title: More expression of BDNF associates with lung squamous cell carcinoma and is critical to the proliferation and invasion of lung cancer cells.
abstract: BACKGROUND
  Brain-derived neurotrophic factor (BDNF) has been reported to promote tumorigenesis and progression in several human malignancies. The purpose of this study was to explore the function of BDNF in lung squamous cell carcinoma (SCC) and adenocarcinoma (ADC).
  
  
  METHODS
  The expression of BDNF was examined in 110 samples of lung SCC and ADC by immunohistochemistry. The protein level of BDNF was examined in 25 lung SCC or ADC samples and paired non-tumors by western blot. BDNF expression was also evaluated in human bronchial epithelial cells (HBE) and 4 lung cancer cell lines using western blot. Three BDNF mRNA variants containing exons IV, VI and IX were evaluated in HBE, two SCC (SK, LK2) and two ADC (A549, LTE) cell lines by RT-PCR. The expression and secretion of BDNF were also determined in cells using western blot and ELISA. Then the shRNA specific for BDNF was transfected into LK2 or A549 cells to further elucidate the BDNF knockdown on cell proliferation, apoptosis and invasion, which were confirmed by MTT, flow cytometry and transwell examinations.
  
  
  RESULTS
  71.8 % (79 out of 110) of lung SCC and ADC samples were detected positive BDNF, and high expression of BDNF was significantly correlated with histological type and T stage. Compared with non-tumorous counterparts, BDNF was apparently overexpressed in SCC and ADC tissues. In cell studies, the extensive expression and secretion of BDNF were demonstrated in lung cancer cells compared with HBE cells. Interestingly, the expressions of BDNF mRNA variant IV and VI were identical in all cells examined. However, more expression of BDNF mRNA variant IX was found in SK and LK2 cells. The apoptotic cells were increased, and the cell proliferation and invasion were both attenuated once the expression of BDNF was inhibited. When retreated by rhBDNF, BDNF knockdown cells showed less apoptotic or more proliferative and invasive.
  
  
  CONCLUSIONS
  Our data show that BDNF probably facilitates the tumorigenesis of lung SCC and ADC. The expression of BDNF mRNA variant IX is probably more helpful to the upregulation of BDNF in SCC, and intervening the production of BDNF could be a possible strategy to lung cancer therapy.
authors.affiliation: Center of Laboratory Technology and Experimental Medicine, China Medical University, No.77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning, People's Republic of China. neko200321063@126.com.
authors.forename: Si-Yang
authors.initials: SY
authors.lastname: Zhang
authors.affiliation: Laboratory Center, the Fourth Affiliated Hospital of China Medical University, No.4 Chongshan East Road, Huanggu District, Shenyang, Liaoning, People's Republic of China. 46236572@qq.com.
authors.forename: Lin-Ping
authors.initials: LP
authors.lastname: Hui
authors.affiliation: Center of Laboratory Technology and Experimental Medicine, China Medical University, No.77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning, People's Republic of China. 1753027976@qq.com.
authors.forename: Chun-Yan
authors.initials: CY
authors.lastname: Li
authors.affiliation: Center of Laboratory Technology and Experimental Medicine, China Medical University, No.77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning, People's Republic of China. cmulab@qq.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.affiliation: Center of Laboratory Technology and Experimental Medicine, China Medical University, No.77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning, People's Republic of China. labczs@mail.cmu.edu.cn.
authors.forename: Ze-Shi
authors.initials: ZS
authors.lastname: Cui
authors.affiliation: Department of Pathology, the First Affiliated Hospital of China Medical University, No.155 Nanjing North Street, Heping District, Shenyang, Liaoning, People's Republic of China. qiuxues@hotmail.com.
authors.forename: Xue-Shan
authors.initials: XS
authors.lastname: Qiu
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000235:genetics; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D060787:Neoplasm Grading; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D047368:Tumor Burden
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D012333:RNA, Messenger; D034741:RNA, Small Interfering