Epidermal growth factor receptor and programmed cell death-1 expression levels in peripheral T cell subsets of patients with non-small cell lung cancer.

Lung cancer is the leading cause of cancer-related deaths, in part due to its late diagnosis. Increased epidermal growth factor receptor (EGFR) expression in cancer cells is associated with a poor prognosis, and EGFR tyrosine kinase inhibitors are widely used in cancer treatment. This study aimed to clarify the relationship between EGFR expression on T cells and cancer prognosis in patients with non-small cell lung cancer (NSCLC). Forty patients with NSCLC and 40 healthy volunteers were included in this study. Peripheral CD4⁺T helper (Th1, Th2, Th9, Th17, Th1Th17, follicular and peripheral Th) and cytotoxic T lymphocyte (CD8⁺follicular and peripheral T) subsets were identified with flow cytometry according to their chemokine receptors. EGFR expression on T lymphocytes in relation to overall survival (OS) was investigated in patients with NSCLC. The patients [mean age (min-max) = 64.03 (45-83); 20 stage I-III and 20 stage IV] had increased EGFR expression on CD3⁺T, CD4⁺Th, Th1, Th2, and Th17 cells compared to the controls (p < 0.05). High EGFR expression on CD3⁺T, CD4⁺Th, Th1, and Th2 cells was associated with poor OS. Also, PD-1 expression on lymphocytes, CD3⁺T, and Th cells was increased in patients with NSCLC compared to controls. The high expression of EGFR and PD-1 on Th cells and the reduced percentage of lymphocytes and Th cells, especially in stage IV patients with NSCLC, revealed that increased EGFR activity may trigger apoptosis of Th cells and promote the development of metastases, while high EGFR expression on CD3⁺T, CD4⁺Th, Th1, and Th2 cells may be an independent poor prognostic marker in NSCLC.