3056 - Effect of Sex on <em>Limosilactobacillus Reuteri </em>Releasing IL-22 (LR-IL-22) Mitigation of Gastrointestinal-Acute Radiation Syndrome
Presenter(s)
D. F. Hamade1, A. Mukherjee2, M. Epperly3, R. Fisher4, D. Shields4, J. P. van Pijkeren5, B. J. Leibowitz1, L. Coffman6, H. Wang7, M. S. S. Huq8, A. B. Kohan4, J. Yu9, E. E. Kershaw4, B. Methe4, T. Hand4, C. J. Rogers10, and J. S. Greenberger3; 1UPMC Hillman Cancer Center, Pittsburgh, PA, 2University Of Pittsburgh, Pittsburgh, PA, 3UPMC-Shadyside Hospital Department of Radiation Oncology, Pittsburgh, PA, 4University of Pittsburgh, Pittsburgh, PA, 5The University of Wisconsin Madison, Madison, WI, 6Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA, 7University of Pittsburgh School of Medicine, Pittsburgh, PA, 8Department of Radiation Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 9University of Southern California, Los Angeles, CA, 10Chromologic LLC, Pasadena, CA
Purpose/Objective(s):
Sex differences exist in terms of response to irradiation, however the mechanism has yet to be determined. The objective is to establish the basis for sex in the irradiation response by focusing on sex hormones such as estrogen in medically castrated female mice, and the role of Tamoxifen (TM) in mediating radioresistance.Materials/Methods:
Adult male and female C57BL/6 mice and germ-free mice received either a single fraction of 9.25 Gy total body irradiation (TBI) or 12 Gy of partial body irradiation (PBI) with one hind limb shielded (5% of bone marrow). Following irradiation, some were treated with oral gavage of LR-IL-22, or subcutaneous slow-release pellets of either ß-Estradiol or TM. Finally, to assess differential gene expression between sex following irradiation, we performed RNAseq analyses of intestinal stem cells using Lgr5+GFP+ mice.Results:
We initially observed that female mice were more radioresistant compared to male mice (p = 0.0304). The significant radioresistance in female mice also correlated with their delayed body weight loss, as males start to lose weight by day 12 while females begin losing weight around day 19. However, the administration of TM led to a significant survival advantage in male mice (p = 0.0293), pointing to a TM mediated downstream signaling pathway that is separate from its anti-estrogen function. Furthermore, when intestinal stem cells were assessed in pregnant female mice and mice treated with ß-estradiol pellets, a significant increase in Lgr5+ stem cells was noted compared to control mice (p = 0.0415) in both sexes. Lgr5+GFP+ stem cells are known to display receptors for estrogen (ER-a and ER-ß) which led us to hypothesize that radioresistance seen in female mice is driven by an estrogen signaling pathway in intestinal stem cells, and that same pathway, when modulated by TM in male mice, significantly improves radioresistance. Moreover, preliminary experiments using irradiation plus LR-IL-22 led to an increase in the number of Lgr5+ intestinal stem cells (p < 0.0001) in both sexes, as well as radioresistance following TBI and PBI. And based on RNAseq analysis of gene transcripts in FACS purified Lgr5+GFP+ intestinal stem cells, we discovered that the mechanism of LR-IL-22 radioprotection involves several estrogen signaling pathways, highlighting the important role of both, LR-IL-22 and TM/estrogen pathway, in promoting radioresistance.Conclusion:
Our data illustrates that female radioresistance is mediated by estrogen and that TM administration after irradiation reverses the radiation sensitivity of male mice by improving their survival through estrogen signaling pathways in intestinal stem cells. Additionally, gavage of LR-IL-22 after irradiation further modulates the intestinal microenvironment which could explain radiation protection by both TM/estrogen pathway and LR-IL-22 gavage.