title: Acidic extracellular pH promotes epithelial mesenchymal transition in Lewis lung carcinoma model.
abstract: BACKGROUND
  Epithelial mesenchymal transition (EMT) is thought to be an essential feature of malignant tumor cells when they spread into the stroma. Despite the extracellular acidity of tumor tissues, the effect of acidic extracellular pH (pH e ) on EMT in carcinoma models, including the Lewis lung carcinoma (LLC) model, remains unclear.
  
  
  METHODS
  High and low metastatic LLC variants were generated by repeated tail vein injection of metastatic cells. DMEM/F12 medium, which has been supplemented with 15 mM HEPES, 4 mM phosphoric acid, and 1 g/L NaHCO3 and adjusted to the desire pH with HCl or NaOH, was used for cell culture. EMT marker gene expression was determined by quantitative reverse transcription-polymerase chain reaction. Migration and invasion activities were analyzed by wound healing assay and the Boyden chamber assay through Matrigel®, respectively.
  
  
  RESULTS
  Low metastatic variant LLCm1 cells showed a cobble-stone like morphology at pH e 7.4. At pH e 6.8, however, their morphology became fibroblastic, similar in shape to high metastatic variant LLCm4 cells. Steady state levels of matrix metalloproteinase-9 (Mmp9) mRNA were induced by acidic pH e , maximizing at pH 6.8, with the levels of Mmp9 mRNA higher in LLCm4 than in LLCm1 cells. Both variants showed decreased levels of E-cadherin and increased levels of vimentin at pH e 6.8. Acidic pH e also induced expression of mRNAs encoding the E-cadherin repressors, Zeb2, Twist1 and Twist2, as well as enhancing cell motility and in vitro invasion through Matrigel®.
  
  
  CONCLUSIONS
  Acidic pH e can induce EMT in some types of carcinoma.
authors.affiliation: Department of Oral Function and Molecular Biology, Ohu University School of Dentistry, Koriyama, Japan ; Department of Oral Physiology and Biochemistry, Ohu University Graduate School of Dentistry, Koriyama, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Department of Oral Function and Molecular Biology, Ohu University School of Dentistry, Koriyama, Japan.
authors.forename: Toyonobu
authors.initials: T
authors.lastname: Maeda
authors.affiliation: Department of General Clinical Medicine, Ohu University School of Dentistry, Koriyama, Japan.
authors.forename: Yuh
authors.initials: Y
authors.lastname: Baba
authors.affiliation: Department of Oral Growth and Development, Ohu University School of Dentistry, Koriyama, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shimamura
authors.affiliation: Department of Oral Function and Molecular Biology, Ohu University School of Dentistry, Koriyama, Japan ; Department of Oral Physiology and Biochemistry, Ohu University Graduate School of Dentistry, Koriyama, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Kato
keywords: Acidic extracellular pH; EMT; Invasion; Lewis lung carcinoma; MMP-9