title: Reactive oxygen species-mediated therapeutic response and resistance in glioblastoma.
abstract: Glioblastoma (GBM) resistance to therapy is the most common cause of tumor recurrence, which is ultimately fatal in 90% of the patients 5 years after initial diagnosis. A sub-population of tumor cells with stem-like properties, glioma stem cells (GSCs), is specifically endowed to resist or adapt to the standard therapies, leading to therapeutic resistance. Several anticancer agents, collectively termed redox therapeutics, act by increasing intracellular levels of reactive oxygen species (ROS). In this study, we investigated mechanisms underlying GSC response and resistance to cannabidiol (CBD), a non-toxic, non-psychoactive cannabinoid and redox modulator. Using primary GSCs, we showed that CBD induced a robust increase in ROS, which led to the inhibition of cell survival, phosphorylated (p)-AKT, self-renewal and a significant increase in the survival of GSC-bearing mice. Inhibition of self-renewal was mediated by the activation of the p-p38 pathway and downregulation of key stem cell regulators Sox2, Id1 and p-STAT3. Following CBD treatment, a subset of GSC successfully adapted, leading to tumor regrowth. Microarray, Taqman and functional assays revealed that therapeutic resistance was mediated by enhanced expression of the antioxidant response system Xc catalytic subunit xCT (SLC7A11 (solute carrier family 7 (anionic amino-acid transporter light chain), member 11)) and ROS-dependent upregulation of mesenchymal (MES) markers with concomitant downregulation of proneural (PN) markers, also known as PN-MES transition. This 'reprogramming' of GSCs occurred in culture and in vivo and was partially due to activation of the NFE2L2 (NRF2 (nuclear factor, erythroid 2-like)) transcriptional network. Using genetic knockdown and pharmacological inhibitors of SLC7A11, we demonstrated that combining CBD treatment with the inhibition of system Xc resulted in synergistic ROS increase leading to robust antitumor effects, that is, decreased GSC survival, self-renewal, and invasion. Our investigation provides novel mechanistic insights into the antitumor activity of redox therapeutics and suggests that combinatorial approaches using small molecule modulators of ROS offer therapeutic benefits in GBM.
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: E
authors.initials: E
authors.lastname: Singer
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Judkins
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors.forename: N
authors.initials: N
authors.lastname: Salomonis
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Matlaf
authors.affiliation: Center for Applied Genomics, UMDNJ, Newark, NJ, USA.
authors.forename: P
authors.initials: P
authors.lastname: Soteropoulos
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: McAllister
authors.affiliation: California Pacific Medical Center Research Institute, San Francisco, CA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Soroceanu
mesh_terms: D027182:Amino Acid Transport System y+ / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002185:Cannabidiol / Q000494:pharmacology / Q000627:therapeutic use; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005909:Glioblastoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008648:Mesoderm / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008819:Mice, Nude; D008954:Models, Biological; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010641:Phenotype; D010879:Piperazines / Q000494:pharmacology / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016019:Survival Analysis; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D027182:Amino Acid Transport System y+; D000975:Antioxidants; D051267:NF-E2-Related Factor 2; D010879:Piperazines; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C118895:SLC7A11 protein, human; C477224:erastin; D002185:Cannabidiol