Death instead of activation - a study of lymphocyte apoptosis in the tumor draining lymph nodes and in the tumor tissue

Background: Apoptosis, or induced cell death, is associated with many pathological conditions, including development of cancer. Lung cancer cells are able to express CD95L, which can stimulate apoptosis of lymphocytes which were exposed to tumor cells. Aim: To assess apoptosis of lymphocytes in the tissues of patients with NSCLC, to confirm its relationship with expression of CD95 antigen (Fas), and to determine the correlation between the estimated parameters and survival time of patients. Material and methods: Mononuclear cells were isolated from blood, tumor and lymph nodes from 30 patients with NSCLC. Assessment of apoptosis, CD95 expression and lymphocyte markers was performed using flow cytometry. Results: We found a significantly higher percentage of apoptotic and dead cells in tumor than in blood and lymph nodes. We observed a positive correlation between the number of apoptotic cells and expression of CD95 on the surface of CD3+ and CD8+. We also found a correlation between the number of dead cells and expression of Fas receptor on surfaces of CD3+, CD4+ and CD8+. The relationship between studied parameters and patients' survival time was found to be significant only in tumor. Conclusions: Our results suggest that activated lymphocytes can be eliminated by the tumor microenvironment. This is disadvantageous in the case of cytotoxic T lymphocytes, which are prepared to eliminate cancer cells. Assessment of immunological parameters in tissues directly involved in the carcinogenesis process may be useful for evaluation of clinical predictions.