Repurposing Itraconazole as an Adjuvant for the Treatment of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is one of the most aggressive human cancers, with a poor prognosis. Despite recent advances in the understanding of GBM's molecular biology, patient outcome continues to be poor due to the disease's incurable, aggressive, and recurrent nature. As a result, novel therapeutic strategies for the management of GBM patients are urgently needed. Itraconazole (ITC), a systemic antifungal, is a key regulator of hedgehog (HH) signalling, which is frequently deregulated in GBM. Because of its inhibitory effects on cell proliferation and tumour angiogenesis, ITC has been identified as a novel potential anticancer agent and is herein investigated in the context of GBM.

In the present study, cell viability and reproductive integrity of GBM cells were assessed by AlamarBlue cell viability and clonogenic assays. Spheroid growth and relative colony cell growth were assessed by spheroid and associated absorbance reading assays. DNA damage levels and cell cycle distribution of the GBM cells were assessed by single cell gel electrophoresis (COMET) and flow cytometry, respectively, and O6-methylguanine DNA methyltransferase (MGMT) and HH protein levels were assessed by western blot analysis. Using these techniques we show that ITC, both alone and in combination treatments, inhibits GBM cell and spheroid growth in vitro, increased IR-induced DNA damage and caused G1 cell cycle arrest. Furthermore, ITC treatment decreased the levels of HH signalling pathway proteins sonic hedgehog (SHH) and smoothened (SMO). Together, these findings indicate that ITC inhibition of HH signalling pathway may increase TMZ, radiation and radiochemotherapy (RCT) responses and so serve as a potential adjunct to RCT in the management of GBM.