Oxidative stress plays a critical role in inactivating mutant BRAF by geldanamycin derivatives.
Oxidative stress plays a critical role in inactivating mutant BRAF by geldanamycin derivatives.
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DOI：
10.1158/0008-5472.can-07-6602
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发表时间：
2008-08-01
期刊：
影响因子：
11.2
通讯作者：
Horikoshi N
中科院分区：
文献类型：
--
作者：
Fukuyo Y;Inoue M;Nakajima T;Higashikubo R;Horikoshi NT;Hunt C;Usheva A;Freeman ML;Horikoshi N
格尔德霉素衍生物17-烯丙基氨基-17-去甲氧基格尔德霉素（17-AAG）和17-二甲氨基乙氨基-17-去甲氧基格尔德霉素（17-DMAG）是抑制热休克蛋白90（HSP 90）功能的有希望的化疗药物。已有研究表明17-AAG/DMAG处理诱导突变型BRAF（V600 E）降解并抑制MAP/ERK 1/2（MEK 1/2）的活化。然而，我们已经发现，在某些细胞中，单独抑制HSP 90不足以有效降解BRAF（V600 E）。结构上与格尔德霉素、根赤霉素和新生霉素无关的HSP 90抑制剂，虽然诱导HSP 90客户蛋白RAF-1的降解，但不能诱导BRAF（V600 E）降解或抑制HT 29人结肠癌细胞中的MEK 1/2活化。此外，在用17-DMAG处理后，残留的未降解的BRAF（V600 E）的激酶活性也丧失。用活性氧（ROS）清除剂N-乙酰半胱氨酸（NAC）孵育细胞，部分恢复了激酶活性，也部分防止了17-DMAG处理引起的BRAF（V600 E）降解。相反，用产生ROS的药物甲萘醌治疗明显抑制MEK 1/2并减少BRAF（V600 E）。这些结果表明，除了直接抑制HSP 90外，格尔德霉素及其衍生物的抗肿瘤作用还通过产生ROS介导，ROS可直接抑制致瘤突变体BRAF（V600 E）。
The geldanamycin derivatives 17-allylamino-17-demethoxygeldanamycin (17-AAG) and 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) are promising chemotherapeutic drugs that inhibit heat shock protein 90 (HSP90) function. Previous studies have shown that 17-AAG/DMAG treatment induces the degradation of mutant BRAF (V600E) and inhibits the activation of MAP/ERK1/2 (MEK1/2). We have found, however, that HSP90 inhibition alone is not sufficient for efficient BRAF(V600E) degradation in some cells. HSP90 inhibitors structurally unrelated to geldanamycin, radicicol and novobiocin, while inducing the degradation of the HSP90 client protein RAF-1 fail to induce BRAF(V600E) degradation or inhibit MEK1/2 activation in HT29 human colon cancer cells ‥ Moreover, after treatment with 17-DMAG, the kinase activity of residual, un-degraded BRAF(V600E) was also lost. Incubation of cells with a reactive oxygen species (ROS) scavenger, N-acetyl cysteine (NAC), partially restored kinase activity and also partially prevented BRAF(V600E) degradation due to 17-DMAG treatment. Conversely, treatment with the ROS producing drug menadione clearly inhibited MEK1/2 and reduced BRAF(V600E). These results suggest that in addition to direct inhibition of HSP90, the anti-tumor effect of geldanamycin and its derivatives is also mediated though the production of ROS which may directly inactivate tumorigenic mutant BRAF(V600E).