Elucidating the role of Perilipin-2-mediated lipid droplet formation in supporting glioblastoma pathogenesis

胶质母细胞瘤是成人恶性脑肿瘤中最常见和最具侵袭性的形式，需要新的和更有效的治疗方法。胶质母细胞瘤的微环境以高水平的氧化应激为特征，氧化应激对肿瘤细胞施加选择性压力，形成适应这些不利条件的机制。最终，这可能导致选择更具侵袭性的肿瘤亚克隆，这些肿瘤亚克隆对放射/化疗具有抗性，其作用机制依赖于氧化应激的诱导。因此，了解胶质母细胞瘤细胞对氧化应激的分子适应可能潜在地揭示出可靶向治疗的脆弱性。最近有研究表明，脂质代谢的一个方面——脂滴的形成，在包括胶质母细胞瘤在内的许多癌症中起着促肿瘤的作用。然而，没有描述此功能背后的机制。值得注意的是，我们发现已建立的人类胶质母细胞瘤细胞系含有高水平的脂滴。同时，我们观察到编码必需脂滴外壳蛋白的基因Perilipin-2 （PLIN2）在多个胶质瘤和胶质母细胞瘤患者的肿瘤组织中与正常脑组织相比显著上调。更重要的是，对这些公共数据库的初步分析显示，在胶质母细胞瘤患者中，PLIN2的高水平表达与较差的总生存率相关，这表明PLIN2是不良预后的临床相关因素。我们的初步研究结果还表明，PLIN2可能在肿瘤细胞对氧化应激的适应中发挥作用，因为外源性氧化应激处理这些细胞增加了PLIN2的表达和脂滴的数量，而敲低PLIN2的表达使细胞对这种处理敏感。在此，我们拟详细研究plin2介导的脂滴在GBM中的生物学功能及临床意义。首先，我们将确定plin2介导的脂滴如何在体外支持胶质母细胞瘤的致瘤性，并阐明它们保护胶质母细胞瘤细胞免受氧化应激的精确分子机制。其次，我们将描述控制胶质母细胞瘤细胞中PLIN2转录调控的分子途径。第三，我们将通过评估大型胶质母细胞瘤患者前瞻性队列中PLIN2表达与临床参数的潜在关联，以及根据肿瘤内区域异质性分析脂滴的临床相关性，进一步探讨PLIN2的临床相关性。总的来说，该项目有望显著促进我们对脂滴在胶质母细胞瘤致病性中的作用的理解，并可能潜在地导致发现PLIN2作为一个有希望的治疗靶点。

Glioblastoma is the most common and aggressive form of malignant brain tumor in adults, for which novel and more efficient therapies are warranted. The microenvironment of glioblastoma is characterized by high levels oxidative stress, which exerts a selective pressure on tumor cells to form adaptive mechanisms to these adverse conditions. Ultimately, this may result in the selection of more aggressive tumor subclones that are resistant to radio/chemotherapy, whose mechanisms of action rely on the induction of oxidative stress. Thus, understanding the molecular adaptations of glioblastoma cells to oxidative stress could potentially reveal vulnerabilities that can be targeted therapeutically. It has recently been described that one aspect of lipid metabolism- the formation of lipid droplets, serves a pro-tumorigenic function in many cancers including glioblastoma. However, the mechanisms underlying this function are not described. Notably, we discovered that established human glioblastoma cell lines contained high levels of lipid droplets. In parallel, we observed that the gene encoding an essential lipid droplet coat protein, Perilipin-2 (PLIN2) was significantly upregulated in tumor tissue from multiple cohorts of glioma and glioblastoma patients, as compared to normal brain tissue. More significantly, preliminary analyses of these public databases revealed that high levels of PLIN2 expression was correlated with poorer overall survival in glioblastoma patients, suggesting that PLIN2 was a clinically relevant factor for poor prognosis. Our preliminary findings also showed that PLIN2 might play a role in the adaptation of tumor cells to oxidative stress, since treatment of these cells with exogenous oxidative stress increased both PLIN2 expression and number of lipid droplets, while knockdown of PLIN2 expression sensitized cells to such treatment. Here, we propose to study in detail the biological function and clinical relevance of PLIN2-mediated lipid droplets in GBM. First, we will determine how PLIN2-mediated lipid droplets support glioblastoma tumorigenicity in vitro, and elucidate the precise molecular mechanisms by which they protect glioblastoma cells against oxidative stress. Second, we will delineate the molecular pathways that govern the transcriptional regulation of PLIN2 in glioblastoma cells. Third, we will further explore the clinical relevance of PLIN2 by assessing the potential association between its expression and clinical parameters of large prospective cohorts of glioblastoma patients, as well as the clinical relevance of lipid droplets according to intra-tumor regional heterogeneity. Overall, the proposed project is expected to significantly contribute to our understanding of the role of lipid droplets in the pathogenicity of glioblastoma, and may potentially lead to the uncovering of PLIN2 as a promising therapeutic target.