BioModels

Modelling combined virotherapy and immunotherapy:strengthening the antitumour immune response mediated byIL-12 and GM-CSF expression
Adrianne L. Jennera, Chae-Ok Yunb, Arum Yoonb, Adelle C. F. Costercand Peter S. Kimaa

School of Mathematics and Statistics, University of Sydney, Sydney, Australia;bDepartment ofBioengineering, Hanyang University, Seoul, Korea;cSchool of Mathematics and Statistics, University of NewSouth Wales, Sydney, Australia

ABSTRACT
Combined virotherapy and immunotherapy has been emergingas a promising and effective cancer treatment for some time.Intratumoural injections of an oncolytic virus instigate an immunereaction in the host, resulting in an influx of immune cells tothe tumour site. Through combining an oncolytic viral vector withimmunostimulatory cytokines an additional antitumour immuneresponse can be initiated, whereby immune cells induce apoptosisin both uninfected and virus infected tumour cells. We developa mathematical model to reproduce the experimental results fortumour growth under treatment with an oncolytic adenovirus co-expressing the immunostimulatory cytokines interleukin 12 (IL-12)and granulocyte-monocyte colony stimulating factor (GM-CSF). Byexploring heterogeneity in the immune cell stimulation by thetreatment, we find a subset of the parameter space for the immunecell induced apoptosis rate, in which the treatment will be lesseffective in a short time period. Therefore, we believe the bivariatenature of treatment outcome, whereby tumours are either completelyeradicated or grow unbounded, can be explained by heterogeneity inthis immune characteristic. Furthermore, the model highlights theapparent presence of negative feedback in the helper T cell and APCstimulation dynamics, when IL-12 and GM-CSF are co-expressed asopposed to individually expressed by the viral vector.