Role of phosphoinositide 3-kinase in the aggressive tumor growth of HT1080 human fibrosarcoma cells
Role of phosphoinositide 3-kinase in the aggressive tumor growth of HT1080 human fibrosarcoma cells
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DOI：
10.1128/mcb.21.17.5846-5856.2001
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发表时间：
2001-09-01
影响因子：
5.3
通讯作者：
Stanbridge, EJ
中科院分区：
文献类型：
--
作者：
Gupta, S;Stuffrein, S;Stanbridge, EJ
我们已经开发了一个人纤维肉瘤细胞系的模型系统，这些细胞系具有或不具有并表达N-ras的致癌突变等位基因。HT 1080细胞含有N-ras的内源性突变等位基因，而衍生的MCH 603细胞系仅含有野生型N-ras。在早期的研究中（S。Gupta等人，摩尔Cell. 20：9294-9306，2000），我们已经表明HT 1080细胞在无胸腺裸鼠中产生快速生长的侵袭性肿瘤，而MCH 603细胞产生生长更缓慢的肿瘤，并被称为弱致瘤性。Ras信号通路（Raf，Rac 1和RhoA）的广泛分析提供了一个潜在的新途径的证据，这是至关重要的侵略性肿瘤发生表型，可以激活水平升高的组成性活性MEK。在这项研究中，我们研究了磷酸肌醇3-激酶（PI 3-激酶）的作用，在HT 1080细胞中表达的转化和侵袭性肿瘤发生表型的调节。HT 1080（突变型N-ras）和MCH 603（野生型N-ras）两者具有相似水平的组成型活性Akt，Akt是活化的PI 3-激酶的下游靶标。我们发现，这两种细胞系组成型表达血小板衍生生长因子（PDGF）和PDGF受体。分别将抑癌基因PTEN cDNA转染HT 1080细胞和具有组成性活性的PI 3-激酶-CAAX cDNA转染MCH 603细胞，得到了一些有趣的新观察结果。PI 3-激酶/Akt通路（包括NF-κ B）的激活对于HT 1080细胞中的侵袭性致瘤表型不是必需的。NF-κ B的激活是复杂的：在MCH 603细胞中，它是由Akt介导的，而在HT 1080细胞中，激活还涉及由突变型Ras激活的其他途径。在MCH 603细胞中，在RhoA、Rac 1和Raf通路发生刺激性串扰之前，需要PI 3-激酶的活化的阈值水平，而没有相应的Ras活化。除了Raf和MEK比HT 1080水平更活跃之外，所观察到的增加的活化水平与在HT 1080细胞中观察到的那些相似。这种串扰导致转化为侵袭性致瘤表型。后一种观察结果与我们先前的观察结果一致，即过度刺激Ras信号传导途径的内源性成员的活性，特别是活化的MEK，是侵袭性致瘤生长的先决条件。
We have developed a model system of human fibrosarcoma cell lines that do or do not possess and express an oncogenic mutant allele of N-ras. HT1080 cells contain an endogenous mutant allele of N-ras, whereas the derivative MCH603 cell line contains only wild-type N-ras. In an earlier study (S. Gupta et al., Mol. Cell. Biol. 20:9294-9306, 2000), we had shown that HT1080 cells produce rapidly growing, aggressive tumors in athymic nude mice, whereas MCH603 cells produced more slowly growing tumors and was termed weakly tumorigenic. An extensive analysis of the Ras signaling pathways (Raf, Rac1, and RhoA) provided evidence for a potential novel pathway that was critical for the aggressive tumorigenic phenotype and could be activated by elevated levels of constitutively active MEK. In this study we examined the role of phosphoinositide 3-kinase (PI 3-kinase) in the regulation of the transformed and aggressive tumorigenic phenotypes expressed in HT1080 cells. Both HT1080 (mutant N-ras) and MCH603 (wild-type N-ras) have similar levels of constitutively active Akt, a downstream target of activated PI 3-kinase. We find that both cell lines constitutively express platelet-derived growth factor (PDGF) and PDGF receptors. Transfection with tumor suppressor PTEN cDNA into HT1080 and constitutively active PI 3-kinase-CAAX cDNA into MCH603 cells, respectively, resulted in several interesting and novel observations. Activation of the PI 3-kinase/Akt pathway, including NF-kappaB, is not required for the aggressive tumorigenic phenotype in HT1080 cells. Activation of NF-kappaB is complex: in MCH603 cells it is mediated by Akt, whereas in HT1080 cells activation also involves other pathway(s) that are activated by mutant Ras. A threshold level of activation of PI 3-kinase is required in MCH603 cells before stimulatory cross talk to the RhoA, Rac1, and Raf pathways occurs, without a corresponding activation of Ras. The increased levels of activation seen were similar to those observed in HT1080 cells, except for Raf and MEK, which were more active than HT1080 levels. This cross talk results in conversion to the aggressive tumorigenic phenotype. This latter observation is consistent with our previous observation that overstimulation of the activity of endogenous members of Ras signaling pathways, activated MEK in particular, is a prerequisite for aggressive tumorigenic growth.