title: Krüppel-like factor 5 promotes apoptosis triggered by tumor necrosis factor α in LNCaP prostate cancer cells via up-regulation of mitogen-activated protein kinase kinase 7.
abstract: OBJECTIVE
  Krüppel-like factor 5 (KLF5) modulates multiple cell processes in different cancers. It is frequently deleted and inactivated in prostate cancer and may exert a tumor suppressor function. However, how KLF5 inhibits the progression of prostate cancer is still not clear. In the present study, we identified how KLF5 and tumor necrosis factor α (TNFα) pathway, which can induce apoptosis in cancer, regulate each other in LNCaP prostate cancer cells.
  
  
  METHODS
  The expression of messenger RNA and protein was detected by real-time polymerase chain reaction assay and western blot analysis, respectively. To identify whether KLF5 regulates the activity of TNFα downstream pathway, we constructed a stable KLF5 knockdown or KLF5 overexpressing cell line with lentivirus-containing short hairpin RNA targeting KLF5 or full-length KLF5 in LNCaP cells. Cell apoptosis was determined through flow cytometry assay. In addition, the regulation of KLF5 on target gene transcription was detected by reporter luciferase activity assay, and the binding of KLF5 on target promoter was detected through oligonucleotides pull-down analysis.
  
  
  RESULTS
  We found that TNFα induced the expression of KLF5 at both messenger RNA and protein levels; moreover, TNFα up-regulated KLF5 through TNF receptor 1 but not through TNF receptor 2 in LNCaP cells. Knockdown of KLF5 decreased apoptosis induced by TNFα, whereas cell apoptosis was increased by KLF5 overexpression. Consistently, expression of cleaved PARP and caspase-3 induced by TNFα was decreased by KLF5 knockdown, whereas it was increased by overexpressed KLF5. JNK activity is essential for the apoptosis induced by TNFα. We found that knockdown of KLF5 not only decreased the phosphorylation of JNK induced by TNFα, but also down-regulated the transcription of mitogen-activated protein kinase kinase 7 (MKK7), an upstream kinase of JNK, by binding to the MKK7 promoter.
  
  
  CONCLUSIONS
  Our results indicate that KLF5 is an essential transcription regulator of MKK7 kinase and promotes the apoptosis induced by TNFα in LNCaP cells. Loss of KLF5 in prostate cancer may decrease cell response to TNFα-inducing apoptosis and facilitate cancer initiation and progression; moreover, KLF5 could be a potential molecular marker for predicting the effect of high-dose TNFα on tumor growth inhibition in prostate cancer.
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Shi
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Shan
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Chong
authors.initials: C
authors.lastname: Du
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Xiao-Shuang
authors.initials: XS
authors.lastname: Tang
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Jia
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Xinyang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Luke
authors.initials: L
authors.lastname: Chang
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China.
authors.forename: Dalin
authors.initials: D
authors.lastname: He
authors.affiliation: Department of Urology, The First Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China. Electronic address: guopeng661@mail.xjtu.edu.cn.
authors.forename: Peng
authors.initials: P
authors.lastname: Guo
mesh_terms: D017209:Apoptosis; D045744:Cell Line, Tumor; D006801:Humans; D051741:Kruppel-Like Transcription Factors; D048688:MAP Kinase Kinase 7 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha; D015854:Up-Regulation
chemical_list: D051741:Kruppel-Like Transcription Factors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D048688:MAP Kinase Kinase 7
keywords: Apoptosis; KLF5; MKK7; Prostate cancer; TNFα