Department of Radiation Oncology, University of California, San Francisco, 1600 Divisadero Street, Suite H-1031, San Francisco, CA, 94143-1708, USA.
Invest New Drugs. 2013 Oct;31(5):1136-41. doi: 10.1007/s10637-013-9928-9. Epub 2013 Jan 26.
A substantial proportion of solid tumors carry the BRAF V600E mutation, which causes activation of the MEK/MAPK pathway and is a poor prognostic indicator. Patients with locally advanced human cancers are often treated with external beam radiation therapy. Given the association of Raf overactivation with radioresistance, we hypothesized that, in BRAF V600E-mutated carcinomas, there would be combinatorial activity between radiation and PLX4720, a specific BRAF V600E-inhibitor.
Two BRAF V600E-mutated cancer cell lines and one BRAF-V600E wildtype (WT) cancer cell line were obtained. We performed cell viability assays and clonogenic assays using combinations of radiation and PLX4720. We assessed MEK and MAPK phosphorylation at different PLX4720 concentrations with western blotting, and cell cycle progression was evaluated by flow cytometry.
Our results show combinatorial, additive activity between radiation and PLX4720 in BRAF V600E-mutated cell lines, but not in the BRAF WT line. In BRAF V600E-mutated cells, there was a PLX4720 concentration-dependent decrease in MEK and MAPK phosphorylation. In cells with BRAF V600E mutations, PLX4720 caused cell cycle arrest at G1, and, when combined with radiation, caused a combined G1 and G2 cell cycle arrest; this pattern of cell cycle effects was not seen in the BRAF WT cell line.
These data suggest additive, combinatorial activity between radiation and PLX4720 in cancers carrying BRAF V600E mutations. Our data has potential for translation into the multimodality treatment of BRAF V600E-mutated cancers.
相当一部分实体瘤携带 BRAF V600E 突变，该突变导致 MEK/MAPK 通路的激活，是预后不良的指标。局部晚期人类癌症患者常采用外照射放疗进行治疗。鉴于 Raf 过度激活与放射抵抗有关，我们假设在 BRAF V600E 突变的癌中，辐射与 PLX4720 之间存在联合作用，PLX4720 是一种特定的 BRAF V600E 抑制剂。
我们获得了两个 BRAF V600E 突变的癌细胞系和一个 BRAF-V600E 野生型（WT）癌细胞系。我们使用辐射和 PLX4720 的组合进行细胞活力测定和集落形成测定。我们使用 Western 印迹法评估不同 PLX4720 浓度下的 MEK 和 MAPK 磷酸化，并通过流式细胞术评估细胞周期进程。
我们的结果表明，在 BRAF V600E 突变细胞系中，辐射与 PLX4720 之间存在联合、相加的作用，但在 BRAF WT 细胞系中没有。在 BRAF V600E 突变细胞中，随着 PLX4720 浓度的增加，MEK 和 MAPK 磷酸化逐渐减少。在具有 BRAF V600E 突变的细胞中，PLX4720 导致细胞周期停滞在 G1 期，当与辐射联合使用时，导致 G1 和 G2 期的细胞周期同时停滞；这种细胞周期效应模式在 BRAF WT 细胞系中未观察到。
这些数据表明，在携带 BRAF V600E 突变的癌症中，辐射与 PLX4720 之间存在相加、联合的作用。我们的数据有可能转化为 BRAF V600E 突变癌症的多模态治疗。
