A self-enforcing CD44s/ZEB1 feedback loop maintains EMT and stemness properties in cancer cells.
Bogdan-Tiberius Preca, Karolina Bajdak, Kerstin Mock, Vignesh Sundararajan, Jessica Pfannstiel, Jochen Maurer, Ulrich Wellner, Ulrich T Hopt, Tilman Brummer, Simone Brabletz, Thomas Brabletz, Marc P Stemmler
Author Information
Bogdan-Tiberius Preca: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Karolina Bajdak: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Kerstin Mock: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Vignesh Sundararajan: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Jessica Pfannstiel: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Jochen Maurer: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Ulrich Wellner: Department of Surgery, University Medical Center Schleswig-Holstein, Campus Lübeck, Germany.
Ulrich T Hopt: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Tilman Brummer: Institute for Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Germany.
Simone Brabletz: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
Thomas Brabletz: Department of Experimental Medicine I, Nikolaus-Fiebiger Center for Molecular Medicine, Friedrich-Alexander University of Erlangen-Nürnberg, D-91054, Erlangen, Germany.
Marc P Stemmler: Department of Visceral Surgery, University Medical Center Freiburg, D-79106, Freiburg, Germany.
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.
