title: Carbon monoxide mediates the anti-apoptotic effects of heme oxygenase-1 in medulloblastoma DAOY cells via K+ channel inhibition.
abstract: Tumor cell survival and proliferation is attributable in part to suppression of apoptotic pathways, yet the mechanisms by which cancer cells resist apoptosis are not fully understood. Many cancer cells constitutively express heme oxygenase-1 (HO-1), which catabolizes heme to generate biliverdin, Fe(2+), and carbon monoxide (CO). These breakdown products may play a role in the ability of cancer cells to suppress apoptotic signals. K(+) channels also play a crucial role in apoptosis, permitting K(+) efflux which is required to initiate caspase activation. Here, we demonstrate that HO-1 is constitutively expressed in human medulloblastoma tissue, and can be induced in the medulloblastoma cell line DAOY either chemically or by hypoxia. Induction of HO-1 markedly increases the resistance of DAOY cells to oxidant-induced apoptosis. This effect was mimicked by exogenous application of the heme degradation product CO. Furthermore we demonstrate the presence of the pro-apoptotic K(+) channel, Kv2.1, in both human medulloblastoma tissue and DAOY cells. CO inhibited the voltage-gated K(+) currents in DAOY cells, and largely reversed the oxidant-induced increase in K(+) channel activity. p38 MAPK inhibition prevented the oxidant-induced increase of K(+) channel activity in DAOY cells, and enhanced their resistance to apoptosis. Our findings suggest that CO-mediated inhibition of K(+) channels represents an important mechanism by which HO-1 can increase the resistance to apoptosis of medulloblastoma cells, and support the idea that HO-1 inhibition may enhance the effectiveness of current chemo- and radiotherapies.
authors.affiliation: Division of Cardiovascular and Neuronal Remodelling, LIGHT, Faculty of Medicine and Health, University of Leeds LS2 9JT, United Kingdom.
authors.forename: Moza M A
authors.initials: MM
authors.lastname: Al-Owais
authors.forename: Jason L
authors.initials: JL
authors.lastname: Scragg
authors.forename: Mark L
authors.initials: ML
authors.lastname: Dallas
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Boycott
authors.forename: Philip
authors.initials: P
authors.lastname: Warburton
authors.forename: Aruna
authors.initials: A
authors.lastname: Chakrabarty
authors.forename: John P
authors.initials: JP
authors.lastname: Boyle
authors.forename: Chris
authors.initials: C
authors.lastname: Peers
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D002248:Carbon Monoxide / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D003958:Diamide / Q000494:pharmacology; D004594:Electrophysiology; D005434:Flow Cytometry; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D008527:Medulloblastoma / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D051669:Shab Potassium Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D011725:Pyridines; D051669:Shab Potassium Channels; D003958:Diamide; D002248:Carbon Monoxide; D051547:Heme Oxygenase-1; C093642:SB 203580