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

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.

3D proteome-wide scale screening and activity evaluation of a new ALKBH5 inhibitor in U87 glioblastoma cell line.

The imidazobenzoxazin-5-thione MV1035, synthesized as a new sodium channel blocker, has been tested on tumoral cells that differ for origin and for expressed NaV pool (U87-MG, H460 and A549). In this paper we focus on the effect of MV1035 in reducing U87 glioblastoma cell line migration and invasiveness. Since the effect of this compound on U87-MG cells seemed not dependent on its sodium channel blocking capability, alternative off-target interaction for MV1035 have been identified using SPILLO-PBSS software. This software performs a structure-based in silico screening on a proteome-wide scale, that allows to identify off-target interactions. Among the top-ranked off-targets of MV1035, we focused on the RNA demethylase ALKBH5 enzyme, known for playing a key role in cancer. In order to prove the effect of MV1035 on ALKBH5 in vitro coincubation of MV1035 and ALKBH5 has been performed demonstrating a consequent increase of N6-methyladenosine (m6A) RNA. To further validate the pathway involving ALKBH5 inhibition by MV1035 in U87-MG reduced migration and invasiveness, we evaluated CD73 as possible downstream protein. CD73 is an extrinsic protein involved in the generation of adenosine and is overexpressed in several tumors including glioblastoma. We have demonstrated that treating U87-MG with MV1035, CD73 protein expression was reduced without altering CD73 transcription. Our results show that MV1035 is able to significantly reduce U87 cell line migration and invasiveness inhibiting ALKBH5, an RNA demethylase that can be considered an interesting target in fighting glioblastoma aggressiveness. Our data encourage to further investigate the MV1035 inhibitory effect on glioblastoma.