Abstract 4578: Macrophages are important source of PD-L1 and PD-L1 expressing on central M2 macrophages leads to the poor prognosis of NSCLC patients: Via macrophage landscape analysis for NSCLC patients with tumor PD-L1 negative

PD-1 antibody has achieved significant clinical efficacy for advanced non-small cell lung cancer (NSCLC), but the ORR is not optimistic for the non-selected patients. PD-L1,as the therapeutic target, is still controversial to be a predictor of efficacy.It was noticed that some patients with tumor cell PD-L1 negative could still benefit from anti-PD-1/PDL1 antibody therapy.Besides the tumor cells, PD-L1 was also known to express in immune cells in TME. Therefore, in this study, we aimed to clarify the factors that affect the PD-L1 expression in TME, and their functions on the NSCLC prognosis and the effect on anti-PD-1/PD-L1 therapy.With the multiple quantitative immunofluorescence staining on 94 tissue specimens of NSCLC patients with PD-L1 expressing negative on tumor cells, we surprisingly found that macrophages,especially M2 macrophages,were the main source of PD-L1 for patients with tumor cells PD-L1 negative.Futhermore, the expression of PD-L1 in central M2 macrophages(M2 macrophages that infiltrate into tumor islets),was important for the poor prognosis of NSCLC patients,suggesting that the expression of PD-L1 in macrophages may also be associated with the benefit of anti-PD-1 therapy, which is an important factor to be considered in evaluating the efficacy of immunotherapy in the future. Note: This abstract was not presented at the meeting. Citation Format: Lili Cao, Xiaofang Che, Xiujuan Qu, Xueshan Qiu, Zhi Li, Bowen Yang, Shuo Wang, Yunpeng Liu. Macrophages are important source of PD-L1 and PD-L1 expressing on central M2 macrophages leads to the poor prognosis of NSCLC patients: Via macrophage landscape analysis for NSCLC patients with tumor PD-L1 negative [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4578.