Intraoral GS-Nitroxide (JP4-039) Reduces Local Mucositis and Distant Marrow Suppression Toxicities In Head and Neck Irradiated Fancd2-/- (FVB/N) Mice

The DNA repair defect in Fanconi Anemia patients limits effective radiotherapy. We quantitated oral cavity tissue damage in Head and Neck irradiated FancD2-/-, Fancd2+/- and FancD2+/+ mice, parameters of femoral bone marrow hematopoiesis and the effect of intraoral administration of mitochondrial targeted JP4-039 delivered in novel F15 liposomes.  Adult 10-12 week mice were irradiated to the head and neck to 24, 26 or 28 Gy, shielding all tissue below the cervical spine.  JP4-039/F15 was administered to a subgroup intraorally 10 min before irradiation.  On day 2 or 5 post irradiation, mice were sacrificed, tongue and femur marrow harvested for histopathology, and marrow was assayed for hematopoietic colony formation.  At 5 days post 26 Gy, FancD2 +/- and Fancd2 -/- mice had significantly greater tongue ulceration (52.8 ± 6.5%, p=0.0014 and 59.4 ± 3.4%, p=0.0001, respectively) compared to FancD2 +/+ mice (21.7±4.7%).  JP4-039/F15 significantly reduced local tongue ulceration in all genotypes: FancD2 +/+ reduced to 12.2 ± 1.0 (p = 0.0049), FancD2 +/- reduced to 10.6 ± 3.5 (p < 0.0001) and FancD2 -/- reduced to 11.0 ± 2.5 (p < 0.0001).  FancD2 -/- and FancD2 +/- mice showed “bystander-effect” reduction in femur marrow CFU-GM at 2 days after 26 Gy compared to nonirradiated controls (p=0.007).  FancD2 -/- mice showed decreased BFU-E at day 2 after 24 Gy (p=0.009), CFU-GEMM after 26 Gy (p=0.048), BFU-E after 26 Gy and significantly less CFU-GM after 26 Gy or 28 Gy (p=0.017 and p=0.028, respectively). Intraoral JP4-039 prevented the marrow cytoreductive effects of head and neck irradiation. No reduction in femur marrow CFU-GM, BFU-E or CFU-GEMM was detected in FancD2+/+ mice.  Biallelic or monoallelic loss of the Fancd2 gene renders mice sensitive to head and neck irradiation and is accompanied by distant femur marrow suppression.  Both local and distant irradiation toxicities are ameliorated by intraoral administration of JP4-039.  FancD2-/- mice are an excellent model for testing new agents to control local and distant “bystander effect” toxicities of ionizing irradiation.