title: HER2-associated radioresistance of breast cancer stem cells isolated from HER2-negative breast cancer cells.
abstract: OBJECTIVE
  To understand the role of HER2-associated signaling network in breast cancer stem cells (BCSC) using radioresistant breast cancer cells and clinical recurrent breast cancers to evaluate HER2-targeted therapy as a tumor eliminating strategy for recurrent HER2(-/low) breast cancers.
  
  
  METHODS
  HER2-expressing BCSCs (HER2(+)/CD44(+)/CD24(-/low)) were isolated from radiation-treated breast cancer MCF7 cells and in vivo irradiated MCF7 xenograft tumors. Tumor aggressiveness and radioresistance were analyzed by gap filling, Matrigel invasion, tumor-sphere formation, and clonogenic survival assays. The HER2/CD44 feature was analyzed in 40 primary and recurrent breast cancer specimens. Protein expression profiling in HER2(+)/CD44(+)/CD24(-/low) versus HER2(-)/CD44(+)/CD24(-/low) BCSCs was conducted with two-dimensional difference gel electrophoresis (2-D DIGE) and high-performance liquid chromatography tandem mass spectrometry (HPLC/MS-MS) analysis and HER2-mediated signaling network was generated by MetaCore program.
  
  
  RESULTS
  Compared with HER2-negative BCSCs, HER2(+)/CD44(+)/CD24(-/low) cells showed elevated aldehyde dehydrogenase (ALDH) activity and aggressiveness tested by Matrigel invasion, tumor sphere formation, and in vivo tumorigenesis. The enhanced aggressive phenotype and radioresistance of the HER2(+)/CD44(+)/CD24(-/low) cells were markedly reduced by inhibition of HER2 via siRNA or Herceptin treatments. Clinical breast cancer specimens revealed that cells coexpressing HER2 and CD44 were more frequently detected in recurrent (84.6%) than primary tumors (57.1%). In addition, 2-D DIGE and HPLC/MS-MS of HER2(+)/CD44(+)/CD24(-/low) versus HER2(-)/CD44(+)/CD24(-/low) BCSCs reported a unique HER2-associated protein profile including effectors involved in tumor metastasis, apoptosis, mitochondrial function, and DNA repair. A specific feature of HER2-STAT3 network was identified.
  
  
  CONCLUSIONS
  This study provides the evidence that HER2-mediated prosurvival signaling network is responsible for the aggressive phenotype of BCSCs that could be targeted to control the therapy-resistant HER2(-/low) breast cancer.
authors.affiliation: Departments of Radiation Oncology, University of California Davis School of Medicine, Sacramento, Ca 95817, USA.
authors.forename: Nadire
authors.initials: N
authors.lastname: Duru
authors.forename: Ming
authors.initials: M
authors.lastname: Fan
authors.forename: Demet
authors.initials: D
authors.lastname: Candas
authors.forename: Cheikh
authors.initials: C
authors.lastname: Menaa
authors.forename: Hsin-Chen
authors.initials: HC
authors.lastname: Liu
authors.forename: Danupon
authors.initials: D
authors.lastname: Nantajit
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Wen
authors.forename: Kai
authors.initials: K
authors.lastname: Xiao
authors.forename: Angela
authors.initials: A
authors.lastname: Eldridge
authors.forename: Brett A
authors.initials: BA
authors.lastname: Chromy
authors.forename: Shiyong
authors.initials: S
authors.lastname: Li
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Spitz
authors.forename: Kit S
authors.initials: KS
authors.lastname: Lam
authors.forename: Max S
authors.initials: MS
authors.lastname: Wicha
authors.forename: Jian Jian
authors.initials: JJ
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D051927:CD24 Antigen / Q000378:metabolism; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects; D005260:Female; D015870:Gene Expression; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D061986:MCF-7 Cells; D053078:Membrane Potential, Mitochondrial / Q000528:radiation effects; D051379:Mice; D016688:Mice, Inbred NOD; D008819:Mice, Nude; D016513:Mice, SCID; D009364:Neoplasm Recurrence, Local / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000528:radiation effects*; D011836:Radiation Tolerance; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D018874:Spheroids, Cellular / Q000378:metabolism; D015533:Transcriptional Activation; D023041:Xenograft Model Antitumor Assays
chemical_list: D051927:CD24 Antigen; D018960:Hyaluronan Receptors; D018719:Erb-b2 Receptor Tyrosine Kinases; D050796:STAT3 Transcription Factor; C497889:CD24 protein, human; C497483:CD44 protein, human; C494086:STAT3 protein, human; C508053:ERBB2 protein, human