Inhibition of CDK4/6 protects against radiation-induced intestinal injury in mice
Liang Wei, … , Lin Zhang, Jian Yu
Liang Wei, … , Lin Zhang, Jian Yu
Published October 4, 2016
Citation Information: J Clin Invest. 2016;126(11):4076-4087. https://doi.org/10.1172/JCI88410.
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Research Article Gastroenterology

Inhibition of CDK4/6 protects against radiation-induced intestinal injury in mice

Abstract

Radiotherapy causes dose-limiting toxicity and long-term complications in rapidly renewing tissues, including the gastrointestinal tract. Currently, there is no FDA-approved agent for the prevention or treatment of radiation-induced intestinal injury. In this study, we have shown that PD 0332991 (PD), an FDA-approved selective inhibitor of cyclin-dependent kinase 4/6 (CDK4/6), prevents radiation-induced lethal intestinal injury in mice. Treating mice with PD or a structurally distinct CDK4/6 inhibitor prior to radiation blocked proliferation and crypt apoptosis and improved crypt regeneration. PD treatment also enhanced LGR5+ stem cell survival and regeneration after radiation. PD was an on-target inhibitor of RB phosphorylation and blocked G1/S transition in the intestinal crypts. PD treatment strongly but reversibly inhibited radiation-induced p53 activation, which blocked p53-upregulated modulator of apoptosis–dependent (PUMA-dependent) apoptosis without affecting p21-dependent suppression of DNA damage accumulation, with a repair bias toward nonhomologous end joining. Further, deletion of PUMA synergized with PD treatment for even greater intestinal radioprotection. Our results demonstrate that the cell cycle critically regulates the DNA damage response and survival of intestinal stem cells and support the concept that pharmacological quiescence is a potentially highly effective and selective strategy for intestinal radioprotection.

Authors

Liang Wei, Brian J. Leibowitz, Xinwei Wang, Michael Epperly, Joel Greenberger, Lin Zhang, Jian Yu

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Figure 1

PD prevents IR-induced lethal GI injury.

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PD prevents IR-induced lethal GI injury. Mice were pretreated with vehic...
Mice were pretreated with vehicle (V) or PD and subjected to 15 Gy ABI or TBI. (A) Schematics of PD and radiation dosing and analyses at various time points. Un, untreated. (B) Kaplan-Meier survival curve of mice subjected to ABI. **P = 0.0035, by log-rank test. (C) Relative BW on day 5 after ABI compared with BW on day 0. N = 10 (V) or 8 (PD). (D) Representative images of H&E-stained intestinal sections with the indicated treatment at 96 hours. Scale bars: 500 μm (top) and 100 μm (bottom). (E) Quantitation of surviving crypts 96 hours after TBI. (F) Villus height at 96 hours. (G) Regenerated crypts marked by BrdU IHC in a cross section at 96 hours. Scale bar: 500 μm. (H) Quantification of regenerated crypts per circumference. (E, F, and H) Values represent the mean ± SEM; N = 3 mice in each group. †††P < 0.001, vehicle versus untreated or PD-treated, by 1-way ANOVA followed by Tukey’s multiple comparisons test; ***P < 0.001 vehicle versus PD treatment, by unpaired, 2-tailed Student’s t test.