Release of MICB molecules by tumor cells: mechanism and soluble MICB in sera of cancer patients

Hum Immunol. 2006 Mar;67(3):188-95. doi: 10.1016/j.humimm.2006.02.008. Epub 2006 Mar 29.


MICA, a ligand of the activating immunoreceptor NKG2D, is released by tumor cells in a soluble form and can be detected in sera of tumor patients at significant levels. Soluble MICA has been proposed to counteract NKG2D-mediated immunosurveillance of tumors. Here, we report that MICB, the second member of the human MIC protein family, is likewise shed by metalloproteases from tumor cells and is present in sera of patients with gastrointestinal tumors. While cell-bound MICB causes downregulation of surface NKG2D, soluble MICB did not alter NKG2D expression on NK cells in vitro. Thus, proteolytic shedding of MICB by tumor cells may impair immunogenicity of tumors primarily by reducing NKG2D-ligand densities on malignant cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • Down-Regulation
  • Gastrointestinal Neoplasms / blood*
  • Hematologic Neoplasms / blood*
  • Histocompatibility Antigens Class I / blood
  • Histocompatibility Antigens Class I / metabolism*
  • Humans
  • Killer Cells, Natural / metabolism
  • Matrix Metalloproteinase 1 / metabolism
  • NK Cell Lectin-Like Receptor Subfamily K
  • Receptors, Immunologic / biosynthesis
  • Receptors, Natural Killer Cell


  • Histocompatibility Antigens Class I
  • KLRK1 protein, human
  • MHC class I-related chain A
  • MICB antigen
  • NK Cell Lectin-Like Receptor Subfamily K
  • Receptors, Immunologic
  • Receptors, Natural Killer Cell
  • Matrix Metalloproteinase 1