Hypoxia induces EMT in low and highly aggressive pancreatic tumor cells but only cells with cancer stem cell characteristics acquire pronounced migratory potential

PLoS One. 2012;7(9):e46391. doi: 10.1371/journal.pone.0046391. Epub 2012 Sep 26.

Abstract

Tumor hypoxia induces epithelial-mesenchymal transition (EMT), which induces invasion and metastasis, and is linked to cancer stem cells (CSCs). Whether EMT generates CSCs de novo, enhances migration of existing CSCs or both is unclear. We examined patient tissue of pancreatic ductal adenocarcinoma (PDA) along with carcinomas of breast, lung, kidney, prostate and ovary. For in vitro studies, five established PDA cell lines classified as less (CSC(low)) and highly aggressive CSC-like cells (CSC(high)) were examined by single and double immunofluorescence microscopy, wound-, transwell-, and time-lapse microscopy. HIF-1α and Slug, as well as HIF-2α and CD133 were co-expressed pointing to a putative co-existence of hypoxia, EMT and CSCs in vivo. CSC(high) cells exhibited high basal expression of the mesenchymal Vimentin protein but low or absent expression of the epithelial marker E-cadherin, with the opposite result in CSC(low) cells. Hypoxia triggered altering of cell morphology from an epithelial to a mesenchymal phenotype, which was more pronounced in CSC(high) cells. Concomitantly, E-cadherin expression was reduced and expression of Vimentin, Slug, Twist2 and Zeb1 enhanced. While hypoxia caused migration in all cell lines, velocity along with the percentage of migrating, polarized and pseudopodia-forming cells was significantly higher in CSC(high) cells. These data indicate that hypoxia-induced EMT occurs in PDA and several other tumor entities. However although hypoxia-induced EMT signaling occurs in all tumor cell populations, only the stem-like cells acquire high migratory potential and thus may be responsible for invasion and metastasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cell Movement / physiology
  • Epithelial-Mesenchymal Transition / physiology*
  • Female
  • Gene Expression Regulation, Neoplastic / genetics
  • Gene Expression Regulation, Neoplastic / physiology
  • Humans
  • Immunohistochemistry
  • Male
  • Neoplastic Stem Cells / metabolism*
  • Neoplastic Stem Cells / pathology
  • Pancreatic Neoplasms / metabolism*
  • Pancreatic Neoplasms / pathology
  • Tumor Cells, Cultured

Grants and funding

This study was supported by grants from the German Cancer Aid (Deutsche Krebshilfe 109362), German Research Community (DFG HE 3186/11-1) and German-Israeli Foundation for Scientific Research and Development (GIF 1058-7.11/2008). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.