title: DEAD-box protein p68 is regulated by β-catenin/transcription factor 4 to maintain a positive feedback loop in control of breast cancer progression.
abstract: BACKGROUND
  Nuclear accumulation of β-catenin is important for cancer development and it is found to overlap with p68 (DDX5) immunoreactivity in most breast cancers, as indicated by both clinical investigations and studies in cell lines. In this study, we aim to investigate the regulation of p68 gene expression through β-catenin/transcription factor 4 (TCF4) signaling in breast cancer.
  
  
  METHODS
  Formalin-fixed paraffin-embedded sections derived from normal human breast and breast cancer samples were used for immunohistochemical analysis. Protein and mRNA expressions were determined by immunoblotting and quantitative RT-PCR respectively. Promoter activity of p68 was checked using luciferase assay. Occupancy of several factors on the p68 promoter was evaluated using chromatin immunoprecipitation. Finally, a syngeneic mouse model of breast cancer was used to assess physiological significance.
  
  
  RESULTS
  We demonstrated that β-catenin can directly induce transcription of p68 promoter or indirectly through regulation of c-Myc in both human and mouse breast cancer cells. Moreover, by chromatin immunoprecipitation assay, we have found that both β-catenin and TCF4 occupy the endogenous p68 promoter, which is further enhanced by Wnt signaling. Furthermore, we have also established a positive feedback regulation for the expression of TCF4 by p68. To the best of our knowledge, this is the first report on β-catenin/TCF4-mediated p68 gene regulation, which plays an important role in epithelial to mesenchymal transition, as shown in vitro in breast cancer cell lines and in vivo in an animal breast tumour model.
  
  
  CONCLUSIONS
  Our findings indicate that Wnt/β-catenin signaling plays an important role in breast cancer progression through p68 upregulation.
authors.affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. kirankumarndkm@gmail.com.
authors.forename: Kiran Kumar Naidu
authors.initials: KK
authors.lastname: Guturi
authors.affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. moumitasarkar.biology@gmail.com.
authors.forename: Moumita
authors.initials: M
authors.lastname: Sarkar
authors.affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. arijitbhoumik@gmail.com.
authors.forename: Arijit
authors.initials: A
authors.lastname: Bhowmik
authors.affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. nilanjana2008@gmail.com.
authors.forename: Nilanjana
authors.initials: N
authors.lastname: Das
authors.affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. mrinal.res@gmail.com.
authors.forename: Mrinal Kanti
authors.initials: MK
authors.lastname: Ghosh
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D018450:Disease Progression; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; C532096:TCF4 protein, human; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051176:beta Catenin; C506749:Ddx5 protein, human; C506751:Ddx5 protein, mouse; D053487:DEAD-box RNA Helicases