A Novel Human AlkB Homologue, ALKBH8, Contributes to Human Bladder Cancer Progression

Abstract

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 (;H2AX), 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/;H2AX-mediated cell death by silencing of ALKBH8. [Cancer Res 2009;69(7):3157-64]

tRNA biology charges to the front

“…Since Trm9 does not appear to have a major effect on the growth of strains requiring tRNA Arg(UCU) to read AGG codons, or tRNA Gly(UCC) to read GGG codons, and each of these tRNAs has an mcm 5 U moiety (Johansson et al 2008), the precise effects of Trm9 on translation may be specific for certain codons or tRNAs. It is intriguing to note also that silencing of human ABH8 also leads to apoptosis of urothelial carcinoma lines and down-regulation of NOX-1-dependent reactive oxygen species, as well as suppression of angiogenesis and invasion (Shimada et al 2009). Since ABH8 does not have demethylase activity (Fu et al 2010), these effects may also be due to the lack of the mcm 5 U moiety of tRNAs.…”

ALKBH3 Contributes to Survival and Angiogenesis of Human Urothelial Carcinoma Cells through NADPH Oxidase and Tweak/Fn14/VEGF Signals

“…We carried out cell cycle analyses by flow cytometry as previously described (4). All experiments were done at least thrice in duplicate.…”

“…The depth of invasion from the CAM surface was defined as the leading front of 3 or more invading cells in 5 randomly selected fields. We assessed angiogenesis as the number of visible blood vessel branch points within a defined area of the sample (4,5). The remaining samples are served for Western blotting.…”

“…We have tried to identify the functional roles of ALKBH members in the progression of several types of human cancer. For example, ALKBH8 is mainly involved in resistance to cell death in human urothelial carcinoma cells, resulting in human bladder cancer development (4). ALKBH3 plays an important role in human pulmonary adenocarcinoma or prostatic adenocarcinoma cell survival and may be a therapeutic target (5,6).…”

m6a RNA Methylation: The Implications for Health and Disease

“…Although no direct evidence has been presented, the role of these pathways in many tumour types suggests that METTL3 may play a role in tumourigenesis. Similarly, no direct evidence exists for a role of ALKBH5 in tumourigenesis, however other members of its family, namely ALKBH2 and ALKBH8, have been implicated in bladder cancer progression [98,99]. Viral driven tumourigenesis is not uncommon, for example human papillomavirus [100], with the potential for RNA viruses to evade the immune system using the m 6 A modification there is the opportunity for this process to occur unabated.…”