Elevated CRAF as a potential mechanism of acquired resistance to BRAF inhibition in melanoma
Elevated CRAF as a potential mechanism of acquired resistance to BRAF inhibition in melanoma
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DOI：
10.1158/0008-5472.can-07-6787
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发表时间：
2008-06-15
期刊：
影响因子：
11.2
通讯作者：
Settleman, Jeffrey
中科院分区：
文献类型：
--
作者：
Montagut, Clara;Sharma, Sreenath V.;Settleman, Jeffrey
激活BRAF激酶突变在所有人类肿瘤中的发生率接近7%，临床前研究已经验证了RAF-促分裂原活化蛋白/细胞外信号调节激酶（ERK）激酶-ERK信号级联作为这种情况下潜在的重要治疗靶点。选择性RAF激酶抑制剂目前正在进行临床开发，根据其他激酶靶向治疗的经验，预计对这些药物的临床反应（如果观察到）将导致大多数情况下最终出现耐药性。因此，重要的是建立这种耐药性的分子机制，以开发有效的治疗策略来克服或预防耐药性。为了预测在治疗过程中对RAF抑制剂获得性耐药的潜在机制，我们从人黑素瘤衍生的细胞系中建立了耐药克隆，该细胞系具有复发性V600 E激活BRAF突变，其对选择性RAF激酶抑制剂AZ 628表现出极高的敏感性。我们确定CRAF蛋白水平升高是这些细胞获得AZ 628耐药性的原因，与肿瘤细胞从BRAF依赖性转换为CRAF依赖性相关。我们还发现，升高的CRAF蛋白水平可能类似地导致BRAF突变肿瘤细胞亚群对RAF抑制的原发性不敏感性。有趣的是，AZ 628耐药细胞表现出对HSP 90抑制剂格尔德霉素的敏感性。格尔德霉素有效地促进CRAF的降解，从而揭示了一种潜在的治疗策略，以克服对BRAF突变肿瘤亚组中RAF抑制的抗性。
Activating BRAF kinase mutations arise in similar to 7% of all human tumors, and preclinical studies have validated the RAF-mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase-ERK signaling cascade as a potentially important therapeutic target in this setting. Selective RAF kinase inhibitors are currently undergoing clinical development, and based on the experience with other kinase-targeted therapeutics, it is expected that clinical responses to these agents, if observed, will lead to the eventual emergence of drug resistance in most cases. Thus, it is important to establish molecular mechanisms underlying such resistance to develop effective therapeutic strategies to overcome or prevent drug resistance. To anticipate potential mechanisms of acquired resistance to RAF inhibitors during the course of treatment, we established drug-resistant clones from a human melanoma-derived cell line harboring the recurrent V600E activating BRAF mutation, which exhibits exquisite sensitivity to AZ628, a selective RAF kinase inhibitor. We determined that elevated CRAF protein levels account for the acquisition of resistance to AZ628 in these cells, associated with a switch from BRAF to CRAF dependency in tumor cells. We also found that elevated CRAF protein levels may similarly contribute to primary insensitivity to RAF inhibition in a subset of BRAF mutant tumor cells. Interestingly, AZ628-resistant cells demonstrating either primary drug insensitivity or acquired drug resistance exhibit exquisite sensitivity to the HSP90 inhibitor geldanamycin. Geldanamycin effectively promotes the degradation of CRAF, thereby revealing a potential therapeutic strategy to overcome resistance to RAF inhibition in a subset of BRAF mutant tumors.