Convection-enhanced delivery of temozolomide and whole cell tumor immunizations in GL261 and KR158 experimental mouse gliomas

Abstract

Background: Glioblastomas (GBM) are therapy-resistant tumors with a profoundly immunosuppressive tumor microenvironment. Chemotherapy has shown limited efficacy against GBM. Systemic delivery of chemotherapeutic drugs is hampered by the difficulty of achieving intratumoral levels as systemic toxicity is a dose-limiting factor. Although some of its effects might be mediated by immune reactivity, systemic chemotherapy can also inhibit induced or spontaneous antitumor immune reactivity. Convection-enhanced delivery of temozolomide (CED-TMZ) can tentatively increase intratumoral drug concentration while reducing systemic side effects. The objective of this study was to evaluate the therapeutic effect of intratumorally delivered temozolomide in combination with immunotherapy and whether such therapy can generate a cellular antitumor immune response. Methods: Single bolus intratumoral injection and 3-day mini-osmotic pumps (Alzet®) were used to deliver intratumoral TMZ in C57BL6 mice bearing orthotopic gliomas. Immunotherapy consisted of subcutaneous injections of irradiated GL261 or KR158 glioma cells. Tumor size and intratumoral immune cell populations were analyzed by immunohistochemistry.Results: Combined CED-TMZ and immunotherapy had a synergistic antitumor effect in the GL261 model, compared to CED-TMZ or immunotherapy as monotherapies. In the KR158 model, immunization cured a small proportion of the mice whereas addition of CED-TMZ did not have a synergistic effect. However, CED-TMZ as monotherapy prolonged the median survival. Moreover, TMZ bolus injection in the GL261 model induced neurotoxicity and lower cure rate than its equivalent dose delivered by CED. In addition, we found that T-cells were the predominant cells responsible for the TMZ antitumor effect in the GL261 model. Finally, CED-TMZ combined with immunotherapy significantly reduced tumor volume and increased the intratumoral influx of T-cells in both models. Conclusions: We show that immunotherapy synergized with CED-TMZ in the GL261 model and cured animals in the KR158 model. Single bolus administration of TMZ was effective with a narrower therapeutic window than CED-TMZ. Combined CED-TMZ and immunotherapy led to an increase in the intratumoral influx of T-cells. These results form part of the basis for the translation of the therapy to patients with GBM but the dosing and timing of delivery will have to be explored in depth both experimentally and clinically.

Successful Partnerships: Exploring the Potential of Immunogenic Signals Triggered by TMZ, CX-4945, and Combined Treatment in GL261 Glioblastoma Cells

“…The use of animal models in oncological research is a key step in the search for new therapeutic strategies. GL261 cells grown in C57BL/6 mice is one of the most investigated immunocompetent models, widely used in GB preclinical studies [ 27 , 28 , 29 , 30 , 31 ]. Wu and Waxman [ 32 ] described an immune friendly cyclophosphamide treatment triggering activation of the immune system against GL261 subcutaneous tumors, which also proved useful with TMZ treatment of an orthotopic GL261 GB model, improving mice survival [ 29 , 33 ] in comparison with previous protocols [ 34 ].…”

Novel theranostic agent for PET imaging and targeted radiopharmaceutical therapy of tumour-infiltrating immune cells in glioma

“…The GL261 orthotopic C57BL/6j-syngeneic glioma model is widely used for preclinical testing of immunotherapies and exhibits robust TAMC accumulation, similar to that of patient gliomas [30] , [31] , [32] . A limitation of many radiometal ion chelates, including Zr-89 bound to the widely used DFO chelator, is poor in vivo stability, which leads to free radionuclide uptake in the bone [ 29 , 33 ].…”

“…Survival times for adults and children with malignant gliomas remain dismal [30] , and an effective theranostic could be a highly attractive approach for treatment. TAMCs express CD11b on their surface and represent a major depot of immunosuppressive cells within gliomas that can directly promote tumour growth, angiogenesis, immunosuppression, immunotherapy resistance, and recruitment of immunoregulatory cells [ 9 , 10 , 46 ].…”

Optimization of catheter placement for convection-enhanced delivery to brain tumors

“…In the future, investigators can verify this optimization method using patient-specific T1W and DWI data and therapyspecific density and viscosity information. Experimental validation using animal models is a critical step in determining the effectiveness of this quantitative tool [31][32][33][34][35][36][37][38][39] .…”