start-ver=1.4
cd-journal=joma
no-vol=5
cd-vols=
no-issue=
article-no=
start-page=
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2005
dt-pub=20050120
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Functional promoter upstream p53 regulatory sequence of IGFBP3 that is silenced by tumor specific methylation
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=<p><b>Background:</b> Insulin-like growth factor binding protein (IGFBP)-3 functions as a carrier of insulinlike
growth factors (IGF<sub>s</sub>) in circulation and a mediator of the growth suppression signal in cells. There are two reported p53 regulatory regions in the IGFBP3 gene; one upstream of the promoter and one intronic. We previously reported a hot spot of promoter hypermethylation of IGFBP-3 in
human hepatocellular carcinomas and derivative cell lines. As the hot spot locates at the putative upstream p53 consensus sequences, these p53 consensus sequences are really functional is a question to be answered.<br />
<b>Methods:</b> In this study, we examined the p53 consensus sequences upstream of the IGFBP-3 promoter for the p53 induced expression of IGFBP-3. Deletion, mutagenesis, and methylation
constructs of IGFBP-3 promoter were assessed in the human hepatoblastoma cell line HepG2 for promoter activity.<br />
Results: Deletions and mutations of these sequences completely abolished the expression of IGFBP-3 in the presence of p53 overexpression. In vitro methylation of these p53 consensus
sequences also suppressed IGFBP-3 expression. In contrast, the expression of IGFBP-3 was not affected in the absence of p53 overexpression. Further, we observed by electrophoresis mobility
shift assay that p53 binding to the promoter region was diminished when methylated.<br />
<b>Conclusion:</b> From these observations, we conclude that four out of eleven p53 consensus sequences upstream of the IGFBP-3 promoter are essential for the p53 induced expression of
IGFBP-3, and hypermethylation of these sequences selectively suppresses p53 induced IGFBP-3 expression in HepG2 cells.</p>
en-copyright=
kn-copyright=

en-aut-name=HanafusaTadashi
en-aut-sei=Hanafusa
en-aut-mei=Tadashi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=ShinjiToshiyuki
en-aut-sei=Shinji
en-aut-mei=Toshiyuki
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=ShirahaHidenori
en-aut-sei=Shiraha
en-aut-mei=Hidenori
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=NousoKazuhiro
en-aut-sei=Nouso
en-aut-mei=Kazuhiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=IwasakiYoshiaki
en-aut-sei=Iwasaki
en-aut-mei=Yoshiaki
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=YumotoEichiro
en-aut-sei=Yumoto
en-aut-mei=Eichiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

en-aut-name=OnoToshiro
en-aut-sei=Ono
en-aut-mei=Toshiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=7
ORCID=

en-aut-name=KoideNorio
en-aut-sei=Koide
en-aut-mei=Norio
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=8
ORCID=

affil-num=1
en-affil=
kn-affil=Okayama University Advanced Science Research Center, Department of Radiation Research, Shikata Laboratory

affil-num=2
en-affil=
kn-affil=Department of Laboratory Medicine, Okayama University Graduate School of Medicine and Dentistry

affil-num=3
en-affil=
kn-affil=First Department of Internal Medicine, Okayama University Graduate School of Medicine and Dentistry

affil-num=4
en-affil=
kn-affil=First Department of Internal Medicine, Okayama University Graduate School of Medicine and Dentistry

affil-num=5
en-affil=
kn-affil=First Department of Internal Medicine, Okayama University Graduate School of Medicine and Dentistry

affil-num=6
en-affil=
kn-affil=First Department of Internal Medicine, Okayama University Graduate School of Medicine and Dentistry

affil-num=7
en-affil=
kn-affil=Okayama University Advanced Science Research Center, Department of Radiation Research, Shikata Laboratory

affil-num=8
en-affil=
kn-affil=Department of Laboratory Medicine, Okayama University Graduate School of Medicine and Dentistry
END