PLGA-encapsulated Disulfiram targets glioblastoma stem cells in vitro and in vivo by modulation of hypoxia-NF-kB pathway

Introduction

Despite decades of research the therapeutic outcome of Glioblastoma Multiforme (GBM) remains dismal as no contemporary chemotherapeutic regimen is effective. Recent understanding of the molecular mechanisms behind chemoresistance has focussed on a small population (~1%) of GBM cancer stem cells (CSCs) which promotes therapeutic resistance and local invasion of GBM cells. Evidence indicates that intra-tumoral hypoxia drives CSC phenotypes in solid tumours via epithelial-to-mesenchymal transition (EMT). Hypoxia inducible factors (HIFs), NF-κB and aldehyde dehydrogenase (ALDH) activity are highly up-regulated in hypoxia-induced CSCs. The insights on how HIFs, NF-κB and ALDH together coordinate the stemness and chemoresistance still remain obscure. Development of drugs that can cross blood brain barrier (BBB) and target CSCs is of significant importance for GBM chemotherapy.

Methods

Disulfiram (DS), a clinically used anti-alcoholism drug, is a strong inhibitor of NF-κB and ALDH. Our previous studies show that DS in combination with copper (Cu) can effectively reverse chemoresistance and block metastasis in multiple cancers. In this study we used an in vitro GBM CSC model of NF-κB-p65 and HIFs transfected GBM cell lines to investigate the relationship between hypoxia induced HIFs, NF-κB activation and ALDH activity and their role in chemoresistance. We also examined the in vitro cytotoxicity and mechanism of action of DS/Cu on GBM CSCs.

Results and Discussion

Although DS is very effective in suppressing GBM in vitro, its clinical application is severely limited by its short half-life in the bloodstream. We recently developed and characterized a poly lactic-co-glycolic acid (PLGA)-encapsulated DS nanoparticles, protecting DS from the degradation in the bloodstream. PLGA encapsulation extended the half-life of DS from shorter than 2 minutes to 7 hours in serum. In combination with copper, DS-PLGA significantly inhibited GBM tumour in both subcutaneous and orthotopic xenograft mouse models at a very low dose (<1/10 of antialcoholism dose).

Conclusions

DS/Cu can effectively suppress GBM tumour both in vitro and in vivo with low/no toxicity to normal tissues and can freely pass through the BBB. Both DS and PLGA are FDA approved products for clinical application. Our study may repurpose DS into cancer indication and lead to a breakthrough in GBM treatment.