The receptor tyrosine kinase Axl regulates cell-cell adhesion and stemness in cutaneous squamous cell carcinoma

Oncogene. 2014 Aug 7;33(32):4185-92. doi: 10.1038/onc.2013.388. Epub 2013 Sep 23.

Abstract

Axl is a receptor tyrosine kinase (RTK) upregulated in various tumors including cutaneous squamous cell carcinoma (SCC). Axl expression correlates with poor prognosis and induction of epithelial-mesenchymal transition (EMT), hence we hypothesized that Axl is involved in the disruption of cell-cell adhesion to allow invasion and chemotherapy resistance of the cancer stem cell population. Cutaneous SCC cell lines with stable knockdown of Axl were generated using retroviral vectors. Axl depletion altered expression of intercellular junction molecules increasing cell-cell adhesion with downregulation of Wnt and TGFβR signaling. Furthermore, Axl expression correlated with the expression of putative cancer stem cell markers, CD44 and ALDH1, increased resistance to chemotherapy drugs, enhanced sphere formation ability and expression of EMT features by cancer stem cells. Axl depletion resulted in loss of tumor formation in an in vivo zebrafish xenograft model. In conclusion, these data suggest that abrogation of Axl results in loss of cancer stem cell properties indicating a role for Axl as a therapeutic target in chemotherapy-resistant cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldehyde Dehydrogenase 1 Family
  • Animals
  • Axl Receptor Tyrosine Kinase
  • Carcinoma, Squamous Cell / metabolism*
  • Cell Adhesion
  • Cell Line, Tumor
  • Cell Survival
  • Epithelial-Mesenchymal Transition
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Hyaluronan Receptors / metabolism
  • Isoenzymes / metabolism
  • Mice
  • Neoplasm Transplantation
  • Neoplastic Stem Cells / cytology*
  • Proto-Oncogene Proteins / physiology*
  • Receptor Protein-Tyrosine Kinases / physiology*
  • Receptors, Transforming Growth Factor beta / metabolism
  • Retinal Dehydrogenase / metabolism
  • Signal Transduction
  • Skin Neoplasms / metabolism*
  • Wnt Proteins / metabolism
  • Zebrafish

Substances

  • CD44 protein, human
  • Hyaluronan Receptors
  • Isoenzymes
  • Proto-Oncogene Proteins
  • Receptors, Transforming Growth Factor beta
  • Wnt Proteins
  • Aldehyde Dehydrogenase 1 Family
  • ALDH1A1 protein, human
  • ALDH1A1 protein, mouse
  • Retinal Dehydrogenase
  • Receptor Protein-Tyrosine Kinases
  • Axl Receptor Tyrosine Kinase