Glioblastoma Multiforme (GBM) is the most common lethal brain tumor associated with dismal survival rate. It is widely accepted that GBM contains a small population of cancer cells (∼1%) expressing CSC markers that promotes therapeutic resistance. High levels of aldehyde dehydrogenase (ALDH) activity, a characteristic feature of CSCs, play a significant role in chemoresistance.
Many recent studies have elucidated that intra-tumoral hypoxia induces CSC phenotypes in tumour via epithelial-to-mesenchymal transition (EMT). Hypoxia inducible factors (HIFs) are master transcriptional regulators under hypoxic conditions. However NF-κB, another key transcription factor, is also highly up-regulated in hypoxia induced CSCs. There are no clear insights on how HIFs and NF-κB together orchestrates the anti-apoptotic signalling, chemo-radiation resistance and maintenance of stemness in CSC phenotypes.
Disulfiram (DS), an anti-alcoholism drug, in combination with copper (Cu) effectively reverses chemoresistance in many cancers. DS/Cu is a strong inhibitor of NF-κB and ALDH and induces apoptosis. In this study we used an in vitro GBM CSC model and 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 cytotoxicity of DS/Cu on GBM CSCs and its effect on the above pathways.
In comparison with adhered cells, the GBM cellsgrown as spheres in specialized neurosphere medium (NS) or normal DMEM (SUS) showed high proportion of hypoxic cells and elevated levels of CSC and EMT markers (ALDH, CD133, CD44, OCT4, SOX2, NANOG, E-cadherin to N-cadherin switch) suggesting hypoxia induced EMT phenotypes inCSCs. Increased levels of HIFs, ALDH (1A3 and 3A1) and NF-κB activity were detected in CSCs. CSCs are highly resistant to conventional anticancer drugs like temozolomide, paclitaxel, vincristine and doxorubicin.
GBM cells transfected with NF-κB-p65 displayed CSC markers, chemoresistance and nuclear translocation of HIFs. Although transfection of HIFs induced expression of CSC markers, the cells did not show NF-κB activation and are not resistant to anticancer drugs. These results indicate the pivotal role of NF-κB in maintaining CSC characteristics and chemoresistance.
DS is cytotoxic to both GBM cell lines and the CSCs derived from them in a Cu-dependent manner.DS/Cu inhibits NF-κB and ALDH activity and triggers intrinsic apoptotic pathway. After short exposure (2 hours) to low concentration of DS/Cu, the CSCs are completely eradicated in the cell culture.
NF-κB plays pivotal role in chemoresistance. DS/Cu inhibits NF-κB, eradicates CSCs and reverses resistance in GBM.DS is an FDA approved drug with low/no toxicity to normal tissues and can freely pass through the BBB. Further study may lead to quick translation of DS into clinical trials.
Citation Format: Vinodh Kannappan, Peng Liu, Sarah Brown, Xiuwu Bian, Tawari Patricia Erebi, Angel L. Armesilla, John L. Darling, Weiguang Wang. Disulfiram targets glioblsatoma stem like cells by modulating aldehyde dehydrogenase and hypoxia-NF-κB pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 222. doi:10.1158/1538-7445.AM2014-222