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Treatment of an Alveolar Rhabdomyosarcoma Allograft with Recombinant Myxoma Virus and Oclacitinib

Authors Ashton LV, Graham B, Afzali MF, Gustafson D, MacNeill AL

Received 6 March 2020

Accepted for publication 5 May 2020

Published 26 May 2020 Volume 2020:9 Pages 17—29


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 2

Editor who approved publication: Dr Tommy Alain

Laura V Ashton,1 Barbara Graham,1 Maryam F Afzali,1 Daniel Gustafson,2 Amy L MacNeill1

1Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA; 2Departiment of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA

Correspondence: Amy L MacNeill Email

Purpose: Rhabdomyosarcomas (RMS) are difficult tumors to treat with conventional therapies. Publications indicate that oncolytic virotherapy (OV) could benefit cancer patients with tumors that are refractory to conventional treatments. It is believed that the efficacy of OV can be enhanced when used in combination with other treatments. This study evaluated the response of mice with aggressive alveolar RMS (ARMS) allografts to treatment with an OV [recombinant myxoma virus (MYXVΔserp2)] in combination with a Janus kinase (JAK) inhibitor (oclacitinib). Oclacitinib is known to inhibit JAK1 and JAK2 cell signaling pathways, which should limit the antiviral Type I interferon response. However, oclacitinib does not inhibit immune pathways that promote antigen presentation, which help stimulate an anti-cancer immune response.
Materials and Methods: To determine if MYXVΔserp2 and oclacitinib could improve outcomes in animals with ARMS, nude mice were inoculated subcutaneously with murine ARMS cells to establish tumors. Immune responses, tumor growth, and clinical signs in mice treated with combination therapy were compared to mice given placebo therapy and mice treated with OV alone.
Results: Combination therapy was safe; no viral DNA was detected in off-target organs, only within tumors. As predicted, viral DNA was detected in tumors of mice given oclacitinib and MYXVΔserp2 for a longer time period than mice treated with OV alone. Although tumor growth rates and median survival times were not significantly different between groups, clinical signs were less severe in mice treated with OV.
Conclusion: Our data indicate that MYXVΔserp2 treatment benefits mice with ARMS by reducing clinical signs of disease and improving quality of life.

Keywords: oncolytic virus, poxvirus, Janus kinase inhibitor, sarcoma

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