Oncolytic virus efficiency inhibited growth of tumour cells with multiple drug resistant phenotype in vivo and in vitro

Developing Oncolytic Viruses for the Treatment of Cervical Cancer

Cervical cancer represents one of the most important malignancies among women worldwide. Current therapeutic approaches for cervical cancer are reported not only to be inadequate for metastatic cervical cancer, but are also considered as cytotoxic for several patients leading to serious side effects, which can have negative implications on the quality of life of women. Therefore, there is an urgent need for the development of innovative and effective treatment options. Oncolytic viruses can eventually become effective biological agents, since they preferentially infect and kill cancer cells, while leaving the normal tissue unaffected. Moreover, they are also able to leverage the host immune system response to limit tumor growth. This review aims to systematically describe and discuss the different types of oncolytic viruses generated for targeting cervical cancer cells, as well as the outcome of the combination of virotherapy with conventional therapies. Although many preclinical studies have evaluated the therapeutic efficacy of oncolytic viruses in cervical cancer, the number of clinical trials so far is limited, while their oncolytic properties are currently being tested in clinical trials for the treatment of other malignancies.

Systems Biology Approaches for the Improvement of Oncolytic Virus-Based Immunotherapies

Oncolytic virus (OV)-based immunotherapy is mainly dependent on establishing an efficient cell-mediated antitumor immunity. OV-mediated antitumor immunity elicits a renewed antitumor reactivity, stimulating a T-cell response against tumor-associated antigens (TAAs) and recruiting natural killer cells within the tumor microenvironment (TME). Despite the fact that OVs are unspecific cancer vaccine platforms, to further enhance antitumor immunity, it is crucial to identify the potentially immunogenic T-cell restricted TAAs, the main key orchestrators in evoking a specific and durable cytotoxic T-cell response. Today, innovative approaches derived from systems biology are exploited to improve target discovery in several types of cancer and to identify the MHC-I and II restricted peptide repertoire recognized by T-cells. Using specific computation pipelines, it is possible to select the best tumor peptide candidates that can be efficiently vectorized and delivered by numerous OV-based platforms, in order to reinforce anticancer immune responses. Beyond the identification of TAAs, system biology can also support the engineering of OVs with improved oncotropism to reduce toxicity and maintain a sufficient portion of the wild-type virus virulence. Finally, these technologies can also pave the way towards a more rational design of armed OVs where a transgene of interest can be delivered to TME to develop an intratumoral gene therapy to enhance specific immune stimuli.

Anti-cancer Virotherapy in Russia: Lessons from the Past, Current Challenges and Prospects for the Future

The idea of using the lytic power of viruses against malignant cells has been entertained for many decades. However, oncolytic viruses gained broad attention as an emerging anti-cancer therapy only recently with the successful implementation of several oncolytic viruses to treat advanced melanoma. Here we review the history of oncolytic viruses in the Russian Federation and recent biotechnological advances in connection with the perspectives of their practical use against aggressive tumors such as glioblastoma or pancreatic cancer. A particular emphasis is made on novel applications of safe non-lytic virus-derived vectors armed with prodrug-converting enzyme transgenes. Rational improvement of oncotropism by conjugation with biopolymers and nanoformulations is also discussed.

Inhibition of MEK-ERK pathway enhances oncolytic vaccinia virus replication in doxorubicin-resistant ovarian cancer

Oncolytic vaccinia virus (OVV) has been reported to induce cell death in various types of cancer; however, the oncolytic activity of OVV in drug-resistant ovarian cancer remains limited. In the present study, we established doxorubicin-resistant ovarian cancer cells (A2780-R) from the A2780 human ovarian cancer cell line. Both A2780 and A2780-R cells were infected with OVV to explore its anticancer effects. Interestingly, OVV-infected A2780-R cells showed reduced viral replication and cell death compared with A2780 cells, suggesting their resistance against OVV-induced oncolysis; to understand the mechanism underlying this resistance, we explored the involvement of protein kinases. Among protein kinase inhibitors, PD0325901, an MEK inhibitor, significantly augmented OVV replication and cell death in A2780-R cells. PD0325901 treatment increased the phosphorylation of STAT3 in A2780-R cells. Moreover, cryptotanshinone, a STAT3 inhibitor, abrogated PD0325901-stimulated OVV replication. Furthermore, trametinib, a clinically approved MEK inhibitor, increased OVV replication in A2780-R cells. Transcriptomic analysis showed that the MEK inhibitor promoted OVV replication via increasing STAT3 activation and downregulating the cytosolic DNA-sensing pathway. Combined treatment with OVV and trametinib attenuated A2780-R xenograft tumor growth. These results suggest that pharmacological inhibition of MEK reinforces the oncolytic efficacy of OVV in drug-resistant ovarian cancer.

Enhancing the Protective Immune Response to Administration of a LIVP-GFP Live Attenuated Vaccinia Virus to Mice

