Alteration of signal-transducing molecules in tumor-infiltrating lymphocytes and peripheral blood T lymphocytes from human colorectal carcinoma patients

Tumor development or growth is accompanied by impaired immune responses, such as a poor proliferative response or down-regulated cytolytic T lymphocyte activity. Although recent reports have suggested that modification of the signal-transducing molecule is responsible for impaired immune responses in tumor-bearing hosts, the causes of defective immune function are not yet completely understood. Furthermore, the clinical significance of the findings is not yet clear. In this study, we investigated the alteration of several signal-transducing molecules in peripheral blood T lymphocytes (T- PBL) as well as in tumor-infiltrating lymphocytes (TIL) from human colorectal carcinoma patients and their relationship with the impaired host immune responses. A greater reduction in CD3ζ chain level was observed in TIL than in T-PBL from tumor-bearing hosts. CD3ζ chain reduction in T-PBL correlated with the clinicopathological stage of a tumor, especially with the status of lymph node metastasis. The levels of p56(lck) and p59(fyn) protein tyrosine kinase in T-PBL were also compared between tumor-bearing hosts and normal healthy volunteers. In T-PBL from tumor-bearing hosts, expression of protein tyrosine kinase p59(fyn) was significantly lower than that of p56(lck). However, the level of CD3ζ chain expression did not correlate with T lymphocyte functions such as T lymphocyte proliferative response or allogeneic target cell lysis.