Siapati, Konstantina Elena; (2001) Neuroblastoma immunotherapy using a novel vector system. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Neuroblastoma is one of the commonest paediatric solid tumours and its treatment using conventional therapy has so far been of limited success. Immunotherapy in the form of tumour vaccination is an alternative therapeutic approach which aims at enhancing the immunogenicity of the tumour and involves the ex vivo manipulation of tumour cells to express certain immunomodulatory molecules. The aim of this project was to develop a cell-based neuroblastoma vaccine expressing Interleukin-2 and/or Interleukin-12, and examine its effect in a murine model for the disease. A non-viral vector system (LID) consisting of an integrin-targeting peptide and Lipofectin was used to deliver the cytokine genes into neuroblastoma cells. Optimisation of the vector components resulted in transfection of neuroblastoma cells at high efficiency (20-60%) utilising an α5β1 integrin-targeting peptide. Examination of the intracellular trafficking of LID complexes in these cells suggested that the LID vector may employ a non-coated pit endocytic or phagocytic pathway to mediate cell entry. Despite the transient nature of transfection, expression of biologically active cytokines persisted above potentially therapeutic levels for at least 10 days, suggesting a sufficient time window for an immune response to be elicited. Indeed, transfection of the mouse Neuro-2A cell line with IL-2 and/or IL-12 completely abrogated its tumourigenicity in a syngeneic mouse model for neuroblastoma. Pre-vaccination with irradiated Neuro-2A cells conferred protective immunity against subsequent challenge with parental cells, which was, however, irrespective of the cytokine expression by the cells. There was a clear effect of IL-12 with reduced tumour growth in the presence of IL-2. In vivo immunodepletion experiments suggest that CD8+ T cells may be responsible for the initial rejection of Neuro-2A cells expressing both IL-2 and IL-12, while tumour regression seems to be mediated by leukocyte infiltration and necrosis. These results indicate that the complex nature of anti-tumour immune responses may require multimodality treatments, such combination of cytokines, for efficient tumour eradication and generation of systemic immunity. The improved anti-tumour immunity of co-transfection of IL-2 and IL-12, therefore, provides a promising immunotherapeutic approach for the treatment of neuroblastoma.

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