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Mechanism of anti-proliferation effects of dehydroepiandrosterone on colon cancer

脱氢表雄酮抗结肠癌增殖作用机制

基本信息

批准号：
10470130
负责人：
TANAKA Naomi
金额：
$ 4.03万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Dehydroepiandrosterone (DHEA) is a naturally occurring steroid synthesized in the adrenal, brain and gastrointestinal tract. In vivo and in vitro administration of DHEA inhibits cancer proliferation. Two hypotheses have been proposed so far, 1) depletion of intracellular ribose due to inhibition of glucose-6-phosphate dehydrogenase (G6PD) activity ; and 2) inhibition of p21ras signal transduction pathway by dawn-regulation of HMG-CoA reductase (HMGR). To clarify the mechanism, the effects of DHEA and related steroids on the enzyme activities were studied in HepG2 cells. Cell growth was evaluated by MTT and bromodeoxyuridine incorporation assays. G6PD activity was measured by spectrophotometric assay, and the activities of HMGR and MAP kinase (MAPK), the final enzyme in the p21ras pathway, were determined by radioisotope incorporation methods. All steroids we tested had inhibitory effects on cell growth. Growth inhibition due to pregnenolone (PGN) and epiandrosterone (EA) was greater th … More an that caused by DHEA, while DHEA-sulfate, 7α-OH DHEA, 7β-OH DHEA and 7-keto DHEA had less inhibitory effects than DHEA.There was no significant correlation between growth inhibition and suppression of G6PD (r=0.552, NS) or HMGR (r=0.498, NS) activities. In contrast, highly significant positive correlation was observed between growth inhibition and suppression of MAPK activity (r=0.905, P<0.01).The same results were obtained when growth inhibition was evaluated by MTT assay. There was no significant correlation between inhibition of MTT assay and inhibition of G6PD activity (r=0.566, n=7, P=0.186) or inhibition of HMG-CoA reductase activity (r=0.442, n=7, P=0.321).In contrast, inhibition of MTT assay and inhibition of MAP-kinase was correlated significantly (r=0.807, n=7, P<0.05). These results demonstrate that not only DHEA but also all other steroids examined in this study have anti-proliferation effects on HepG2 cells. Inhibition of MAPK or some upstream molecules in the signal transduction appears to be more responsible for the anti-proliferation effects of these steroids than inhibition of G6PD or HMGR activity. Less

脱氢表雄酮（DHEA）是一种在肾上腺、大脑和胃肠道中合成的天然类固醇。体内和体外给药脱氢表雄酮抑制肿瘤增殖。目前提出了两种假说：1)由于抑制葡萄糖-6-磷酸脱氢酶（G6PD）活性导致细胞内核糖的耗竭；2)通过调控HMG-CoA还原酶（HMGR）抑制p21ras信号转导通路。为了阐明其作用机制，我们在HepG2细胞中研究了脱氢表雄酮和相关类固醇对酶活性的影响。采用MTT法和溴脱氧尿苷掺入法测定细胞生长情况。用分光光度法测定G6PD活性，用放射性同位素掺入法测定HMGR和MAP激酶（MAPK）活性，MAPK是p21ras途径的最终酶。我们测试的所有类固醇都对细胞生长有抑制作用。孕烯醇酮（PGN）和表雄酮（EA）对脱氢表雄酮（DHEA）的抑制作用大于脱氢表雄酮（DHEA），而硫酸脱氢表雄酮、7α-OH脱氢表雄酮、7- β- oh脱氢表雄酮对脱氢表雄酮的抑制作用小于脱氢表雄酮（DHEA）。生长抑制与G6PD （r=0.552， NS）和HMGR （r=0.498， NS）活性无显著相关。相反，生长抑制与MAPK活性抑制呈极显著正相关（r=0.905， P<0.01）。用MTT法评价生长抑制作用，得到了相同的结果。抑制MTT检测与抑制G6PD活性（r=0.566, n=7， P=0.186）或抑制HMG-CoA还原酶活性（r=0.442, n=7， P=0.321）无显著相关性。MTT抑制与map -激酶抑制呈显著相关（r=0.807, n=7， P<0.05）。这些结果表明，除DHEA外，本研究检测的所有其他类固醇均对HepG2细胞具有抗增殖作用。抑制MAPK或信号转导中的一些上游分子似乎比抑制G6PD或HMGR活性更能发挥这些类固醇的抗增殖作用。少