Novel treatments of glioblastoma in experimental models

Abstract: One of the major problems with malignant brain tumours, such as glioblastoma multiforme, is that despite being able to remove the major bulk of the tumour through surgery and treating the patients with chemotherapy and radiotherapy, we know that tumour cells have already spread throughout the brain. Furthermore, we now know that the glioblastoma cells effectively suppress the patients’ own anti-tumour response. One key part of the immune response, the complement system, acts as a functional bridge between innate and adaptive immunity. Here we wanted to further investigate the complement system in both glioblastoma patients and in laboratory animals by looking at the role of CRP and C1-inhibitor (C1-INH). In order not to rely solely on old glioblastoma models, which have been passed in vitro for decades, we also developed a new glioblastoma model.Initially we studied an experimental treatment, ITPP, which had previously shown promising results in other cancer models. This was done using the old glioblastoma model RG2. Subsequently we went on to develop a new GFPpositive glioblastoma model called NS1. The NS1 cell line was then used to further investigate the role of the complement system, both in vitro and in vivo, by treating the cells and animals with anti-C1-INH and anti-CRP. The in vivo experiments involved intratumoral treatment of both intracranial and subcutaneous tumours. Additionally, tumour material from glioblastoma patients was examined on the gene and protein level and compared to tumour data available from public databases.Treatment with ITPP showed no survival advantage in the RG2 model, and the route of ITPP administration did not affect outcome. The NS1 model turned out to generate infiltrative CNS tumours with perivascular growth and characteristics of a glioblastoma upon histopathological examination. With MRI tumour could easily be detected within 14 days after inoculation. We could demonstrate a significantly increased survival in vivo in animals inoculated intracerebrally with NS1 glioblastoma cells pre-coated with anti-C1-INH antibodies. On the contrary no effect of coating glioblastoma cells with anti-CRP antibodies prior to intracranial inoculation was seen. In the subcutaneous NS1 tumour model, intratumoral anti-C1-INH treatment showed a significant survival advantage andthere was a significant decrease in tumour size over time following treatment with anti-C1-INH. Using data fram a publicly available database and our own mRNA material from glioblastoma patients, we found an upregulation ofC1-INH in human glioblastoma cells. Furthermore, by using immunohistochemistry, we could demonstrate the presence of both C1-INH and CRP on glioma cells in vitro from humans and rats.We could conclude that C1-INH seems to play an important role in glioblastoma. This could possibly be explained by effects on the complement system, but also other effects are possible, since C1-INH has many biological functions. The exact role and mechanisms of anti-C1-INH treatment are topics for future studies.