Tumor-initiating cells escape tumor immunity via CCL8 from tumor-associated macrophages in mice
Shuang Chen, … , Heping Li, Demeng Chen
Shuang Chen, … , Heping Li, Demeng Chen
Published January 7, 2025
Citation Information: J Clin Invest. 2025;135(5):e180893. https://doi.org/10.1172/JCI180893.
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Research Article Oncology

Tumor-initiating cells escape tumor immunity via CCL8 from tumor-associated macrophages in mice

Abstract

Tumor-initiating cells (TICs) play a key role in cancer progression and immune escape. However, how TICs evade immune elimination remains poorly characterized. Combining single-cell RNA-Seq (scRNA-Seq), dual-recombinase–based lineage tracing, and other approaches, we identified a WNT-activated subpopulation of malignant cells that act as TICs in vivo. We found intensive reciprocal interactions between TICs and immune-regulatory tumor-associated macrophages (Reg-TAMs) via growth arrest–specific 6/AXL receptor tyrosine kinase/MER proto-oncogene, tyrosine kinase (GAS6/AXL/MERTK) signaling pathways, which facilitated the immune escape of TICs. In this study, we used chemical inhibitors and Axl/Mertk conditional double-KO (cDKO) mice to demonstrate that inhibiting the interaction between TIC-derived GAS6 and AXL/MERTK in Reg-TAMs reactivated antitumor immune responses. We identified CCL8 as a critical mediator of the GAS6/AXL/MERTK pathway, primarily by inhibiting Treg infiltration into the tumor. Furthermore, the AXL/MERTK signaling blockade sensitized tumor cells to anti–programmed cell death 1 (anti–PD-1) treatment. Thus, we elucidated a detailed mechanism by which TICs evade tumor immunity, providing insights into strategies to eradicate TICs that escape conventional immunotherapy.

Authors

Shuang Chen, Chensong Huang, Kang Li, Maosheng Cheng, Caihua Zhang, Jianqi Xiong, Guoli Tian, Ruoxing Zhou, Rongsong Ling, Xiaochen Wang, Gan Xiong, Zhihui Zhang, Jieyi Ma, Yan Zhu, Bin Zhou, Liang Peng, Zhenwei Peng, Heping Li, Demeng Chen

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Figure 4

GAS6 is highly expressed and plays an important role in TIC maintenance in ICC.

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GAS6 is highly expressed and plays an important role in TIC maintenance ...
(A) Circle plots show interaction strength and number of interactions in cell-cell communication among 6 major clusters (left) using CellChat and between epithelial and other cells (right). Line width correlates with communication probability. (B) Dot plots depict the significance (–log10 P value) and strength (log2 mean value) of detailed ligand-receptor pairs between epithelial and other cell types analyzed by CellphoneDB. (C) Violin plot displays the Gas6 expression differences between WNThi and WNTlo epithelial cell subclusters. (D) Violin plots show Axl and Mertk expression in MoMϕDC subclusters. (E–H) Flow plots (E) show Tom+GAS6+ tumor-infiltrating cells and the levels of MRC1, MERTK, and AXL expression in infiltrating Reg-TAMs. Graphs depict statistical analysis of GAS6+ in Tom+/– cells in mouse ICC (F) as well as AXL+ (G) and MERTK+ (H) expression in MRC1+/– cells in ICC. (I) Treatment strategy with anti-GAS6/IgG in ICC mice. (J) Representative liver morphology image for survival outcome analysis after anti-GAS6 treatment. (K) Kaplan-Meier OS curve for ICC mice after anti-GAS6 treatment. (L) Representative liver morphology image after 6 weeks of anti-GAS6 treatment (left) and statistical analysis of liver-to-body weight ratio (right). (M) Fluorescence images of lineage tracing (left) (scale bar: 50 μm). Statistical analysis of Tom+ cell numbers (middle), and Tom+ cell area (right) after treatment. (N–S) Representative images of GAS6 staining in human ICC tissue from SYSUCC cohort 1 (N) (scale bar: 200 μm) and FAHSYSU cohort 2 (Q) (scale bar: 100 μm). Kaplan-Meier curves based on GAS6 expression in ICC: OS and DFS for SYSUCC cohort 1 (O and P), and OS and RFS for FAHSYSU cohort 2 (R and S). Data represent the mean ± SD (F–H, L, and M). P value were calculated by 2-tailed,, unpaired Student’s t test (C, F–H, L, and M), log-rank test (K, O, P, R, and S).