoma Xenografts following Treatment with Oncolytic Vaccinia Virus GLV-1h68

Canine mammary carcinoma is a highly metastatic tumor that is poorly responsive to available treatment. Therefore, there is an urgent need to identify novel agents for therapy of this disease. Recently, we reported that the oncolytic vaccinia virus GLV-1h68 could be a useful tool for therapy of canine mammary adenoma in vivo. In this study we analyzed the therapeutic effect of GLV-1h68 against canine mammary carcinoma. Cell culture data demonstrated that GLV-1h68 efficiently infected and destroyed cells of the mammary carcinoma cell line MTH52c. Furthermore, after systemic administration, this attenuated vaccinia virus strain primarily replicated in canine tumor xenografts in nude mice. Finally, infection with GLV-1h68 led to strong inflammatory and oncolytic effects resulting in significant growth inhibition of the tumors. In summary, the data showed that the GLV-1h68 virus strain has promising potential for effective treatment of canine mammary carcinoma

Use of a recombinant Salmonella enterica serovar Typhimurium strain expressing C-Raf for protection against C-Raf induced lung adenoma in mice

BACKGROUND: Serine-threonine kinases of the Raf family (A-Raf, B-Raf, C-Raf) are central players in cellular signal transduction, and thus often causally involved in the development of cancer when mutated or over-expressed. Therefore these proteins are potential targets for immunotherapy and a possible basis for vaccine development against tumors. In this study we analyzed the functionality of a new live C-Raf vaccine based on an attenuated Salmonella enterica serovar Typhimurium aroA strain in two Raf dependent lung tumor mouse models. METHODS: The antigen C-Raf has been fused to the C-terminal secretion signal of Escherichia coli α-hemolysin and expressed in secreted form by an attenuated aroA Salmonella enterica serovar Typhimurium strain via the α-hemolysin secretion pathway. The effect of the immunization with this recombinant C-Raf strain on wild-type C57BL/6 or lung tumor bearing transgenic BxB mice was analyzed using western blot and FACS analysis as well as specific tumor growth assays. RESULTS: C-Raf antigen was successfully expressed in secreted form by an attenuated Salmonella enterica serovar Typhimurium aroA strain using the E. coli hemolysin secretion system. Immunization of wild-type C57BL/6 or tumor bearing mice provoked specific C-Raf antibody and T-cell responses. Most importantly, the vaccine strain significantly reduced tumor growth in two transgenic mouse models of Raf oncogene-induced lung adenomas. CONCLUSIONS: The combination of the C-Raf antigen, hemolysin secretion system and Salmonella enterica serovar Typhimurium could form the basis for a new generation of live bacterial vaccines for the treatment of Raf dependent human malignancies

Preclinical Evaluation of Oncolytic Vaccinia Virus for Therapy of Canine Soft Tissue Sarcoma

Virotherapy using oncolytic vaccinia virus (VACV) strains is one promising new strategy for canine cancer therapy. In this study we describe the establishment of an in vivo model of canine soft tissue sarcoma (CSTS) using the new isolated cell line STSA-1 and the analysis of the virus-mediated oncolytic and immunological effects of two different Lister VACV LIVP1.1.1 and GLV-1h68 strains against CSTS. Cell culture data demonstrated that both tested VACV strains efficiently infected and destroyed cells of the canine soft tissue sarcoma line STSA-1. In addition, in our new canine sarcoma tumor xenograft mouse model, systemic administration of LIVP1.1.1 or GLV-1h68 viruses led to significant inhibition of tumor growth compared to control mice. Furthermore, LIVP1.1.1 mediated therapy resulted in almost complete tumor regression and resulted in long-term survival of sarcoma-bearing mice. The replication of the tested VACV strains in tumor tissues led to strong oncolytic effects accompanied by an intense intratumoral infiltration of host immune cells, mainly neutrophils. These findings suggest that the direct viral oncolysis of tumor cells and the virus-dependent activation of tumor-associated host immune cells could be crucial parts of anti-tumor mechanism in STSA-1 xenografts. In summary, the data showed that both tested vaccinia virus strains and especially LIVP1.1.1 have great potential for effective treatment of CSTS

