title: Bit1 knockdown contributes to growth suppression as well as the decreases of migration and invasion abilities in esophageal squamous cell carcinoma via suppressing FAK-paxillin pathway.
abstract: BACKGROUND
  There is growing evidence that Bit1 exerts different roles in the development and progression of human cancers. Although Bit1 was highly exhibited in ESCC tissues in our previous study, its roles and molecular mechanisms implicated in development and progression of ESCC remain unknown.
  
  
  METHODS
  Bit1 protein expression in ESCC cell lines and normal esophageal epithelial cell was detected by Western blotting. Bit1 protein expression mediated by Bit1 shRNA was investigated by Western blotting. MTT, migration assay, invasion experiment, ELISA and Flow cytometry were utilized to determine the effects of Bit1 knockdown on cell proliferation, migration, invasion and apoptosis, respectively. A xenograft model was used to examine in vivo tumourigenicity, and immunohistochemistry and TUNEL were utilized to evaluate the related protein expression and apoptosis. Gene microarray was determined by Agilent SurePrint G3 Human GE 8 × 60 K Microarray, the interaction of Bit1 and FAK proteins were detected by Immunoprecipitation and the key protein expressions of FAK-paxillin pathway were detected by Western blotting.
  
  
  RESULTS
  We found Bit1 expression in all human ESCC cell lines tested was significantly higher than that in normal esophageal epithelial cell Het-1A (P < 0.05), in which EC9706 presented the highest Bit1 level. Bit1 protein level was significantly downregulated at day 1 after transfection with specific shRNA against Bit1 (P < 0.05). At days 2 and 3, Bit1 level reached the lowest value after transfection with Bit1 shRNA. Moreover, Bit1 depletion contributed to growth inhibition in vitro and in vivo, reduced cell migration and invasion abilities, and induced cell apoptosis in EC9706 and TE1 cells. More importantly, Bit1 downregulation significantly lowered Bcl-2 and MMP-2 levels in EC9706 xenografted tumor tissues, meanwhile triggered apoptosis after treatment with different doses of Bit1 shRNA. Further gene microarray revealed that 23 genes in Bit1-RNAi group were markedly downregulated, whereas 16 genes were obviously upregulated. Notably, Bit1 intrinsically interacted with FAK protein in EC9706 cells. Moreover, paxillin was downregulated at mRNA and protein levels in Bit1 shRNA group, coupled with the decreases of FAK mRNA and protein expressions.
  
  
  CONCLUSIONS
  Bit1 may be an important regulator in cell growth, apoptosis, migration and invasion of ESCC via targeting FAK-paxillin pathway, and thereby combinative manipulation of Bit1 and FAK-paxillin pathway may be the novel and promising therapeutic targets for the patients with ESCC.
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. fantianlipp@163.com.
authors.forename: Tianli
authors.initials: T
authors.lastname: Fan
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. chenjing314919@163.com.|Department of Oncology, the Zhengzhou Central Hospital Affiliated to Zhengzhou University, Zhengzhou, Henan, 450007, P.R. China. chenjing314919@163.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. lrzhang@zzu.edu.cn.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. 823195194@qq.com.
authors.forename: Pan
authors.initials: P
authors.lastname: Gao
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. 18737123365@163.com.
authors.forename: Yiran
authors.initials: Y
authors.lastname: Hui
authors.affiliation: School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. xupr717171@sina.com.
authors.forename: Peirong
authors.initials: P
authors.lastname: Xu
authors.affiliation: Laboratory for Cell Biology, College of Life Sciences of Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. zhangxq2010@126.com.
authors.forename: Xiaqing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Laboratory for Cell Biology, College of Life Sciences of Zhengzhou University, Zhengzhou, Henan, 450001, P.R. China. liuht1230@126.com.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Liu
mesh_terms: D000818:Animals; D017209:Apoptosis; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D063646:Carcinogenesis / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D015536:Down-Regulation; D004938:Esophageal Neoplasms / Q000473:pathology*; D000077277:Esophageal Squamous Cell Carcinoma; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D008819:Mice, Nude; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D020411:Oligonucleotide Array Sequence Analysis; D051419:Paxillin / Q000378:metabolism*; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D023041:Xenograft Model Antitumor Assays
chemical_list: D024101:Mitochondrial Proteins; D051419:Paxillin; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051416:Focal Adhesion Protein-Tyrosine Kinases; D002265:Carboxylic Ester Hydrolases; C483418:PTH2 protein, human; D020778:Matrix Metalloproteinase 2