Second-Generation Probiotic Lactobacillus Reuteri Producing IL-22 (LR-IL-22) Protects the Intestine to Facilitate Whole Abdomen Irradiation (WAI) in Ovarian Cancer.

Purpose/Objective(s) We delivered intraoral (gavage) of LR-IL-22 (Zhang, et al., In Vivo, 34: 139-150, 2020) prior to whole abdominal irradiation (WAI) of C57BL/6J mice and quantitated survival, intestinal barrier integrity, and levels of irradiation-induced inflammatory cytokines. We measured the effect on fractionated WAI of LR-IL-22 in transgenic C57BL/6J-MUC1 (human-MUC1) female mice with widespread intra-abdominal cisplatin-resistant ovarian cancer. Materials/Methods C57BL/6J mice were irradiated to 19.75 Gy WAI, then evaluated for the primary endpoint of improved 30-day survival. Fluorescent beads (F13083 FluoSpheres™ Polystyrene Microspheres, 1.0 μm, red fluorescent (580/605), for tracer studies) were administered intraorally three hours prior to sacrifice at days 2 or 5 after WAI, and blood was assayed for beads. Luminex assay of plasma and intestinal cells were also assayed at days 0, 1, 2, 3, and 5 after WAI for radiation-induced inflammatory cytokines. Murine ovarian cancer 2F8cis cells were injected intraperitoneally into female transgenic C57BL/6J-MUC1 mice (1 × 106 cells per mouse). Seventy-two hours later, mice were irradiated to 16 Gy WAI and followed for tumor growth. In a separate experiment, female mice harboring 2F8cis tumors were irradiated to 6 Gy WAI daily for 4 successive days. Overall survival was compared between groups: irradiation only, LR-IL-22 gavage three hours prior to each fraction, and/or weekly anti-PD-L1 antibody treatment. Results Mice receiving LR-IL-22 (109 bacteria in 100 µL of saline) 24-hours and 3-hours prior to a single fraction of 19.75 Gy WAI, and 24-hours following irradiation, showed improved survival and barrier integrity compared to those receiving control LR or IL-22 protein (P = 0.0167 or 0.0276, n = 15). LR-IL-22 gavage maintained intestinal barrier integrity and decreased levels of intestinal pro-inflammatory cytokines, including KC (CXCL1) (P = 0.002), and IFN- γ (P = 0.0024), as well as profibrotic plasma Eotaxin (CCL11) (P = 0.0088). In MUC1 transgenic female mice with tumors, nonirradiated mice had over 100 disseminated tumor nodules throughout the abdomen at day 10, while control WAI mice or those treated with intraoral LR-IL-22 had less than 10 nodules at day 10 (P = 0.0471); furthermore, LR-IL-22 treated mice showed reduced intestinal edema. C57BL/6J-MUC1 female mice with intra-abdominal 2F8cis tumor showed significantly improved 30-day survival by adding LR-IL-22 and anti-PD-L1 to 6 Gy × 4 WAI (P = 0.0004). Conclusion Intraoral LR-IL-22 prior to WAI protects the intestine from radiation-induced toxicity and facilitates fractionated therapeutic WAI to improve survival in cis-platinum resistant ovarian cancer. Author Disclosure D.F. Hamade: None. M. Epperly: None. R. Fisher: None. W. Hou: None. J.S. Greenberger: None.