High-Throughput Chemical Screens Identify Disulfiram as an Inhibitor of Human Glioblastoma Stem Cells

Abstract

Glioblastoma Multiforme (GBM) continues to have a poor patient prognosis despite optimal standard of care. Glioma stem cells (GSCs) have been implicated as the presumed cause of tumor recurrence and resistance to therapy. With this in mind, we screened a diverse chemical library of 2,000 compounds to identify therapeutic agents that inhibit GSC proliferation and therefore have the potential to extend patient survival. High-throughput screens (HTS) identified 78 compounds that repeatedly inhibited cellular proliferation, of which 47 are clinically approved for other indications and 31 are experimental drugs. Several compounds (such as digitoxin, deguelin, patulin and phenethyl caffeate) exhibited high cytotoxicity, with half maximal inhibitory concentrations (IC50) in the low nanomolar range. In particular, the FDA approved drug for the treatment of alcoholism, disulfiram (DSF), was significantly potent across multiple patient samples (IC50 of 31.1 nM). The activity of DSF was potentiated by copper (Cu), which markedly increased GSC death. DSF–Cu inhibited the chymotrypsin-like proteasomal activity in cultured GSCs, consistent with inactivation of the ubiquitin-proteasome pathway and the subsequent induction of tumor cell death. Given that DSF is a relatively non-toxic drug that can penetrate the blood-brain barrier, we suggest that DSF should be tested (as either a monotherapy or as an adjuvant) in pre-clinical models of human GBM. Data also support targeting of the ubiquitin-proteasome pathway as a therapeutic approach in the treatment of GBM.

Disulfiram when Combined with Copper Enhances the Therapeutic Effects of Temozolomide for the Treatment of Glioblastoma

“…Thus, the independent validation of activity against the patient-derived glioma cells, DSF's low nanomolar efficacy on these cells, BBB penetration, and its extensive multi-decade clinical use with very little evidence of adverse drug reactions made it desirable to pursue in a rigorous preclinical assessment regime. DSF requires copper for effective killing and inhibition of self-renewal of genetically distinct patient-derived BTICs As described above, DSF was found to be highly effective at killing a wide range of patient-derived BTICs, an observation consistent with recent in vitro reports using human glioma cell lines (17,18,41,43); however, in vivo testing has not been performed and discrepancies with respect to the IC 50 and the requirement of copper for its therapeutic effects exist (17,18). We found that while some patient-derived BTICs were sensitive to the treatment with DSF alone (Fig.…”

“…We therefore focused upon further assessment of disulfiram. While the evaluation of DSF is certainly not unique in the cancer setting (14-16, 19, 25, 27, 40), including studies in glioma (17,41,42), in vivo preclinical assessment for glioblastoma has not been performed. Thus, the independent validation of activity against the patient-derived glioma cells, DSF's low nanomolar efficacy on these cells, BBB penetration, and its extensive multi-decade clinical use with very little evidence of adverse drug reactions made it desirable to pursue in a rigorous preclinical assessment regime.…”

“…Recently, several independent groups, including this study, have identified DSF through high-throughput screens as a potential therapeutic for the treatment of various cancers including glioblastoma (14)(15)(16)(17)(18)(19). As DSF has been used clinically for over 60 years to treat alcoholism, its pharmacokinetics has been extensively studied and shown to have an excellent safety record at FDArecommended doses (20,21).…”

Identification of Mitoxantrone as a TRAIL-sensitizing agent for Glioblastoma Multiforme

“…Accordingly, we identified 13 drugs that were effective as single agents. Some of them were previously suggested as therapeutic candidates for GBM as single agents such as Doxorubicin hydrochloride, 21 Camptothecine (S,C), 22 Proscillaridin A, 15 Pyrivinium pamoate, 23 and Niclosamide. 24 We report Alexidine dihydrochloride, Monensin sodium salt, Lanatoside C, Digitoxigenin, Digoxigenin, Digoxin, Quinacrine dihydrochloride, Terfenadine and Astemizole as novel drugs that can be therapeutic candidates for GBM.…”

Development and characterisation of disulfiram-loaded PLGA nanoparticles for the treatment of non-small cell lung cancer

“…Therefore the discovery of a CSC-targeting drug would significantly improve chemotherapy outcomes for NSCLC patients. The antialcoholism drug disulfiram (DSF) has been shown to have an anticancer effect against prostate cancer, breast cancer, brain tumours, leukaemia, cervical adenocarcinoma and NSCLC [21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Furthermore, DSF has been shown to be an irreversible aldehyde dehydrogenase (ALDH) inhibitor targeting CSCs [22,[35][36].…”