title: Decreased NKG2D expression on NK cells correlates with impaired NK cell function in patients with gastric cancer.
abstract: BACKGROUND
  Although malignant diseases are known to be associated with immune suppression, the detailed mechanisms involved are still unknown. NKG2D is an activating cell surface receptor expressed by natural killer (NK) cells and CD8+ T cells, and the engagement of NKG2D is extremely important for NK cell activation. Although decreased NKG2D expression on NK cells is closely related to immune evasion by some cancers, the immunopathological importance of this phenomenon in gastric cancer patients remains unclear.
  
  
  METHODS
  NKG2D expression on NK cells was determined, using multicolor flow cytometry, to investigate the mechanisms responsible for immune evasion in gastric cancer patients.
  
  
  RESULTS
  NKG2D expression on NK cells from gastric cancer patients was significantly lower than that in healthy controls. Also, NKG2D expression in advanced gastric cancer was significantly lower than that in early gastric cancer. NK cells from patients with lymph node metastasis expressed significantly lower levels of NKG2D than the NK cells from those without lymph node metastasis, and NKG2D expression on NK cells in gastric cancer tissue was significantly lower than that of circulating NK cells. NKG2D expression on NK cells obtained from cancer patients was restored after 48 h in culture with RPMI containing 10% AB serum. Furthermore, NKG2D expression on NK cells obtained after surgery was significantly higher than that before surgery.
  
  
  CONCLUSIONS
  Decreased NKG2D expression on NK cells may be one of the key mechanisms responsible for NK cell dysfunction in gastric cancer.
authors.affiliation: Division of Surgical Oncology, Department of Surgery, Tottori University School of Medicine, 36-1 Nishi-cho, Yonago, Japan. sai10@med.tottori-u.ac.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Saito
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Osaki
authors.forename: Masahide
authors.initials: M
authors.lastname: Ikeguchi
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism*; D008207:Lymphatic Metastasis; D008875:Middle Aged; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery
chemical_list: C527085:KLRK1 protein, human; D055655:NK Cell Lectin-Like Receptor Subfamily K