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CD47 stabilizes ROBO2 to regulate glioblastoma progression by preventing ITCH mediated ubiquitination

ABSTRACT: CD47 is a key innate immune checkpoint that inhibits phagocytosis by myeloid cells, contributing to immune evasion by cancer cells. Although CD47-blocking antibodies have shown promise in treating various malignancies, their efficacy in glioblastoma (GBM) remains limited, and the cell-intrinsic role of CD47 is poorly understood. In this study, we show that CD47 is highly expressed at the invasive edge of GBM tumors, and its elevated expression correlates with poor patient survival. We demonstrate that CD47 loss impairs GBM cell proliferation, migration, and invasion, independent of immune activity and leads to reduced tumor burden and prolonged survival in vivo. Our study reveals ROBO2 signaling as the downstream effector of CD47 and loss of ROBO2 also attenuates GBM cell proliferation and migration. Importantly, we have uncovered that CD47 stabilizes ROBO2 by sequestering the E3 ubiquitin ligase ITCH, thereby blocking ubiquitination and proteasomal degradation of ROBO2. These findings establish CD47 as a key regulator of GBM cell plasticity, and highlight the therapeutic potential of targeting CD47-ROBO2 signaling in GBM.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

DISEASE(S): Glioblastoma

SUBMITTER: Ghizal Siddiqui

LAB HEAD: Nirmal Robinson

PROVIDER: PXD071366 | Pride | 2026-03-05

REPOSITORIES: Pride

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			Action	DRS
	HF220230831GS_P22_0566-NirmR_Exp5_1.raw	Raw
	HF220230831GS_P22_0566-NirmR_Exp5_10.raw	Raw
	HF220230831GS_P22_0566-NirmR_Exp5_11.raw	Raw
	HF220230831GS_P22_0566-NirmR_Exp5_12.raw	Raw
	HF220230831GS_P22_0566-NirmR_Exp5_13.raw	Raw

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Project description:A significant challenge for chimeric antigen receptor (CAR) T cell therapy against glioblastoma (GBM) is its immunosuppressive tumor microenvironment (TME), which is densely populated and supported by protumoral glioma-associated microglia and macrophages (GAMs). Targeting CD47, a don't-eat-me signal overexpressed by tumor cells, disrupts the CD47-SIRPalpha axis and induces GAM phagocytic function. However, antibody-mediated CD47 blockade monotherapy is associated with toxicity and low bioavailability in solid tumors. To overcome these limitations, we combined local CAR T cell therapy with paracrine GAM modulation to effectively eliminate GBM. To this end, we engineered a new CAR T cell against epidermal growth factor receptor variant III (EGFRvIII) that constitutively secretes a signal regulatory protein gamma (SIRPgamma)-related protein (SGRP) with high affinity to CD47. Anti-EGFRvIII-SGRP CAR T cells eliminated EGFRvIII+ GBM in a dose-dependent manner in vitro and eradicated orthotopically xenografted EGFRvIII-mosaic GBM by locoregional application in vivo. This resulted in significant tumor-free long-term survival, followed by partial tumor control upon tumor re-challenge. Combining anti-CD47 antibodies with anti-EGFRvIII CAR T cells failed to achieve a similar therapeutic effect, underscoring the importance of sustained paracrine GAM modulation. Multidimensional brain immunofluorescence microscopy and in-depth spectral flow cytometry on GBM-xenografted brains showed that anti-EGFRvIII-SGRP CAR T cells accelerated GBM clearance, increased CD68+ cell trafficking to tumor scar sites and promoted GAM-mediated tumor cell uptake. In a peripheral lymphoma mouse xenograft model, anti-CD19-SGRP CAR T cells had superior efficacy to conventional anti-CD19 CAR T cells. Validation on human GBM explants revealed that anti-EGFRvIII-SGRP CAR T cells had a similar tumor-killing capacity to anti-EGFRvIII CAR monotherapy but showed a slight improvement in the maintenance of tumor-infiltrated CD14+ cells. Thus, local anti-EGFRvIII-SGRP CAR T cell therapy combines the potent antitumor effect of engineered T cells with the modulation of the surrounding innate immune TME. This results in the additive elimination of bystander EGFRvIII- tumor cells in a manner that overcomes the main mechanisms of CAR T cell therapy resistance, including tumor innate immune suppression and antigen escape.

Project description:Recently, ‘don’t eat me’-signals like CD47 have emerged as novel innate immune checkpoints, enabling cancer cells to evade clearance by phagocytes such as microglia (MG) or monocyte-derived cells (MdCs). Here, we aim at defining the role of inhibitory Siglec-9 in human and its mouse homologue Siglec-E in innate-centered immunotherapy against GBM. TCGA RNA-sequencing data revealed a significant correlation between high expression of immunoinhibitory SIGLEC9 and poor survival in GBM patients (log-rank p = 0.02). Using a CT-2A orthotopic GBM mouse model with MG-specific spatio-temporal deletion of Siglece (Sall1CreERT2 x Sigleceflox), we observed high MG-proliferation upon Siglece knockout (Ki-67+ MG 14.8% in Creneg vs. 34.9% in Crepos, p < 0.0001) accompanied by an enhanced microglial GBM-cell uptake (5.6% in Creneg vs. 12.3% in Crepos, p < 0.001). By extending the Siglece knockout to the MdC compartment (Cx3cr1CreERT2 x Sigleceflox) we observed a significantly prolonged survival in the Crepos population (21d in Creneg vs. 27d post-tumor injection in Crepos, p = 0.018), which could be further promoted by combining Siglece knockout with CD47 blockade (11% long-term remission in Crepos + anti-CD47). Proteomics analysis revealed increased antigen processing and presentation capabilities of SigleceKO MdCs which was confirmed by ex-vivo OT-1 cross-presentation assays. This increased T cell priming upon MdC SigleceKO was further boosted by addition of anti-PD1 antibody to the SigleceKO + anti-CD47 combination. Resulting in 23% of animals experiencing long-term remission in the triple treatment arm, even after tumor re-challenge. Genetic targeting of sialic acids, the ligand for Siglec receptors, on CT-2A cells (GNE-KO), resulted in increased GBM-cell phagocytosis by MG and MdCs and less exhausted tumor-infiltrating CD8+ T cells (14.8% in WT vs. 5.9% in GNE-KO, p = 0.003). In a translational approach, we are currently testing anti-Siglec-9 treatment regimens in patient GBM explants, cultured for 5 days in perfusion bioreactors.

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CD47 stabilizes ROBO2 to regulate glioblastoma progression by preventing ITCH mediated ubiquitination

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