CAR-T Therapy Expands Beyond Leukemia: GPNMB Protein Emerges as Promising Target for Glioblastoma and Rare Soft Tissue Sarcoma
CAR-T therapy has revolutionized the treatment of certain blood cancers, yet it has struggled to achieve comparable success against solid tumors of internal organs. The core challenge lies not in the immune cells themselves but in identifying reliable molecular targets. Cells within solid tumors vary widely in their surface protein profiles, allowing therapy-resistant subpopulations to drive disease recurrence.
Two independent research groups have now converged on the same surface protein, GPNMB, as a promising solution that addresses multiple obstacles simultaneously. Genetically modified lymphocytes targeting GPNMB successfully eliminated glioblastoma and alveolar soft part sarcoma cells in laboratory models, slowed tumor growth in mice, and, in one project, were administered to a human patient for the first time.
How CAR-T Therapy Works
CAR-T treatment begins with a patient’s own T-lymphocytes, which are extracted from blood, genetically engineered to express a chimeric antigen receptor (CAR), and then reinfused. The CAR functions as a highly specific sensor that recognizes a pre-selected molecule on the surface of cancer cells, enabling the lymphocytes to locate and destroy them. While this approach has proven highly effective for leukemias and some lymphomas—where most malignant cells share a common surface protein—it has been far less successful against solid tumors.
Overcoming Solid-Tumor Barriers
Solid tumors present two major difficulties. First, even within a single tumor, different cells express different surface proteins, so some escape attack and continue proliferating. Second, the tumor microenvironment—composed of connective tissue, blood vessels, and immune cells—often suppresses anti-tumor responses and hinders CAR-T function. Researchers therefore sought a target present on both tumor cells and the immune cells that shield the tumor.
Glioblastoma Study Highlights Dual Attack
One team focused on glioblastoma, the most aggressive brain tumor. By comparing patient samples, scientists identified GPNMB as the most promising surface protein on the most dangerous tumor cells. After genetic modification, the resulting CAR-T cells nearly completely eradicated tumor cells grown from patient tissues. In mouse experiments, treatment slowed disease progression and extended survival. Importantly, GPNMB was also expressed on immune cells that normally help the tumor evade destruction, allowing the therapy to attack both the tumor and its protective microenvironment.
Alveolar Soft Part Sarcoma Research and First-in-Human Use
The second study examined alveolar soft part sarcoma, a rare and aggressive soft-tissue cancer often driven by a fusion gene. Screening again pointed to GPNMB, whose expression correlated directly with the activity of the fusion gene. CAR-T cells targeting this protein eliminated tumors and blocked metastasis formation in mice. Prior to human testing, researchers confirmed safety using mice engrafted with human skin; only transient inflammation occurred, with no lasting tissue damage. The therapy was then given to a patient with recurrent, metastatic disease. A single infusion led to rapid expansion of the modified lymphocytes, which persisted for about a month without severe cytokine-release syndrome or other major complications. Imaging showed reduction in lung metastases and disease stabilization lasting approximately three months.
Future Directions and Limitations
Both teams noted that adding drugs to block remaining immunosuppressive cells further enhanced tumor clearance in mouse models. The researchers conclude that effective CAR-T targets should be sought not only on cancer cells but also on the immune cells that support tumor growth. While GPNMB is not yet a universal solution and clinical data remain limited to a single patient, the independent validation across two different solid-tumor types marks a significant step toward expanding CAR-T therapy beyond leukemia.