Bioluminescence imaging of a tumor-selective, thymidine kinase-defective vaccinia virus Guang9 strain after intratumoral or intraperitoneal administration in mice

Combined anti-tumor efficacy of somatostatin fusion protein and vaccinia virus on tumor cells with high expression of somatostatin receptors

Somatostatin, a growth hormone-release inhibiting peptide, exerts antiproliferative and antiangiogenic effects on tumor cells. However, the short half-life of somatostatin limits its application in human therapy, and long-acting somatostatin fusion protein is also limited by its severe terminal degradation. Therefore, oncolytic virus delivery system was introduced to express somatostatin fusion protein and the anti-tumor effects of both somatostatin and oncolytic virus were combined to destroy tumor tissues. Here, a vaccinia VG9/(SST-14)₂-HSA recombinant was constructed by replacing somatostatin fusion gene into TK locus of attenuated VG9 strain via homologous recombination. Results showed that vaccinia VG9/(SST-14)₂-HSA possessed a combined anti-tumor effect on sstr-positive tumor cells in vitro. In the tumor burden models, BALB/c mice with complete immunity are most suitable for evaluating tumor regression and immune activation. Complete tumor regression was observed in 3 out of 10 mice treated with vaccinia VG9/TK⁻ or VG9/(SST-14)₂-HSA, and the survival of all mice in both groups was significantly prolonged. Besides, vaccinia VG9/(SST-14)₂-HSA is more effective in prolonging survival than VG9/TK⁻. Vaccinia VG9/(SST-14)₂-HSA exerts a combined anti-tumor efficacy including the oncolytic ability provided by the virus and the anti-tumor effect contributed by (SST-14)₂-HSA, which is expected to become a potent therapeutic agent for cancer treatment.

Evaluation of Tumor Specificity and Immunity of Thymidine Kinase-Deleted Vaccinia Virus Guang9 Strain

Purpose

Oncolytic viruses are emerging as promising options for clinical cancer treatment due to their inherent ability of tumor tropism and oncolytic property. Aside from tumor lysis, oncolytic viruses can induce host immune responses against tumor cells and may thus be viewed as a form of immunotherapy.

Methods

The attenuated vaccinia VG9-Luc, which originated from Chinese vaccinia Tian Tan strain, was constructed to express firefly luciferase for bioluminescence imaging and to disrupt the thymidine kinase gene for promoting tumor specificity. An in vivo bioluminescence imaging was performed to observe the virus distribution in live mice. The titers of neutralizing antiviral and antitumor antibodies in plasma were determined by time-resolved fluoroimmunoassay.

Results

Except BALB/c mice treated with intravenous virus injection, all immunocompromised and immunocompetent mice showed obvious tumor targeting ability of vaccinia VG9-Luc. Besides, host immune response activated by vaccinia VG9-Luc showed the production of antiviral and antitumor antibodies, the process of which was similar between intravenous and intratumoral viral delivery systems. The results indicated that virus infection promoted tumor-specific immunity by increasing the production of antitumor antibodies. Moreover, virus reinjection was performed and a more rapid viral clearance was observed in immunocompetent mice compared with first virus infection.

Conclusion

The thymidine kinase-deleted vaccinia Guang9 strain, which has the properties of tumor specificity and antitumor immunity, is a promising candidate vector for cancer therapy.

Antitumor efficacy of cytosine deaminase-armed vaccinia virus plus 5-fluorocytosine in colorectal cancers

Background

Vaccinia viruses have emerged as attractive therapeutic candidates for cancer treatment due to their inherent ability of tumor tropism and oncolytic property. Cytosine deaminase (CD), which is derived from bacteria or yeast, can convert a relatively nontoxic prodrug 5-fluorocytosine (5-FC) into the active anticancer drug 5-Fluorouracil (5-FU). Vaccinia virus armed with the prodrug-activator CD gene would result in augmented antitumor effects that combined the effect of vaccinia virus and 5-FU together, and particularly limited the anticancer drug to tumor regions.

Methods

The attenuated vaccinia Tian Tan strain Guang 9 (VG9), with active yeast CD expression and thymidine kinase (TK) deficiency, was successfully constructed. Then, in vitro and in vivo antitumor efficacy of vaccinia VG9-CD plus 5-FC administration was evaluated in colorectal cancer cells.

Results

Vaccinia viruses displayed different oncolytic potency in vitro cells, no relationship with whether they were cancer cells or normal cells. In colorectal tumor models, mice treated with vaccinia VG9-TK^- showed better tumor remission ability and prolonged survival. Moreover, vaccinia VG9-CD in combination with gavage administration of 5-FC displayed the best antitumor efficacy, especially for the prolongation of survival.

Conclusions

Vaccinia VG9-CD in combination with 5-FC plays combined effect of vaccinia virus and chemotherapy, and becomes a promising virotherapy for cancer.

Oncolytic Activity of a Novel Influenza A Virus Carrying Granulocyte-Macrophage Colony-Stimulating Factor in Hepatocellular Carcinoma

Oncolytic virotherapy is a promising strategy for the treatment of cancer. Influenza A virus has shown potential as an oncolytic agent. In this study, a recombinant PR8 influenza viral vector, called delNS1-GM-CSF, was generated with a partial deletion in NS and the granulocyte-macrophage colony-stimulating factor (GM-CSF) coding sequence inserted into the influenza nonstructural protein 1 gene. The morphological characteristics of delNS1-GM-CSF were examined. The delNS1-GM-CSF virus replicated well in various cell lines, including MDCK, A549, SMCC7721, and HepG2 cells. Moreover, selective cytotoxicity of the virus was observed in various hepatocellular carcinoma (HCC) cell lines, while no effect was demonstrated in the normal liver cell line LO2, as indicated by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide and crystal violet assays. Importantly, using a model based on the growth of HepG2 cells as a xenograft in nude mice, it was found that a reassortant delNS1-GM-CSF virus inhibited tumor growth significantly following intratumoral injection in a dose-dependent manner. Ex vivo results showed that the tumor inhibition efficacy of delNS1-GM-CSF was observed in HCC clinical samples. Taken together, these results are the first to demonstrate that influenza A viruses may have potential as oncolytic virotherapeutic agents against HCC.