Comparative analysis of chemotherapeutic responses between the U87-MG and U87-IDH1m cell lines

Glioblastoma is one of the most common and, moreover, a very aggressive brain tumor for which no cure exists to this day. Currently, patients are treated via a standard protocol with chemotherapy in the form of an alkylating agent, temozolomide, followed by radiation therapy, and several weeks later, chemotherapy again. These are DNA-damaging therapies intended to inhibit cell proliferation and induce cell death. However, glioblastoma possesses intrinsic DNA damage repair mechanisms, making it resistant to chemoradiotherapy. Additionally, the neurological damage caused by chemoradiotherapy, which harms brain tissue, demonstrates the need for a more effective treatment. When a mutation of the IDH1 gene occurs, it results in a better prognosis, with the tumor growing more slowly and responding better to therapy. IDH1 mutant tumors produce the oncometabolite 2-HG, which influences the epigenetic regulation of genes. There is also often methylation of MGMT, an enzyme capable of repairing DNA damage, which results in higher treatment sensitivity. Furthermore, cellular differentiation is inhibited, which hinders the growth of the tumor. Due to the alternative molecular mechanisms and responses to treatment, it is of great importance that personalized therapy can be offered in the future, which most effectively targets the tumor. Vorasidenib and bortezomib are two alternative chemotherapeutics currently undergoing clinical trials. Vorasidenib is an inhibitor of IDH mutant enzyme, aiming to reduce 2-HG production and slow down tumor progression. Bortezomib is a proteasome inhibitor that downregulates certain proteins such as MGMT and can have a priming effect for further treatment according to the standard protocol. Furthermore, in microcephaly, a medical condition characterized by reduced brain volume, mutations have been identified in genes that play an important role in cell proliferation. Since the formation of glioblastoma parallels brain development, targeting these microcephaly proliferation genes could be a potential new treatment strategy. In this thesis, I contributed to identifying differences in response between the U87-MG cell line and the U87-IDH1m cell line, which model IDH wildtype glioblastoma and IDH mutant astrocytoma, respectively, to the standard of care, vorasidenib, and bortezomib treatment. No clear conclusion was drawn regarding the effectiveness of the treatments in terms of cell proliferation, only apoptosis was induced by treatment, with a higher expression in the U87-IDH1m cell line. Both cell lines were also cultured in Neurobasal medium, which should further support their stemness character, but again, there was only a clear induction of apoptosis, with a stronger effect observed in the IDH1 mutant cell line. Furthermore, qPCRs were conducted on DNA damage response genes and microcephaly genes to assess the response of gene expression levels to the different chemotherapeutics and the possibility of influencing them as a potential treatment strategy. DNA damage response genes were upregulated upon treatment, indicating the DNA repair capacity of glioblastoma. Microcephaly genes were also upregulated, which strongly contradicted the expectations.