Effects of ionising and non-ionising radiation in cell systems and a rat model for immuno-therapy

Abstract: The most malignant brain tumour, glioblastoma multiforme (GBM), has an utterly bad prognosis. In spite of all available therapy, the mean survival time is less than a year. In the unique BRIGTT project (Brain Immuno Gene Tumour Therapy), patients at the Dept of Neurosurgery. Lund University Hospital, are immunised with their own glioma cells, which have been transfected with the immunostimulatory Interferon-gamma gene by adenoviral vector technique. The thesis describes the development of the culturing techniques necessary for the BRIGTT project. A 75% success rate in achieving pure malignant cell cultures for treatment has been reached. These cells must not divide after injection intradermally but should survive long enough in the patient to alert the immune system. Therefore they must be irradiated before immunisation of the patient. The appropriate absorbed dose had to be identified and 100 Gy was found to be safe and has been used for all 9 treated patients in the study which has shown significantly prolonged survival in the treated patients, all above 50 years of age, but all have developed recurrences. Thus it is important to seek for other new therapies possible to combine with the immunotherapy. A novel possible method is the use of Pulsed Electric Fields (PEF) for local permeabilisation of cell membranes for release of tumour antigens to alert the immune system. In a rat model with glioma cells inoculated subcutaneously in either one or both thighs, where gliomas develop, we have studied the effect of combined PEF and Radiation Therapy (RT). In the rats with unilateral tumour we have shown complete remissions after repeated combined treatments. Based upon the results in this study, we have also developed a new mathematical model which offers a simple way to evaluate Tumour Growth Rate (TGR) and synergistic effects of combined therapies. As the basis for our clinical therapy is to stimulate the immune system, we continued the work by examining the possible immunological effects of PEF and/or RT in the rat model with bilaterally implanted thigh tumours. By treating only one of them, we could investigate the so called abscopal effect (distant effect) on the other, non-treated tumour. The TGR of the treated tumours was significantly reduced in all the treatment groups and also in the non-treated contralateral tumours in the RT and PEF + RT groups. The conclusion of this is that an abscopal effect is evident and that the possibility to add PEF to immunotherapy protocols such as BRIGTT may an important step in the search for a cure for the malignant gliomas