头序木叶中三萜化学成分的研究

从头序木（ＡｒａｌｉａｄａｓｙｐｈｙｌａＭｉｑ）叶中分离到６个三萜化合物，用化学方法和波谱（ＵＶ，ＩＲ，ＭＳ，１ＨＮＭＲ，１３ＣＮＭＲ，１３ＣＤＥＰＴ，ＨＭＱＣ，ＨＭＢＣ）分析，确定其中４种化合物的结构，分别为齐墩果酸（Ｉ），１６β羟基１８βＨ齐墩果酸（Ｉ），齐墩果酸２８ＯβＤ吡喃葡萄糖甙（ＩＩ）和１６β羟基１８βＨ齐墩果酸２８ＯβＤ吡喃葡萄糖甙（ＩＶ）。用ＮＯＥＳＹ谱确定化合物Ｉ的立体构型。以上４个化合物均为首次从该植物中分离到，化合物ＩＶ为新化合物。     

Two transforming C-RAF germ-line mutations identified in patients with therapy-related acute myeloid leukemia

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.