Search

Background Glioblastoma survival remains unchanged despite continuing therapeutic innovation. Herein, we aim to (i) develop chimeric antigen receptor (CAR) T cells with a specificity to a unique antigen, carbonic anhydrase IX (CAIX), which is expressed in the hypoxic microenvironment characteristic of glioblastoma, and (ii) demonstrate its efficacy with limited off-target effects. Methods First we demonstrated expression of CAIX in patient-derived glioblastoma samples and available databases. CAR T cells were generated against CAIX and efficacy was assessed in 4 glioblastoma cell lines and 2 glioblastoma stem cell lines. Cytotoxicity of anti-CAIX CAR T cells was assessed via interferon gamma, tumor necrosis factor alpha, and interleukin-2 levels when co-cultured with tumor cells. Finally, we assessed efficacy of direct intratumoral injection of the anti-CAIX CAR T cells on an in vivo xenograft mouse model using the U251 luciferase cell line. Tumor infiltrating lymphocyte analyses were performed. Results We confirm that CAIX is highly expressed in glioblastoma from patients. We demonstrate that CAIX is a suitable target for CAR T-cell therapy using anti-CAIX CAR T cells against glioblastoma in vitro and in vivo. In our mouse model, a 20% cure rate was observed without detectable systemic effects. Conclusions By establishing the specificity of CAIX under hypoxic conditions in glioblastoma and highlighting its efficacy as a target for CAR T-cell therapy, our data suggest that anti-CAIX CAR T may be a promising strategy to treat glioblastoma. Direct intratumoral injection increases anti-CAIX CAR T-cell potency while limiting its off-target effects.

Atypical teratoid rhabdoid tumor (ATRT) is a pediatric brain tumor with a high mortality rate characterized by mutations in/ deletions of SWI/SNF matrix-associated actin-dependent regulator of chromatin sub-family B member 1 (SMARCB1). We previously showed that loss of SMARCB1 causes up-regulation and release of HML-2 subfamily of human endogenous retrovirus K envelope protein (HML-2 ENV), resulting in maintenance of pluripotency. Here, we investigated intracellular trafficking and release of HML-2 ENV. Further, we demonstrate two potential therapeutic strategies to decrease intracellular HML-2 ENV: 1) inhibition of calcium influx by ouabain, a cardiac glycoside toxic to neural stem cells, and 2) targeted inhibition of cyclin-dependent kinase 5 (CDK5), which is restricted to neurons by p35, its activator protein, by TP5. ATRT cell lines and tumor tissue obtained from patients were confirmed for SMARCB1 loss and increased HML-2 ENV. Cell viability and intracellular HML-2 ENV concentration were measured after treatment with ouabain and TP5 (CDK5 antagonist). We evaluated the calcium-mediated effect of ouabain on HML-2 intracellular concentration by treating the cells with ouabain, the calcium chelators calcimycin and EGTA, and calpeptin, a calpain inhibitor, which activates CDK5, and measuring HML-2 ENV and p35. We evaluated HML-2 ENV for a CDK5 consensus phosphorylation site and performed co-immunoprecipitation to evaluate direct interaction. We evaluated activity of CDK5 in ATRT cell lines by autoradiography. Both Ouabain and TP5 caused a decrease in cell viability in a dose-dependent manner. Further, ouabain treatment decreased HML-2 ENV intracellular concentration. We found that HML-2 ENV contains a consensus phosphorylation site for CDK5. We discovered that HML-2 ENV was bound to CDK5. We established that ATRT cell lines had hyperactive CDK5. Finally, we established that the effect of ouabain on HML-2 ENV was due to indirect inhibition of calcium-mediated activation of calpain and thus CDK5.

BACKGROUND: The need for novel therapies for GBM treatment is well established. While chimeric antigen receptor (CAR)-engineered T cells represent a promising cancer treatment modality, highly expressed unique cell surface antigens are essential. We postulated that tumor-specific surface antigens related to hypoxia signaling may have potential. Carbonic Anhydrase IX (CAIX) is active in settings of unbalanced pH driving proton transport to the extracellular medium in response to decreased oxygen tension. We provide evidence that CAIX is highly expressed in GBM and thus a potentially suitable target which we investigated using CAIX-specific CAR-T cells against GBM cells. METHODS: Patient GBM tissues were evaluated for CAIX protein expression. Antitumor CAIX-specific CAR T cells were developed and tested against four GBM cell lines: U251, LN 229, T98G, and A172. Cytotoxicity of CAIX CAR-T cells was assessed using the levels of IFN-γ, TNF-α, and IL-2 released when co-cultured with tumor cells. Direct intra-tumor injection of CAR-T cells into intracranial GBM xenograft mouse model was used for in vivo testing. RESULTS: We confirmed high expression of CAIX in of human GBM. The viral construct of CAIX-specific CAR-T cells generated was tested against GBM cell lines. In vitro, CAIX-specific CAR-T cells displayed enhanced GBM cells cytolysis and increased IFN-γ, TNF-α, and IL-2 production. The CAR-T cells showed a specific CAIX-dependent recognition of GBM cells. Direct intra-tumor injection of the CAR-T cells into an intracranial GBM xenograft mouse model efficiently suppressed the growth of GBM cells and significantly prolonged mouse survival. In approximately 20%, CAIX specific CAR-T cells completely eradicated GBM tumors. CONCLUSIONS: The present study demonstrates the specificity of CAIX under hypoxic conditions in GBM. The results also show that CAIX represents a viable target for CAR-T cells and may be a promising strategy to treat GBM.