title: Chronic oxaliplatin resistance induces epithelial-to-mesenchymal transition in colorectal cancer cell lines.
abstract: OBJECTIVE
  Epithelial-to-mesenchymal transition (EMT) is a process whereby cells acquire molecular alterations that facilitate cell motility and invasion. In preliminary studies, we observed that oxaliplatin-resistant (OxR) colorectal cancer (CRC) cells underwent morphologic changes suggestive of a migratory phenotype, leading us to hypothesize that OxR CRC cells undergo EMT.
  
  
  METHODS
  The human CRC cell lines KM12L4 and HT29 were exposed to increasing doses of oxaliplatin to establish stable cell lines resistant to oxaliplatin. Migration and invasion were assessed by modified Boyden chamber assays. Morphologic and molecular changes characteristic of EMT were determined by immunofluorescence staining and Western blot analyses.
  
  
  RESULTS
  The OxR cells showed phenotypic changes consistent with EMT: spindle-cell shape, loss of polarity, intercellular separation, and pseudopodia formation. KM12L4 and HT29 OxR cells exhibited an approximately 8- to 15-fold increase in migrating and invading cells, respectively (P < 0.005 for both). Immunofluorescence staining of OxR cells revealed translocation of E-cadherin and beta-catenin from their usual membrane-bound complex to the cytoplasm and nucleus, respectively. The OxR cells also had decreased expression of the epithelial adhesion molecules E-cadherin and plakoglobin and an increase in the mesenchymal marker vimentin. The KM12L4 OxR cells exhibited increased nuclear expression of Snail, an EMT-regulatory transcription factor, whereas the HT29 OxR cells exhibited an increase in nuclear expression of the EMT-associated transcription factor nuclear factor kappaB.
  
  
  CONCLUSIONS
  We hypothesize that induction of EMT may contribute to the decreased efficacy of therapy in chemoresistant CRC, as the tumor cells switch from a proliferative to invasive phenotype. Further understanding of the mechanisms of chemoresistance in CRC will enable improvements in chemotherapy for metastatic disease.
authors.affiliation: Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77230-1402, USA.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Fan
authors.forename: E Ramsay
authors.initials: ER
authors.lastname: Camp
authors.forename: George
authors.initials: G
authors.lastname: van Buren
authors.forename: Wenbiao
authors.initials: W
authors.lastname: Liu
authors.forename: Ray
authors.initials: R
authors.lastname: Somcio
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gray
authors.forename: Haiyun
authors.initials: H
authors.lastname: Cheng
authors.forename: Paulo M
authors.initials: PM
authors.lastname: Hoff
authors.forename: Lee M
authors.initials: LM
authors.lastname: Ellis
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D019008:Drug Resistance, Neoplasm; D004848:Epithelium / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008648:Mesoderm / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D008941:Spindle Apparatus
chemical_list: D000970:Antineoplastic Agents; D015820:Cadherins; D009944:Organoplatinum Compounds; D000077150:Oxaliplatin