Perrone Federica, Tabano Silvia, Colombo Federica, Dagrada Gianpaolo, Birindelli Sarah, Gronchi Alessandro, Colecchia Maurizio, Pierotti Marco A, Pilotti Silvana
Unit of Experimental Molecular Pathology, Department of Pathology, Istituto Nazionale per lo Studio e la Cura dei Tumori di Milano, Via G. Venezian 1, 20133 Milan, Italy.
Clin Cancer Res. 2003 Sep 15;9(11):4132-8.
Malignant peripheral nerve sheath tumor (MPNST) can arise sporadically or in association with neurofibromatosis type 1. Deletions at the 9p21 locus have been reported in these tumors. To additionally characterize the status of this chromosomal region, in this study we performed a comprehensive, mostly PCR-based molecular analysis of the three tumor suppressor genes p15(INK4b), p14(ARF) and p16(INK4a) located at the 9p21 locus in 26 cryopreserved MPNSTs.
Fourteen neurofibromatosis type 1-related and 12 sporadic cases were investigated for homozygous deletion coupled with fluorescent in situ hybridization, promoter methylation, and mutational analysis, as well as m-RNA expression.
The results showed that an inactivation of one or more genes occurred in 77% of MPNSTs and was mainly achieved through homozygous deletion (46%), which, in turn, encompassed all of the three tandemly linked genes in 83% of the deleted cases. Promoter methylation was at a less extent involved in gene silencing (18%), and no mutations were found. Loss of function at DNA level strongly correlated with loss of mRNA expression accounting for 80% of the cases. Because of the close relationship between p14(ARF) and TP53 and between p15(INK4b)/p16(INK4a) and Rb, these results support a model of a coinactivation of TP53 and Rb pathways in 75% of MPNSTs, with functional consequences on cell growth control and apoptosis.
The inactivation of the 9p21 locus is a frequent and peculiar hallmark of MPNST genetic profile leading also to an impaired apoptosis that could be taken into account in treatment planning of these tumors.
恶性外周神经鞘瘤（MPNST）可散发性发生或与1型神经纤维瘤病相关。这些肿瘤中已报道9p21位点存在缺失。为进一步明确该染色体区域的状态，在本研究中，我们对26例冷冻保存的MPNST中位于9p21位点的三个肿瘤抑制基因p15（INK4b）、p14（ARF）和p16（INK4a）进行了全面的、主要基于PCR的分子分析。
对14例与1型神经纤维瘤病相关的病例和12例散发性病例进行了纯合缺失研究，并结合荧光原位杂交、启动子甲基化、突变分析以及mRNA表达研究。
结果显示，77%的MPNST中一个或多个基因发生失活，主要通过纯合缺失实现（46%），而在83%的缺失病例中，纯合缺失又累及所有三个串联的基因。启动子甲基化在基因沉默中参与程度较低（18%），未发现突变。DNA水平的功能丧失与mRNA表达缺失高度相关，占病例的80%。由于p14（ARF）与TP53以及p15（INK4b）/p16（INK4a）与Rb之间关系密切，这些结果支持了75%的MPNST中TP53和Rb通路共同失活的模型，对细胞生长控制和凋亡产生功能影响。
9p21位点失活是MPNST基因谱中常见且独特的特征，也导致凋亡受损，这在这些肿瘤的治疗规划中应予以考虑。
