MV1035 Overcomes Temozolomide Resistance in Patient-Derived Glioblastoma Stem Cell Lines

SIMPLE SUMMARY: Since 2005, temozolomide (TMZ) has been used as a standard first-line treatment for glioblastoma (GBM, grade IV glioma), and despite many studies and efforts no better alternatives have emerged. Tumor recurrences and TMZ resistance are common and the prognosis is very poor with a median overall survival of 14–16 months. The development of new pharmacological strategies is even more difficult due to the presence of glioma stem cells (GSCs). In this multidisciplinary study, we tested the imidazobenzoxazin-5-thione MV1035, alone and in combination with TMZ, in U87-MG and patient-derived (PD) GSCs in order to demonstrate a putative synergic effect. MV1035 was tested following its in silico predicted ability to act as an inhibitor against ALKBH2 and ALKBH5, both involved in maintaining the tumorigenicity of glioblastoma. ABSTRACT: Glioblastoma (GBM, grade IV glioma) represents the most aggressive brain tumor and patients with GBM have a poor prognosis. Until now surgical resection followed by radiotherapy and temozolomide (TMZ) treatment represents the standard strategy for GBM. We showed that the imidazobenzoxazin-5-thione MV1035 is able to significantly reduce GBM U87-MG cells migration and invasiveness through inhibition of the RNA demethylase ALKBH5. In this work, we focus on the DNA repair protein ALKBH2, a further MV1035 target resulting from SPILLO-PBSS proteome-wide scale in silico analysis. Our data demonstrate that MV1035 inhibits the activity of ALKBH2, known to be involved in GBM TMZ resistance. MV1035 was used on both U87-MG and two patient-derived (PD) glioma stem cells (GSCs): in combination with TMZ, it has a significant synergistic effect in reducing cell viability and sphere formation. Moreover, MV1035 induces a reduction in MGMT expression in PD-GSCs cell lines most likely through a mechanism that acts on MGMT promoter methylation. Taken together our data show that MV1035 could act as an inhibitor potentially helpful to overcome TMZ resistance and able to reduce GBM migration and invasiveness.