Targeting tumor-resident mast cells for effective anti-melanoma immune responses
Susanne Kaesler, Florian Wölbing, Wolfgang Eberhard Kempf, Yuliya Skabytska, Martin Köberle, Thomas Volz, Tobias Sinnberg, Teresa Amaral, Sigrid Möckel, Amir Yazdi, Gisela Metzler, Martin Schaller, Karin Hartmann, Benjamin Weide, Claus Garbe, Hans-Georg Rammensee, Martin Röcken, Tilo Biedermann
Susanne Kaesler, Florian Wölbing, Wolfgang Eberhard Kempf, Yuliya Skabytska, Martin Köberle, Thomas Volz, Tobias Sinnberg, Teresa Amaral, Sigrid Möckel, Amir Yazdi, Gisela Metzler, Martin Schaller, Karin Hartmann, Benjamin Weide, Claus Garbe, Hans-Georg Rammensee, Martin Röcken, Tilo Biedermann
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Research Article Immunology Oncology

Targeting tumor-resident mast cells for effective anti-melanoma immune responses

Abstract

Immune checkpoint blockade has revolutionized cancer treatment. Patients developing immune mediated adverse events, such as colitis, appear to particularly benefit from immune checkpoint inhibition. Yet, the contributing mechanisms are largely unknown. We identified a systemic LPS signature in melanoma patients with colitis following anti–cytotoxic T lymphocyte–associated antigen 4 (anti–CTLA-4) checkpoint inhibitor treatment and hypothesized that intestinal microbiota–derived LPS contributes to therapeutic efficacy. Because activation of immune cells within the tumor microenvironment is considered most promising to effectively control cancer, we analyzed human and murine melanoma for known sentinels of LPS. We identified mast cells (MCs) accumulating in and around melanomas and showed that effective melanoma immune control was dependent on LPS-activated MCs recruiting tumor-infiltrating effector T cells by secretion of CXCL10. Importantly, CXCL10 was also upregulated in human melanomas with immune regression and in patients with colitis induced by anti–CTLA-4 antibody. Furthermore, we demonstrate that CXCL10 upregulation and an MC signature at the site of melanomas are biomarkers for better patient survival. These findings provide conclusive evidence for a “Trojan horse treatment strategy” in which the plasticity of cancer-resident immune cells, such as MCs, is used as a target to boost tumor immune defense.

Authors

Susanne Kaesler, Florian Wölbing, Wolfgang Eberhard Kempf, Yuliya Skabytska, Martin Köberle, Thomas Volz, Tobias Sinnberg, Teresa Amaral, Sigrid Möckel, Amir Yazdi, Gisela Metzler, Martin Schaller, Karin Hartmann, Benjamin Weide, Claus Garbe, Hans-Georg Rammensee, Martin Röcken, Tilo Biedermann

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Figure 5

MC-derived CXCL10 mediates melanoma immune control by TIL recruitment.

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MC-derived CXCL10 mediates melanoma immune control by TIL recruitment. (...
(A) Cytokine array performed with supernatants from untreated (upper left) and LPS-stimulated bone marrow–derived MCs (BMMCs) (lower left) and the 2 cytokines with the strongest LPS induction as determined by densitometric quantification (right). (B) Induction of CCL2 and CXCL10 in LPS-exposed BMMCs compared with untreated BMMCs as determined by quantitative ELISA. Means ± standard deviation of 3 independent experiments are shown; P value was calculated with unpaired Student’s t test. (C–E) Tumor volume over time (left) and at the endpoint (right) according to the protocol outlined in Figure 2A. (C) KitW–sh/W–sh mice with or without MC reconstitution demonstrating loss of tumor immune control with Cxcl10–/– MCs (n = 6–8 per group). (D) According to the protocol in Figure 2A, WT C57BL/6 mice were exposed to LPS or PBS or CXCL10 by peritumoral injections (n = 14–16 per group). (E) Tumor analysis in Tlr4–/– KitW–sh/W–sh mice with or without MC reconstitution compared with WT C57BL/6 mice (n = 6–10 per group). (F) LPS-induced Cxcl10 expression in the skin of Tlr4–/– KitW–sh/W–sh mice reconstituted with WT MCs. (Means ± standard deviation; n = 6 per group; unpaired Student’s t test.) (G) In vitro Transwell migration assay with OT-I and OT-II TCs in the presence of either CXCL10 (left) or supernatant from LPS-exposed BMMCs (right) used as chemoattractants. Blocking anti-CXCL10 antibody was used as a specificity control (means ± SEM; n = 7–9 per group; unpaired Student’s t test). (H and I) CD3+ TC infiltration (TIL) adjacent to and within melanomas of the experiment depicted in E. (H) Representative immunofluorescence tissue sections oriented with the epidermis to the top and the tumor to the bottom (red, TCs; green, nuclear stain; scale bar: 50 μm). (I) Flow cytometry analysis showing TILs (means ± standard deviation). (J) According to the protocol in Figure 2A, 14 days after B16-OVA inoculation, tumor volume (left) and TILs were determined by flow cytometry (right) in Tlr4–/– KitW–sh/W–sh mice reconstituted with Cxcl10–/– MCs or WT MCs. P values calculated with 2-way ANOVA and Tukey’s test (C–E and I) or with unpaired Student’s t test (J). *, #P < 0.05; **, ##P < 0.005; ***, ###P < 0.0005; ****, ####P < 0.0001.