Cancer Cell CD44 Mediates Macrophage/Monocyte-Driven Regulation of Head and Neck Cancer Stem Cells

Cancer Res. 2020 Oct 1;80(19):4185-4198. doi: 10.1158/0008-5472.CAN-20-1079. Epub 2020 Aug 14.


Tumor-associated macrophages (TAM) in the tumor microenvironment (TME) cooperate with cancer stem cells (CSC) to maintain stemness. We recently identified cluster of differentiation 44 (CD44) as a surface marker defining head and neck squamous cell carcinoma (HNSCC) CSC. PI3K-4EBP1-SOX2 activation and signaling regulate CSC properties, yet the upstream molecular control of this pathway and the mechanisms underlying cross-talk between TAM and CSC in HNSCC remain largely unknown. Because CD44 is a molecular mediator in the TME, we propose here that TAM-influenced CD44 signaling could mediate stemness via the PI3K-4EBP1-SOX2 pathway, possibly by modulating availability of hyaluronic acid (HA), the main CD44 ligand. HNSCC IHC was used to identify TAM/CSC relationships, and in vitro coculture spheroid models and in vivo mouse models were used to identify the influence of TAMs on CSC function via CD44. Patient HNSCC-derived TAMs were positively and negatively associated with CSC marker expression at noninvasive and invasive edge regions, respectively. TAMs increased availability of HA and increased cancer cell invasion. HA binding to CD44 increased PI3K-4EBP1-SOX2 signaling and the CSC fraction, whereas CD44-VCAM-1 binding promoted invasive signaling by ezrin/PI3K. In vivo, targeting CD44 decreased PI3K-4EBP1-SOX2 signaling, tumor growth, and CSC. TAM depletion in syngeneic and humanized mouse models also diminished growth and CSC numbers. Finally, a CD44 isoform switch regulated epithelial-to-mesenchymal plasticity as standard form of CD44 and CD44v8-10 determined invasive and tumorigenic phenotypes, respectively. We have established a mechanistic link between TAMs and CSCs in HNSCC that is mediated by CD44 intracellular signaling in response to extracellular signals. SIGNIFICANCE: These findings establish a mechanistic link between tumor cell CD44, TAM, and CSC properties at the tumor-stroma interface that can serve as a vital area of focus for target and drug discovery.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Cell Cycle Proteins / metabolism
  • Cell Line, Tumor
  • Feedback, Physiological
  • Female
  • Head and Neck Neoplasms / metabolism
  • Head and Neck Neoplasms / pathology*
  • Humans
  • Hyaluronan Receptors / genetics
  • Hyaluronan Receptors / immunology
  • Hyaluronan Receptors / metabolism*
  • Hyaluronic Acid / metabolism
  • Male
  • Mice, Inbred NOD
  • Monocytes / metabolism
  • Monocytes / pathology
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Phosphatidylinositol 3-Kinases / metabolism
  • SOXB1 Transcription Factors / metabolism
  • Squamous Cell Carcinoma of Head and Neck / metabolism
  • Squamous Cell Carcinoma of Head and Neck / pathology*
  • Tumor Microenvironment
  • Tumor-Associated Macrophages / metabolism
  • Tumor-Associated Macrophages / pathology*
  • Xenograft Model Antitumor Assays
  • Zinc Finger E-box-Binding Homeobox 1 / genetics
  • Zinc Finger E-box-Binding Homeobox 1 / metabolism


  • Adaptor Proteins, Signal Transducing
  • CD44 protein, human
  • Cell Cycle Proteins
  • EIF4EBP1 protein, human
  • Hyaluronan Receptors
  • SOX2 protein, human
  • SOXB1 Transcription Factors
  • ZEB1 protein, human
  • Zinc Finger E-box-Binding Homeobox 1
  • Hyaluronic Acid