Radiation-Induced Autophagy in Human Pancreatic Cancer Cells is Critically Dependent on G2 Checkpoint Activation: A Mechanism of Radioresistance in Pancreatic Cancer
| Autor: | Mayuka Anko, Ken-ichiro Matsumoto, Sumitaka Hasegawa, Motofumi Suzuki, Maki Ohara |
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| Rok vydání: | 2020 |
| Předmět: |
Cancer Research
Cell cycle checkpoint endocrine system diseases Pyrimidinones Radiation Tolerance 030218 nuclear medicine & medical imaging 03 medical and health sciences Mice 0302 clinical medicine Adenosine Triphosphate Radioresistance Pancreatic cancer Cell Line Tumor Autophagy Medicine Animals Humans Radiology Nuclear Medicine and imaging Radiosensitivity Mice Inbred BALB C Radiation business.industry Cell cycle G2-M DNA damage checkpoint medicine.disease G2 Phase Cell Cycle Checkpoints Pancreatic Neoplasms Thiazoles Oncology Cell culture 030220 oncology & carcinogenesis Cancer research Quinolines Pyrazoles Female business Carcinoma Pancreatic Ductal |
| Zdroj: | International journal of radiation oncology, biology, physics. 111(1) |
| ISSN: | 1879-355X |
| Popis: | Purpose Autophagy and cell-cycle checkpoints act in concert to confer cellular radioresistance. We investigated the functional interaction between radiation-induced autophagy and G2 checkpoint activation in highly radioresistant human pancreatic ductal adenocarcinoma (PDAC) cells. Methods and Materials Four human PDAC cell lines (MIA PaCa-2, KP-4, Panc-1, and SUIT-2) were analyzed. These cells were first irradiated using x-rays, and their cell cycle status, autophagy, and cell cycle checkpoint marker expression and ATP production levels were evaluated. Autophagic flux assays and siRNA knockdown were used to evaluate autophagy activity. Double thymidine block experiments were performed to synchronize the cells. Two inhibitors (MK-1775 and SCH 900776) were used to attenuate G2 checkpoint activation. Cell survival assays and animal experiments were performed to evaluate the radiosensitizing effects of the G2 checkpoint inhibitors. Results Autophagy and G2/M accumulation were synchronously induced in human PDAC cells with an activated G2 checkpoint at 12 hours after x-ray irradiation of 6 Gy. Radiation-induced autophagy produced the ATP levels required for cell survival. Double thymidine block experiments revealed that no autophagy occurred in cells that were solely in G2 phase. MK-1775 or SCH 900776 exposure attenuated not only G2 checkpoint activation but also postirradiation autophagy, indicating the dependence of radiation-induced autophagy on an activated G2 checkpoint. The inhibitors demonstrated a higher radiosensitizing effect in the PDAC cells than the autophagy inhibitor chloroquine. MK-1775 in combination with x-rays significantly suppressed the tumor growth of MIA PaCa-2 xenografts compared with other treatment groups, including radiation or drug exposure alone, to enhance the radiosensitivity of PDAC cells in vivo. Conclusions Biological crosstalk exists between the G2 checkpoint activation and radiation-induced autophagy processes that are believed to independently contribute to the radioresistance of human PDAC cells. These findings have important implications for the development of future radiation therapy strategies for PDAC. |
| Databáze: | OpenAIRE |
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