Endothelial interleukin-6 defines the tumorigenic potential of primary human cancer stem cells

Stem Cells. 2014 Nov;32(11):2845-57. doi: 10.1002/stem.1793.


Head and neck squamous cell carcinomas (HNSCC) contain a small subpopulation of stem cells endowed with unique capacity to generate tumors. These cancer stem cells (CSC) are localized in perivascular niches and rely on crosstalk with endothelial cells for survival and self-renewal, but the mechanisms involved are unknown. Here, we report that stromal interleukin (IL)-6 defines the tumorigenic capacity of CSC sorted from primary human HNSCC and transplanted into mice. In search for the cellular source of Interleukin-6 (IL-6), we observed a direct correlation between IL-6 levels in tumor-associated endothelial cells and the tumorigenicity of CSC. In vitro, endothelial cell-IL-6 enhanced orosphere formation, p-STAT3 activation, survival, and self-renewal of human CSC. Notably, a humanized anti-IL-6R antibody (tocilizumab) inhibited primary human CSC-mediated tumor initiation. Collectively, these data demonstrate that endothelial cell-secreted IL-6 defines the tumorigenic potential of CSC, and suggest that HNSCC patients might benefit from therapeutic inhibition of IL-6/IL-6R signaling.

Keywords: Angiogenesis; Perivascular niche; Self-renewal; Squamous cell carcinoma; Survival.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carcinoma, Squamous Cell / metabolism*
  • Carcinoma, Squamous Cell / pathology*
  • Endothelial Cells / metabolism*
  • Head and Neck Neoplasms / metabolism*
  • Head and Neck Neoplasms / pathology*
  • Humans
  • Interleukin-6 / metabolism*
  • Mice
  • Neoplastic Stem Cells / cytology*
  • STAT3 Transcription Factor / metabolism
  • Signal Transduction / physiology
  • Squamous Cell Carcinoma of Head and Neck


  • IL6 protein, human
  • Interleukin-6
  • STAT3 Transcription Factor
  • Stat3 protein, mouse