A novel human AlkB homologue, ALKBH8, contributes to human bladder cancer progression.
We recently identified a novel human AlkB homologue, ALKBH8, which is expressed in various types of human cancers including human urothelial carcinomas. In examining the role and function of ALKBH8 in human bladder cancer development in vitro, we found that silencing of ALKBH8 through small interfering RNA transfection reduced reactive oxygen species (ROS) production via down-regulation of NAD(P)H oxidase-1 (NOX-1) and induced apoptosis through subsequent activation of c-jun NH(2)-terminal kinase (JNK) and p38. However, we also found that JNK and p38 activation resulted in phosphorylation of H2AX (gammaH2AX), a variant of mammalian histone H2A, which contributes to the apoptosis induced by silencing ALKBH8 and NOX-1. Silencing of ALKBH8 significantly suppressed invasion, angiogenesis, and growth of bladder cancers in vivo as assessed both in the chorioallantoic membrane assay and in an orthotopic mouse model using green fluorescent protein-labeled KU7 human urothelial carcinoma cells. Immunohistochemical examination showed high expression of ALKBH8 and NOX-1 proteins in high-grade, superficially and deeply invasive carcinomas (pT(1) and >pT(2)) as well as in carcinoma in situ, but not in low-grade and noninvasive phenotypes (pT(a)). These findings indicate an essential role for ALKBH8 in urothelial carcinoma cell survival mediated by NOX-1-dependent ROS signals, further suggesting new therapeutic strategies in human bladder cancer by inducing JNK/p38/gammaH2AX-mediated cell death by silencing of ALKBH8.
Shimada
Keiji
K
Department of Pathology, Nara Medical University School of Medicine, Shijo-cho, Kashihara, Nara, Japan.
Nakamura
Mitsutoshi
M
Anai
Satoshi
S
De Velasco
Marco
M
Tanaka
Motoyoshi
M
Tsujikawa
Kazutake
K
Ouji
Yukiteru
Y
Konishi
Noboru
N
D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D000818:Animals; D045744:Cell Line, Tumor; D002642:Chick Embryo; D045643:DNA Repair Enzymes / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D018450:Disease Progression; D004789:Enzyme Activation; D020868:Gene Silencing; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000473:pathology; D009842:Oligopeptides / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D001749:Urinary Bladder Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D009842:Oligopeptides; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C499236:ALKBH1 protein, human; D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases; C402799:NOX1 protein, human; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D045643:DNA Repair Enzymes