MEK1 mutations confer resistance to MEK and B-RAF inhibition
MEK1 mutations confer resistance to MEK and B-RAF inhibition
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DOI：
10.1073/pnas.0905833106
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发表时间：
2009-12-01
影响因子：
11.1
通讯作者：
Garraway, Levi A.
中科院分区：
文献类型：
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作者：
Emery, Caroline M.;Vijayendran, Krishna G.;Garraway, Levi A.
激活丝裂原活化蛋白激酶（MAP激酶）通路的基因改变在癌症中普遍存在。例如，大多数黑色素瘤在BRAF癌基因中存在突变，据推测这会使其对药物性MAP激酶抑制（例如RAF或MEK抑制剂）的敏感性增强。我们通过对体外MEK1随机诱变筛选产生的耐药克隆以及用变构MEK抑制剂AZD6244治疗后复发患者的肿瘤进行大规模平行测序，研究了黑色素瘤中MEK依赖性的临床相关性。大多数在体外导致对MEK抑制产生耐药性的突变位于变构药物结合口袋或α-螺旋C，并且对变构MEK抑制表现出很强的（约100倍）耐药性。其他突变影响位于N末端负调控螺旋（螺旋A）内或与其相邻的MEK1密码子，这些密码子在心脏 - 面部 - 皮肤（CFC）综合征中也会发生功能性获得的种系突变。在一名接受AZD6244治疗的黑色素瘤患者出现的耐药转移灶中鉴定出一种这样的突变，即MEK1(P124L)。MEK1(P124L)和破坏螺旋A的MEK1(Q56P)都对选择性B - RAF抑制剂PLX4720产生交叉耐药性。然而，将BRAF突变的黑色素瘤细胞同时暴露于AZD6244和PLX4720可防止耐药克隆的出现。这些结果证实了MEK依赖性在BRAF突变黑色素瘤中的重要性，并提出了对MEK和B - RAF抑制剂耐药的新机制，这可能具有重要的临床意义。
Genetic alterations that activate the mitogen-activated protein kinase (MAP kinase) pathway occur commonly in cancer. For example, the majority of melanomas harbor mutations in the BRAF oncogene, which are predicted to confer enhanced sensitivity to pharmacologic MAP kinase inhibition (e. g., RAF or MEK inhibitors). We investigated the clinical relevance of MEK dependency in melanoma by massively parallel sequencing of resistant clones generated from a MEK1 random mutagenesis screen in vitro, as well as tumors obtained from relapsed patients following treatment with AZD6244, an allosteric MEK inhibitor. Most mutations conferring resistance to MEK inhibition in vitro populated the allosteric drug binding pocket or alpha-helix C and showed robust (approximate to 100-fold) resistance to allosteric MEK inhibition. Other mutations affected MEK1 codons located within or abutting the N-terminal negative regulatory helix (helix A), which also undergo gain-of-function germline mutations in cardio-facio-cutaneous (CFC) syndrome. One such mutation, MEK1(P124L), was identified in a resistant metastatic focus that emerged in a melanoma patient treated with AZD6244. Both MEK1(P124L) and MEK1(Q56P), which disrupts helix A, conferred cross-resistance to PLX4720, a selective B-RAF inhibitor. However, exposing BRAF-mutant melanoma cells to AZD6244 and PLX4720 in combination prevented emergence of resistant clones. These results affirm the importance of MEK dependency in BRAF-mutant melanoma and suggest novel mechanisms of resistance to MEK and B-RAF inhibitors that may have important clinical implications.