Abstract
PURPOSE: Immune checkpoint inhibitors (ICIs) have been developed for clinical application and proven effective for non-small cell lung cancer (NSCLC). Blockade of the programmed cell death 1 (PD-1) protein can partially reinvigorate circulating exhausted-phenotype CD8+ T cells (Tex cells) in preclinical models, however the clinical implication in anti-PD-1-based immunotherapy in NSCLC is unknown. METHODS: Serum specimens were obtained before and during treatment from 145 patients with NSCLC patients who received anti-PD-1 treatment and their prognoses were followed-up. Indicators such as cell subpopulations, T cell invigoration were detected by clinical laboratory testing. Survival curves were estimated by the Kaplan-Meier method, Cox regression analysis was used to identify factors associated with prognoses of NSCLC patients. RESULTS: The expressions of Ki-67 in PD-1+/CD8+ T cells in most NSCLC patients (97 of 145 cases) increased after treatment. The responding Ki-67+/CD8+ T cell population was mainly CD45RAlo CD27hi, containing cells with high expression of CTLA-4, PD-1, and 2B4 and low expression of NKG2-D (P < 0.0001). The maximum fold change of Ki-67+/PD-1+/CD8+T cells in treatment cycles and the tumor burden determined by imaging may be associated with survival. Patients with higher Ki-67 expression on PD-1+CD8+ T-cells (pretreatment) had statistically significant increased progression-free survival (PFS). A Ki-67 expression to tumor burden ratio greater than 0.6 at the 1st cycle of anti-PD-1 immunotherapy was associated with improvement of PFS and overall survival (P < 0.05). CONCLUSION: Activation of circulating Tex cells before or during therapy related to tumor burden may be associated with clinical efficacy of anti-PD-1 immune therapy in NSCLC.