Pozo-Guisado Eulalia, Lorenzo-Benayas M Jesús, Fernández-Salguero Pedro M
Facultad de Ciencias, Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz, Spain.
Int J Cancer. 2004 Mar 20;109(2):167-73. doi: 10.1002/ijc.11720.
Resveratrol (RES), a natural phytoalexin, has antiproliferative activity in human-derived cancer cells and in rodent models of tumor development. We have previously shown that RES induced apoptotic death in estrogen-responsive MCF-7 human breast cancer cells. Recent data have indicated that the estrogen receptor-alpha (ERalpha), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, nonnuclear function of the ERalpha potentially relevant in cell proliferation and apoptosis. In our study, using MCF-7, we have analyzed the ability of RES to modulate the ERalpha-dependent PI3K pathway. Immunoprecipitation and kinase activity assays showed that RES increased the ERalpha-associated PI3K activity with a maximum stimulatory effect at concentrations close to 10 microM; concentrations >50 microM decreased PI3K activity. Stimulation of PI3K activity by RES was ERalpha-dependent since it could be blocked by the antiestrogen ICI 182,780. RES did not affect p85 protein expression but induced the proteasome-dependent degradation of the ERalpha. Nevertheless, the amount of PI3K immunoprecipitated by the ERalpha remained unchanged in presence of RES, indicating that ERalpha availability was not limiting PI3K activity. Phosphoprotein kinase B (pPKB/AKT) followed the pattern of PI3K activity, whereas RES did not affect total PKB/AKT expression. PKB/AKT downstream target glycogen synthase kinase 3 (GSK3) also showed a phosphorylation pattern that followed PI3K activity. We propose a mechanism through which RES could inhibit survival and proliferation of estrogen-responsive cells by interfering with an ERalpha-associated PI3K pathway, following a process that could be independent of the nuclear functions of the ERalpha.
白藜芦醇（RES）是一种天然植保素，在人源癌细胞和肿瘤发生的啮齿动物模型中具有抗增殖活性。我们之前已经表明，RES可诱导雌激素反应性MCF-7人乳腺癌细胞发生凋亡性死亡。最近的数据表明，雌激素受体α（ERα）通过与p85相互作用来调节磷酸肌醇3激酶（PI3K）的活性，揭示了ERα在细胞增殖和凋亡中可能相关的一种生理、非核功能。在我们的研究中，使用MCF-7细胞，我们分析了RES调节ERα依赖性PI3K途径的能力。免疫沉淀和激酶活性测定表明，RES增加了与ERα相关的PI3K活性，在浓度接近10微摩尔时具有最大刺激作用；浓度>50微摩尔时降低PI3K活性。RES对PI3K活性的刺激是ERα依赖性的，因为它可被抗雌激素ICI 182,780阻断。RES不影响p85蛋白表达，但诱导了ERα的蛋白酶体依赖性降解。然而，在RES存在的情况下，由ERα免疫沉淀的PI3K量保持不变，表明ERα的可用性不是PI3K活性的限制因素。磷酸化蛋白激酶B（pPKB/AKT）遵循PI3K活性模式，而RES不影响总PKB/AKT表达。PKB/AKT的下游靶点糖原合酶激酶3（GSK3）也显示出一种遵循PI3K活性的磷酸化模式。我们提出了一种机制，通过该机制RES可以通过干扰与ERα相关的PI3K途径来抑制雌激素反应性细胞的存活和增殖，该过程可能独立于ERα的核功能。
