Analysis of germline mutations in TP53 tumor suppressor gene in pediatric patients with solid tumors

VALVA, P.; STREITENBERGER, P.; GARCÍA, M.; BECKER, P.; GUZMÁN, C.; REY, G.; MARIA VICTORIA PRECIADO

Ginebra

Congreso; 38th Congress of the International Society of Paediatric Oncology; 2006

International Society of Pediatric Oncology

TP53 gene is not only mutated in approximately 50% of human cancers at somatic level but also in germline. Patients with low age at tumor diagnosis, mostly patients with additional history of malignancy, should be considered as potential TP53 germline mutation carriers. Our aim was to determine TP53 germline mutations incidence in pediatric patients. We analyzed 14 peripheral blood mononuclear cell (PBMC) samples from patients with solid tumor (1 schwannoma, 3 rhabdomyosarcoma, 3 retinoblastoma, 1 medulloblastoma, 3 Ewing sarcoma, 1 ependymoma, 1 hepatoblastoma, 1 paratesticular tumor); age range: 3m-13a, median: 14m and naïve of treatment, attending at our hospital´s Oncology Unit. 7/14 patients also have malignancy family history. Additionally, a sample from one of the patients´ mother, who has a concurrent diagnosis of breast tumor, was analyzed. All samples were screened for sequence alterations in exons 5-8 and in the corresponding introns of TP53 gene. Briefly, purified genomic DNA was obtained, exons 5-8 and the corresponding introns were amplified by PCR, amplicons were purified and automatically sequenced. Analysis of mutation spectra was carried out with the CLUSTALW program using sequence X54156 (Genbank) as reference. There were no exonic mutations in the 15 PBMC samples. However, one sample from a patient with ependymoma displayed two previously described polymorphisms in intron 7 (IARC database) associated with genetic susceptibility to different neoplasms. They comprise nucleotide positions 14181 CàT and 14201 TàG. Despite our study include only a selected group of children at risk of displaying TP53 gene alterations, exons mutations were absent. This is in accordance with the very low prevalence of germline p53 mutations in cancer free general population and with < 1% prevalence among cancer patients. Nevertheless, further study of a larger series to assess the frequency and involvement of germline mutation is being carried out by our research group.