The Role of PDGFR in Medulloblastoma Progression

髓母细胞瘤是儿童最常见的恶性脑肿瘤。探讨……的问题 为了有效的治疗，必须首先了解人类髓母细胞瘤的进展。我们假设 )小板源生长因子(PDGFR)介导的信号转导增强肿瘤细胞的反应 促进髓母细胞瘤的生长和转移，并表明：(1)PDGFR是 转移性髓母细胞瘤显著过表达，(Ii)髓母细胞瘤细胞PDGFR抑制物 活性降低下游信号转导靶点MAPK的磷酸化，改变基因表达，以及 减少细胞迁移和存活以及(Iii)对135个已知转移基因的电子分析 髓母细胞瘤微阵列基因表达的独立数据集，只有三个基因，包括 在分析的所有肿瘤中，至少有三分之一的肿瘤中有可检测到的mRNA表达。 转移性肿瘤在每个数据集中的显著过度表达。这些数据，结合初步的 数据显示，受体的α(PDGFRA)和β(PDGFRb)亚型均表达于 髓母细胞瘤和细胞的RNA和蛋白质水平，2)正常脑组织表达稀少，3) 在髓母细胞瘤细胞中以自分泌和旁分泌的方式激活，以及4)能够诱导 选择性抑制剂诱导髓母细胞瘤细胞凋亡的剂量依赖性研究 提示PDGFR在髓母细胞瘤中可能起重要作用的机制 成长和进步。因此，PDGFR是一种潜在的治疗干预新靶点。为了测试这一点 假设我们将使用人髓母细胞瘤细胞系。我们将(I)在体外进行全面的 研究确定PDGFR信号级联及其对生存、增殖、黏附、 迁移和侵袭，(Ii)确定PDGFR信号诱导的关键基因表达的变化 这些细胞通过可诱导的siRNA产生PDGFR表达缺陷的髓母细胞瘤细胞 每个PDGFR的特异性转染，并确定抑制的表达和活性的影响 体外存活、增殖和迁移以及体内生长和转移，以及(Iv)确定 磷酸化PDGFR蛋白在肺癌中的表达及其与转移和预后的关系 人髓母细胞瘤作为一种评估PDGFR抑制剂治疗该疾病的潜在临床效用的方法

Medulloblastoma is the most common malignant brain tumor in children. To approach the problem of effective therapy, the progression of human medulloblastoma must first be understood. We hypothesize that )latelet-derived growth factor (PDGFR)-mediated signal transduction enhances tumor cell responses that promote the growth and metastatic spread of medulloblastoma, and have shown that (i) PDGFR is significantly overexpressed by metastatic medulloblastomas, (ii)inhibitors of medulloblastoma cell PDGFR activity decrease phosphorylation of the downstream signaling target, MAPK, alter gene expression, and decrease cell migration and survival and (iii) in silico analysis of 135 known pro-metastatic genes within ndependent datasets of microarraygene expression of medulloblastomas, only three genes, including DDGFR, demonstrated detectable mRNA expression in at least one third of all tumors analyzed and significant overexpression by metastatic tumors in each dataset. These data, combined with the preliminary data showing that both alpha (PDGFRA) and beta (PDGFRB) subtypes of the receptor are 1) expressed on the RNA and protein level by medulloblastoma tumors and cells, 2) sparsely expressed by normal brain, 3) activated in an autocrine and paracrine fashion in medulloblastoma cells, and 4) capable of inducing apoptosis of medulloblastoma cells in a dose-dependent manner following treatment with a selective inhibitor of PDGFR tyrosine kinase activity, suggest a mechanism by which PDGFR may be vital for medulloblastoma growth and progression. Thus, PDGFR is a potential novel target for therapeutic intervention. To test this hypothesis we will employ human medulloblastoma cell lines. We will (i) conduct comprehensive in vitro studies to determine the PDGFR signaling cascade and its effects on survival, proliferation, adhesion, migration and invasion, (ii) determine the key gene expression changes induced by PDGFR signaling in these cells, (iii) develop medulloblastoma cells with deficient PDGFR expression by inducible siRNA transfection specific for each PDGFR and determine the effect of inhibited expression and activity on survival, proliferation and migration in vitro and growth and metastasis in vivo, and (iv) determine the expression pattern of phbsphorylated PDGFR protein and its correlation with metastasis and outcome in human medulloblastomas as a way to assessthe potential clinical utility of PDGFR inhibitors for this disease