Single-dose radiotherapy disables tumor cell homologous recombination via ischemia/reperfusion injury
Sahra Bodo, … , Richard Kolesnick, Zvi Fuks
Sahra Bodo, … , Richard Kolesnick, Zvi Fuks
Published November 27, 2018
Citation Information: J Clin Invest. 2019;129(2):786-801. https://doi.org/10.1172/JCI97631.
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Research Article Oncology Vascular biology

Single-dose radiotherapy disables tumor cell homologous recombination via ischemia/reperfusion injury

Abstract

Tumor cure with conventional fractionated radiotherapy is 65%, dependent on tumor cell–autonomous gradual buildup of DNA double-strand break (DSB) misrepair. Here we report that single-dose radiotherapy (SDRT), a disruptive technique that ablates more than 90% of human cancers, operates a distinct dual-target mechanism, linking acid sphingomyelinase–mediated (ASMase-mediated) microvascular perfusion defects to DNA unrepair in tumor cells to confer tumor cell lethality. ASMase-mediated microcirculatory vasoconstriction after SDRT conferred an ischemic stress response within parenchymal tumor cells, with ROS triggering the evolutionarily conserved SUMO stress response, specifically depleting chromatin-associated free SUMO3. Whereas SUMO3, but not SUMO2, was indispensable for homology-directed repair (HDR) of DSBs, HDR loss of function after SDRT yielded DSB unrepair, chromosomal aberrations, and tumor clonogen demise. Vasoconstriction blockade with the endothelin-1 inhibitor BQ-123, or ROS scavenging after SDRT using peroxiredoxin-6 overexpression or the SOD mimetic tempol, prevented chromatin SUMO3 depletion, HDR loss of function, and SDRT tumor ablation. We also provide evidence of mouse-to-human translation of this biology in a randomized clinical trial, showing that 24 Gy SDRT, but not 3×9 Gy fractionation, coupled early tumor ischemia/reperfusion to human cancer ablation. The SDRT biology provides opportunities for mechanism-based selective tumor radiosensitization via accessing of SDRT/ASMase signaling, as current studies indicate that this pathway is tractable to pharmacologic intervention.

Authors

Sahra Bodo, Cécile Campagne, Tin Htwe Thin, Daniel S. Higginson, H. Alberto Vargas, Guoqiang Hua, John D. Fuller, Ellen Ackerstaff, James Russell, Zhigang Zhang, Stefan Klingler, HyungJoon Cho, Matthew G. Kaag, Yousef Mazaheri, Andreas Rimner, Katia Manova-Todorova, Boris Epel, Joan Zatcky, Cristian R. Cleary, Shyam S. Rao, Yoshiya Yamada, Michael J. Zelefsky, Howard J. Halpern, Jason A. Koutcher, Carlos Cordon-Cardo, Carlo Greco, Adriana Haimovitz-Friedman, Evis Sala, Simon N. Powell, Richard Kolesnick, Zvi Fuks

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Figure 2

I/R, not endothelial apoptosis, impairs DSB repair.

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I/R, not endothelial apoptosis, impairs DSB repair. (A) Time-dependent (...
(A) Time-dependent (after 15 Gy) and dose effects (registered at 6 hours after radiation) on γH2AX focus resolution after SDRT in MCA/129 fibrosarcomas (left panel) and B16F1 melanomas (right panel). Each data point represents mean ± SEM (2–4 tumors) with high-power microscopic fields scanned for each time/dose focus count. (B) Kinetics of γH2AX, MDC1, and 53BP1 focus resolution in HCT116 xenografts after 15 Gy SDRT. (A and B) Data represent mean ± SEM. *P < 0.05 asmase+/+ (designated WT) vs. asmase–/– (designated KO) tumor host. (C) Impact of mechanical I/R on focus resolution in HCT116 xenografts at 6 hours after 15 Gy SDRT. Mechanical percutaneous clamping (designated C) of large tumor-feeding vessels was applied immediately after SDRT in I/R-inert BQ-123–inhibited tumors in asmase+/+ (WT) hosts or tumors in asmase–/– (KO) hosts. BQ-123 (designated B) was injected i.p. (2 mg/kg) at 30 minutes before SDRT. Data represent median ± IQR. ****P < 0.0001, B and KO vs. WT, Bonferroni correction (threshold: α = 0.05/4 = 0.0125). (D) Tumor pretreated with BQ-123 fails to impact SDRT-induced endothelial apoptosis. Representative apoptotic endothelial cells (arrows) double-stained with pan-endothelial MECA-32 (blue) and TUNEL (brown) in irradiated MCA/129 fibrosarcoma (top), quantified (bottom) in HCT116 tumor xenografts in asmase+/+ hosts. Data represent mean ± 95% CI, P = 0.7. Scale bar: 20 μm. Data are collated from 2 × 103 to 4 × 103 nuclei per point using 3–5 mice per group in A–C, and from 6 mice per group in D.