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 Article has an altmetric score of 11

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 3

Slit2 promotes blood vessel dysmorphia in GBM.

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Slit2 promotes blood vessel dysmorphia in GBM. (A) In vivo 2-photon imag...
(A) In vivo 2-photon images of ROSAmTmG mice bearing day 21 CT-2A shCTRL or shSlit2 tumors. (B and C) Quantification of vessel diameter (B) and branchpoints (C) (n = 8 mice per group, 1-way ANOVA). (D) In vivo 2-photon images of ROSAmTmG mice bearing day 18 CT-2A shSlit2 or shSlit2 + hSLIT2 tumors. (E and F) Quantification of vessel diameter (E) and branchpoints (F) (n = 7 mice per group, 1-way ANOVA). (G–I) Left: 2-photon in vivo imaging following intravenous injection of Alexa Fluor 647–conjugated Dextran highlighting unperfused blood vessel segments in the tumor core (asterisks) of day 21 CT-2A shCTRL and shSlit2 tumors. Right: representative pictures of whole brains of day 21 shCTRL or shSlit2 CT-2A tumors following Evans blue injection. (H) Quantification of unperfused blood vessel segments in the tumor mass presented in G (n = 5 mice per group, Mann-Whitney U test). (I) Quantification of Evans blue extravasation in (G) (n = 5 mice per group, Mann-Whitney U test). (J–L) Quantifications of Glut1+ hypoxic areas in the tumor (J) and Glut1 blood vessel coverage (K) from immunohistochemistry on sections (L) (n = 5 mice per group, Mann-Whitney U test). (M) qPCR analyses from FACS-sorted ECs (n = 3 tumors/group, Mann-Whitney U test). Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001.