title: Cancer stem-like cell characteristics induced by EB virus-encoded LMP1 contribute to radioresistance in nasopharyngeal carcinoma by suppressing the p53-mediated apoptosis pathway.
abstract: Emerging evidence confirms that cancer stem cells (CSCs) are responsible for the chemoradioresistance of malignancies. EBV-encoded latent membrane protein 1 (LMP1) is associated with tumor relapse and poor prognosis of nasopharyngeal carcinoma (NPC). However, whether LMP1 induces the development of CSCs and the mechanism by which this rare cell subpopulation leads to radioresistance in NPC remain unclear. In the present study, LMP1-transformed NPC cells showed significant radioresistance compared to the empty vector control. We found that LMP1 up-regulated the expression of several stemness-related genes, increased the cell number of side population (SP) by flow cytometry analysis, enhanced the self-renewal properties of the cells in a spherical culture and enhanced the in vivo tumor initiation ability. We also found that LMP1 positively regulated the expression of the CSC marker CD44. The CD44(+/High) subpopulation of the LMP1-transformed NPC cells displayed more significant CSC characteristics than the CD44(-/Low) subpopulation of the LMP1-transformed NPC cells; these characteristics included the upregulation of stemness-related genes, in vitro self-renewal and in vivo tumor initiation ability. Importantly, the CD44(+/High) subpopulation displayed more radioresistance than the CD44(-/Low) subpopulation. Our results also demonstrated that phosphorylation of the DNA damage response (DDR) proteins, ATM, Chk1, Chk2 and p53, was inactivated in the LMP1-induced CD44(+/High) cells in response to DNA damage, and this was accompanied by a downregulation of the p53-targeted proapoptotic genes, which suggested that the inactivation of the p53-mediated apoptosis pathway was responsible for the radioresistance in the CD44(+/High) cells. Taken together, we found that LMP1 induced an increase in CSC-like CD44(+/High) cells, and we determined the molecular mechanism underlying the radioresistance of the LMP1-activated CSCs, highlighting the need of CSC-targeted radiotherapy in EBV-positive NPC.
authors.affiliation: Department of Cancer Chemotherapy, The People's Hospital of Gaozhou, Guangdong Province, China.
authors.forename: Chang-Fu
authors.initials: CF
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Peng
authors.affiliation: Department of Nuclear Medicine, The Second People's Hospital of Shenzhen, Shenzhen, China.
authors.forename: Tie-Jun
authors.initials: TJ
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Guang-Da
authors.initials: GD
authors.lastname: Yang
authors.affiliation: School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Qiao-Qiao
authors.initials: QQ
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Li-Sheng
authors.initials: LS
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Hong-Bing
authors.initials: HB
authors.lastname: Huang
authors.affiliation: Department of Cancer Chemotherapy, The People's Hospital of Gaozhou, Guangdong Province, China.
authors.forename: Mao-De
authors.initials: MD
authors.lastname: Cai
authors.affiliation: Department of Medicine, Division of Infectious Diseases, University of Pennsylvania School of Medicine, Philadelphia, USA.
authors.forename: Jia-Ling
authors.initials: JL
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Ran-Yi
authors.initials: RY
authors.lastname: Liu
authors.affiliation: Department of Biochemistry & Molecular Biology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Zhen-Yu
authors.initials: ZY
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Nasopharyngeal Carcinoma, Sun Yat-Sen University Cancer Center, Guangzhou, China. Electronic address: qianchn@sysucc.org.cn.
authors.forename: Chao-Nan
authors.initials: CN
authors.lastname: Qian
authors.affiliation: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China; Department of Experimental Research, Sun Yat-Sen University Cancer Center, Guangzhou, China. Electronic address: huangbj@sysucc.org.cn.
authors.forename: Bi-Jun
authors.initials: BJ
authors.lastname: Huang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D002277:Carcinoma; D004854:Herpesvirus 4, Human / Q000378:metabolism; D006801:Humans; D007259:Infrared Rays; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy / Q000821:virology*; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000528:radiation effects* / Q000821:virology*; D011836:Radiation Tolerance; D015398:Signal Transduction / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014763:Viral Matrix Proteins / Q000096:biosynthesis*
chemical_list: C037662:EBV-associated membrane antigen, Epstein-Barr virus; D016159:Tumor Suppressor Protein p53; D014763:Viral Matrix Proteins
keywords: Cancer stem cells (CSCs); Epstein–Barr virus (EBV); Latent membrane protein 1 (LMP1); Nasopharyngeal carcinoma (NPC); Radioresistance; p53 signalling pathway