Prognostic Significance of Tumor-infiltrating CD8+ or CD3+ T Lymphocytes and Interleukin-2 Expression in Radically Resected Non-small Cell Lung Cancer

BACKGROUND Altered immunoresponse is associated with tumorigenesis and cancer progression. This study assessed the levels of tumor-infiltrating CD3 + or CD8 + T lymphocytes and interleukin-2 (IL-2) protein in radically resected non-small cell lung cancer (NSCLC) tissues to predict overall survival (OS) of the patients. METHODS Paraffin-embedded tissue specimens from 129 NSCLC patients were retrospectively collected for immunostaining of CD8 + , CD3 + , and IL-2 expression. Clinicopathological and survival data were collected and analyzed using the Chi-squared test, Kaplan-Meier curves, and the log-rank test or the Cox regression model. RESULTS The data showed a significant inverse association between CD8 + T lymphocyte levels and IL-2 expression (r = -0.927; P = 0.000) and between the levels of CD8 + and CD3 + T lymphocytes (r = -0.722; P = 0.000), but a positive association between CD3 + T lymphocyte levels and IL-2 expression (r = 0.781; P = 0.000) in NSCLC tissues. Furthermore, the levels of CD3 + and CD8 + T lymphocytes and IL-2 expression were associated with tumor stage (P = 0.023, 0.006, and 0.031, respectively) and the level of CD8 + T lymphocytes was associated with the patient gender (P = 0.024). In addition, the levels of CD8 + T lymphocytes were associated with an unfavorable 5-year OS, whereas patients with high levels of CD3 + T lymphocytes in tumor lesions and IL-2-expressing tumors had significantly better 5-year OS rates than patients with low levels. CONCLUSIONS The levels of CD8 + T cells in tumor lesions and IL-2 expression were both independent predictors of OS for these NSCLC patients. Thus, the detection of tumor-infiltrating CD3 + or CD8 + T lymphocytes and IL-2 expression could be useful to predict the prognosis of radically resected NSCLC patients.