PD-1 Affects the Immunosuppressive Function of Group 2 Innate Lymphoid Cells in Human Non-Small Cell Lung Cancer

Abstract

BackgroundThere is increasing evidence that group 2 innate lymphoid cells (ILC2s) play an essential role in allergy and parasitic infection. However, the role of ILC2s in human lung cancer remains unclear.MethodsILC2s from peripheral blood mononuclear cells (PBMCs) obtained from healthy donors (HDs) and non-small cell lung cancer (NSCLC) patients, and NSCLC tumor tissues were analyzed via multicolor flow cytometry. ILC2s or CD14+ cells were sorted by fluorescence-activated cell sorting. qPCR and flow cytometry were performed to assess the gene and protein expression of the indicated molecules. M1-like and M2-like macrophages were induced from CD14+ monocytes in vitro.ResultsILC2s were significantly more enriched in PBMCs and tumor tissues from NSCLC patients than in HDs. After screening for the main immune checkpoint molecules, we found that PD-1 was upregulated in ILC2s in NSCLC patients. Functionally, PD-1high ILC2s from tumor tissues expressed higher levels of IL-4 and IL-13 regarding both mRNA and protein levels than PD-1low ILC2s. Furthermore, PD-1high ILC2s robustly boosted M2-like macrophage polarization in vitro, by secreting IL-4 and IL-13, while neutralization of IL-4 and IL-13 by antibodies abrogated M2-like macrophage polarization.ConclusionILC2s are enriched in NSCLC patients and upregulate PD-1 expression. Upregulation of PD-1 facilitates the immunosuppressive function of ILC2s. PD-1high ILC2s enhance M2-like macrophage polarization by secreting IL-4 and IL-13. PD-1 acts as a positive regulator of the immunosuppressive function of ILC2s in human NSCLC.

Immune Checkpoints and Innate Lymphoid Cells—New Avenues for Cancer Immunotherapy

“…In addition, blood and tumor-infiltrating human ILC1 were shown to express PD-1/ PDCD1 [ 111 ]. These include non-small cell lung, breast and gastrointestinal tumor-infiltrating ILC1 [ 124 , 163 ].…”

“…We, and others, have shown that IL-33 and γc cytokines also induce PD-1 expression [ 44 , 46 , 170 , 179 , 180 ]. PD-1 is mainly expressed by KLRG1 + ILC2 [ 170 ] and negatively regulates ILC2 proliferation and cytokine expression [ 44 , 46 , 124 , 163 , 170 , 178 , 179 , 181 , 214 ] ( Figure 2 ). PD-1-deficient mice ( Pdcd1 −/− ) have increased peripheral ILC2 [ 46 , 170 ], with enhanced KLRG1 expression and cytokine production [ 170 ] compared with wildtype animals.…”

“…In humans, circulating PD-1 + ILC2 from healthy donors displayed a decrease in cytokine expression and proliferation compared with their PD-1 − counterparts [ 170 ], indicating that PD-1 engagement potentially regulates similar pathways between mouse and human ILC2. A growing body of work indicates that tumor-infiltrating ILC2 express high levels of PD-1, which regulates ILC2 function and cancer prognosis [ 44 , 46 , 49 , 124 , 163 , 178 ]. Increased PD-1 expression was reported on ILC2 in inflammation-induced colorectal tumors as tumor development progresses.…”

“…The analysis of PBMCs, peri-lesions and tumor lesions from breast and gastrointestinal cancer patients has revealed increased levels of PD-1 expression on tumor-infiltrating ILC2 compared with non-tumoral control tissues [ 124 ]. In NSCLC, ILC2 accumulated in tumor lesions and expressed higher levels of PD-1 than circulating ILC2 [ 163 ]. This phenotype was associated with increased IL-4 and IL-13 expression which, together, promoted macrophage M2 polarization [ 163 ].…”

“…In NSCLC, ILC2 accumulated in tumor lesions and expressed higher levels of PD-1 than circulating ILC2 [ 163 ]. This phenotype was associated with increased IL-4 and IL-13 expression which, together, promoted macrophage M2 polarization [ 163 ]. These results suggest that ILC2 may contribute to the tumor immunosuppressive environment, promoting tumor growth and progression.…”