BIOLOGY OF SOLID PEDIATRIC TUMORS

p53突变已在许多肿瘤中检测到，并被解释为晚期肿瘤。 肿瘤发生中的事件，可能涉及肿瘤进展，而不是 肿瘤发展 最近的研究表明， 在某些Li-Fraumeni家系中存在生殖系p53突变， p53突变与人类癌症遗传易感性 横纹肌肉瘤是一种常见的软组织肉瘤， Li-Fraumeni综合征，发现有p53突变。 但 这种突变在儿科肿瘤中的频率仍然未知。 我们有 最近建立了一种非放射性同位素方法来检测突变。 这 该方法是基于DNA异源双链体的形成， 突变检测增强（MDE）凝胶中的运动性。 因此，突变可以 甚至从石蜡包埋的组织中提取的PCR扩增DNA中也可检测到 组织中 利用这种方法，我们研究了跨越外显子的PCR片段， 13例横纹肌肉瘤（RMS）中p53基因的4、5、6、7和8（大多数为 石蜡块）。 高比例的研究肿瘤（46%）表现出 p53突变，更常见于外显子7，其次是外显子8和5。 的 在某些情况下，用标准单克隆抗体证实了突变的存在。 链构象多态性（SSCP）方法和直接 通过不对称PCR获得的单链DNA的测序方法。 我们 目前已将研究扩展到包括更多RMS， 以及其他实体儿科肿瘤，如神经母细胞瘤和外周 和中央PNET/尤文肉瘤病例。 患者的生存期 突变和非突变肿瘤将进行比较，以探索潜在的 p53突变在这组肿瘤中的预后作用。

p53 mutations have been detected in many tumors and interpreted as a late event in tumorigenesis, probably involved in tumor progression rather than tumor development. Recent studies have demonstrated the presence of germline p53 mutations in some Li-Fraumeni pedigrees and hence a role of p53 mutations in hereditary susceptibility to human cancer. Rhabdomyosarcoma, a common soft tissue sarcoma in the families with the Li-Fraumeni syndrome, was found to have p53 mutations. However, the frequency of such mutations in pediatric tumors remains unknown. We have recently established a non-radioisotopic method to detect mutations. This method is based on the formation of DNA hetero-duplexes with variable motility in mutation detection enhancement (MDE) gels. Mutations can thus be detected in PCR-amplified DNA extracted even from paraffin embedded tissues. Using this method, we have studied PCR fragments spanning exons 4, 5, 6, 7, and 8 of the p53 gene from 13 rhabdomyosarcomas (RMS) (mostly paraffin blocks). A high percentage of the studied tumors (46%) exhibited p53 mutations, more often in exon 7, followed by exons 8 and 5. The presence of mutations was confirmed in some cases with the standard single stranded conformational polymorphism (SSCP) method and with a direct sequencing method of single stranded DNA obtained by asymmetric PCR. We have currently expanded the study to include a larger number of RMS, as well as other solid pediatric tumors, such as neuroblastoma and peripheral and central PNET/Ewing's sarcoma cases. The survival of patients with mutated and non-mutated tumors will be compared to explore a potential prognostic role of p53 mutations in this group of tumors.