Guo Hua, Zhang Hong-ying, Wang Shou-li, Ye Lü, Yang Guang-hua, Bu Hong
Department of Pathology, Peking University First Hospital, Beijing 100034, China.
Chin Med J (Engl). 2007 Mar 20;120(6):515-21.
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-activated 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.
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.
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 ERK2 and 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 overexpression of ERK2 and Smad4 had no indicative effects on histological subtypes, histological grading, gender, age, and prognosis.
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-β）在细胞正常生理过程的调节中起重要作用。TGF-β已被证明可调节多种上皮细胞中的几种丝裂原活化蛋白激酶（MAPK）途径。然而，TGF-β对软组织肉瘤的影响鲜有报道。我们之前的研究表明，除了Smads之外，应该还有其他一些信号转导途径，这些途径对调节人胚胎性横纹肌肉瘤（RMS）细胞的生长很重要。在本研究中，我们检测了细胞外信号调节激酶2（ERK2）和Smad4在人RMS组织及RMS细胞系RD中的表达及功能关系。
用TGF-β1处理RD细胞和正常人原代骨骼肌成肌细胞（Mb），通过RT-PCR和免疫荧光检测ERK2在mRNA和蛋白水平的表达谱。采用免疫组织化学法检测50例人RMS组织标本和23例正常骨骼肌标本中ERK2和Smad4的表达。标本随访6个月至70个月。
RD细胞和人RMS组织中ERK2和Smad4的表达在蛋白水平和mRNA水平均高于正常对照。而且，外源性TGF-β1刺激可导致ERK2表达升高及其核转位，因此TGF-β1也可激活MAPK（ERK2）途径，使ERK2持续激活至少2小时。然而，免疫组织化学分析显示ERK2和Smad4蛋白之间无相关性。ERK2和Smad4的过表达对组织学亚型、组织学分级、性别、年龄及预后均无指示作用。
在RMS中，TGF-β1从细胞表面到细胞核的信号传导除了TGF-β1/Smads途径外，还可通过MAPK（ERK2）途径进行。TGF-β1对ERK2的激活可能不依赖Smad4。此外，TGF-β1/Smads途径与参与肿瘤细胞发生、侵袭和转移的MAPK途径之间可能还存在其他复杂关系。
