Immunotherapy with subcutaneous immunogenic autologous lysate against glioblastoma : Immunotherapie met subcutaan immunogeen autoloog tumor lysaat tegen glioblastomen

Being diagnosed with glioblastoma (GBM) is related to a grim future, with patients showing a median overall survival of less than 15 months despite intensive radio- and chemotherapy. As a consequence, the scientific community is searching for adjuvant treatment modalities that might improve the outcome of this devastating disease. In this regard, immunotherapy has gained great interest. One immunotherapeutic strategy uses dendritic cells (DCs) to generate an anti-tumor response induced by the patient's own immune system. This DC-based active immunotherapy consists of two groups using either ex vivo grown DCs or in vivo targeting of these cells. The latter condition might be preferred because of efficiency, variable response rates of ex vivo grown DCs plus limited migration to lymphoid tissue, as well as practical and economic reasons (time-consuming, labour-intensive process requiring sterile handling leading to an expensive vaccine). In order to induce a broader immune response against the cancer cells and because of the strong heterogeneity of these tumors, whole tumor cell lysate is being preferred as an antigenic source in glioma. Moreover, we were wondering if the tumor lysate vaccination could benefit from the implementation of nanoparticles (NPs) in this treatment. These small particles are able to improve DC immunotherapy for example by their variable physicochemical properties, by combining antigen and adjuvant internalisation and by rendering the opportunity to target DCs in vivo. To achieve this goal, a nanovaccine was generated by surface loading polystyrene NPs with whole tumor lysate and this way aiming for a passive targeting of DCs following subcutaneous injection. Based on the knowledge our research group obtained concerning the strength of the immunogenic signature of our lysate product, we investigated the potential effect and immune mechanisms of naked autologous immunogenic tumor lysate and lysate-NP conjugates, without the addition of DCs or adjuvants, to treat GBM in a preclinical mouse model. Following proof of antigen internalisation by DCs in vitro and subsequent antigen processing and presentation, a positive survival effect in preclinical murine glioma models was observed by subcutaneous lysate injections. Next, the process of nanovaccine generation was started by stably conjugating lysate to the surface of NPs. Following an optimisation process which judged size, antigen conjugation, in vitro DC internalisation and, in a limited manner, toxicity, the most ideal nanovaccine composition was tested in the glioma mouse models. Comparable results as for autologous lysate treatment were observed, showing survival benefit of subcutaneous nanovaccine administrations. In both treatment modalities, the immune response was characterized by an increase of T cells and a diminished immune suppression in the brain, with the induction of a tumor-specific immunological memory. Finally, combinatorial treatment strategies of autologous lysate vaccination or nanovaccine with TMZ chemotherapy lead to ameliorated survival outcome in glioma-bearing mice. The presented work demonstrated that subcutaneous injection of autologous whole tumor lysate can dose-dependently initiate an immune response that suppresses tumor growth of gliomas. The effectiveness of lysate treatment for gliomas offers a time and cost-effective approach in comparison to DC therapy, and thus it should be considered as a potential adjuvant treatment for glioma. With the nanovaccine research we aimed for a feasibility proof-of-concept study for using lysate-loaded NPs in the treatment of GBM that can be expanded in future. Further optimisation of a nanovaccine e.g. by co-delivery of antigens and immune adjuvants or active targeting of DCs, might be the future for autologous lysate vaccination. status: published