Taniguchi M, Iwamoto T, Nakashima I, Nakayama A, Ohbayashi M, Matsuyama M, Takahashi M
Department of Pathology, Nagoya University School of Medicine, Japan.
Oncogene. 1992 Aug;7(8):1491-6.
We established a cell line (designated Mel-ret) from a melanocytic tumor developed in a metallothionein/ret transgenic mouse. Unlike primary melanocytic tumors, which did not show malignant features, when the Mel-ret cells were transplanted into nude mice they invaded into surrounding tissues and had metastatic ability. Although the Ret proteins were expressed at similar levels in the cell line and the primary tumors, the level of tyrosine phosphorylation in the Mel-ret cells was much higher than that in the primary tumors. In particular, an 85-kDa tyrosine-phosphorylated band was specifically detected in the Mel-ret cells. These results suggest that the increase in tyrosine phosphorylation may be responsible for malignant transformation of the Mel-ret cells. Immunofluorescence and cell fractionation studies showed that the Ret proteins and most of tyrosine-phosphorylated proteins in the Mel-ret cells localized in the membrane fraction. No activation of phosphatidyl-inositol-3 kinase (PI-3 kinase), a target protein for several tyrosine kinases, was detected in the Mel-ret cells.
我们从一只金属硫蛋白/Ret转基因小鼠身上发生的黑素细胞瘤中建立了一个细胞系（命名为Mel-ret）。与未表现出恶性特征的原发性黑素细胞瘤不同，当将Mel-ret细胞移植到裸鼠体内时，它们会侵入周围组织并具有转移能力。尽管Ret蛋白在细胞系和原发性肿瘤中的表达水平相似，但Mel-ret细胞中的酪氨酸磷酸化水平远高于原发性肿瘤。特别是，在Mel-ret细胞中特异性检测到一条85 kDa的酪氨酸磷酸化条带。这些结果表明酪氨酸磷酸化的增加可能是Mel-ret细胞恶性转化的原因。免疫荧光和细胞分级分离研究表明，Mel-ret细胞中的Ret蛋白和大多数酪氨酸磷酸化蛋白定位于膜部分。在Mel-ret细胞中未检测到几种酪氨酸激酶的靶蛋白磷脂酰肌醇-3激酶（PI-3激酶）的激活。
