The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma
Radiotherapy using high linear energy transfer (LET) radiation results in effectively killing tumor cells while minimizing dose (biological effective) to normal tissues to block toxicity. It is well known that high LET radiation leads to lower cell survival per absorbed dose than low LET radiation....
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MDPI AG
2020-05-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/21/11/3766 |
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| author | Ju Yeon Oh Yeon-Joo Lee Sei Sai Tatsuya Ohno Chang-Bae Kong Sun Ha Lim Eun Ho Kim |
| author_facet | Ju Yeon Oh Yeon-Joo Lee Sei Sai Tatsuya Ohno Chang-Bae Kong Sun Ha Lim Eun Ho Kim |
| author_sort | Ju Yeon Oh |
| collection | DOAJ |
| description | Radiotherapy using high linear energy transfer (LET) radiation results in effectively killing tumor cells while minimizing dose (biological effective) to normal tissues to block toxicity. It is well known that high LET radiation leads to lower cell survival per absorbed dose than low LET radiation. High-linear energy transfer (LET) neutron treatment induces autophagy in tumor cells, but its precise mechanisms in osteosarcoma are unknown. Here, we investigated this mechanism and the underlying signaling pathways. Autophagy induction was examined in gamma-ray-treated KHOS/NP and MG63 osteosarcoma cells along with exposure to high-LET neutrons. The relationship between radiosensitivity and autophagy was assessed by plotting the cell surviving fractions against autophagy levels. Neutron treatment increased autophagy rates in irradiated KHOS/NP and MG63 cells; neutrons with high-LETs showed more effective inhibition than those with lower LET gamma-rays. To determine whether the unfolded protein response and Akt-mTOR pathways triggered autophagy, phosphorylated eIF2α and JNK levels, and phospho-Akt, phosphor-mTOR, and phospho-p70S6 levels were, respectively, investigated. High-LET neutron exposure inhibited Akt phosphorylation and increased Beclin 1 expression during the unfolded protein response, thereby enhancing autophagy. The therapeutic efficacy of high-LET neutron radiation was also assessed in vivo using an orthotopic mouse model. Neutron-irradiated mice showed reduced tumor growth without toxicity relative to gamma-ray-treated mice. The effect of high-LET neutron exposure on the expression of signaling proteins LC3, p-elF2a, and p-JNK was investigated by immunohistochemistry. Tumors in high-LET-neutron radiation-treated mice showed higher apoptosis rates, and neutron exposure significantly elevated LC3 expression, and increased p-elF2a and p-JNK expression levels. Overall, these results demonstrate that autophagy is important in radiosensitivity, cell survival, and cellular resistance against high-LET neutron radiation. This correlation between cellular radiosensitivity and autophagy may be used to predict radiosensitivity in osteosarcoma. |
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| language | English |
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| publishDate | 2020-05-01 |
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| spelling | doaj.art-cd01a3090a6c44aca3eeb61e9692fd2f2023-11-20T01:50:37ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672020-05-012111376610.3390/ijms21113766The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for OsteosarcomaJu Yeon Oh0Yeon-Joo Lee1Sei Sai2Tatsuya Ohno3Chang-Bae Kong4Sun Ha Lim5Eun Ho Kim6Laboratory of Biochemistry, Division of Life Sciences, Korea University, Seongbuk-gu, Seoul 02841, KoreaDivision of Radiation Biomedical Research, Korea Institute of Radiological and Medical Sciences, Seoul 01812, KoreaDepartment of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263–8555, JapanGunma University Heavy Ion Medical Center, 3–39–22 Showa-machi, Maebashi 371–8511, JapanDepartment of Orthopedic Surgery, Korea Institute of Radiological and Medical Sciences, Seoul 139–706, KoreaDepartment of Biochemistry, School of Medicine, Daegu Catholic University, Duryugongwon-ro, Nam-gu, Daegu 42472, KoreaDepartment of Biochemistry, School of Medicine, Daegu Catholic University, Duryugongwon-ro, Nam-gu, Daegu 42472, KoreaRadiotherapy using high linear energy transfer (LET) radiation results in effectively killing tumor cells while minimizing dose (biological effective) to normal tissues to block toxicity. It is well known that high LET radiation leads to lower cell survival per absorbed dose than low LET radiation. High-linear energy transfer (LET) neutron treatment induces autophagy in tumor cells, but its precise mechanisms in osteosarcoma are unknown. Here, we investigated this mechanism and the underlying signaling pathways. Autophagy induction was examined in gamma-ray-treated KHOS/NP and MG63 osteosarcoma cells along with exposure to high-LET neutrons. The relationship between radiosensitivity and autophagy was assessed by plotting the cell surviving fractions against autophagy levels. Neutron treatment increased autophagy rates in irradiated KHOS/NP and MG63 cells; neutrons with high-LETs showed more effective inhibition than those with lower LET gamma-rays. To determine whether the unfolded protein response and Akt-mTOR pathways triggered autophagy, phosphorylated eIF2α and JNK levels, and phospho-Akt, phosphor-mTOR, and phospho-p70S6 levels were, respectively, investigated. High-LET neutron exposure inhibited Akt phosphorylation and increased Beclin 1 expression during the unfolded protein response, thereby enhancing autophagy. The therapeutic efficacy of high-LET neutron radiation was also assessed in vivo using an orthotopic mouse model. Neutron-irradiated mice showed reduced tumor growth without toxicity relative to gamma-ray-treated mice. The effect of high-LET neutron exposure on the expression of signaling proteins LC3, p-elF2a, and p-JNK was investigated by immunohistochemistry. Tumors in high-LET-neutron radiation-treated mice showed higher apoptosis rates, and neutron exposure significantly elevated LC3 expression, and increased p-elF2a and p-JNK expression levels. Overall, these results demonstrate that autophagy is important in radiosensitivity, cell survival, and cellular resistance against high-LET neutron radiation. This correlation between cellular radiosensitivity and autophagy may be used to predict radiosensitivity in osteosarcoma.https://www.mdpi.com/1422-0067/21/11/3766autophagylinear energy transferneutron beamosteosarcomaradiosensitivityunfolded protein response |
| spellingShingle | Ju Yeon Oh Yeon-Joo Lee Sei Sai Tatsuya Ohno Chang-Bae Kong Sun Ha Lim Eun Ho Kim The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma International Journal of Molecular Sciences autophagy linear energy transfer neutron beam osteosarcoma radiosensitivity unfolded protein response |
| title | The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma |
| title_full | The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma |
| title_fullStr | The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma |
| title_full_unstemmed | The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma |
| title_short | The Unfolded Protein Response: Neutron-Induced Therapy Autophagy as a Promising Treatment Option for Osteosarcoma |
| title_sort | unfolded protein response neutron induced therapy autophagy as a promising treatment option for osteosarcoma |
| topic | autophagy linear energy transfer neutron beam osteosarcoma radiosensitivity unfolded protein response |
| url | https://www.mdpi.com/1422-0067/21/11/3766 |
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