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 7

R428 treatment sensitizes murine ICC cells to anti–PD-1 treatment.

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R428 treatment sensitizes murine ICC cells to anti–PD-1 treatment. (A) E...
(A) Experimental strategies for ICC mice with the indicated treatment. The mice were sacrificed when large tumors developed. (B) Representative liver morphology images from ICC mice under the indicated treatment for survival outcome analysis (left). The time point at which mice developed lethal tumor burden is shown. Kaplan-Meier OS curve for mice with ICC subjected to the indicated treatment. P values were calculated by log-rank test. (C and D) Representative images of whole liver morphology from ICC mice subjected to the indicated treatment. Statistical analysis of liver-to-body weight ratio from ICC mice with the indicated treatment. Values represent the mean ± SD from 6 independent biological replicates (n = 6 mice). P values were calculated by 1-way ANOVA with Tukey’s multiple-comparison test. (E–J) Representative images of H&E (E) and KRT19 (F) staining of liver sections from ICC mice under different treatments. Scale bars: 200 μm. Statistical analyses of ICC tumor number (G), ICC tumor diameter (H), KRT19+ area (I), and KRT19+ cells (J) in different treatment groups. Values represent the mean ± SD from 6 independent biological replicates (n = 6 mice). P values were calculated by 1-way ANOVA with Tukey’s multiple-comparison test. (K–N) Representative images of MKI67 (K) and active caspase 3 (L) staining of liver sections from ICC mice under the indicated treatments. Scale bars:100 μm. Statistical analyses of MKI67+ cells (M) and active caspase 3+ cells (N). Values represent the mean ± SD from 6 independent biological replicates (n = 12 fields from 6 mice). P values were calculated by 1-way ANOVA with Tukey’s multiple-comparison test. (O–Q) Fluorescence staining for F4/80 (green) and MRC1 (red) expression in liver sections from ICC mice under the indicated treatments. Scale bar: 50 μm (O). (P and Q) Statistical analyses of F4/80+MRC1+ cells and F4/80+ cells. Data represent the represent the mean ± SD from 3 independent experiments (n = 9 fields from 3 mice). P values were calculated by 1-way ANOVA with Tukey’s multiple-comparison test.