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

脑膜瘤的脑侵袭性生长是一个高度相关的临床问题，对复发率和总存活率有负面影响。关于驱动脑膜瘤侵袭的机制的知识还不是很清楚。小分子GTP酶RhoA、Rac-1和CDC42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在侵袭性脑膜瘤中起到作用，因为在一项研究中，在大约39%的脑膜瘤中发现了激活突变。此外，RAC-1和CDC42与已知在侵袭性/侵袭性脑膜瘤中被激活的PI3激酶结合。失去肿瘤抑制基因NF2/Merlin的神经鞘瘤细胞表现出RAC-1和CDC42活性增加。大约50%的散发性人类脑膜瘤的特征是NF2的改变，而脑膜中NF2的敲除会导致小鼠脑膜瘤的形成。最近的研究表明，Rho-GTPase信号通路的成员在脑膜瘤中的表达取决于NF2的状态。在这个项目中，我们旨在详细地确定RhoA、Rac-1和CDC42在调节脑膜瘤细胞侵袭和运动中的作用，与NF2/Merlin相关。我们将使用已建立的细胞培养模型，包括稳定敲除NF2/Merlin的同基因脑膜瘤细胞对，以及异种移植和遗传小鼠模型，以确定RhoA、RAC-1或CDC42是否与脑膜瘤细胞的运动和侵袭密切相关。Michel Kalamardes(Paris)以前建立的遗传性脑膜瘤模型是基于Cre介导的局部NF2基因敲除，并已在我们实验室使用。这些小鼠可以与三个GTP酶中的每一个小鼠杂交，从而深入了解它们对基于NF2基因敲除的脑膜瘤生长和脑侵袭的调控。为了确定GTPase信号调控的潜在治疗效果，我们将使用我们成熟的脑膜瘤异种移植小鼠模型来研究Rho激酶(ROCK)抑制剂法舒地尔。我们期望该项目的结果能显著提高对脑膜瘤细胞侵袭机制的理解，特别是与NF2/Merlin相关的机制。对特定抑制剂的临床前评估将为不符合手术或放射等传统治疗策略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.