Smad4 and ERK2 stimulated by transforming growth factor beta1 in rhabdomyosarcoma

　　人类横纹肌中Smad4 and ERK2 转化生长因子

　　Background Transforming growth factor beta (TGF-beta) plays an essential role in the regulation of normal physiologic processes of cells. TGF-beta has been shown to regulate several mitogen-a ctivated protein kinases (MAPK) pathways in several epithelial cells. However, the effects of TGF-beta on soft tissue sarcoma are seldom reported. Our previous studies suggested that there should be some other signal transduction pathways besides Smads, which are important to regulate the growth of human embryonal rhabdomyosarcoma (RMS) cells.

　　In the present study, we examined the expression and functional relations of extracellular signal-regulated kinase 2 (ERK2) and Smad4 in human RMS tissue and a RMS cell line, RD.Methods RD cells and normal human primary skeletal myoblasts (Mb) were treated with TGF-beta1 to establish the expression profile of ERK2 at the mRNA and protein levels detected by RT-PCR and immunofluorescence.Immunohistochemistry was used to detect the expression of ERK2 and Smad4 in 50 tissue specimens of human RMS and 23 specimens of normal skeletal muscles.

　　Follow-up of specimens was performed 6 months to 70 months later.Results RD cells and human RMS tissues showed the higher expression of ERK2 and Smad4 than the normal control,either the protein level or the mRNA level. And, exogenous TGF-beta1 stimulation can lead to higher expression of ERK2and its nuclear translocation, so TGF-beta1 can also activated MAPK (ERK2) pathway, resulting in a sustained activation of ERK2 for at least 2 hours. Immunohistochemistry analysis, however, showed that there was no correlation between ERK2 and Smad4 protein. The over expression of ERK2 and Smad4 had no indicative effects on histological subtypes,histological grading, gender, age, and prognosis.Conclusions In RMS, signaling of TGF-beta1 from cell surface to nucleus can also be directed through the MAPK (ERK2) pathway besides the TGF-beta1/Smads pathway. The activation of ERK2 by TGF-beta1 may be Smad4 independent. Moreover, there may be some other tanglesome relationships between the TGF-beta1/Smads pathway and the MAPK pathway which takes part in the development, invasion and metastasis of tumor cells.

　　转化生长因子β(TGF-beta)在正常细胞生长过程起到极其重要的作用。TGF-beta 控制一些丝裂原-上皮细胞的丝裂原活化蛋白激酶(mitogen-activated protein kinase, MAPK)通径。然而，TGF-beta 对于软组织肉瘤影响罕见。以前的研究显示其他的信号转导途径包括Smads在内，对人调节人类胚胎横纹肌肉瘤(RMS)细胞 起重要作用。目前研究中，我们在人体 RMS 组织和 RMS 的细胞水平检查细胞外信号调节激酶 (ERK2) and Smad4表达和功能关系。TGF-beta1治疗横纹肌肉瘤RD细胞和人类胚胎来源成肌细胞 Mb ，使其ERK2的表达，然后在人类信使RNA和蛋白质水平上 用反转录酶-聚合酶链锁反应及免疫荧光检测。免疫组织化学法用于检查人类50种组织标本和23种正常骨骼肌的标本中ERK2 and Smad4的表达。观察标本6个月到70个月后。RD细胞和人类RMS组织中ERK2和Smad4表达比正常细胞旺盛，不管是蛋白质还是信使RNA。并且，外源性TGF-beta1刺激导致ERK2表达更旺盛及核运转，所以TGF-beta1 能激活MAPK(ERK2)通路，导致ERK2处于至少2个小时激活状态。然而，免疫组织化学分析，ERK2 and Smad4 没有任何的联系。 ERK2 and Smad4过度表达对组织学亚型，组织学级别，性别，年龄及预后没有确切的影响。结论：在RMS，从细胞表面到细胞核的TGF-beta1信号也可以直接通过MAPK通路(ERK2)除了TGF-beta1 / Smads途径。TGF-beta1可以单独激活ERK2或Smad4 。此外，TGF-beta1 / Smads途径之间可能会有一些其他的复杂的关系和MAPK通路，这些关系和通路参与肿瘤的发生，浸润及转移。