PURPOSE: Some studies suggest that the immunoreceptor NKG2D expression on CD8(+) T cells is down-regulated and this reduction may be involved in immune evasion in cancer patients. The present study was designed to investigate NKG2D expression on CD8(+) T lymphocytes and its relationship to immune evasion in gastric cancer patients. EXPERIMENTAL DESIGN: NKG2D expression on both circulating and tumor-infiltrating CD8(+) T cells was evaluated by multicolor flow cytometry. Soluble MHC class I chain-related gene A (MICA) in the sera was quantitated by ELISA. Transwell experiments were carried out to determine the effect of cancer cells on NKG2D expression. RESULTS: NKG2D expression on circulating CD8(+) T cells was down-regulated and significantly correlated with IFN-gamma production in gastric cancer patients (r = 0.68; P = 0.007). NKG2D expression was closely related to undifferentiated cancer (P = 0.021) as was the depth of invasion (P = 0.012). There was no difference in soluble MICA between gastric cancer patients and normal controls. NKG2D expression on CD8(+) T cells was remarkably reduced in the tissue of gastric cancer compared with peripheral blood (P = 0.046). Complete removal of tumor by surgery restored NKG2D expression on CD8(+) T cells (P = 0.0049). Transwell experiments showed that this down-regulation was induced by direct contact between cancer cells and CD8(+) T cells and that soluble factors did not affect the NKG2D expression. This phenomenon was blocked by the addition of anti-MICA antibodies. CONCLUSIONS: Decreased NKG2D expression may be one of the key mechanisms responsible for immune evasion by tumors in gastric cancer.
PURPOSE: Some studies suggest that the immunoreceptor NKG2D expression on CD8(+) T cells is down-regulated and this reduction may be involved in immune evasion in cancerpatients. The present study was designed to investigate NKG2D expression on CD8(+) T lymphocytes and its relationship to immune evasion in gastric cancerpatients. EXPERIMENTAL DESIGN:NKG2D expression on both circulating and tumor-infiltrating CD8(+) T cells was evaluated by multicolor flow cytometry. Soluble MHC class I chain-related gene A (MICA) in the sera was quantitated by ELISA. Transwell experiments were carried out to determine the effect of cancer cells on NKG2D expression. RESULTS:NKG2D expression on circulating CD8(+) T cells was down-regulated and significantly correlated with IFN-gamma production in gastric cancerpatients (r = 0.68; P = 0.007). NKG2D expression was closely related to undifferentiated cancer (P = 0.021) as was the depth of invasion (P = 0.012). There was no difference in soluble MICA between gastric cancerpatients and normal controls. NKG2D expression on CD8(+) T cells was remarkably reduced in the tissue of gastric cancer compared with peripheral blood (P = 0.046). Complete removal of tumor by surgery restored NKG2D expression on CD8(+) T cells (P = 0.0049). Transwell experiments showed that this down-regulation was induced by direct contact between cancer cells and CD8(+) T cells and that soluble factors did not affect the NKG2D expression. This phenomenon was blocked by the addition of anti-MICA antibodies. CONCLUSIONS: Decreased NKG2D expression may be one of the key mechanisms responsible for immune evasion by tumors in gastric cancer.
Authors: Naela A Arreygue-Garcia; Adrian Daneri-Navarro; Alicia del Toro-Arreola; Angel Cid-Arregui; Oscar Gonzalez-Ramella; Luis F Jave-Suarez; Adriana Aguilar-Lemarroy; Rogelio Troyo-Sanroman; Alejandro Bravo-Cuellar; Vidal Delgado-Rizo; Trinidad Garcia-Iglesias; Georgina Hernandez-Flores; Susana Del Toro-Arreola Journal: BMC Cancer Date: 2008-01-21 Impact factor: 4.430