LAUSR

Purpose: Aim of this study is to explore the intrinsic expression, functional role and therapeutic modulation of PD-1 receptor in Non Small Cell Lung Cancer (NSCLC) cells. We previously reported (Sanlorenzo M et al. Clinical Cancer Res 2018) that PD-1+ melanoma cells may sustain disease relapse following treatment with BRAF/MEK inhibitors. We hypothesized that PD-1+ tumor cells may characterize a “stem-like” compartment also in NSCLC, sustaining chemo-resistance and disease relapse with potential therapeutic implications. Experimental procedures: The expression of PD-1 by NSCLC cells was explored by flow cytometry, western blot (WB) and RT-PCR. Its presence and role in lung cancer stem cells (CSC) was explored by sphere formation essays. CSC were further visualized by tumor-engineering with a lentiviral CSC-detector vector (LV-CSC) encoding eGFP under control of the OCT4 stem gene promoter. Selective PD-1 blockade and PD-1 stimulation with soluble ligand (PD-L1) were used to study the functional role and therapeutic modulation of intrinsic PD-1 in NSCLC. Results: PD-1 is intrinsically expressed by a small subset of NSCLC cells with stemness features. We found PD-1 consistently expressed on the membrane of a small tumor cell fraction (2% ± 0.3) within 6 NSCLC cell lines (H1975, EBC-1, H23, H820, HCC827), including a primary patient-derived NSCLC culture (SL1). Data were confirmed by RT-PCR and WB. Viable PD-1+ tumor cells were significantly enriched in NSCLC spheres generated in stem conditioned cultures, compared with the monolayer controls (10% [4-36] vs 2% [1-5] P Conclusions: PD-1 is intrinsically expressed by NSCLC cells with stemness features and mediates pro-tumorigenic activity. PD-1+ NSCLC cells are enriched after chemotherapy and may be inhibited by selective PD-1 blockade. We report a new, intrinsic, expression pattern of PD-1 in NSCLC, providing rationale to explore a lymphocyte-independent activity of anti-PD1 antibodies. Citation Format: Ramona Rotolo, Valeria Leuci, Chiara Donini, Martina Sanlorenzo, Igor Vujic, Giovanni Medico, Francesca Vita, Loretta Gammaitoni, Luisella Righi, Chiara Riganti, Elisa Vigna, Lorenzo D9Ambrosio, Giovanni Grignani, Giorgio V. Scagliotti, Silvia Novello, Massimo Aglietta, Dario Sangiolo. PD-1 is intrinsically expressed by lung cancer cells with stemness features inhibited by PD-1 blockade [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 3234.