title: Radiation-induced immune responses: mechanisms and therapeutic perspectives.
abstract: Recent advancement in the radiotherapy technology has allowed conformal delivery of high doses of ionizing radiation precisely to the tumors while sparing large volume of the normal tissues, which have led to better clinical responses. Despite this technological advancement many advanced tumors often recur and they do so within the previously irradiated regions. How could tumors recur after receiving such high ablative doses of radiation? In this review, we outlined how radiation can elicit anti-tumor responses by introducing some of the cytokines that can be induced by ionizing radiation. We then discuss how tumor hypoxia, a major limiting factor responsible for failure of radiotherapy, may also negatively impact the anti-tumor responses. In addition, we highlight how there may be other populations of immune cells including regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs) that can be recruited to tumors interfering with the anti-tumor immunity. Finally, the impact of irradiation on tumor hypoxia and the immune responses according to different radiotherapy regimen is also delineated. It is indeed an exciting time to see that radiotherapy is being combined with immunotherapy in the clinic and we hope that this review can add an excitement to the field.
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
authors.forename: Hoibin
authors.initials: H
authors.lastname: Jeong
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
authors.forename: Seoyeon
authors.initials: S
authors.lastname: Bok
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
authors.forename: Beom-Ju
authors.initials: BJ
authors.lastname: Hong
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
authors.forename: Hyung-Seok
authors.initials: HS
authors.lastname: Choi
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Korea.
authors.forename: G-One
authors.initials: GO
authors.lastname: Ahn
keywords: Cancer; Hypoxia; Immune system; Radiotherapy