Hypoxia increases tumor cell shedding of MHC class I chain-related molecule: role of nitric oxide.

The MHC class I chain-related (MIC) molecules play important roles in tumor immune surveillance through their interaction with the NKG2D receptor on natural killer and cytotoxic T cells. Thus, shedding of the MIC molecules from the tumor cell membrane represents a potential mechanism of escape from NKG2D-mediated immune surveillance. Tumor hypoxia is associated with a poor clinical outcome for cancer patients. We show that hypoxia contributes to tumor cell shedding of MIC through a mechanism involving impaired nitric oxide (NO) signaling. Whereas hypoxia increased MIC shedding in human prostate cancer cells, activation of NO signaling inhibited hypoxia-mediated MIC shedding. Similar to incubation in hypoxia, pharmacologic inhibition of endogenous NO signaling increased MIC shedding. Parallel studies showed hypoxia-mediated tumor cell resistance to lysis by interleukin 2-activated peripheral blood lymphocytes (PBL) and NO-mediated attenuation of this resistance to lysis. Inhibition of NO production also led to resistance to PBL-mediated lysis. Interference of MIC-NKG2D interaction with a blocking anti-MIC antibody abrogated the effect of hypoxia and NO signaling on tumor cell sensitivity to PBL-mediated lysis. Finally, continuous transdermal delivery of the NO mimetic glyceryl trinitrate (7.3 mug/h) attenuated the growth of xenografted MIC-expressing human prostate tumors. These findings suggest that the hypoxic tumor microenvironment contributes to resistance to immune surveillance and that activation of NO signaling is of potential use in cancer immunotherapy.
AuthorsD Robert Siemens, Nianping Hu, Abdol Karim Sheikhi, Eugene Chung, Lisa J Frederiksen, Hugh Pross, Charles H Graham
JournalCancer research (Cancer Res) Vol. 68 Issue 12 Pg. 4746-53 (Jun 15 2008) ISSN: 1538-7445 [Electronic] United States
PMID18559521 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Histocompatibility Antigens Class I
  • Interleukin-2
  • KLRK1 protein, human
  • Klrk1 protein, mouse
  • MHC class I-related chain A
  • NK Cell Lectin-Like Receptor Subfamily K
  • Nitric Oxide Donors
  • Receptors, Immunologic
  • Receptors, Natural Killer Cell
  • Nitric Oxide
  • Nitroglycerin
  • Oxygen
  • Adenocarcinoma (metabolism, pathology)
  • Animals
  • Anoxia (metabolism)
  • Cells, Cultured
  • Histocompatibility Antigens Class I (metabolism)
  • Humans
  • Immunologic Surveillance
  • Interleukin-2 (metabolism)
  • Leukocytes (cytology, metabolism)
  • Male
  • Mice
  • Mice, Nude
  • NK Cell Lectin-Like Receptor Subfamily K
  • Nitric Oxide (metabolism)
  • Nitric Oxide Donors (pharmacology)
  • Nitroglycerin (pharmacology)
  • Oxygen (metabolism)
  • Prostatic Neoplasms (metabolism, pathology)
  • Receptors, Immunologic (metabolism)
  • Receptors, Natural Killer Cell
  • Signal Transduction
  • Tumor Cells, Cultured
  • Tumor Escape
  • Xenograft Model Antitumor Assays

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