title: Reduced p21(WAF1/CIP1) via alteration of p53-DDX3 pathway is associated with poor relapse-free survival in early-stage human papillomavirus-associated lung cancer.
abstract: OBJECTIVE
  DDX3 alteration has been shown to participate in hepatocellular tumorigenesis via p21(WAF1/CIP1) (p21) deregulation. We observed that DDX3 and p21 expression in lung tumors was negatively associated with E6 expression. Therefore, the aim of this study was to clarify whether deregulation of p21 by DDX3 via an E6-inactivated p53 pathway would enhance tumor progression in HPV-associated lung cancers.
  
  
  METHODS
  Real-time PCR, luciferase assays, immunoprecipitation, and chromatin immunoprecipitation (ChIP) were performed to determine whether DDX3 was regulated by p53 to synergistically enhance p21 transcriptional activity. Cell proliferation was examined by cell counting and colony formation assays. DDX3 and p21 expression were evaluated in 138 lung tumors by real-time PCR and immunohistochemistry. The prognostic value of p21 expression on relapse-free survival (RFS) was analyzed by Kaplan-Meier analysis.
  
  
  RESULTS
  Real-time PCR, luciferase assays, and ChIP assays indicated that three putative p53 binding sites, located at -1,080/-1,070, -695/-685, and -283/-273 on the DDX3 promoter, were required for DDX3 transcription. DDX3 deregulation by the E6-inactivated p53 pathway could promote cell proliferation and the ability to form colonies via reduced Sp1 binding activity on the p21 promoter. Among tumors, p21 expression was positively associated with DDX3 expression and negatively related with E6 expression, particularly in early-stage (I + II) tumors. Interestingly, low p21 expression was associated with a poor RFS in early-stage lung cancer.
  
  
  CONCLUSIONS
  The reduction of p21 by the alteration of the p53-DDX3 pathway plays an essential role in early-stage HPV-associated lung tumorigenesis and is correlated with poor RFS of lung cancer patients.
authors.affiliation: Institute of Medical and Molecular Toxicology, Chung Shan Medical University, Taichung, Taiwan, ROC.
authors.forename: De-Wei
authors.initials: DW
authors.lastname: Wu
authors.forename: Wen-Shan
authors.initials: WS
authors.lastname: Liu
authors.forename: John
authors.initials: J
authors.lastname: Wang
authors.forename: Chih-Yi
authors.initials: CY
authors.lastname: Chen
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Cheng
authors.forename: Huei
authors.initials: H
authors.lastname: Lee
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D018572:Disease-Free Survival; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D052162:Human papillomavirus 16; D006801:Humans; D053208:Kaplan-Meier Estimate; D019394:Ki-67 Antigen / Q000378:metabolism; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008175:Lung Neoplasms / Q000378:metabolism / Q000401:mortality / Q000473:pathology / Q000821:virology*; D008297:Male; D009364:Neoplasm Recurrence, Local; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016329:Sp1 Transcription Factor; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C068651:E6 protein, Human papillomavirus type 16; D019394:Ki-67 Antigen; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D008156:Luciferases; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases