Fig. 1: Complementary immune checkpoints HLA-E:CD94-NKG2A and HLA-C:KIR2DL1 between CTCs and NKs.

a Cell type characterization of primary, circulating (hepatic portal vein, HPV), and metastatic lesions from PDACs (n = 18 samples, 74,206 cells). b, c Clustering of NK cells by cell type (b) and tissue origin (c). d, e The levels of indicated marker genes in each subtype of NKs are presented by t-SNE plots (d) and quantified by violin plots (e). f The immune checkpoint molecules between tumor cells/CTCs and NKs in each corresponding tissue origin were analyzed by CellPhoneDB (version 2.0). The color represents the mean expression of ligand–receptor pairs, while the dot size indicates statistical significance. g The expression of HLA-E and HLA-C on tumor cells from indicated tissues. Mean ± SE, two sides Wilcoxon test, ****P < 0.0001. h Multivariate kernel density plots depict the bimodal distribution of KLRC1 (NKG2A) and KIR2DL1 on NKs of HPV blood. i NKG2A⁺ and KIR2DL1⁺ NKs from the blood of PDAC patient 1 are presented. j The proportion of NKG2A⁺ and KIR2DL1⁺ NKs from the blood of PDAC patients were quantified by flow cytometry. k, l Tumor cells metastasizing to the lung were visualized (k) and quantified (l) by bioluminescence imaging system 15 days after intravenous injection (i.v.) inoculation of H2-T23 (HLA-E) or/and H2-D1 (HLA-C) pre-knockdown KPC-Luc cells. m, n The metastatic tumor nodules in the lung were counted (m), and representative images were displayed (n). *P < 0.05; **P < 0.01; ***P < 0.001, t-test. o Pathological aberrancy of lungs from (n) was evaluated by H&E staining. p Kaplan–Meier plot shows the overall survival of mice (n = 5) with indicated treatments. q Schematic diagram of complementary immune checkpoints HLA-E:CD94-NKG2A- and HLA-C:KIR2DL1-mediated evasion of CTCs from NKs immune surveillance.