Department of Medical Oncology, Center for Cancer Genome Discovery, Dana Farber Cancer Institute, Boston, MA 02115, USA.
Cancer Res. 2013 Aug 1;73(15):4840-51. doi: 10.1158/0008-5472.CAN-12-4089. Epub 2013 Jun 4.
Melanomas that contain B-RAF(V600E) mutations respond transiently to RAF and MEK inhibitors; however, resistance to these agents remains a formidable challenge. Although B- or C-RAF dysregulation represents prominent resistance mechanisms, resistance-associated point mutations in RAF oncoproteins are surprisingly rare. To gain insights herein, we conducted random mutagenesis screens to identify B- or C-RAF mutations that confer resistance to RAF inhibitors. Whereas bona fide B-RAF(V600E) resistance alleles were rarely observed, we identified multiple C-RAF mutations that produced biochemical and pharmacologic resistance. Potent C-RAF resistance alleles localized to a 14-3-3 consensus binding site or a separate site within the P loop. These mutations elicited paradoxical upregulation of RAF kinase activity in a dimerization-dependent manner following exposure to RAF inhibitors. Knowledge of resistance-associated C-RAF mutations may enhance biochemical understanding of RAF-dependent signaling, anticipate clinical resistance to novel RAF inhibitors, and guide the design of "next-generation" inhibitors for deployment in RAF- or RAS-driven malignancies.
含有 B-RAF(V600E)突变的黑色素瘤对 RAF 和 MEK 抑制剂有短暂的反应；然而，对这些药物的耐药性仍然是一个巨大的挑战。尽管 B 或 C-RAF 失调代表了突出的耐药机制，但 RAF 癌蛋白中的耐药相关点突变却出奇地罕见。为了深入了解这一点，我们进行了随机诱变筛选，以确定赋予 RAF 抑制剂耐药性的 B 或 C-RAF 突变。虽然很少观察到真正的 B-RAF(V600E)耐药等位基因，但我们发现了多种产生生化和药理耐药性的 C-RAF 突变。有效的 C-RAF 耐药等位基因定位于 14-3-3 共有结合位点或 P 环内的单独位点。这些突变在暴露于 RAF 抑制剂后以二聚化依赖性的方式引起 RAF 激酶活性的反常上调。对耐药相关 C-RAF 突变的了解可能会增强对 RAF 依赖性信号的生化理解，预测对新型 RAF 抑制剂的临床耐药性，并指导“下一代”抑制剂的设计，以用于 RAF 或 RAS 驱动的恶性肿瘤。