Following the WHO announcement of smallpox eradication, discontinuation of smallpox vaccination with vaccinia virus (VACV) was recommended. However, interest in VACV was soon renewed due to the opportunity of genetic engineering of the viral genome by directed insertion of foreign genes or introduction of mutations or deletions into selected viral genes. This genomic technology enabled production of stable attenuated VACV strains producing antigens of various infectious agents. Due to an increasing threat of human orthopoxvirus re-emergence, the development of safe highly immunogenic live orthopoxvirus vaccines using genetic engineering methods has been the challenge in recent years. In this study, we investigated an attenuated VACV LIVP-GFP (TK^-) strain having an insertion of the green fluorescent protein gene into the viral thymidine kinase gene, which was generated on the basis of the LIVP (Lister-Institute for Viral Preparations) strain used in Russia as the first generation smallpox vaccine. We studied the effect of A34R gene modification and A35R gene deletion on the immunogenic and protective properties of the LIVP-GFP strain. The obtained data demonstrate that intradermal inoculation of the studied viruses induces higher production of VACV-specific antibodies compared to their levels after intranasal administration. Introduction of two point mutations into the A34R gene, which increase the yield of extracellular enveloped virions, and deletion of the A35R gene, the protein product of which inhibits presentation of antigens by MHC II, enhances protective potency of the created LIVP-TK^--A34R*-dA35R virus against secondary lethal orthopoxvirus infection of BALB/c mice even at an intradermal dose as low as 10³ plaque forming units (PFU)/mouse. This virus may be considered not only as a candidate attenuated live vaccine against smallpox and other human orthopoxvirus infections but also as a vector platform for development of safe multivalent live vaccines against other infectious diseases using genetic engineering methods.

Effect of the Route of Administration of the Vaccinia Virus Strain LIVP to Mice on Its Virulence and Immunogenicity

The mass smallpox vaccination campaign has played a crucial role in smallpox eradication. Various strains of the vaccinia virus (VACV) were used as a live smallpox vaccine in different countries, their origin being unknown in most cases. The VACV strains differ in terms of pathogenicity exhibited upon inoculation of laboratory animals and reactogenicity exhibited upon vaccination of humans. Therefore, each generated strain or clonal variant of VACV needs to be thoroughly studied in in vivo systems. The clonal variant 14 of LIVP strain (LIVP-14) was the study object in this work. A comparative analysis of the virulence and immunogenicity of LIVP-14 inoculated intranasally (i.n.), intradermally (i.d.), or subcutaneously (s.c.) to BALB/c mice at doses of 108, 107, and 106 pfu was carried out. Adult mice exhibited the highest sensitivity to the i.n. administered LIVP-14 strain, although the infection was not lethal. The i.n. inoculated LIVP-14 replicated efficiently in the lungs. Furthermore, this virus was accumulated in the brain at relatively high concentrations. Significantly lower levels of LIVP-14 were detected in the liver, kidneys, and spleen of experimental animals. No clinical manifestations of the disease were observed after i.d. or s.c. injection of LIVP-14 to mice. After s.c. inoculation, the virus was detected only at the injection site, while it could disseminate to the liver and lungs when delivered via i.d. administration. A comparative analysis of the production of virus-specific antibodies by ELISA and PRNT revealed that the highest level of antibodies was induced in i.n. inoculated mice; a lower level of antibodies was observed after i.d. administration of the virus and the lowest level after s.c. injection. Even at the lowest studied dose (106 pfu), i.n. or i.d. administered LIVP-14 completely protected mice against infection with the cowpox virus at the lethal dose. Our findings imply that, according to the ratio between such characteristics as pathogenicity/immunogenicity/protectivity, i.d. injection is the optimal method of inoculation with the VACV LIVP-14 strain to ensure the safe formation of immune defense after vaccination against orthopoxviral infections.

Therapeutic potency of oncolytic virotherapy-induced cancer stem cells targeting in brain tumors, current status, and perspectives

Brain tumors are the most common form of solid tumors in children and is presently a serious therapeutic challenge worldwide. Traditional treatment with chemotherapy and radiotherapy was shown to be unsuccessful in targeting brain tumor cancer stem cells (CSCs), leading to recurrent, treatment-resistant secondary malignancies. Oncolytic virotherapy (OV) is an effective antitumor therapeutic strategy which offers a novel, targeted approach for eradicating pediatric brain tumor CSCs by utilizing mechanisms of cell killing that differ from conventional therapies. A number of studies and some clinical trials have therefore investigated the effects of combined therapy of radiations or chemotherapies with oncolytic viruses which provide new insights regarding the effectiveness and improvement of treatment responses for brain cancer patients. This review summarizes the current knowledge of the therapeutic potency of OVs-induced CSCs targeting in the treatment of brain tumors for a better understanding and hence a better management of this disease.

Virotherapy of the Malignant U87 Human Glioblastoma in the Orthotopic Xenotransplantation Mouse SCID Model

The possibility of glioblastoma virotherapy at intravenous injection of the LIVP-GFP recombinant virus was studied in experimental model of orthotopic xenotransplantation of human glioblastoma cell line U87 to SCID laboratory mice. The LIVP-GFP recombinant virus deficient for thymidine kinase exhibited a significantly greater oncolytic capacity than the original LIVP virus, and an intravenous injection of LIVP-GFP at the early stages of tumorigenesis in mouse brain in most cases resulted in the lysis of the tumor.

Oncolytic Viruses for Tumor Precision Imaging and Radiotherapy

In 2003 in China, Peng et al. invented the recombinant adenovirus expressing p53 (Gendicine) for clinical tumor virotherapy. This was the first clinically approved gene therapy and tumor virotherapy drug in the world. An oncolytic herpes simplex virus expressing granulocyte-macrophage colony-stimulating factor (Talimogene laherparepvec) was approved for melanoma treatment in the United States in 2015. Since then, oncolytic viruses have been attracting more and more attention in the field of oncology, and may become novel significant modalities of tumor precision imaging and radiotherapy after further improvement. Oncolytic viruses carrying reporter genes can replicate and express genes of interest selectively in tumor cells, thus improving in vivo noninvasive precision molecular imaging and radiotherapy. Here, the latest developments and molecular mechanisms of tumor imaging and radiotherapy using oncolytic viruses are reviewed, and perspectives are given for further research. Various types of tumors are discussed, and special attention is paid to gastrointestinal tumors.