HER2-specific T cells target primary glioblastoma stem cells and induce regression of autologous experimental tumors

PURPOSE

Glioblastoma multiforme (GBM) is the most aggressive human primary brain tumor and is currently incurable. Immunotherapies have the potential to target GBM stem cells, which are resistant to conventional therapies. Human epidermal growth factor receptor 2 (HER2) is a validated immunotherapy target, and we determined if HER2-specific T cells can be generated from GBM patients that will target autologous HER2-positive GBMs and their CD133-positive stem cell compartment.

EXPERIMENTAL DESIGN

HER2-specific T cells from 10 consecutive GBM patients were generated by transduction with a retroviral vector encoding a HER2-specific chimeric antigen receptor. The effector function of HER2-specific T cells against autologous GBM cells, including CD133-positive stem cells, was evaluated in vitro and in an orthotopic murine xenograft model.

RESULTS

Stimulation of HER2-specific T cells with HER2-positive autologous GBM cells resulted in T-cell proliferation and secretion of IFN-gamma and interleukin-2 in a HER2-dependent manner. Patients' HER2-specific T cells killed CD133-positive and CD133-negative cells derived from primary HER2-positive GBMs, whereas HER2-negative tumor cells were not killed. Injection of HER2-specific T cells induced sustained regression of autologous GBM xenografts established in the brain of severe combined immunodeficient mice.

CONCLUSIONS

Gene transfer allows the reliable generation of HER2-specific T cells from GBM patients, which have potent antitumor activity against autologous HER2-positive tumors including their putative stem cells. Hence, the adoptive transfer of HER2-redirected T cells may be a promising immunotherapeutic approach for GBM.

Identification of immunologic biomarkers associated with clinical response after immune-based therapy for cancer

The identification of immunologic biomarkers associated with clinical response after immune intervention for cancer is an area of intensive investigation. The field would benefit from a more systemic and directed approach for biomarker identification and evaluation. Lessons can be learned from other fields, such as cancer diagnostics, as to how to develop response-associated biomarkers. Studies in both human in vitro models as well as murine models of cancer can significantly inform and streamline the choice of candidates. Adoptive T-cell therapy is an interesting model for exploring potential immunologic surrogates that may predict clinical response. Most likely the clinical effectiveness of immune-based treatments will be predicted by panels of markers rather than single assays of a specific immune effector cell.