Martinho O, Longatto-Filho A, Lambros M B K, Martins A, Pinheiro C, Silva A, Pardal F, Amorim J, Mackay A, Milanezi F, Tamber N, Fenwick K, Ashworth A, Reis-Filho J S, Lopes J M, Reis R M
Life and Health Sciences Research Institute, School of Health Sciences, University of Minho, 4710 Braga, Portugal.
Br J Cancer. 2009 Sep 15;101(6):973-82. doi: 10.1038/sj.bjc.6605225. Epub 2009 Aug 25.
Malignant gliomas are the most prevalent type of primary brain tumours but the therapeutic armamentarium for these tumours is limited. Platelet-derived growth factor (PDGF) signalling has been shown to be a key regulator of glioma development. Clinical trials evaluating the efficacy of anti-PDGFRA therapies on gliomas are ongoing. In this study, we intended to analyse the expression of PDGFA and its receptor PDGFRA, as well as the underlying genetic (mutations and amplification) mechanisms driving their expression in a large series of human gliomas.
PDGFA and PDGFRA expression was evaluated by immunohistochemistry in a series of 160 gliomas of distinct World Health Organization (WHO) malignancy grade. PDGFRA-activating gene mutations (exons 12, 18 and 23) were assessed in a subset of 86 cases by PCR-single-strand conformational polymorphism (PCR-SSCP), followed by direct sequencing. PDGFRA gene amplification analysis was performed in 57 cases by quantitative real-time PCR (QPCR) and further validated in a subset of cases by chromogenic in situ hybridisation (CISH) and microarray-based comparative genomic hybridisation (aCGH).
PDGFA and PDGFRA expression was found in 81.2% (130 out of 160) and 29.6% (48 out of 160) of gliomas, respectively. Its expression was significantly correlated with histological type of the tumours; however, no significant association between the expression of the ligand and its receptor was observed. The absence of PDGFA expression was significantly associated with the age of patients and with poor prognosis. Although PDGFRA gene-activating mutations were not found, PDGFRA gene amplification was observed in 21.1% (12 out of 57) of gliomas. No association was found between the presence of PDGFRA gene amplification and expression, excepting for grade II diffuse astrocytomas.
The concurrent expression of PDGFA and PDGFRA in different subtypes of gliomas, reinforce the recognised significance of this signalling pathway in gliomas. PDGFRA gene amplification rather than gene mutation may be the underlying genetic mechanism driving PDGFRA overexpression in a portion of gliomas. Taken together, our results could provide in the future a molecular basis for PDGFRA-targeted therapies in gliomas.
恶性胶质瘤是最常见的原发性脑肿瘤类型，但针对这些肿瘤的治疗手段有限。血小板衍生生长因子（PDGF）信号通路已被证明是胶质瘤发展的关键调节因子。评估抗PDGFRA疗法对胶质瘤疗效的临床试验正在进行。在本研究中，我们旨在分析PDGFA及其受体PDGFRA的表达，以及在一系列人类胶质瘤中驱动其表达的潜在遗传（突变和扩增）机制。
通过免疫组织化学评估160例不同世界卫生组织（WHO）恶性等级的胶质瘤中PDGFA和PDGFRA的表达。通过聚合酶链反应-单链构象多态性（PCR-SSCP）对86例患者的子集进行PDGFRA激活基因突变（外显子12、18和23）评估，随后进行直接测序。通过定量实时PCR（QPCR）对57例患者进行PDGFRA基因扩增分析，并通过显色原位杂交（CISH）和基于微阵列的比较基因组杂交（aCGH）在部分病例子集中进一步验证。
分别在81.2%（160例中的130例）和29.6%（160例中的48例）的胶质瘤中发现了PDGFA和PDGFRA的表达。其表达与肿瘤的组织学类型显著相关；然而，未观察到配体与其受体表达之间的显著关联。PDGFA表达缺失与患者年龄和预后不良显著相关。虽然未发现PDGFRA基因激活突变，但在21.1%（57例中的12例）的胶质瘤中观察到了PDGFRA基因扩增。除II级弥漫性星形细胞瘤外，未发现PDGFRA基因扩增与表达之间的关联。
PDGFA和PDGFRA在不同亚型胶质瘤中的同时表达，强化了该信号通路在胶质瘤中公认的重要性。PDGFRA基因扩增而非基因突变可能是部分胶质瘤中驱动PDGFRA过表达的潜在遗传机制。综上所述，我们的结果未来可为胶质瘤中针对PDGFRA的治疗提供分子基础。
