Increased PD-1 and EGFR expression levels of T lymphocytes in patients with non-small cell lung cancer.

Abstract

e21018 Background: Programmed cell death protein 1 (PD-1) and its ligand (PD-L1) are proteins that negatively regulate immune responses. Increased expression of PD-L1 in cancer cells leads to inhibition of the immune response against cancer, and causes cancer development and metastasis. Epidermal growth factor receptor (EGFR) activation upregulates PD-L1 expression in lung cancer cells and contribute to escape from immune response. In this study, we aimed to investigate the circulating T lymphocyte subsets and, PD-1 and EGFR expression levels of these cells in non-small cell lung cancer (NSCLC) progression. Methods: 40 NSCLC patients with 63.8 ± 8.0 mean age and 40 healthy controls with 60.9 ± 14.6 mean age were included in the study. In the peripheral blood samples of the patients taken at the time of diagnosis and controls, CD4+ T helper (Th) subsets (Th1, Th2, Th9, Th17, Th1Th17, CD4+ follicular T [Tfc] and peripheral T cells [Tpcs]), CD8+ cytotoxic T cell (CTL) subsets (CD8+ Tfcs and Tpcs), EGFR and PD-1 expression levels of T cells were determined by flow cytometric analysis. Results: Total lymphocyte ratio was decreased in patients with NSCLC compared to control (11.5 ± 5.2 in patients and 17.6 ± 6.1 in controls, p = 0.001), but there was no significant difference in CD3+ total T, Th and CTLs as well as their subsets (p < 0.05). Increased PD-1 expression level (mean fluorescence intensity-MFI) on total lymphocyte (p = 0.001), CD3+ T (p = 0.001), CD4+ Th (p = 0.001), CTL (p = 0.016), CD4+ Tpc (p = 0.002) and CD8+ Tpc subsets (p = 0.017) were determined in the patients compared with controls. EGFR expressions were also increased on total lymphocyte, CD3+ T, Th and Th2 cells (p = 0.034, p = 0.020, p = 0.030, respectively). 19 NSCLC patients were metastatic, while 21 patients were non-metastatic. There was no significant difference in mean age between metastatic and non-metastatic NSCLC patients. Reduced total lymphocytes and Th cells, increased Th1Th17 cells were found in metastatic NSCLC patients (p = 0.003, p = 0.046 and p = 0.022, respectively). The percentage of EGFR in CD3+ T cell and Th17 cells decreased in metastatic patients. Conclusions: This study showed the increased PD-1 and EGFR expression levels of T lymphocytes in patients with NSCLC. Cancer cells may upregulate PD-1 expression by inducing EGFR activation on lymphocytes to suppress immune responses, leading to programmed cell death of lymphocytes and a decrease in the percentage of these cells in NSCLC. Therapeutic approaches focused on changing EGFR need to be considered for the distribution of T cell subsets and EGFR expressions.