Efficient Colonization and Therapy of Human Hepatocellular Carcinoma (HCC) Using the Oncolytic Vaccinia Virus Strain GLV-1h68

Virotherapy using oncolytic vaccinia virus strains is one of the most promising new strategies for cancer therapy. In this study, we analyzed for the first time the therapeutic efficacy of the oncolytic vaccinia virus GLV-1h68 in two human hepatocellular carcinoma cell lines HuH7 and PLC/PRF/5 (PLC) in cell culture and in tumor xenograft models. By viral proliferation assays and cell survival tests, we demonstrated that GLV-1h68 efficiently colonized, replicated in, and did lyse these cancer cells in culture. Experiments with HuH7 and PLC xenografts have revealed that a single intravenous injection (i.v.) of mice with GLV-1h68 resulted in a significant reduction of primary tumor sizes compared to uninjected controls. In addition, replication of GLV-1h68 in tumor cells led to strong inflammatory and oncolytic effects resulting in intense infiltration of MHC class II-positive cells like neutrophils, macrophages, B cells and dendritic cells and in up-regulation of 13 pro-inflammatory cytokines. Furthermore, GLV-1h68 infection of PLC tumors inhibited the formation of hemorrhagic structures which occur naturally in PLC tumors. Interestingly, we found a strongly reduced vascular density in infected PLC tumors only, but not in the non-hemorrhagic HuH7 tumor model. These data demonstrate that the GLV-1h68 vaccinia virus may have an enormous potential for treatment of human hepatocellular carcinoma in man

Bacterial glucuronidase as general marker for oncolytic virotherapy or other biological therapies

Background: Oncolytic viral tumor therapy is an emerging field in the fight against cancer with rising numbers of clinical trials and the first clinically approved product (Adenovirus for the treatment of Head and Neck Cancer in China) in this field. Yet, until recently no general (bio)marker or reporter gene was described that could be used to evaluate successful tumor colonization and/or transgene expression in other biological therapies. Methods: Here, a bacterial glucuronidase (GusA) encoded by biological therapeutics (e.g. oncolytic viruses) was used as reporter system. Results: Using fluorogenic probes that were specifically activated by glucuronidase we could show 1) preferential activation in tumors, 2) rena l excretion of the activated fluorescent compounds and 3) reproducible detection of GusA in the serum of oncolytic vaccinia virus treated, tumor bearing mice in several tumor models. Time course studies revealed that reliable differentiation between tumor bearing and healthy mice can be done as early as 9 days post injection of the virus. Regarding the sensitivity of the newly developed assay system, we could show that a single infected tumor cell could be reliably detected in this assay. Conclusion: GusA therefore has the potential to be used as a general marker in the preclinical and clinical evaluation of (novel) biological therapies as well as being useful for the detection of rare cells such as circulating tumor cell

A modified limiting dilution method for monoclonal stable cell line selection using a real-time fluorescence imaging system: A practical workflow and advanced applications

Stable cell lines are widely used in laboratory research and pharmaceutical industry. They are mainly applied in recombinant protein and antibody productions, gene function studies, drug screens, toxicity assessments, and for cancer therapy investigation. There are two types of cell lines, polyclonal and monoclonal origin, that differ regarding their homogeneity and heterogeneity. Generating a high-quality stable cell line, which can grow continuously and carry a stable genetic modification without alteration is very important for most studies, because polyclonal cell lines of multicellular origin can be highly variable and unstable and lead to inconclusive experimental results. The most commonly used technologies of single cell originate monoclonal stable cell isolation in laboratory are fluorescence-activated cell sorting (FACS) sorting and limiting dilution cloning. Here, we describe a modified limiting dilution method of monoclonal stable cell line selection using the real-time fluorescence imaging system IncuCyte^®S3