Fritsche-Guenther Raphaela, Witzel Franziska, Kempa Stefan, Brummer Tilman, Sers Christine, Blüthgen Nils
Max-Delbrück-Center for Molecular Medicin (MDC) Berlin Buch, The Berlin Institute for Medical Systems Biology (BIMSB), 13125 Berlin, Germany.
Institute of Pathology, Molecular Tumor Pathology, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.
Oncotarget. 2016 Feb 16;7(7):7960-9. doi: 10.18632/oncotarget.6959.
Targeted therapies within the RAS/RAF/MEK/ERK signalling axis become increasingly popular, yet cross-talk and feedbacks in the signalling network lead to unexpected effects. Here we look systematically into how inhibiting RAF and MEK with clinically relevant inhibitors result in changes in PI3K/AKT activation. We measure the signalling response using a bead-based ELISA, and use a panel of three cell lines, and isogenic cell lines that express mutant forms of the oncogenes KRAS and BRAF to interrogate the effects of the MEK and RAF inhibitors on signalling. We find that treatment with the RAF inhibitors have opposing effects on AKT phosphorylation depending on the mutational status of two important oncogenes, KRAS and BRAF. If these two genes are in wildtype configuration, RAF inhibitors reduce AKT phosphorylation. In contrast, if BRAF or KRAS are mutant, RAF inhibitors will leave AKT phosphorylation unaffected or lead to an increase of AKT phosphorylation. Down-regulation of phospho-AKT by RAF inhibitors also extends to downstream transcription factors, and correlates with apoptosis induction. Our results show that oncogenes rewire signalling such that targeted therapies can have opposing effects on parallel pathways, which depend on the mutational status of the cell.
RAS/RAF/MEK/ERK信号轴内的靶向治疗越来越受欢迎，但信号网络中的相互作用和反馈会导致意想不到的效果。在这里，我们系统地研究了使用临床相关抑制剂抑制RAF和MEK如何导致PI3K/AKT激活的变化。我们使用基于珠子的ELISA测量信号反应，并使用一组三种细胞系以及表达致癌基因KRAS和BRAF突变形式的同基因细胞系来研究MEK和RAF抑制剂对信号传导的影响。我们发现，根据两个重要致癌基因KRAS和BRAF的突变状态，使用RAF抑制剂治疗对AKT磷酸化有相反的影响。如果这两个基因处于野生型构型，RAF抑制剂会降低AKT磷酸化。相反，如果BRAF或KRAS是突变型，RAF抑制剂将不会影响AKT磷酸化或导致AKT磷酸化增加。RAF抑制剂对磷酸化AKT的下调也延伸至下游转录因子，并与凋亡诱导相关。我们的结果表明，致癌基因会重新连接信号，使得靶向治疗可能对平行途径产生相反的影响，这取决于细胞的突变状态。
