Defective CD3ζ chain expression in Herpesvirus saimiri (HVS)-derived T-cell lines in gastric adenocarcinoma

Low expression of the CD3ζ chain has been reported in patients with cancer and it has been suggested that tumor-derived factors are involved in its downregulation. The expression of CD3ζ chain was measured in T-cell lines from patients with gastric adenocarcinoma and healthy volunteers and grown in vitro for several months and, hence, in the absence of any tumor-derived factors. T-cell lines of mucosal origin were obtained by Herpesvirus saimiri transformation from gastric cancer patients. The expression of CD3ζ and CD3ε was measured by flow cytometry and Western-blot analysis. Calcium mobilization and apoptosis rate were also measured. The levels of CD3ζ, but not CD3ε, chain on the cell surface were significantly reduced in T-cell lines derived from patients with gastric cancer when cultured in the absence of IL-2. Western-blot analysis of total cell extracts or lipid raft fractions confirmed this finding. Calcium mobilization, a measure of signal transduction, was reduced in T cell lines from patients with gastric cancer. We conclude that T cells from patients with cancer express lower levels of CD3ζ. This downregulation is not caused by a direct effect of tumor-derived factors but, rather, it appears to be inherent to the patient cells. The low CD3ζ expression would render T lymphocytes unable to control the growth of tumor cells.