FcRγ chain does not replace CD3ζ chain in CD3ζ-deficient T lymphocytes of patients with gastric adenocarcinoma

Defective CD3ζ chain expression has been reported in T lymphocytes of patients with inflammatory diseases, such as systemic lupus erythematosus or osteoarthritis, and with cancer. In lupus, the absent CD3ζ chain is replaced by the FcRγ chain, rendering the T cells hyper responsive. However, there are no data on T lymphocytes from patients with cancer. In this study, the presence of the FcRγ chain and its associated kinase, Syk, was analysed in patients with gastric adenocarcinoma and healthy subjects. Western blot and immunoprecipitation experiments were carried out with total cell or lipid raft extracts from fresh peripheral blood mononuclear cells or T lymphocytes, and Herpesvirus saimiri-derived T-cell lines (of blood or tissue origin). Our results revealed that the absent CD3ζ chain in cancer T lymphocytes was not replaced by FcRγ either in fresh T cells or T-cell lines, in contrast to lupus T cells. This altered expression of signalling molecules in T lymphocytes of cancer patients, would explain their low proliferative capacity. Our T-cell lines represent tools to unveil the signalling abnormalities of cancer T lymphocytes.