Molecular mechanisms of meningioma invasion: Function and therapeutic relevance of small GTPases in relation to NF2/Merlin

脑膜瘤的脑浸润性生长是一个高度相关的临床问题，对复发率和总生存率有负面影响。关于脑膜瘤侵袭机制的知识还不太清楚。小GTP酶RhoA、RAC-1和cdc 42是调节肿瘤细胞运动和侵袭的重要分子。很少有数据表明RAC-1在侵袭性脑膜瘤中的作用，因为在一项研究中在约39%的脑膜瘤中发现了激活突变。此外，RAc-1和cdc 42与PI 3激酶结合，已知PI 3激酶在侵袭性脑膜瘤中被激活。肿瘤抑制因子NF 2/merlin缺失的神经鞘瘤细胞显示RAC-1和cdc 42的活性增加。大约50%的散发性人脑膜瘤的特征是NF 2的改变，并且脑膜敲低NF 2导致小鼠脑膜瘤形成。近年来有研究发现Rho-GT3信号通路的成员在脑膜瘤中的表达与NF 2的表达有关，本研究的目的是探讨RhoA、RAC-1和cdc 42在脑膜瘤细胞侵袭和运动中的作用。我们将使用已建立的细胞培养模型，包括稳定敲除NF 2/merlin的脑膜瘤细胞的同基因对，以及异种移植和遗传小鼠模型，以确定RhoA，RAC-1或cdc 42是否实质上参与脑膜瘤细胞的运动和侵袭。Michel Kalamarides（巴黎）先前建立的遗传性脑膜瘤模型是基于Cre介导的局部NF 2敲低，并已在我们的实验室中使用。这些小鼠可以与三种GTP酶中的每一种的floxed小鼠杂交，从而深入了解它们对基于NF 2敲除的脑膜瘤生长和脑侵袭的调节。为了建立GTdR信号操纵的潜在治疗影响，我们将使用我们完善的脑膜瘤异种移植小鼠模型研究Rho激酶（ROCK）抑制剂法舒地尔。我们期望从该项目的结果中，对脑膜瘤细胞侵袭的驱动机制的理解有显著的提高，特别是与NF 2/merlin相关的机制。特异性抑制剂的临床前评价将为不适合常规治疗策略（如手术或放疗）的脑膜瘤患者提供新的治疗选择。

Brain-invasive growth of meningioma comprises a highly-relevant clinical problem with negative effects on recurrency rates and overall survival. The knowledge regarding the mechanisms driving meningioma invasion are less-well characterized. The small GTPases RhoA, RAC-1, and cdc42 are important molecules for the regulation of tumor cell motility and -invasion. Few data suggest a role of RAC-1 in aggressive meningiomas, because activating mutations have been found in about 39% of meningiomas in one study. Furthermore, RAc-1 and cdc42 binds to PI3 kinase, which is known to be activated in aggressive/invasive meningiomas. Schwannoma cells with loss of the tumor suppressor NF2/merlin show increased activity of RAC-1 and cdc42. About 50 percent of sporadic human meningiomas are characterized by alterations of NF2, and meningeal knockdown of NF2 leads to meningioma formation in mice. It was recently reported that members of the Rho-GTPase signaling pathway are differentially expressed in meningiomas depending on the NF2 condition.In this project, we aim to define the role of RhoA, RAC-1, and cdc42 for the regulation of meningioma cell invasion and motility in relation the NF2/merlin in detail. We will use established cell culture models including syngenic pairs of meningioma cells with stable knockdown of NF2/merlin, as well as xenograft and genetic mouse models to define whether RhoA, RAC-1, or cdc42 are substantially involved in meningioma cell motility and invasion. The genetic meningioma model previously established by Michel Kalamarides (Paris) is based on Cre-mediated local NF2 knockdown and is already used in our laboratory. These mice can be crossed with floxed mice for each of the three GTPases, providing insight into their regulation of NF2-knockout based meningioma growth and brain invasion. To establish a potential therapeutic impact of GTPase signaling manipulation, we will study the Rho kinase (ROCK) inhibitor Fasudil using our well-established meningioma xenograft mouse model. We expect from the results of the project a significant improvement in the understanding of mechanisms driving meningioma cell invasion, especially in relation to NF2/merlin. The preclinical evaluation of specific inhibitors will bridge to new therapeutic options for meningioma patients not eligible for conventional treatment strategies like surgery or irradiation.