SLIT2/ROBO signaling in tumor-associated microglia and macrophages drives glioblastoma immunosuppression and vascular dysmorphia
Luiz H. Geraldo, … , Anne Eichmann, Thomas Mathivet
Luiz H. Geraldo, … , Anne Eichmann, Thomas Mathivet
Published June 28, 2021
Citation Information: J Clin Invest. 2021;131(16):e141083. https://doi.org/10.1172/JCI141083.
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Research Article Oncology Vascular biology

SLIT2/ROBO signaling in tumor-associated microglia and macrophages drives glioblastoma immunosuppression and vascular dysmorphia

Abstract

SLIT2 is a secreted polypeptide that guides migration of cells expressing Roundabout 1 and 2 (ROBO1 and ROBO2) receptors. Herein, we investigated SLIT2/ROBO signaling effects in gliomas. In patients with glioblastoma (GBM), SLIT2 expression increased with malignant progression and correlated with poor survival and immunosuppression. Knockdown of SLIT2 in mouse glioma cells and patient-derived GBM xenografts reduced tumor growth and rendered tumors sensitive to immunotherapy. Tumor cell SLIT2 knockdown inhibited macrophage invasion and promoted a cytotoxic gene expression profile, which improved tumor vessel function and enhanced efficacy of chemotherapy and immunotherapy. Mechanistically, SLIT2 promoted microglia/macrophage chemotaxis and tumor-supportive polarization via ROBO1- and ROBO2-mediated PI3K-γ activation. Macrophage Robo1 and Robo2 deletion and systemic SLIT2 trap delivery mimicked SLIT2 knockdown effects on tumor growth and the tumor microenvironment (TME), revealing SLIT2 signaling through macrophage ROBOs as a potentially novel regulator of the GBM microenvironment and immunotherapeutic target for brain tumors.

Authors

Luiz H. Geraldo, Yunling Xu, Laurent Jacob, Laurence Pibouin-Fragner, Rohit Rao, Nawal Maissa, Maïté Verreault, Nolwenn Lemaire, Camille Knosp, Corinne Lesaffre, Thomas Daubon, Joost Dejaegher, Lien Solie, Justine Rudewicz, Thomas Viel, Bertrand Tavitian, Steven De Vleeschouwer, Marc Sanson, Andreas Bikfalvi, Ahmed Idbaih, Q. Richard Lu, Flavia R.S. Lima, Jean-Leon Thomas, Anne Eichmann, Thomas Mathivet

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Figure 4

Slit2 promotes TAM recruitment and polarization in mouse gliomas.

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Slit2 promotes TAM recruitment and polarization in mouse gliomas. (A) Im...
(A) Immunohistochemistry on sections of late-stage CT-2A shCTRL, shSlit2, or shSlit2 + hSLIT2 tumors for F4/80, MHC-II, and MRC1+ cells (green). (B) Quantifications of A (n = 7 mice per group, 5 fields per tumor, 2-way ANOVA). (C and D) FACS analysis of day 21 CT-2A shCTRL and shSlit2 tumors for quantification of TAMs (n = 10 tumors/group; Student’s t test and 2-way ANOVA). (E) qPCR analysis from FACS-sorted TAMs (n = 6 tumors/group, Mann-Whitney U test). (F–H) ELISA from protein samples extracted from FACS-sorted TAMs from shCTRL and shSlit2 tumors to quantify IFN-γ (F), IL-10 (G), and VEGFa (H) (n = 5 tumors/group, Mann-Whitney U test). (I) Representative images and quantification of soluble-Flt1 binding to sections of day 21 CT-2A shCTRL, shSlit2, and day 18 shSlit2 + hSLIT2 tumors (n = 7 mice per group, 5 fields per tumor, 1-way ANOVA). *P < 0.05, **P < 0.01, ***P < 0.001.