Zebisch Armin, Staber Philipp B, Delavar Ali, Bodner Claudia, Hiden Karin, Fischereder Katja, Janakiraman Manickam, Linkesch Werner, Auner Holger W, Emberger Werner, Windpassinger Christian, Schimek Michael G, Hoefler Gerald, Troppmair Jakob, Sill Heinz
Division of Hematology, Medical University of Graz, Auenbruggerplatz 38, A-8036 Graz, Austria.
Cancer Res. 2006 Apr 1;66(7):3401-8. doi: 10.1158/0008-5472.CAN-05-0115.
Mutations leading to activation of the RAF-mitogen-activated protein kinase/extracellular signal-regulated (ERK) kinase (MEK)-ERK pathway are key events in the pathogenesis of human malignancies. In a screen of 82 acute myeloid leukemia (AML) samples, 45 (55%) showed activated ERK and thus were further analyzed for mutations in B-RAF and C-RAF. Two C-RAF germ-line mutations, S427G and I448V, were identified in patients with therapy-related AML in the absence of alterations in RAS and FLT3. Both exchanges were located within the kinase domain of C-RAF. In vitro and in vivo kinase assays revealed significantly increased activity for (S427G)C-RAF but not for (I448V)C-RAF. The involvement of the S427G C-RAF mutation in constitutive activation of ERK was further confirmed through demonstration of activating phosphorylations on C-RAF, MEK, and ERK in neoplastic cells, but not in nonneoplastic cells. Transformation and survival assays showed oncogenic and antiapoptotic properties for both mutations. Screening healthy individuals revealed a <1/400 frequency of these mutations and, in the case of I448V, inheritance was observed over three generations with another mutation carrier suffering from cancer. Taken together, these data are the first to relate C-RAF mutations to human malignancies. As both mutations are of germ-line origin, they might constitute a novel tumor-predisposing factor.
导致RAF-丝裂原活化蛋白激酶/细胞外信号调节激酶（MEK）-ERK通路激活的突变是人类恶性肿瘤发病机制中的关键事件。在对82例急性髓系白血病（AML）样本的筛查中，45例（55%）显示ERK激活，因此进一步分析B-RAF和C-RAF中的突变。在治疗相关AML患者中鉴定出两个C-RAF种系突变，S427G和I448V，且RAS和FLT3无改变。两种交换均位于C-RAF的激酶结构域内。体外和体内激酶分析显示，（S427G）C-RAF的活性显著增加，而（I448V）C-RAF则不然。通过在肿瘤细胞而非非肿瘤细胞中证实C-RAF、MEK和ERK上的激活磷酸化，进一步证实了S427G C-RAF突变参与ERK的组成性激活。转化和存活分析显示两种突变均具有致癌和抗凋亡特性。对健康个体的筛查显示这些突变的频率<1/400，对于I448V，观察到三代遗传，另一名突变携带者患有癌症。综上所述，这些数据首次将C-RAF突变与人类恶性肿瘤联系起来。由于两种突变均起源于种系，它们可能构成一种新的肿瘤易感因素。
