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Subclone of resistant CT26 murine tumor shows high sensitivity to VA7 virotherapy: A novel system to study innate immunity and antigen dominance in oncolytic immuno-virotherapy

ABSTRACT: Recently, attenuated Semliki Forest virus vector VA7 completely eliminated type I interferon (IFN) unresponsive human U87 glioma xenografts while IFN responsive mouse GL261 and CT-2A gliomas proved refractory to the oncolytic virotherapy. Here we describe in two clones of a well established Balb/c mouse tumor cell line, CT26 murine colon carcinoma, diametrically opposed IFN responsiveness and sensitivity to oncolytic virus. Both CT26WT and CT26LacZ clones secreted biologically active type I IFN in vitro upon infection but virus replication was self-limiting only in CT26WT cells. Total transcriptome sequencing (RNA-Seq) and western blotting experiments revealed that in sharp contrast to CT26LacZ cells, CT26WT cells had strong constitutive expression of 56 different genes associated with pattern recognition and type I interferon signaling pathways, spanning two reported anti-RNA virus gene signatures and22 genes that have been reported to have direct anti-Alphaviral activity. Correspondingly, only CT26LacZ tumors were infectable in vivo, resulting in rapid central necrosis of the tumors by 96 hours post infection and complete tumor eradication both in immunocompetent and in SCID mice. CT26LacZ tumor eradication by oncolysis induced 100% protective immunity against homologous CT26LacZ challenge but only 50% protection against heterologous CT26WT challenge, indicating LacZ immune dominance over shared antigens. We believe the two clone CT26 system described herein constitutes a challenging yet realistic model for clonally and immunologically heterogeneous cancer where a strong therapy efficacy bias toward sensitive tumor subpopulations might falsely predict therapeutic success on a broad patient scale highlighting the necessity of successful pre-screening for responsive tumors.

ORGANISM(S): Mus musculus

PROVIDER: GSE53001 | GEO | 2014/09/05

SECONDARY ACCESSION(S): PRJNA230647

REPOSITORIES: GEO

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Project description:Previously we reported that a recombinant vaccinia virus (VACV) carrying a light-emitting fusion gene enters, replicates in, and reveals the locations of tumors in mice. A new recombinant VACV, 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, b-galactosidase, and b-glucuronidase) into the F14.5L, J2R (encoding thymidine kinase, TK), and A56R (encoding hemagglutinin, HA) loci of the viral genome, respectively. Intravenous (i.v.) injections of GLV-1h68 (1 Ã 107 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. Objective: To determine the gene expression changes induced by GLV-1h68 vaccinia virus injection in mouse carrying human breast cancer implant and leading to tumor eradication. Methods: Gene expression was analyzed using oligonucleotide microarrays. Responsiveness to vaccina virus injection was assessed by toxicity and survival study, gene expression anaysis and tumor volume change. Result: 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. Conclusion: Our 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. Experiment Overall Design: tumor tissues 3 and 6 weeks post virus injection

Project description:Previously we reported that a recombinant vaccinia virus (VACV) carrying a light-emitting fusion gene enters, replicates in, and reveals the locations of tumors in mice. A new recombinant VACV, 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, b-galactosidase, and b-glucuronidase) into the F14.5L, J2R (encoding thymidine kinase, TK), and A56R (encoding hemagglutinin, HA) loci of the viral genome, respectively. Intravenous (i.v.) injections of GLV-1h68 (1 × 107 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. Objective: To determine the gene expression changes induced by GLV-1h68 vaccinia virus injection in mouse carrying human breast cancer implant and leading to tumor eradication. Methods: Gene expression was analyzed using oligonucleotide microarrays. Responsiveness to vaccina virus injection was assessed by toxicity and survival study, gene expression anaysis and tumor volume change. Result: 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. Conclusion: Our 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. Keywords: Responsiveness to vaccina virus injection

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Subclone of resistant CT26 murine tumor shows high sensitivity to VA7 virotherapy: A novel system to study innate immunity and antigen dominance in oncolytic immuno-virotherapy

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