Side population of pancreatic cancer cells predominates in TGF-beta-mediated epithelial to mesenchymal transition and invasion

Int J Cancer. 2009 Jun 15;124(12):2771-9. doi: 10.1002/ijc.24349.


We report here side population (SP) cells, a cancer stem cell enriched fraction from pancreatic cancer cell line, have enormous superior potential of the epithelial to mesenchymal transition (EMT), invasion, and metastasis. In an isolated SP cell culture, the cells rapidly expressed and up-regulated E-cadherin, an epithelial phenotypic marker, and the cells formed tightly contacted cell cluster, which is a representative epithelial phenotypic appearance. When the SP cells were incubated in the presence of TGF-beta, SP cells changed their shape into mesenchymal-like appearance including spindle shaped assembly. This alteration was associated with significant reduction of E-cadherin expression level. TGF-beta induced EMT-associated gene alteration such as reduction of E-cadherin mRNA and induction of Snail mRNA and matrixmetalloproteinase (MMP)-2 mRNA. Finally, SP cells exerted notable matrigel invasion activity in response to TGF-beta treatment, whereas MP cells did not respond to TGF-beta-mediated invasion. In conclusion, these results suggest that SP cells from pancreatic cancer cell line possess superior potentials of phenotypic switch, i.e., EMT/MET, micro-invasion, and in vivo metastasis, as compared to MP cells. Because micro-invasion and metastasis are key mechanisms of cancer malignant potential, SP cells would be the attractive target for preventing cancer progression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cadherins / genetics
  • Cell Line, Tumor
  • Cell Transdifferentiation / drug effects
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology*
  • Flow Cytometry
  • Fluorescent Antibody Technique, Indirect
  • Humans
  • Immunoblotting
  • Liver Neoplasms / secondary*
  • Matrix Metalloproteinase 2 / genetics
  • Mesoderm / metabolism
  • Mesoderm / pathology*
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • Neoplasm Invasiveness
  • Neoplastic Stem Cells / pathology*
  • Pancreatic Neoplasms / metabolism
  • Pancreatic Neoplasms / pathology*
  • Polymerase Chain Reaction
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Snail Family Transcription Factors
  • Transcription Factors / genetics
  • Transforming Growth Factor beta / pharmacology*


  • Cadherins
  • RNA, Messenger
  • Snail Family Transcription Factors
  • Transcription Factors
  • Transforming Growth Factor beta
  • Matrix Metalloproteinase 2