A Self-Enforcing CD44s/ZEB1 Feedback Loop Maintains EMT and Stemness Properties in Cancer Cells

Int J Cancer. 2015 Dec 1;137(11):2566-77. doi: 10.1002/ijc.29642. Epub 2015 Jun 30.

Abstract

Invasion and metastasis of carcinomas are often activated by induction of aberrant epithelial-mesenchymal transition (EMT). This is mainly driven by the transcription factor ZEB1, promoting tumor-initiating capacity correlated with increased expression of the putative stem cell marker CD44. However, the direct link between ZEB1, CD44 and tumourigenesis is still enigmatic. Remarkably, EMT-induced repression of ESRP1 controls alternative splicing of CD44, causing a shift in the expression from the variant CD44v to the standard CD44s isoform. We analyzed whether CD44 and ZEB1 regulate each other and show that ZEB1 controls CD44s splicing by repression of ESRP1 in breast and pancreatic cancer. Intriguingly, CD44s itself activates the expression of ZEB1, resulting in a self-sustaining ZEB1 and CD44s expression. Activation of this novel CD44s-ZEB1 regulatory loop has functional impact on tumor cells, as evident by increased tumor-sphere initiation capacity, drug-resistance and tumor recurrence. In summary, we identified a self-enforcing feedback loop that employs CD44s to activate ZEB1 expression. This renders tumor cell stemness independent of external stimuli, as ZEB1 downregulates ESRP1, further promoting CD44s isoform synthesis.

Keywords: cancer stem cells; differential splicing; drug resistance; epithelial-mesenchymal transition (EMT); metastasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology*
  • Cell Line
  • Cell Line, Tumor
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / pathology
  • Down-Regulation / genetics
  • Drug Resistance, Neoplasm / genetics
  • Epithelial-Mesenchymal Transition / genetics*
  • Female
  • Gene Expression Regulation, Neoplastic / genetics
  • HEK293 Cells
  • Homeodomain Proteins / genetics*
  • Humans
  • Hyaluronan Receptors / genetics*
  • MCF-7 Cells
  • Neoplasm Recurrence, Local / genetics
  • Neoplasm Recurrence, Local / pathology
  • Pancreatic Neoplasms / genetics*
  • Pancreatic Neoplasms / pathology*
  • RNA-Binding Proteins / genetics
  • Transcription Factors / genetics*
  • Zinc Finger E-box-Binding Homeobox 1

Substances

  • CD44 protein, human
  • ESRP1 protein, human
  • Homeodomain Proteins
  • Hyaluronan Receptors
  • RNA-Binding Proteins
  • Transcription Factors
  • ZEB1 protein, human
  • Zinc Finger E-box-Binding Homeobox 1