Toll-like receptor 2 ligands regulate monocyte Fcγ receptor expression and function

J Biol Chem. 2013 Apr 26;288(17):12345-52. doi: 10.1074/jbc.M113.449983. Epub 2013 Mar 15.

Abstract

Fcγ receptor (FcγR) clustering on monocytes/macrophages results in phagocytosis and inflammatory cytokine production, which serve to eliminate antibody-opsonized targets and activate neighboring immune cells. Toll-like receptor 2 (TLR2), which recognizes a range of both bacterial and fungal components, elicits strong proinflammatory responses in these cells when stimulated by ligands, either natural or synthetic. Thus, we explored the possibility that TLR2 agonists could strengthen FcγR activity within the context of antibody therapy. Human peripheral blood monocytes treated with the TLR2 agonist Pam2CSK4 showed significantly enhanced FcγR-mediated cytokine production as well as phagocytic ability. An examination of the molecular mechanism behind this enhancement revealed increased expression of both FcγRIIa and the common γ subunit following Pam2CSK4 treatment. Interestingly however, expression of the inhibitory receptor FcγRIIb was also modestly increased. Further investigation revealed that Pam2CSK4 also dramatically decreased the expression of SHIP, the major mediator of FcγRIIb inhibitory activity. Using a murine Her2/neu solid tumor model of antibody therapy, we found that Pam2CSK4 significantly enhanced the ability of anti-Her2 antibody to reduce the rate of tumor growth. To verify that the FcγR enhancement was not unique to the diacylated Pam2CSK4, we also tested Pam3CSK4, a related triacylated TLR2 agonist. Results showed significant enhancement in FcγR function and expression. Taken together, these findings indicate that TLR2 activation can positively modulate FcγR and suggest that TLR2 agonists should be considered for testing as adjuvants for antitumor antibody therapy.

Publication types

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

MeSH terms

  • Animals
  • Antibodies, Neoplasm / pharmacology
  • Humans
  • Lipopeptides / pharmacology*
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Monocytes / metabolism*
  • Monocytes / pathology
  • Neoplasms, Experimental / drug therapy
  • Neoplasms, Experimental / genetics
  • Neoplasms, Experimental / metabolism
  • Neoplasms, Experimental / pathology
  • Receptor, ErbB-2 / genetics
  • Receptor, ErbB-2 / metabolism
  • Receptors, IgG / biosynthesis*
  • Receptors, IgG / genetics
  • Toll-Like Receptor 2 / agonists
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / metabolism*

Substances

  • Antibodies, Neoplasm
  • FCGR2A protein, human
  • FCGR2B protein, human
  • Fcgr2b protein, mouse
  • Lipopeptides
  • Pam2CSK4 lipopeptide
  • Receptors, IgG
  • TLR2 protein, human
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • ERBB2 protein, human
  • Erbb2 protein, mouse
  • Receptor, ErbB-2