@article{20df3d6d8be1475cb3fcc83b826e81b5,
title = "Effects of Ultra-high doserate FLASH Irradiation on the Tumor Microenvironment in Lewis Lung Carcinoma: Role of Myosin Light Chain",
abstract = "Purpose: To investigate whether the vascular collapse in tumors by conventional dose rate (CONV) irradiation (IR) would also occur by the ultra-high dose rate FLASH IR. Methods and Materials: Lewis lung carcinoma (LLC) cells were subcutaneously implanted in mice. This was followed by CONV or FLASH IR at 15 Gy. Tumors were harvested at 6 or 48 hours after IR and stained for CD31, phosphorylated myosin light chain (p-MLC), γH2AX (a surrogate marker for DNA double strand break), intracellular reactive oxygen species (ROS), or immune cells such as myeloid and CD8α T cells. Cell lines were irradiated with CONV IR for Western blot analyses. ML-7 was intraperitoneally administered daily to LLC-bearing mice for 7 days before 15 Gy CONV IR. Tumors were similarly harvested and analyzed. Results: By immunostaining, we observed that CONV IR at 6 hours resulted in constricted vessel morphology, increased expression of p-MLC, and much higher numbers of γH2AX-positive cells in tumors, which were not observed with FLASH IR. Mechanistically, MLC activation by ROS is unlikely, because FLASH IR produced significantly more ROS than CONV IR in tumors. In vitro studies demonstrated that ML-7, an inhibitor of MLC kinase, abrogated IR-induced γH2AX formation and disappearance kinetics. Lastly, we observed that CONV IR when combined with ML-7 produced some effects similar to FLASH IR, including reduction in the vasculature collapse, fewer γH2AX-positive cells, and increased immune cell influx to the tumors. Conclusions: FLASH IR produced novel changes in the tumor microenvironment that were not observed with CONV IR. We believe that MLC activation in tumors may be responsible for some of the microenvironmental changes differentially regulated between CONV and FLASH IR.",
author = "Kim, {Young Eun} and Gwak, {Seung Hee} and Hong, {Beom Ju} and Oh, {Jung Min} and Choi, {Hyung Seok} and Kim, {Myeoung Su} and Dawit Oh and Lartey, {Frederik M.} and Marjan Rafat and Emil Sch{\"u}ler and Kim, {Hyo Soo} and {von Eyben}, Rie and Weissman, {Irving L.} and Koch, {Cameron J.} and Maxim, {Peter G.} and Loo, {Billy W.} and Ahn, {G. One}",
note = "Funding Information: This work was supported by a grant NRF-2019M2D2A1A02059246 from the Ministry of Science and Information, Communication, and Technology, Korea (to G.-O.A.); Seoul National University Research Grant in 2020 (to G.-O.A.); BK21 FOUR Future Veterinary Medicine Leading Education and Research Center, Seoul National University ( A0449-20200100 ). B.W.L. reports funding from the Swedish Childhood Cancer Foundation , the American Association for Cancer Research , the Weston Havens Foundation , the Wallace H. Coulter Foundation , the Department of Radiation Oncology (Stanford University), the Office of the Dean (School of Medicine, Stanford University), the Office of the Provost (Stanford University), and SLAC National Accelerator Laboratory . I.L.W. reports funding from the Ludwig Cancer Foundation . Y.E.K. ( NRF-2012H1A2A1002871 ) and B.-J.H. ( NRF -2013H1A2A1032808 ) are global PhD fellows supported by the Ministry of Science and Information, Communication, and Technology, Korea . Funding Information: This work was supported by a grant NRF-2019M2D2A1A02059246 from the Ministry of Science and Information, Communication, and Technology, Korea (to G.-O.A.); Seoul National University Research Grant in 2020 (to G.-O.A.); BK21 FOUR Future Veterinary Medicine Leading Education and Research Center, Seoul National University (A0449-20200100). B.W.L. reports funding from the Swedish Childhood Cancer Foundation, the American Association for Cancer Research, the Weston Havens Foundation, the Wallace H. Coulter Foundation, the Department of Radiation Oncology (Stanford University), the Office of the Dean (School of Medicine, Stanford University), the Office of the Provost (Stanford University), and SLAC National Accelerator Laboratory. I.L.W. reports funding from the Ludwig Cancer Foundation. Y.E.K. (NRF-2012H1A2A1002871) and B.-J.H. (NRF -2013H1A2A1032808) are global PhD fellows supported by the Ministry of Science and Information, Communication, and Technology, Korea.Disclosures: B.W.L. has received research support from Varian Medical Systems and is a co-founder and board member of TibaRay. All other authors reported no disclosures or conflicts of interest. Publisher Copyright: {\textcopyright} 2020 The Authors",
year = "2021",
month = apr,
day = "1",
doi = "10.1016/j.ijrobp.2020.11.012",
language = "English (US)",
volume = "109",
pages = "1440--1453",
journal = "International Journal of Radiation Oncology Biology Physics",
issn = "0360-3016",
publisher = "Elsevier Inc.",
number = "5",
}