Radiation Biology

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SU_39_2397 - Effects of Total Body Irradiation and the Radiation Mitigator MMS350 On Senescence in Fanconi Anemia, Fanca-/-, Mice

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Effects of Total Body Irradiation and the Radiation Mitigator MMS350 On Senescence in Fanconi Anemia, Fanca-/-, Mice
A. P. Sivananthan1, D. Shields2, R. Fisher2, D. Franicola2, W. Hou2, X. Zhang2, P. Wipf2, M. Epperly1, and J. S. Greenberger3; 1UPMC Hillman Cancer Center, Pittsburgh, PA, 2University of Pittsburgh, Pittsburgh, PA, 3UPMC-Shadyside Hospital, Pittsburgh, PA

Purpose/Objective(s): Ionizing irradiation induced senescence may be a mechanism underlying late effects through the senescence-associated secretory phenotype or loss of proliferation. We sought to determine the effect of the Fanconi Anemia (Fanca-/-) genotype and MMS350 on irradiation-induced senescence.

Materials/Methods: Fanca+/+, 129Sv+/+ (WT), and 129Sv Fanca-/- bone marrow stromal cells were irradiated to doses up to 10Gy, grown in the presence or absence of 400 µM MMS350, and assayed at day 3. Cells were plated at sub-confluence, then irradiated using a cesium irradiator. Senescence was determined by chromogenic beta-galactosidase assay (percent positive b-gal). 129Sv+/+ and 129Sv Fanca-/- mice received total body irradiation (TBI) using a Mark I Gamma Cell Irradiator. Subgroups of TBI and control mice were maintained on regular water or with 400uM MMS350 (Kalash, et al., Radiat Res, 180:474, 2013). Subgroups were sacrificed at 7days or 1 year after irradiation. Organs were immediately sectioned and scored for b-gal at 40x magnification. Statistical analysis was carried out using student’s t-test.

Results: Control non-irradiated cells showed no significant effect of genotype on senescence-associated b-gal staining at baseline (0.23% +/- 0.23% in WT vs 0.23% +/- 0.23% in Fanca-/-). By day 3 after 10Gy, b-gal staining was significantly induced in both WT (3.06% +/- 1.08%, p=0.007) and Fanca-/- cell lines (10.5% +/- 1.17%, p=0.001). Fanca-/- showed significantly higher induction compared to WT (p<0.0001). Growth in MMS350 after 10Gy reduced senescence in Fanca-/- cell lines (8.12% +/- 1.2%, p=0.04). Seven days after 7Gy TBI, the spleen showed a significant increase in b-gal staining in both WT (0.74 +/- 0.07 at 0Gy vs 1.81 +/- 0.39 at 7Gy, p=0.020) and in Fanca-/- (0.38 +/- 0.20 at 0Gy vs 1.5 +/- 0.45 at 7Gy, p=0.029). At 1 year, WT showed a higher baseline staining compared to Fanca-/- in spleen (1.43 +/- 0.10 in WT vs 0.83 +/- 0.14 in Fanca-/-, p=0.025). In contrast, 7.5 Gy caused a significant decrease in b-gal in WT at 1 yr (0.81 +/- 0.12, p=0.036) with little effect of MMS350. In Fanca-/- spleen, there was an increase at 1 yr (1.58 +/- 0.13 after 7.5 Gy, p=0.0009), which was reduced by MMS350 (1.17 +/- 0.13). The brain showed no significant effect of time or genotype between groups.

Conclusion: Fanca-/- bone marrow stromal cell lines showed greater irradiation induction of senescence over time compared to WT. MMS350 caused a reduction in the senescence in Fanca-/-. In vivo, the spleen showed a significant radiation induction in Fanca-/- and WT at 7 days. In contrast, WT spleen showed decreased senescence at 1 year after irradiation, while Fanca-/- spleen showed an increase. In the Fanca-/- mice, MMS350 reduced senescence at 1 year after irradiation.

Author Disclosure: A.P. Sivananthan: None. D. Shields: None. R. Fisher: None. D. Franicola: None. W. Hou: None. X. Zhang: None. P. Wipf: None.

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