Chang Gon Kim,¹ Gamin Kim,¹ Kyung Hwan Kim,² Seyeon Park,³ Sunhye Shin,¹ Dahee Yeo,¹ Hyo Sup Shim,⁴ Hong In Yoon,² Seong Yong Park,^5,* Sang-Jun Ha,^3,* Hye Ryun Kim^1,*

¹Division of Medical Oncology, Department of Internal Medicine, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
²Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Republic of Korea
³Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea
⁴Department of Pathology, Yonsei University College of Medicine, Seoul, Republic of Korea
⁵Department of Thoracic and Cardiovascular Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea

CGK and GK are joint first authors.

^*Correspondence to Professor Hye Ryun Kim; Professor Sang-Jun Ha; Professor Seong Yong Park; 

Background 
Reinvigoration of T-cell exhaustion with antibodies has shown promising efficacy in patients with non-small-cell lung cancer (NSCLC). However, the characteristics of T-cell exhaustion with regard to tumor-infiltrating lymphocytes (TILs) are poorly elucidated in NSCLC. Here, we investigated the exhaustion status of TILs in NSCLC patients at the intraindividual and interindividual levels.

Methods 
We obtained paired peripheral blood, normal adjacent tissues, peritumoral tissues, and tumor tissues from 96 NSCLC patients. Features of T-cell exhaustion were analyzed by flow cytometry. T cells were categorized according to their programmed cell death-1 (PD-1) expression (PD-1high, PD-1int, and PD-1neg cells). Patients were classified based on the presence or absence of discrete PD-1high CD8+ TILs. Production of effector cytokines by CD8+ TILs was measured after T-cell stimulation with or without antibodies against immune checkpoint receptors.

Results 
Progressive T-cell exhaustion with marked expression of exhaustion-related markers and diminished production of effector cytokines was observed in PD-1high CD8+ TILs compared with PD-1int and PD-1neg CD8+ TILs. Patients with distinct PD-1high CD8+ TILs (PD-1high expressers) exhibited characteristics associated with a favorable anti-PD-1 response compared with those without these lymphocytes (non-PD-1high expressers). Combined inhibition of dual immune checkpoint receptors further restored effector cytokine production by CD8+ TILs following T-cell stimulation. PD-1high CD8+ T lymphocyte populations in the peripheral blood and tumors were significantly correlated.

Conclusions 
T-cell exhaustion was differentially regulated among individual patients and was prominent in a subgroup of NSCLC patients who may benefit from PD-1 blockade or combined blockade of other immune checkpoint receptors.