Glioblastoma grant generously funded by ‘Vikes Kicks Cancer’ event in honour of MacKenzie Rigg

Sheila Singh – McMaster University

Project Title: “Targeting Glioblastoma Recurrence with anti-ROBO1 Immunotherapy”

Description of Project:

Therapy failure and disease recurrence are hallmarks of glioblastoma, the most common and lethal tumour in adults that originates in the brain.

Recently, we applied a large-scale functional genetic approach, known as CRISPR screening, to discover key genes that enable the tumour to resist therapy and grow at recurrence. We found that recurrent tumour cells rely heavily on cellular activity initiated by a protein known as Roundabout guidance receptor 1 (ROBO1), such that genetic disruption of this protein’s activity or targeting ROBO1 using synthetic antibodies is lethal to tumour cells.

In fact, ROBO1 is present at greater levels on the surface of tumour cells at recurrence as compared to normal brain cells, making it a suitable candidate for therapeutic intervention. Given our strong track record in developing immunotherapies for glioblastoma, we propose to arm immune cells called T cells with a synthetic protein that binds to ROBO1, allowing these chimeric antigen receptor (CAR) T cells to recognize ROBO1 on tumour cells and destroy them.

By developing a therapy that specifically targets tumour cells at recurrence, we hope to alleviate disease burden and extend survival of glioblastoma patients.

What receiving this award means:

Accounting for nearly half of all primary malignant brain tumours in adults, glioblastoma (GBM) remains an incurable disease with a median survival of ~15 months. My lab and I are extremely grateful to Brain Tumour Foundation of Canada for supporting this promising work on the development of immunotherapy for GBM.  By developing a therapy that specifically targets tumour cells at recurrence, we hope to alleviate disease burden and extend survival of GBM patients. Thank you Brain Tumour Foundation of Canada!

Mid-point Report: April 2022

No standardized treatment exists for patients with recurrent glioblastoma (GBM). Given the aggressive nature of the disease and difficulty in modeling tumor recurrence, minimal efforts have been made to design rational therapies against it. The roundabout guidance receptor 1 (ROBO1) protein is involved in axonal guidance during neurodevelopment and is aberrantly upregulated in glioma where it mediates glioma cell migration. We have found that ROBO1 is highly expressed on the surface of malignant and treatment-refractory brain tumor initiating cells (BTICs), prompting the development of an anti-ROBO1 CAR-T cell therapy. Using the binding region of an antibody targeting ROBO1, we developed second-generation anti-ROBO1 CAR-T cells specific and effective against ROBO1-expressing BTICs. Upon antigen exposure, anti-ROBO1 CAR-T cells upregulated markers of activation and degranulation, demonstrating therapeutic potential for treating brain malignancies.

Final Report: April 2023

Unfortunately, recurrent GBM (rGBM) patients have no standardized treatment options aside from enrollment in a clinical trial. High failure rate of current clinical trials underscores the necessity to focus on new therapeutic options such as immunotherapy. High surface expression of ROBO1 on the surface of malignant and treatment-refractory brain tumor initiating cells (BTICs) in recurrent rGBM, lead to the development of an anti-ROBO1 CAR-T cell therapy. We validated anti-ROBO1 CAR-T cells in vitro and in vivo using our established patient-derived GBM models. In vitro studies demonstrated upregulation of activation markers, enhanced cytokine release, and induction of potent and specific tumor cell death with ROBO1 CAR-T cells as compared to untransduced T cells (UT). These findings were further validated in vivo using rGBM BTIC lines. ROBO1 CAR-T showed significant reduction in tumor burden and increase in survival of the mice treated with ROBO1 CAR-T cells in multiple samples. Thus, targeting ROBO1 could be a therapeutically tractable strategy for treating rGBM.