HSP27: A modulator and therapeutic target of SPARC-induced glioma invasion.

描述（申请人提供）：胶质母细胞瘤（GBMs）是恶性程度最高的脑肿瘤。患者很少在最初诊断后存活超过一年，主要是由于这些肿瘤的高度浸润/侵袭性行为，以及它们对化疗的耐药性。提出的研究源于我们努力了解胶质瘤的侵袭特性，作为确定独特治疗靶点的方法。我们已经确定的靶点之一是分泌蛋白酸性和富含半胱氨酸（SPARC），这是一种分泌到细胞外基质中的基质细胞蛋白。我们已经证明SPARC在胶质瘤中高度表达，并且在体外和体内促进胶质瘤的侵袭。此外，我们发现SPARC通过激活p38 MAPK-MAPKAPK2-HSP27信号通路诱导迁移和侵袭。HSP27是小热休克蛋白的一员，其功能是调节肌动蛋白细胞骨架和迁移。我们已经证明，抑制HSP27可以抑制sparc诱导的PTEN-缺失胶质瘤细胞的形态、迁移和侵袭的变化。我们也证明了PTEN（一种在胶质母细胞瘤中经常丢失或突变的肿瘤抑制基因）的重新表达抑制了sparc诱导的体外迁移和体内侵袭。因此，我们认为PTEN缺失通过磷酸化HSP27使sparc诱导的迁移和入侵成为可能。为了验证这一假设，我们提出以下目标。特异性目的1：在细胞系和人体组织中，在PTEN缺失或存在的情况下，表征SPARC诱导的HSP27的激活。特异性目的2：用不同SPARC和PTEN状态的肿瘤细胞，确定单独抑制HSP27或联合放疗和/或化疗是否会降低肿瘤的体外存活。特异性目的3：利用不同PTEN状态的肿瘤细胞，确定单独抑制HSP27，或联合放疗和/或化疗，是否能降低sparc诱导的肿瘤细胞在体内的侵袭和存活，并提高动物存活率。我们认为，在常见的sparc阳性、pten缺失的GBMs中，抑制pHSP27对抑制胶质瘤细胞侵袭有显著影响，是胶质瘤患者的重要临床策略。

DESCRIPTION (provided by applicant): Glioblastomas (GBMs) are the most malignant brain tumors. Patients rarely survive more than a year after the initial diagnosis, primarily due to the highly infiltrative/invasive behavior of these tumors, and their resistance to chemotherapy. The proposed studies arise from our efforts to understand the invasive properties of gliomas as an approach to identify unique therapeutic targets. One of the targets we have identified is Secreted Protein Acidic and Rich in Cysteine (SPARC), which is a matricellular protein that is secreted into the extracellular matrix. We have demonstrated that SPARC is highly expressed in gliomas, and that it promotes glioma invasion in vitro and in vivo. Furthermore, we found that SPARC induces migration and invasion via the activation of p38 MAPK-MAPKAPK2-HSP27 signaling pathway. HSP27 is a member of the small heat shock proteins that function to modulate the actin cytoskeleton and migration. We have demonstrated that inhibition of HSP27 suppresses SPARC-induced changes in cell morphology, migration and invasion in vitro in PTEN- null glioma cells. We have also demonstrated that the re-expression of PTEN, a tumor suppressor gene commonly lost or mutated in glioblastomas, suppresses SPARC-induced migration in vitro and invasion in vivo. We therefore propose that PTEN loss enables SPARC-induced migration and invasion via phosphorylation of HSP27. To test this hypothesis we propose the following aims. SPECIFIC AIM 1: Characterize SPARC- induced activation of HSP27 in the absence or presence of PTEN in cell lines and human tissues. SPECIFIC AIM 2: Determine whether inhibition of HSP27 alone, or in combination with radiation and/or chemotherapy, reduces tumor survival in vitro using tumor cells with different SPARC and PTEN status. SPECIFIC AIM 3: Determine whether inhibition of HSP27 alone, or in combination with radiation and/or chemotherapy, reduces SPARC-induced tumor cell invasion and survival in vivo and increases animal survival, using tumor cells with different PTEN status. We propose that pHSP27 inhibition in the commonly occurring SPARC-positive, PTEN-deleted GBMs can have a significant impact on inhibiting glioma cell invasion and is an important clinical strategy for glioma patients.