title: α5-GABAA receptors negatively regulate MYC-amplified medulloblastoma growth.
abstract: Neural tumors often express neurotransmitter receptors as markers of their developmental lineage. Although these receptors have been well characterized in electrophysiological, developmental and pharmacological settings, their importance in the maintenance and progression of brain tumors and, importantly, the effect of their targeting in brain cancers remains obscure. Here, we demonstrate high levels of GABRA5, which encodes the α5-subunit of the GABAA receptor complex, in aggressive MYC-driven, "Group 3" medulloblastomas. We hypothesized that modulation of α5-GABAA receptors alters medulloblastoma cell survival and monitored biological and electrophysiological responses of GABRA5-expressing medulloblastoma cells upon pharmacological targeting of the GABAA receptor. While antagonists, inverse agonists and non-specific positive allosteric modulators had limited effects on medulloblastoma cells, a highly specific and potent α5-GABAA receptor agonist, QHii066, resulted in marked membrane depolarization and a significant decrease in cell survival. This effect was GABRA5 dependent and mediated through the induction of apoptosis as well as accumulation of cells in S and G2 phases of the cell cycle. Chemical genomic profiling of QHii066-treated medulloblastoma cells confirmed inhibition of MYC-related transcriptional activity and revealed an enrichment of HOXA5 target gene expression. siRNA-mediated knockdown of HOXA5 markedly blunted the response of medulloblastoma cells to QHii066. Furthermore, QHii066 sensitized GABRA5 positive medulloblastoma cells to radiation and chemotherapy consistent with the role of HOXA5 in directly regulating p53 expression and inducing apoptosis. Thus, our results provide novel insights into the synthetic lethal nature of α5-GABAA receptor activation in MYC-driven/Group 3 medulloblastomas and propose its targeting as a novel strategy for the management of this highly aggressive tumor.
authors.affiliation: Department of Neurology, Boston Children's Hospital, Boston, MA, USA.
authors.forename: Soma
authors.initials: S
authors.lastname: Sengupta
authors.forename: Shyamal Dilhan
authors.initials: SD
authors.lastname: Weeraratne
authors.forename: Hongyu
authors.initials: H
authors.lastname: Sun
authors.forename: Jillian
authors.initials: J
authors.lastname: Phallen
authors.forename: Sundari K
authors.initials: SK
authors.lastname: Rallapalli
authors.forename: Natalia
authors.initials: N
authors.lastname: Teider
authors.forename: Bela
authors.initials: B
authors.lastname: Kosaras
authors.forename: Vladimir
authors.initials: V
authors.lastname: Amani
authors.forename: Jessica
authors.initials: J
authors.lastname: Pierre-Francois
authors.forename: Yujie
authors.initials: Y
authors.lastname: Tang
authors.forename: Brian
authors.initials: B
authors.lastname: Nguyen
authors.forename: Furong
authors.initials: F
authors.lastname: Yu
authors.forename: Simone
authors.initials: S
authors.lastname: Schubert
authors.forename: Brianna
authors.initials: B
authors.lastname: Balansay
authors.forename: Dimitris
authors.initials: D
authors.lastname: Mathios
authors.forename: Mirna
authors.initials: M
authors.lastname: Lechpammer
authors.forename: Tenley C
authors.initials: TC
authors.lastname: Archer
authors.forename: Phuoc
authors.initials: P
authors.lastname: Tran
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Reimer
authors.forename: James M
authors.initials: JM
authors.lastname: Cook
authors.forename: Michael
authors.initials: M
authors.lastname: Lim
authors.forename: Frances E
authors.initials: FE
authors.lastname: Jensen
authors.forename: Scott L
authors.initials: SL
authors.lastname: Pomeroy
authors.forename: Yoon-Jae
authors.initials: YJ
authors.lastname: Cho
mesh_terms: D000818:Animals; D001569:Benzodiazepines / Q000494:pharmacology; D002453:Cell Cycle / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002528:Cerebellar Neoplasms / Q000378:metabolism* / Q000473:pathology; D002945:Cisplatin / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D018755:GABA Agonists / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008527:Medulloblastoma / Q000378:metabolism* / Q000473:pathology; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D051379:Mice; D018408:Patch-Clamp Techniques; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D018755:GABA Agonists; C489213:HOXA5 protein, human; D018398:Homeodomain Proteins; D016271:Proto-Oncogene Proteins c-myc; C000592796:QH-II-66; D011978:Receptors, Nicotinic; D016159:Tumor Suppressor Protein p53; C577601:nicotinic receptor alpha5 subunit, human; D001569:Benzodiazepines; D005680:gamma-Aminobutyric Acid; D002945:Cisplatin