1. Academic Validation
  2. DNA-dependent protein kinase regulates cytosolic double-stranded DNA secretion from irradiated macrophages to increase radiosensitivity of tumors

DNA-dependent protein kinase regulates cytosolic double-stranded DNA secretion from irradiated macrophages to increase radiosensitivity of tumors

  • Radiother Oncol. 2024 Jan 28:193:110111. doi: 10.1016/j.radonc.2024.110111.
Taerim Oh 1 Gi-Sue Kang 1 Hye-Ju Jo 1 Hye-Joon Park 2 Ye-Rim Lee 1 G-One Ahn 3
Affiliations

Affiliations

  • 1 College of Veterinary Medicine, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea.
  • 2 College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 03080, Korea.
  • 3 College of Veterinary Medicine, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea; College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 03080, Korea. Electronic address: goneahn@snu.ac.kr.
Abstract

Background and purpose: To investigate the molecular mechanism by which irradiated macrophages secrete cytosolic double-stranded DNA (c-dsDNA) to increase radiosensitivity of tumors.

Materials and methods: Irradiated bone marrow-derived macrophages (BMDM) were co-incubated with irradiated EO771 or MC38 Cancer cells to determine clonogenic survival. c-dsDNA were measured by Agarose gel or enzyme-linked immunosorbent assay. BMDM or Cancer cells were analyzed with immunostaining or western blot. Subcutaneously implanted MC38 cells in myeloid-specific Prkdc knockout (KO) mice or littermate control mice were irradiated with 8 Gy to determine radiosensitivity of tumors.

Results: We observed that irradiated BMDM significantly increased radiosensitivity of Cancer cells. By performing immunostaining, we found that there was a dose-dependent increase in the formation of c-dsDNA and phosphorylation in DNA-dependent protein kinase (DNA-PK) in irradiated BMDM. Importantly, c-dsDNA in irradiated BMDM could be secreted to the extracellular milieu and this process required DNA-PK, which phosphorylated Myosin light chain to regulate the secretion. The secreted c-dsDNA from irradiated BMDM then activated toll-like receptor-9 and subsequent nuclear factor kappa-light-chain-enhancer of activated B cells signaling in the adjacent Cancer cells inhibiting radiation-induced DNA double strand break repair. Lastly, we observed that irradiated tumors in vivo had a significantly increased number of tumor-associated macrophages (TAM) with phosphorylated DNA-PK expression in the cytosol. Furthermore, tumors grown in myeloid-specific Prkdc KO mice, in which TAM lacked phosphorylated DNA-PK expression were significantly more radioresistant than those of the wild-type control mice.

Conclusions: Irradiated macrophages can increase antitumor efficacy of radiotherapy through secretion of c-dsDNA under the regulation of DNA-PK.

Keywords

DNA repair; DNA-PK; Macrophages; Radiosensitivity; cytosolic dsDNA.

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