Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Invest Ophthalmol Vis Sci. 2011 Sep 14;52(10):7248-55. doi: 10.1167/iovs.11-7398.
Inhibitors of B-Raf and MEK kinases hold promise for the management of cutaneous melanomas harboring BRAF mutations. BRAF mutations are rare in uveal melanomas (UMs), but somatic mutations in the G protein α subunits Gαq and Gα11 (encoded by GNAQ and GNA11, respectively) occur in a mutually exclusive pattern in ∼80% of UMs. The impact of B-Raf and MEK inhibitors on Gα-mutant UMs remains unknown.
The impact of the B-Raf inhibitor PLX4720, the MEK inhibitor AZD6244, and the Akt inhibitor MK2206 on UM cell lines was assessed with the use of cell viability, proliferation, and apoptosis assays and immunoblot analysis.
BRAF-mutant UM cells were sensitive to both PLX4720 and AZD6244, undergoing cell cycle arrest but not apoptosis. UM cells with a Gα-protein mutation (GNAQ or GNA11) were mildly sensitive to AZD6244 but completely resistant to PLX4720. In fact, PLX4720 paradoxically increased ERK phosphorylation in Gα-mutant UM cells. The combination of AZD6244 with PLX4720 had synergistic anticancer activity in BRAF-mutant cells but not in Gα-mutant cells. The Akt inhibitor MK2206 sensitized BRAF-mutant cells to both PLX4720 and AZD6244 and sensitized Gα-mutant cells to AZD6244 but did not overcome the resistance of the Gα-mutant cells to PLX4720.
The response of UM cells to inhibition of B-Raf, MEK, and Akt depends on their genotype. Future use of such targeted therapies in clinical trials of UM patients will require careful design and patient selection based on genotype to provide personalized and effective therapy.
B-Raf 和 MEK 激酶抑制剂有望用于治疗携带 BRAF 突变的皮肤黑色素瘤。BRAF 突变在葡萄膜黑色素瘤（UM）中罕见，但 G 蛋白α亚基 Gαq 和 Gα11（分别由 GNAQ 和 GNA11 编码）中的体细胞突变以相互排斥的模式发生在约 80%的 UM 中。B-Raf 和 MEK 抑制剂对 Gα 突变 UM 的影响尚不清楚。
使用细胞活力、增殖和凋亡测定和免疫印迹分析评估了 B-Raf 抑制剂 PLX4720、MEK 抑制剂 AZD6244 和 Akt 抑制剂 MK2206 对 UM 细胞系的影响。
BRAF 突变的 UM 细胞对 PLX4720 和 AZD6244 均敏感，发生细胞周期停滞而不是凋亡。具有 Gα-蛋白突变（GNAQ 或 GNA11）的 UM 细胞对 AZD6244 轻度敏感，但对 PLX4720 完全耐药。事实上，PLX4720 反常地增加了 Gα-突变 UM 细胞中 ERK 的磷酸化。AZD6244 与 PLX4720 的联合在 BRAF 突变细胞中具有协同抗癌活性，但在 Gα 突变细胞中没有。Akt 抑制剂 MK2206 使 BRAF 突变细胞对 PLX4720 和 AZD6244 敏感，并使 Gα 突变细胞对 AZD6244 敏感，但不能克服 Gα 突变细胞对 PLX4720 的耐药性。
UM 细胞对 B-Raf、MEK 和 Akt 抑制的反应取决于其基因型。在 UM 患者的临床试验中，未来对这些靶向治疗的使用将需要根据基因型进行精心设计和患者选择，以提供个性化和有效的治疗。
