Hedgehog signaling promotes tumor-associated macrophage polarization to suppress intratumoral CD8+ T cell recruitment
Amy J. Petty, … , Xiaopei Huang, Yiping Yang
Amy J. Petty, … , Xiaopei Huang, Yiping Yang
Published October 22, 2019
Citation Information: J Clin Invest. 2019;129(12):5151-5162. https://doi.org/10.1172/JCI128644.
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Research Article Immunology

Hedgehog signaling promotes tumor-associated macrophage polarization to suppress intratumoral CD8+ T cell recruitment

Abstract

Tumor-associated macrophages (TAMs) usually display an antiinflammatory M2-like phenotype to facilitate tumor growth. However, what drives M2 polarization of TAMs and how TAMs suppress antitumor immunity within the tumor microenvironment (TME) remain largely undefined. Using several murine tumor models, we showed that hedgehog (Hh) signaling in myeloid cells is critical for TAM M2 polarization and tumor growth. We also found that tumor cells secrete sonic hedgehog (SHH), an Hh ligand, and that tumor-derived SHH drives TAM M2 polarization. Furthermore, Hh-induced functional polarization in TAMs suppresses CD8+ T cell recruitment to the TME through the inhibition of CXCL9 and CXCL10 production by TAMs. Last, we demonstrated that Krüppel-like factor 4 (Klf4) mediates Hh-dependent TAM M2 polarization and the immunosuppressive function. Collectively, these findings highlight a critical role for tumor-derived SHH in promoting TAM M2 polarization, a mechanism for TAM-mediated immunosuppression, and may provide insights into the design of new cancer immunotherapeutic strategies.

Authors

Amy J. Petty, Ang Li, Xinyi Wang, Rui Dai, Benjamin Heyman, David Hsu, Xiaopei Huang, Yiping Yang

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Figure 6

Hh-induced M2 TAM polarization and function are mediated by Klf4.

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Hh-induced M2 TAM polarization and function are mediated by Klf4. (A) Kl...
(A) Klf2, Klf4, Stat6, Pparg, and Cebpb mRNA levels in control and SHH-treated macrophages were measured by qRT-PCR. Expression was normalized to Actb and compared with control. (B) Klf4 mRNA levels in Smofl/fl and SmoΔM TAMs were measured by qRT-PCR. Expression was normalized to reference gene Actb and compared with that of Smofl/fl. (C) Gli1 transcription factor binds to the Klf4 promoter region as demonstrated by ChIP. Gli1 activity was inhibited using 5 μM GANT61 or constitutively activated using SmoCM macrophages. (D) Tumor volumes of Hepa1-6 hepatoma cells inoculated s.c. in Klf4fl/fl and Klf4ΔM mice on day 18 at sacrifice. (E) Expression of Arg1, Mrc1, Il10, and Tnf mRNAs in Klf4fl/fl and Klf4ΔM TAMs was quantified by qRT-PCR. Expression was normalized to reference gene Actb and compared with that of Klf4fl/fl TAMs. (F) Percentages of tumor CD8+ T cell infiltration into tumors from Klf4fl/fl and Klf4ΔM mice. (G) CXCL9 and CXCL10 production by SmoCM and SmoCMKlf4ΔM TAMs was measured by ELISA. (H) Tumor volumes of Hepa1-6 hepatoma cells inoculated s.c. in SmoCM and SmoCMKlf4ΔM mice on day 18 at sacrifice. (I) Expression of Arg1, Mrc1, Il10, and Tnf mRNAs in SmoCM and SmoCMKlf4ΔM TAMs was quantified by qRT-PCR. Expression was normalized to reference gene Actb and compared with that of SmoCM TAMs. (J) Percentages of tumor CD8+ T cell infiltration in tumors from SmoCM and SmoCMKlf4ΔM mice. Values are the mean ± SEM of a minimum of 3 independent experiments. *P < 0.05; **P < 0.005; ***P < 0.0005. n = 5 biological replicates per group (A and B); n = 3 technical replicates per group (C); n = 6 biological replicates per group (D–J). Two-tailed Student’s t test (A, B, D, and J).