30PDivergent PD-1 expression in tissue and circulating CD8 lymphocytes defines an immune profile predictive of the response to nivolumab in advanced NSCLC

Background: To predict the response to immunotherapy, tissue and circulating cytotoxic lymphocytes, potentially targeted by anti-PD-1/PD-L1 drugs, were simultaneously assessed in NSCLC. Methods: Twenty-six advanced NSCLC patients receiving nivolumab were included. Tissue samples were immunohistochemically analyzed to quantify PD‐L1 (H‐score) and CD3, CD8, CD4 and PD-1 positive TILs. Peripheral blood (PB) immune profile at baseline (T0) and after 2 (T1) and 4 (T2) cycles of bi-weekly nivolumab was performed by FACS analysis of CD3, CD8, CD4, NK (CD56), Treg (FOXP3) and MDSC. Changes in their number, and functional (PD-1, Granzyme B, Perforin) and proliferative (Ki67) hallmarks were determined. Integrated tissue and circulating parameters were correlated to treatment response (RECIST 1.1). Results: At tissue level, in association with variable PD-L1 degrees, low PD-1 expression in CD8pos TILs was present in 100% of patients with clinical benefit (CB, n 9) compared to only 20% of non-responders (NR, p < 0.001). At baseline, PB of CB patients showed higher number of NK, which tended to increase at T1 and T2, while in NR a progressive decline in NK, CD3, CD8 and CD4 was observed (p < 0.05). Moreover, a significant 2.5-fold increase in the incidence of circulating CD8pos/PD-1pos cells was detected at baseline in CB vs NR (p < 0.001). Saturation of PD-1 sites was apparent in PB of both groups following nivolumab. Cycling Ki67poscytotoxic lymphocytes were higher in CB at baseline (12.4%), T1 and T2 while in NR proliferating CD8 (T0: 7.7%) progressively decreased to halve at T2 (p < 0.001). Intriguingly, one of the two patients with a complete response had the highest baseline value of both PD-1pos (176.3/μl) and Ki67pos CD8 cells (52%); conversely NR patients with rapidly progressive disease displayed the lowest range of both Ki67 labelling (1.3-3.9%) and PD-1 expression (18.3-22.4/μl). Conclusions: The inhibitory and activating PD-1 pathways, respectively translated in low tissue PD-1posCD8pos TILs, to escape PD-L1 pressure and high peripheral blood PD-1posCD8pos, rescued by PD-1 targeting, may identify a specific immune profile predictive of the response to immunotherapy. Legal entity responsible for the study: University Hospital of Parma Funding: AIRC project grant Disclosure: All authors have declared no conflicts of interest.