title: Over-expression of BCAT1, a c-Myc target gene, induces cell proliferation, migration and invasion in nasopharyngeal carcinoma.
abstract: BACKGROUND
  Nasopharyngeal carcinoma (NPC) is a common malignant tumor in southern China and Southeast Asia, but its molecular mechanisms of pathogenesis are poorly understood. Our previous work has demonstrated that BCAT1 mRNA is over expressed in NPC and knocking down its expression in 5-8F NPC cell line can potently inhibit cell cycle progression and cell proliferation. However, the mechanism of BCAT1 up-regulation and its functional role in NPC development remain to be elucidated yet.
  
  
  METHODS
  Immunohistochemistry (IHC) method was utilized to detect the expression of BCAT1 protein in NPC at different pathological stages. The roles of gene mutation, DNA amplification and transcription factor c-Myc in regulating BCAT1 expression were analyzed using PCR-sequencing, quantitative polymerase chain reaction (qPCR), IHC, ChIP and luciferase reporter system, respectively. The functions of BCAT1 in colony formation, cell migration and invasion properties were evaluated by RNA interference (RNAi).
  
  
  RESULTS
  The positive rates of BCAT1 protein expression in normal epithelia, low-to-moderate grade atypical hyperplasia tissues, high-grade atypical hyperplasia tissues and NPC tissues were 23.6% (17/72), 75% (18/24), 88.9% (8/9) and 88.8% (71/80), respectively. Only one SNP site in exon1 was detected, and 42.4% (12/28) of the NPC tissues displayed the amplification of microsatellite loci in BCAT1. C-Myc could directly bind to the c-Myc binding site in promoter region of BCAT1 and up-regulate its expression. The mRNA and protein of c-Myc and BCAT1 were co-expressed in 53.6% (15/28) and 59.1% (13/22) of NPC tissues, respectively, and BCAT1 mRNA expression was also down-regulated in c-Myc knockdown cell lines. In addition, BCAT1 knockdown cells demonstrated reduced proliferation and decreased cell migration and invasion abilities.
  
  
  CONCLUSIONS
  Our study indicates that gene amplification and c-Myc up-regulation are responsible for BCAT1 overexpression in primary NPC, and overexpression of BCAT1 induces cell proliferation, migration and invasion. The results suggest that BCAT1 may be a novel molecular target for the diagnosis and treatment of NPC.
authors.affiliation: Cancer Research Institute, Xiang-Ya School of Medicine, Key Laboratory for Carcinogenesis of Chinese Ministry of Health, Key Laboratory for Carcinogenesis & Cancer Invasion of Chinese Ministry of Education, Central South University, Xiangya Road 110, 410078, Changsha, Hunan, P R China.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhou
authors.forename: Xiangling
authors.initials: X
authors.lastname: Feng
authors.forename: Caiping
authors.initials: C
authors.lastname: Ren
authors.forename: Xingjun
authors.initials: X
authors.lastname: Jiang
authors.forename: Weidong
authors.initials: W
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Liu
authors.forename: Zan
authors.initials: Z
authors.lastname: Li
authors.forename: Liang
authors.initials: L
authors.lastname: Zeng
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Zhu
authors.forename: Jia
authors.initials: J
authors.lastname: Shi
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Chang
authors.initials: C
authors.lastname: Zhang
authors.forename: Yanyu
authors.initials: Y
authors.lastname: Liu
authors.forename: Kaitai
authors.initials: K
authors.lastname: Yao
mesh_terms: D000818:Animals; D001483:Base Sequence; D002277:Carcinoma; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D005091:Exons; D005784:Gene Amplification; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D009154:Mutation; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D000637:Transaminases / Q000235:genetics / Q000378:metabolism*; D014410:Tumor Stem Cell Assay
chemical_list: D016271:Proto-Oncogene Proteins c-myc; C490590:BCAT1 protein, human; D000637:Transaminases