Plasminogen Activator Inhibitor 1 Promotes Immunosuppression in Human Non-Small Cell Lung Cancers by Enhancing TGF-Β1 Expression in Macrophage

Cell Physiol Biochem. 2017;44(6):2201-2211. doi: 10.1159/000486025. Epub 2017 Dec 13.

Abstract

Background: Plasminogen activator inhibitor-1 (PAI-1) has been regarded as a risk factor for thrombosis and atherosclerosis. Since it has been shown that PAI-1 can activate macrophages through Toll-like receptor-4, we sought to investigate the role of PAI-1 in the tumor microenvironment.

Methods: The expression and distribution patterns of PAI-1 and transforming growth factor beta (TGF-β) were measured in 60 non-small cell lung cancer (NSCLC) tumors. A statistical correlation analysis was performed between PAI-1 and TGF-β expression and distribution in each tumor. The distribution of tumor-associated macrophages (TAMs) was also measured and its correlation to PAI-1 levels was analyzed. Levels of secreted CCL-17, CCL-22, IL-6 and TGF-β were measured in cell cultures of human macrophage cell lines THP-1 and U937 treated with PAI-1. Levels of secreted PAI-1 were monitored in cell cultures of human NSCLCs cell lines 95D and A549 treated with TGF-β. Secreted proteins were measured in cell culture supernatants using ELISA. Changes in downstream signaling pathways were investigated using western blot.

Results: PAI-1 and TGF-β were found to be overexpressed in human NSCLCs. PAI-1 expression was tightly correlated to TGF-β expression as well as the percentage of TAMs. PAI-1 treatment increased the expression of TAM-associated cytokines and chemokines, including CCL-17, CCL-22, and IL-6. PAI-1 treatment was also observed to enhance TGF-β expression in macrophage cell lines through an IL-6 autocrine/paracrine manner. The effects on TGF-β expression were blocked by NF-κB and STAT3 inhibition. Interestingly, TGF-β also increased levels of secreted PAI-1 in NSCLC cells through SMAD3-dependent signaling, therefore resulting in a feed-forward loop. However, this loop could be blocked by NF-κB, STAT3 and SMAD3 signaling inhibition, as well as treatment with a high concentration of TGF-β.

Conclusion: PAI-1 and TGF-β promote NSCLC tumor cells and TAMs and might be valuable targets for cancer immunosuppression.

Keywords: Hegdhr; NSCLC; PAI-1; TAMs; TGF-β.

MeSH terms

  • Carcinoma, Non-Small-Cell Lung / immunology*
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Line, Tumor
  • Female
  • Humans
  • Immune Tolerance*
  • Interleukin-6 / analysis
  • Interleukin-6 / immunology
  • Lung / immunology
  • Lung / pathology
  • Lung Neoplasms / immunology*
  • Lung Neoplasms / pathology
  • Macrophages / immunology*
  • Macrophages / pathology
  • Male
  • NF-kappa B / analysis
  • NF-kappa B / immunology
  • Plasminogen Activator Inhibitor 1 / analysis
  • Plasminogen Activator Inhibitor 1 / immunology*
  • Toll-Like Receptor 4 / analysis
  • Toll-Like Receptor 4 / immunology
  • Transforming Growth Factor beta1 / analysis
  • Transforming Growth Factor beta1 / immunology*

Substances

  • Interleukin-6
  • NF-kappa B
  • Plasminogen Activator Inhibitor 1
  • SERPINE1 protein, human
  • TLR4 protein, human
  • Toll-Like Receptor 4
  • Transforming Growth Factor beta1