656. Combined Oncolysis and Anti-Angiogenesis Gene Therapy Using a Herpes Simplex Virus Expressing Endostatin in a Murine Lung Cancer Model
Authors: Michael Lanuti, JonathanM. Goodwin, KennethK. Tanabe
Journal: Molecular Therapy (2006)

Malignant pleural mesothelioma is unresponsive to most forms of therapy and often recurs after multimodality regimens. Oncolytic gene therapy using a replication-conditional Herpes virus in combination with anti-angiogenesis strategies may provide a novel adjunct to the treatment of this resistant tumor. The aim of this study is to evaluate a novel treatment strategy in a murine model of malignant mesothelioma. Since Herpes-mediated viral oncolysis alone is not sufficient to completely eradicate tumors in many animal models, we employed the use of angiogenesis inhibition to augment the anti-tumor effect. Endostatin is derived from the carboxyl-terminal end of collagen XVIII and is a potent inhibitor of endothelial cell migration, proliferation and vascular permeability. To measure the in-vivo efficacy of endostatin, we created a stable transfectant expressing mouse endostatin in a murine mesothelioma cell line (AB12pEndo). In vitro proliferation of this transformed cell line demonstrated similar growth speed to the parent cell line. Compared to the parent cell line (AB12), tumor growth was markedly reduced (mean volume = 1274mm3 vs. 8 mm3 at 3 weeks) in a syngeneic flank model (see Figure 1). Circulating endostatin was elevated in the serum of mice bearing the transformed cell line when compared to control. Expression of endostatin and its associated anti-tumor affects were then evaluated in a replication-conditional Herpes virus constructed to harbor the endostatin transgene (HSV-endo). This HSV mutant replicates preferentially in neoplastic cells by virtue of inactivation of the gene (UL39) encoding viral ribonucleotide reductase. Quantitative western blot analysis demonstrated superior expression of endostatin in-vitro using HSV-endo at low multiplicity of infection (MOI) when compared to an equivalent cell number of AB12pEndo. Intra-tumoral treatment with HSV-endo displayed a marked anti-tumor effect compared to PBS treatment in a flank model of murine mesothelioma, but was virtually identical to a control Herpes virus harboring a lacZ transgene in lieu of endostatin. In conclusion, murine mesothelioma (AB12) appears quite sensitive to the oncolytic effect of this Herpes vector, but may be too sensitive to effectively evaluate the relative contribution of angiogenesis inhibition. Cell lines relatively resistant to Herpes oncolysis should be considered to adequately evaluate this novel reagent. Malignant pleural mesothelioma is unresponsive to most forms of therapy and often recurs after multimodality regimens. Oncolytic gene therapy using a replication-conditional Herpes virus in combination with anti-angiogenesis strategies may provide a novel adjunct to the treatment of this resistant tumor. The aim of this study is to evaluate a novel treatment strategy in a murine model of malignant mesothelioma. Since Herpes-mediated viral oncolysis alone is not sufficient to completely eradicate tumors in many animal models, we employed the use of angiogenesis inhibition to augment the anti-tumor effect. Endostatin is derived from the carboxyl-terminal end of collagen XVIII and is a potent inhibitor of endothelial cell migration, proliferation and vascular permeability. To measure the in-vivo efficacy of endostatin, we created a stable transfectant expressing mouse endostatin in a murine mesothelioma cell line (AB12pEndo). In vitro proliferation of this transformed cell line demonstrated similar growth speed to the parent cell line. Compared to the parent cell line (AB12), tumor growth was markedly reduced (mean volume = 1274mm3 vs. 8 mm3 at 3 weeks) in a syngeneic flank model (see Figure 1). Circulating endostatin was elevated in the serum of mice bearing the transformed cell line when compared to control. Expression of endostatin and its associated anti-tumor affects were then evaluated in a replication-conditional Herpes virus constructed to harbor the endostatin transgene (HSV-endo). This HSV mutant replicates preferentially in neoplastic cells by virtue of inactivation of the gene (UL39) encoding viral ribonucleotide reductase. Quantitative western blot analysis demonstrated superior expression of endostatin in-vitro using HSV-endo at low multiplicity of infection (MOI) when compared to an equivalent cell number of AB12pEndo. Intra-tumoral treatment with HSV-endo displayed a marked anti-tumor effect compared to PBS treatment in a flank model of murine mesothelioma, but was virtually identical to a control Herpes virus harboring a lacZ transgene in lieu of endostatin. In conclusion, murine mesothelioma (AB12) appears quite sensitive to the oncolytic effect of this Herpes vector, but may be too sensitive to effectively evaluate the relative contribution of angiogenesis inhibition. Cell lines relatively resistant to Herpes oncolysis should be considered to adequately evaluate this novel reagent.