Induction of epithelial differentiation and DNA demethylation in hamster malignant oral keratinocyte by ornithine decarboxylase antizyme

Abstract

The hamster ornithine decarboxylase antizyme (ODCAz) cDNA was transfected into the hamster malignant oral keratinocyte cell line, HCPC-1. Ectopic expression of ODC-Az resulted in the reversion of malignant phenotypes and alteration of DNA methylation status of CCGG sites. The phenotypes examined include ODC enzymatic activity, doubling time, morphological change, anchorage dependent growth, tumorigenicity in nude mice, induction of epithelial dierentiation marker protein (involucrin), and change of cell cycle position. Comparison of CCGG DNA methylation status of the ODC-Az and control vector transfectants revealed a signi®cant increase in demethylation of 5-methyl cytosines (m 5 C) of CCGG sites in the ODC-Az transfectants. Ectopic expression of ODC-Az gene in hamster malignant oral keratinocytes led to reduce ODC activity and the subsequent demethylation of 5-methyl cytosines, presumably via the ODC/ polyamines/ decarboxylated S-adenosylmethionine (dc-AdoMet) pathways. Our data suggest that ODC-Az shared the same pathway of polyamines/ dc-AdoMet/DNA methyltransferase (DNA MTase). We propose that ODC-Az mediates a novel mechanism in tumor suppression by DNA demethylation and presumably re-activation of key cellular genes silenced by DNA hypermethylation during cancer development. Oncogene (2001) 20, 24 ± 33.

Antizyme, a mediator of ubiquitin-independent proteasomal degradation and its inhibitor localize to centrosomes and modulate centriole amplification

“…Since elevated ODC activity is associated with most forms of human malignancies (Gerner and Meyskens, 2004), it was suggested early on that antizyme 1 may function as a tumor suppressor. Supporting this hypothesis, it has been shown that antizyme 1 overexpression leads to cell cycle arrest, apoptosis and reduced cell proliferation in vitro, (Iwata et al, 1999;Koike et al, 1999) and inhibits tumor growth in several mouse models in vivo (Iwata et al, 1999;Tsuji et al, 2001;Fong et al, 2003).…”

Antizyme Affects Cell Proliferation and Viability Solely through Regulating Cellular Polyamines

“…Az is a small polyamine-induced protein that inhibits mammalian cell proliferation and is therefore regarded as a tumor suppressor (12)(13)(14)(15). Az binds to transient ODC monomeric subunits, preventing their association to form active dimers and targeting them to ubiquitin-independent degradation by the 26 S proteasome (7,10).…”

“…In addition, Az inhibits uptake and stimulates excretion of polyamines via a yet unresolved mechanism (11). Az inhibits cell proliferation and displays antitumor activity, and therefore, it is regarded as a tumor suppressor (12)(13)(14)(15). Mammalian cells express three characterized members of the Az family of proteins (6,16).…”

Biological Effects of Polyamines on the Prevention of Aging-associated Diseases and on Lifespan Extension

“…ODC activities, or due to a deficit in the activities for spermine synthesis, the intracellular concentrations of dcSAM increase (Frostesjo et al, 1997;Pegg et al, 2011;Shantz et al, 1992;Yamamoto et al, 2010). Simultaneously, such cells have been reported to have enhanced demethylation status of the entire genome (Papazafiri & Osborne, 1987;Tsuji et al, 2001). …”

“…The methylation of genes indicates the conversion from cytosine to methyl-cytosine by the addition of a methyl group from SAM due to the action of DNA methyltransferase (Dnmt) (Goll & Bestor, 2005). The increase in SAM enriches the supply of methyl groups to a gene, whereas an increase in dcSAM acts to inhibit Dnmt activities (Tsuji et al, 2001;Yamamoto et al, 2010) (Fig. 4).…”