Using targeted virotherapy to treat a resistant Ewing sarcoma model: from the bedside to the bench and back

Will Next-Generation Immunotherapy Overcome the Intrinsic Diversity and Low Immunogenicity of Sarcomas to Improve Clinical Benefit?

Sarcomas are a rare type of a heterogeneous group of tumours arising from mesenchymal cells that form connective tissues. Surgery is the most common treatment for these tumours, but additional neoadjuvant or adjuvant chemotherapy or radiation therapies may be necessary. Unfortunately, a significant proportion of patients treated with conventional therapies will develop metastatic disease that is resistant to therapies. Currently, there is an urgent need to develop more effective and durable therapies for the treatment of sarcomas. In recent years immunotherapies have revolutionised the treatment of a variety of cancers by restoring patient anti-tumour immune responses or through the adoptive infusion of immune effectors able to kill and eliminate malignant cells. The clinicopathologic and genetic heterogeneity of sarcomas, together with the generally low burden of somatic mutations potentially generating neoantigens, are currently limited to broad application of immunotherapy for patients with sarcomas. Nevertheless, a better understanding of the microenvironmental factors hampering the efficacy of immunotherapy and the identification of new and suitable therapeutic targets may help to overcome current limitations. Moreover, the recent advances in the development of immunotherapies based on the direct exploitation or targeting of T cells and/or NK cells may offer new opportunities to improve the treatment of sarcomas, particularly those showing recurrence or resistance to standard of care treatments.

Novel Near-Infrared Fluorescence-Guided Surgery With Vesicular Stomatitis Virus for Complete Surgical Resection of Osteosarcomas in Mice

Attempts have been made to visualize tumor cells intraoperatively with fluorescence guidance. However, the clear demarcation and complete tumor resection have always been a challenging task. To address this, we have developed a novel fluorescence bioimaging system with vesicular stomatitis virus (VSV) incorporating Katushka, near-infrared fluorescent protein. VSV is tumor-specific owing to the deficiency of antiviral interferon signaling pathways in tumor cells. We aimed to evaluate the tumor specificity of the recombinant VSV-Katushka (rVSV-K) in osteosarcoma cells and to assess the feasibility of complete tumor resection by the rVSV-K fluorescence guidance. In in vitro experiments, mouse and human osteosarcoma cell lines and normal human mesenchymal stem cells were infected with rVSV-K and observed by fluorescence microscopy. Near-infrared fluorescence was observed only in osteosarcoma cells, even at a low-concentration of virus infections. In in vivo experiments, mouse osteosarcoma (LM8) cells were transplanted subcutaneously into the back of immune-competent mice to produce an osteosarcoma, which was then injected with rVSV-K. The areas emitting fluorescence were resected using a bioimaging system. The distance between the surgical and tumor margins of the fluorescence-guided resection with rVSV-K group was significantly larger than that of the non-guided resection groups. The local recurrence rate was significantly lower in the fluorescence-guided resection with rVSV-K group than in the non-guided resection groups. The distant metastasis rate and average survival rate were not significantly different between all groups. These results suggest that the rVSV-K is specific to osteosarcoma cells and enables complete tumor resection of osteosarcomas in mice. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Potential approaches to the treatment of Ewing's sarcoma

Ewing’s sarcoma (ES) is a highly aggressive and metastatic tumor in children and young adults caused by a chromosomal fusion between the Ewing sarcoma breakpoint region 1 (EWSR1) gene and the transcription factor FLI1 gene. ES is managed with standard treatments, including chemotherapy, surgery and radiation. Although the 5-year survival rate for primary ES has improved, the survival rate for ES patients with metastases or recurrence remains low. Several novel molecular targets in ES have recently been identified and investigated in preclinical and clinical settings, and targeting the function of receptor tyrosine kinases (RTKs), the fusion protein EWS-FLI1 and mTOR has shown promise. There has also been increasing interest in the immune responses of ES patients. Immunotherapies using T cells, NK cells, cancer vaccines and monoclonal antibodies have been considered for ES, especially for recurrent patients. Because understanding the pathogenesis of ES is extremely important for the development of novel treatments, this review focuses on the mechanisms and functions of targeted therapies and immunotherapies in ES. It is anticipated that integrating the knowledge obtained from basic research and translational and clinical studies will lead to the development of novel therapeutic strategies for the treatment of ES.

Recent advances in vesicular stomatitis virus-based oncolytic virotherapy: a 5-year update

Oncolytic virus (OV) therapy is an anti-cancer approach that uses viruses that preferentially infect, replicate in and kill cancer cells. Vesicular stomatitis virus (VSV, a rhabdovirus) is an OV that is currently being tested in the USA in several phase I clinical trials against different malignancies. Several factors make VSV a promising OV: lack of pre-existing human immunity against VSV, a small and easy to manipulate genome, cytoplasmic replication without risk of host cell transformation, independence of cell cycle and rapid growth to high titres in a broad range of cell lines facilitating large-scale virus production. While significant advances have been made in VSV-based OV therapy, room for improvement remains. Here we review recent studies (published in the last 5 years) that address 'old' and 'new' challenges of VSV-based OV therapy. These studies focused on improving VSV safety, oncoselectivity and oncotoxicity; breaking resistance of some cancers to VSV; preventing premature clearance of VSV; and stimulating tumour-specific immunity. Many of these approaches were based on combining VSV with other therapeutics. This review also discusses another rhabdovirus closely related to VSV, Maraba virus, which is currently being tested in Canada in phase I/II clinical trials.

Recent advances of biomaterials in biotherapy

Biotherapy mainly refers to the intervention and the treatment of major diseases with biotechnologies or bio-drugs, which include gene therapy, immunotherapy (vaccines and antibodies), bone marrow transplantation and stem-cell therapy. In recent years, numerous biomaterials have emerged and were utilized in the field of biotherapy due to their biocompatibility and biodegradability. Generally, biomaterials can be classified into natural or synthetic polymers according to their source, both of which have attracted much attention. Notably, biomaterials-based non-viral gene delivery vectors in gene therapy are undergoing rapid development with the emergence of surface-modified or functionalized materials. In immunotherapy, biomaterials appear to be attractive means for enhancing the delivery efficacy and the potency of vaccines. Additionally, hydrogels and scaffolds are ideal candidates in stem-cell therapy and tissue engineering. In this review, we present an introduction of biomaterials used in above biotherapy, including gene therapy, immunotherapy, stem-cell therapy and tissue engineering. We also highlighted the biomaterials which have already entered the clinical evaluation