Fibroblast activation protein-positive fibroblasts promote tumor progression through secretion of CCL2 and interleukin-6 in esophageal squamous cell carcinoma

Lab Invest. 2019 Jun;99(6):777-792. doi: 10.1038/s41374-018-0185-6. Epub 2019 Jan 25.

Abstract

Esophageal squamous cell carcinoma (ESCC) is a highly aggressive tumor with frequent recurrence even after curative resection. The tumor microenvironment, which consists of non-cancer cells, such as cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs), was recently reported to promote several cancers, including ESCC. However, the role of CAF as a coordinator for tumor progression in ESCC remains to be elucidated. In our immunohistochemical investigation of ESCC tissues, we observed that the intensity of expression of two CAF markers-alpha smooth muscle actin (αSMA) and fibroblast activation protein (FAP)-in the tumor stroma was significantly correlated with the depth of tumor invasion, lymph node metastasis, advanced pathological stage, and poor prognosis. We co-cultured human bone marrow-derived mesenchymal stem cells (MSCs) with ESCC cells and confirmed the induction of FAP expression in the co-cultured MSCs. These FAP-positive MSCs (which we defined as CAF-like cells) promoted the cell growth and migration of ESCC cells and peripheral blood mononuclear cell-derived macrophage-like cells. CAF-like cells induced the M2 polarization of macrophage-like cells. A cytokine array and ELISA revealed that CAF-like cells secreted significantly more CCL2, Interleukin-6, and CXCL8 than MSCs. These cytokines promoted the migration of tumor cells and macrophage-like cells. The silencing of FAP in CAF-like cells attenuated cytokine secretion. We compared cell signaling of MSCs, CAF-like cells, and FAP-silenced CAF-like cells; PTEN/Akt and MEK/Erk signaling were upregulated and their downstream targets, NF-κB and β-catenin, were also activated with FAP expression. Silencing of FAP attenuated these effects. Cytokine secretion from CAF-like cells were attenuated by inhibitors against these signaling pathways. These findings indicate that the collaboration of CAFs with tumor cells and macrophages plays a pivotal role in tumor progression, and that FAP expression is responsible for the tumor promotive and immunosuppressive phenotypes of CAFs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Cancer-Associated Fibroblasts / metabolism*
  • Carcinoma, Squamous Cell / immunology
  • Carcinoma, Squamous Cell / metabolism*
  • Carcinoma, Squamous Cell / mortality
  • Carcinoma, Squamous Cell / pathology
  • Cell Line, Tumor
  • Chemokine CCL2 / metabolism*
  • Endopeptidases
  • Esophageal Neoplasms / immunology
  • Esophageal Neoplasms / metabolism*
  • Esophageal Neoplasms / mortality
  • Esophageal Neoplasms / pathology
  • Esophagus / pathology
  • Gelatinases / metabolism*
  • Humans
  • Interleukin-6 / metabolism*
  • Interleukin-8 / metabolism
  • Japan / epidemiology
  • MAP Kinase Signaling System
  • Membrane Proteins / metabolism*
  • Mesenchymal Stem Cells / metabolism
  • Serine Endopeptidases / metabolism*
  • Tumor Microenvironment

Substances

  • ACTA2 protein, human
  • Actins
  • CCL2 protein, human
  • CXCL8 protein, human
  • Chemokine CCL2
  • IL6 protein, human
  • Interleukin-6
  • Interleukin-8
  • Membrane Proteins
  • Endopeptidases
  • Serine Endopeptidases
  • fibroblast activation protein alpha
  • Gelatinases