T-cell exhaustion and pre-existing T-cell immunity in circulation as predictive biomarkers for immunotherapy in NSCLC patients.

Abstract

2553 Background: Pre-existing cancer-antigen specific T-cells describe the endogenous adaptive immunity before any treatment that may represent a valuable novel predictive biomarker for ICI. In a recent publication we have shown a positive correlation of pre-existing cancer-antigen specific CD8 + T-cells with the response to ICI. Here, we analyze the major differences of exhausted T-cells between pre-existing positive (PreI + ) and pre-existing negative immunity (PreI - ) NSCLC patients as well as, between different stages of the disease. Methods: Blood was collected from 82 patients with NSCLC, 38 with stage III and 44 with stage IV, before ICI therapy. PBMCs were isolated with Ficoll density gradient centrifugation from patients and 15 healthy donors (HD). PreI was calculated by detecting endogenous IFNg expressing cells with FACS after in-vivo co-cultures of PBMCs with mixes of hTERT, MAGEA1, NY-ESO-1 και Survivin cancer-associated antigens. T-exhausted signatures were detected by multi-color flow cytometry using antibodies against CD3, CD4, CD8, PD-1 and TCF1. Results: 47% (18/38) of patients with stage III disease and 41% (18/44) of stage IV had peptide specific T-cells (PreI + patients). Survival analysis revealed better OS only in stage III PreI + compared to PreI – patients (Log-rank = 0.04), while for stage IV (p=0.081) there was only a trend. The percentages of CD8 T-cells that were PD-1 + TCF1 + (p=0.030) and PD-1 + TCF1 - (p=0.041) were higher in patients compared to HD, and additionally both T-cell populations harbored higher levels of PD-1 protein expression (p=0.003 and p=0.032 for stage III) as it was shown with mean fluorescence intensity (MFI). Moreover, low percentages of PD-1 + TCF1 + ware associated with longer survival (p= 0.037) only in stage III patients. By subgrouping stage III patients, we observed that all patients with PreI + harboring low percentages of exhausted PD-1 + TCF1 + were alive at the end of the follow up. Conclusions: Combinatorial analysis of Pre-existing tumor-antigen specific immunity and the status of T-cells before initiation of ICI in stage III NSCLC could serve as a good predictive factor of response. The study is ongoing.