Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 7, 2017; 23(13): 2308-2317
Published online Apr 7, 2017. doi: 10.3748/wjg.v23.i13.2308
CMA down-regulates p53 expression through degradation of HMGB1 protein to inhibit irradiation-triggered apoptosis in hepatocellular carcinoma
Jing-Hua Wu, Jia-Pei Guo, Jun Shi, Hui Wang, Lei-Lei Li, Bin Guo, Dian-Xing Liu, Qing Cao, Zhi-Yong Yuan
Jing-Hua Wu, Zhi-Yong Yuan, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin’s Clinical Research Center for Cancer, Tianjin 300000, China
Jing-Hua Wu, Jia-Pei Guo, Jun Shi, Hui Wang, Lei-Lei Li, Bin Guo, Dian-Xing Liu, North China University of Science and Technology Affiliated Hospital, Tangshan 063000, Hebei Province, China
Qing Cao, Hebei Medical University Second Hospital, Shijiazhuang 050000, Hebei Province, China
Author contributions: Wu JH participated in literature search, study design, data collection, data analysis, data interpretation, and wrote the manuscript; Guo JP, Shi J and Wang H carried out the data collection and analysis, and provided the critical revision; Li LL, Guo B, Liu DX and Cao Q conceived of the study, and participated in its design and coordination; Yuan ZY participated in study design and provided the critical revision.
Supported by Natural Science Foundation of Hebei Province, China, No. H2016209007.
Institutional review board statement: The study was reviewed and approved by the North China University of Science and Technology Affiliated Hospital Institutional Review Board.
Institutional animal care and use committee statement: The study was approved by the Institutional Animal Care and Use Committee of North China University of Science and Technology Affiliated Hospital. All operations were performed according to international guidelines concerning the care and treatment of experimental animals.
Conflict-of-interest statement: All authors in this paper declared that there is no conflicts of interest to this work.
Data sharing statement: No additional unpublished data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dr. Zhi-Yong Yuan, Professor, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin’s Clinical Research Center for Cancer, Huanhu West Road, Tianjin 300000, China. tswujinghua@163.com
Telephone: +86-315-3725732 Fax: +86-315-2852195
Received: January 9, 2017
Peer-review started: January 10, 2017
First decision: February 23, 2017
Revised: February 27, 2017
Accepted: March 6, 2017
Article in press: March 6, 2017
Published online: April 7, 2017
Processing time: 86 Days and 19.7 Hours
Abstract
AIM

To investigate the mechanism of chaperone-mediated autophagy (CMA)-induced resistance to irradiation-triggered apoptosis through regulation of the p53 protein in hepatocellular carcinoma (HCC).

METHODS

Firstly, we detected expression of lysosome-associated membrane protein 2a (Lamp-2a), which is the key protein of CMA, by western blot in HepG2 and SMMC7721 cells after irradiation. We further used shRNA Lamp-2a HCC cells to verify the radioresistance induced by CMA. Next, we detected the HMGB1 and p53 expression after irradiation by western blot, and we further used RNA interference and ethyl pyruvate (EP), as a HMGB1 inhibitor, to observe changes of p53 expression. Finally, an immunoprecipitation assay was conducted to explore the interaction between Lamp-2a and HMGB1, and the data were analyzed.

RESULTS

We found the expression of Lamp-2a was increased on irradiation while apoptosis decreased in HepG2 and SMMC7721 cells. The apoptosis was increased markedly in the shRNA Lamp-2a HepG2 and SMMC7721 cells as detected by western blot and colony formation assay. Next, we found p53 expression was gradually reduced on irradiation but obviously increased in shRNA Lamp-2a cells. Furthermore, p53 increased the cell apoptosis on irradiation in Hep3B (p53-/-) cells. Finally, p53 levels were regulated by HMGB1 as measured through RNA interference and the EP treatment. HMGB1 was able to combine with Lamp-2a as seen by immunoprecipitation assay and was degraded via the CMA pathway. The decreased HMGB1 inhibited p53 expression induced by irradiation and further reduced the apoptosis in HCC cells.

CONCLUSION

CMA pathway activation appears to down-regulate the susceptibility of HCC to irradiation by degrading HMGB1 with further impact on p53 expression. These findings have clinical relevance for radiotherapy of HCC.

Keywords: Hepatocellular carcinoma; Radioresistance; Chaperone-mediated autophagy; HMGB1; p53

Core tip: The activation of chaperone-mediated autophagy plays an important role in reducing hepatocellular carcinoma (HCC) cell apoptosis in response to irradiation through degraded HMGB1 protein which reduces p53 expression. The discovery of this mechanism will be beneficial for inhibiting radioresistance of HCC and has a promising value in clinical treatment strategy.