MRI of combination immunotherapy in an epithelial ovarian cancer preclinical model.

Immunotherapies such as checkpoint inhibitors (i.e. anti-PD-1) and peptide-based therapies (DPX-Survivac) have strong potential for treatment of epithelial ovarian cancer, the most lethal gynecological malignancy. Magnetic resonance imaging (MRI) can be used to track tumor growth and iron-labeled immune cells longitudinally at the individual level. We studied MRI immune cell tracking in a murine model of ovarian cancer using a clinically relevant treatment combination of DPX-Survivac, anti-PD-1, and an intermittent low dose of Cyclophosphamide (CPA). HHD-DR1 mice were orthotopically implanted with mouse ovarian surface epithelial (MOSE) cancer cells. Myeloid and CD8 cells were isolated from matched donor mice, labeled with superparamagnetic iron oxide (SPIO) and were scanned using MRI on days 42, 49 and 56. Tumor volumes in the treatment group as measured by MRI were significantly lower than in the control group (p < 0.01). The density of SPIO-labeled myeloid and CD8 T cells in tumors was higher in the treatment group than in the control group. This study provides insights into how MRI can be used in concert with biological assays to study how immunotherapy and chemotherapy combinations exert their antitumor effects.