RHABDOSARCOMA--DIFFERENTIATION AND THERAPY

在上一个融资期，我们已经证明：1） 横纹肌肉瘤（RMS）表达生肌调节因子MyoD。 然而，在通过表达 PAX/ALV，MyoD的功能减弱。 因此，MyoD表达 不能反式激活报告基因，不能将细胞阻滞在G1期 当过度表达时。 2)我们还表明，几个RMS细胞， 细胞系依赖于胰岛素样生长因子（Gfs）， 增殖 I型IGF受体（IGF-IR）的抑制抑制了 生长，增加G1期细胞的比例。 第三章 IGF-IR依赖性生长受到一个显性基因表达的抑制， p21 Ras阴性，但受体依赖性并不因致癌作用而消失。 K-RAS表达。 4)IGF-IR反义核酸的组成型表达 降低RMS细胞的致瘤性，并导致 高比例多核肌管样细胞。 5)增长 IGF-IR依赖性细胞系对抑制剂高度敏感。 诱导G1期阻滞的大环内酯类抗生素雷帕霉素的活性 和差异化。 基于这些发现，我们建议检验以下假设： 1. IGF-I受体介导的RMS细胞有丝分裂需要 信号转导通过p21 Ras，并通过一个独特的， 定义路径。 2. IGF-IR信号需要哺乳动物TOR（雷帕霉素靶标） 参与，并且mTOR代表潜在的治疗靶点 用于治疗横纹肌肉瘤。 3. IGF-IR信号激活了一种激酶， MyoD的DNA结合结构域中Thr 115的磷酸化导致 在RMS细胞中的衰减功能。 4.通过IGF-IR的信号传导保护细胞免受细胞毒性剂的侵害， 而雷帕霉素可能会逆转这种保护作用。 我们认为，拟议的研究将使人们了解新的 RMS的治疗方法，并具体确定 潜在的雷帕霉素类似物的临床试验进展。 研究将确定IGF-I受体信号传导是否保护RMS 细胞毒性剂，以及阻断这种作用对 化学增敏

In the previous period of funding we have demonstrated that 1) rhabdomycosarcomas (RMS) express the myogenic regulatory factor MyoD. However, in the context of cells transformed by the expression of PAX/ALV, the function of MyoD is attenuated. Thus, MyoD expression fails to transactivate reporter genes, and fails to arrest cells in G1 phase when overexpressed. 2) We have shown also that several RMS cell lines are dependent on insulin like growth factors (Gfs) for proliferation. Inhibition of the type I IGF receptor (IGF-IR) inhibits growth, increasing the proportion of cells in G1 phase. 3) IGF-IR-dependent growth is inhibited by expression of a dominant negative p21Ras, but receptor dependence is not abrogated by oncogenic K-RAS expression. 4) Constitutive expression of IGF-IR antisense reduces tumorigenicity of RMS cells, and leads to accumulation of a high proportion of multinucleate myotube-like cells. 5) Growth of IGF-IR-dependent cell lines is highly sensitive to the inhibitory activity of the macrolide antibiotic rapamycin which induces G1 arrest and differentiation. Based upon these findings we propose to test the following hypotheses: 1. That IGF-I receptor mediated mitogenesis in RMS cells requires both transduction of signal through p21Ras, and through a distinct yet to be defined pathway. 2. That IGF-IR signaling requires mammalian TOR (Target Of Rapamycin) participation, and that mTOR represents a potential therapeutic target for therapy of rhabdomyosarcomas. 3. That IGF-IR signaling activates a kinase responsible for phosphorylation of Thr115 in the DNA binding domain of MyoD resulting in attenuated function in RMS cells. 4. That signaling through IGF-IR protects cells from cytotoxic agents, and that rapamycin may reverse this protection. We consider that the proposed studies will allow insight into new approaches to treatment of RMS, and specifically determine the potenital for rapamycin analogues for advancement to clinical trials. Studies will determine whether IGF-I receptor signaling protects RMS cells from cytotoxic agents, and the impact of blocking this on chemosensitization.