Bortezomib administered prior to temozolomide depletes MGMT, chemosensitizes glioblastoma with unmethylated MGMT promoter and prolongs animal survival

Abstract

BackgroundResistance to temozolomide (TMZ) is due in part to enhanced DNA repair mediated by high expression of O6-methyl guanine DNA methyltransferase (MGMT) that is often characterised by unmethylated promoter. Here, we investigated pre-treatment of glioblastoma (GBM) cells with the 26S-proteasome inhibitor bortezomib (BTZ) as a strategy to interfere with MGMT expression and thus sensitise them to TMZ.MethodsCell lines and patient GBM-derived cells were examined in vitro, and the latter also implanted orthotopically into NOD-SCID C.B.-Igh-1b/lcrTac-Prkdc mice to assess efficacy and tolerability of BTZ and TMZ combination therapy. MGMT promoter methylation was determined using pyrosequencing and PCR, protein signalling utilised western blotting while drug biodistribution was examined by LC-MS/MS. Statistical analysis utilised Analysis of variance and the Kaplan–Meier method.ResultsPre-treatment with BTZ prior to temozolomide killed chemoresistant GBM cells with unmethylated MGMT promoter through MGMT mRNA and protein depletion in vitro without affecting methylation. Chymotryptic activity was abolished, processing of NFkB/p65 to activated forms was reduced and corresponded with low MGMT levels. BTZ crossed the blood–brain barrier, diminished proteasome activity and significantly prolonged animal survival.ConclusionBTZ chemosensitized resistant GBM cells, and the schedule may be amenable for temozolomide refractory patients with unmethylated MGMT promoter.

Sequential bortezomib and temozolomide treatment promotes immunological responses in glioblastoma patients with positive clinical outcomes: A phase 1B study

“…The ultimate aim was to attain combination treatment with BTZ and TMZ at 200 mg/m 2 which was closest to the most effective dose in the preclinical study. 22 Total treatment duration per patient was estimated for 6 to 12 months unless disease progression.…”

“…It has been established that NF-κB binding sites are present within the MGMT promoter region, that MGMT messenger RNA (mRNA) is induced by NF-κB/ p65, and that MGMT expression correlates with NF-κB activation regardless of promoter methylation status. 15,22 NF-κB activation requires 26S proteasomal processing. 23 Bortezomib (BTZ) is a proteasome inhibitor that has been approved for treatment of multiple myeloma, mantle cell lymphoma and trialed in early phase trials for treatment of GBM.…”

“…This correlated with reduced MGMT protein and mRNA expression by 70%-80% and sensitized the GBM cells to TMZ chemotherapy. 22 Two other studies also investigated MGMT depletion via mechanisms associated with activation of NFκB, MAPK, STAT3, and HIF-1α pathways after BTZ treatment. 16,18 As well as depleting the tumor's cytoprotective mechanisms, agents that simultaneously promote tumor recognition by cells of the immune system may be attractive anticancer candidates.…”

“…24 Sequential combination of BTZ 48 hours before TMZ 164 mg/m 2 treatment, depleted MGMT mRNA in vivo, attenuated tumor growth and significantly prolonged animal survival. 22 Thus, this phase IB of our BORTEM-17 clinical trial (NCT03643549) was launched to investigate whether pretreatment of recurrent GBM patients with BTZ 1.3 mg/m 2 on days 1, 4, and 7, to deplete MGMT levels 48 hours before TMZ, commencing on days 3 to 7 every 4th week, might sensitize MGMT unmethylated GBM to TMZ chemotherapy. We assessed the maximal safe escalated TMZ dose administered in sensitization schedule with BTZ and whether treatment enhanced differentiation of cytotoxic immune subsets to impact treatment responses.…”

Selective Inhibition of HDAC1 by Macrocyclic Polypeptide for the Treatment of Glioblastoma: A Binding Mechanistic Analysis Based on Molecular Dynamics

“…Glioblastoma (GBM) is the most common and aggressive intracranial malignant brain tumor with the median survival duration <2 years in spite of chemotherapy, radiation or surgical resection (Natsume et al, 2019). In the current chemotherapies, such as temozolomide, drug resistance is the predominant obstacle (Zhang et al, 2012;Chen et al, 2019;Kim et al, 2019;Rahman et al, 2019;Su et al, 2019;Xingyi et al, 2019). On the basis of the latest experimental results obtained from the large-scale profiling which included the whole exome and RNA sequencing, it can be learnt that genetic and epigenetic mechanisms are involved in the occurrence and progress of glioma cells (Cancer Genome Atlas Research, 2008;Brennan et al, 2013), especially the aberrant epigenetic silencing of genes caused by histone deacetylation (Vaissiere et al, 2008;Cartron et al, 2013).…”