沃特曼宁
LY294002型
细胞培养
激酶
分子生物学
磷脂酰肌醇
氧气张力
生物
赫拉
缺氧(环境)
Gα亚单位
PI3K/AKT/mTOR通路
基因表达
缺氧诱导因子
细胞
癌症研究
细胞生物学
化学
蛋白质亚单位
信号转导
生物化学
基因
氧气
有机化学
遗传学
作者
Štefan Kaluz,Milota Kaluzová,Adrián Chrastina,Peggy L. Olive,Silvia Pastoreková,Jaromı́r Pastorek,Michael I. Lerman,Eric J. Stanbridge
出处
期刊:PubMed
日期:2002-08-01
卷期号:62 (15): 4469-77
被引量:48
摘要
Transcription of the gene coding for the tumor-associated antigen MN/carbonic anhydrase IX (CAIX) is regulated by hypoxia-inducible factor 1 (HIF-1). Previous studies identified CAIX expression in areas adjacent to hypoxic regions in solid tumors and suggested supplementary/alternative modes of regulation. To better understand the mechanisms activating CAIX expression, we characterized the cell density-dependent induction of CAIX in HeLa cells. This process is anchorage and serum independent and is not mediated by a soluble factor, decreased pH, or lowered glucose concentration. Stabilization of HIF-1 alpha was not observed in dense cultures. In contrast to sparse cell culture conditions, phosphatidylinositol 3'-kinase (PI3K) activity was significantly increased in dense HeLa cultures. The PI3K inhibitors LY294002 and wortmannin inhibited CAIX expression in dense cultures in a dose-dependent manner, specifically targeting the CA9 promoter (-173/+31 region) that was transactivated by constitutively active p110 PI3K subunit. The mechanism controlling CAIX expression in dense cultures is, however, dependent on lowered O(2) tension because stirring abrogates induction of CAIX expression. Hypoxia- and cell density-induced CAIX expressions were mediated by two seemingly independent mechanisms, as documented by the additive effect of increased cell density and treatment with the hypoxia-mimic CoCl(2) on levels of CAIX expression. The minimal cell density-dependent region within the CA9 promoter consists of the juxtaposed protected region 1 and hypoxia-response elements. However cell density-dependent CAIX expression was abrogated in the HIF-1 alpha-deficient Kal3.5 cells, suggesting an important role of HIF-1 in the corresponding mechanism. Thus, induction of CAIX in high-density cultures requires separate but interdependent pathways of PI3K activation and a minimal level of HIF-1 alpha. These interdependent pathways function at a lowered O(2) concentration that is, however, above that necessary for HIF-1 alpha stabilization.
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