REGULATORY PATHWAYS IN THE DIFFERENTIATION OF HUMAN RHABDOSARCOMA IN VITRO

我们以前已经发现，5-氮胞苷(5-azacytidine，5-aza)诱导和 转化生长因子-b抑制人成纤维细胞分化 横纹肌肉瘤(RMS)细胞体外培养。5-AZA的作用是相关的 随着肌肉决定基因表达水平的增加 Myo(D1)。然而，Myo(D1)基因的表达发生了显著变化 加入1 ng/ml(4×10(-11)M)后，未观察到转化生长因子-β。 尽管在最近的一项研究中发现Myo(D1)的表达被抑制 转化生长因子-β1，这是在100倍的药物浓度下实现的， 并在5-aza处理的成肌细胞中得到证实。 多潜能细胞系，而不是RMS。在其他研究中，发现 4×10~(-10)M的转化生长因子-β阻断功能性 抑制分化心肌细胞内钙离子通道的表达 二氢吡啶受体(DHPR)基因，即骨骼肌 具体的。Myo(D1)基因的表达不受影响。 我们已经获得了DHPR的cDNA，我们将研究DHPR的变化 该基因和Myo(D1)在5株人横纹肌肉瘤细胞系中的表达 用不同浓度的转化生长因子-β处理。尽管目前还不知道 DHP敏感的钙通道是生肌过程中的必要事件 分化，细胞外钙是肌肉发育所必需的。 DHPR基因可能可检测到的变化与 转化生长因子-β和Myo(D1)基因的表达将提示钙离子 通道可能是控制细胞内机制的一部分 肌肉发生。

We have found previously that 5-Azacytidine (5-AZA) induces and Transforming Growth Factor (TGF)-b inhibits differentiation of human rhabdomyosarcoma (RMS) cells in vitro. The effect of 5-AZA was associated with increased levels of expression of the muscle determination gene Myo(D1). However, remarkable changes in the expression of the Myo(D1) gene after addition of 1 ng/ml (4 x 10(-11) M) TGF-b were not observed. Although in a recent study Myo(D1) expression has been found repressed by TGF-b1, this was achieved at a 100-fold higher concentration of the agent, and was demonstrated in myoblasts derived from a 5-AZA treated pluripotential cell line and not RMS. In other studies, it was found that TGF-b at a concentration of 4xlO(-10) M blocks the appearance of functional slow Ca2+ channels in differentiated myocytes by inhibiting the expression of the dihydropyridine receptor (DHPR) gene, which is skeletal muscle specific. The expression of Myo(D1) gene was not influenced. We have obtained the DHPR cDNA and we will investigate changes of the expression of this gene, and Myo(D1) in 5 human rhabdomyosarcoma cell lines treated with various concentrations of TGF-b. Although it is not known if the DHP-sensitive Ca2+ channels are necessary events in the myogenic differentiation, extracellular Ca2+ is necessary for muscle development. Possible detectable changes of the DHPR gene in relation to the action of TGF-B and the expression of the Myo(D1) gene will suggest that Ca2+ channels may be part of the intracellular mechanisms that control myogenesis.