Table of Contents
CancerMail from the National Cancer Institute
UI - 21385712
AU - Malkin D; Chilton-MacNeill S; Meister LA; Sexsmith E; Diller L; Garcea RL
TI - Tissue-specific expression of SV40 in tumors associated with the Li-Fraumeni syndrome.
SO - Oncogene 2001 Jul 27;20(33):4441-9
AD - Division of Hematology/Oncology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8. firstname.lastname@example.org
Inactivation of wild-type p53 tumor suppressor function is the primary mechanism of tumor initiation in Li-Fraumeni syndrome (LFS) individuals with germline p53 mutations. Tumors derived from LFS patients frequently retain the normal p53 allele, suggesting that alternative mechanisms in addition to gene deletion must be involved in inactivating wild-type p53 protein. DNA tumor viruses, such as SV40, target p53 for inactivation through the action of viral oncoproteins. We studied the probands from two unrelated LFS families, each of whom presented with multiple malignant neoplasms. Patient 1 developed an embryonal rhabdomyosarcoma (RMS) and a choroid plexus carcinoma (CPC), while patient 2 developed a CPC and subsequently presented with both an osteosarcoma (OS) and renal cell carcinoma (RCC). We utilized DNA sequence analysis and immunohistochemistry to determine p53 gene status in the germline and tumors, as well as evidence for SV40 T-antigen oncoprotein expression. Each patient harbored a heterozygous germline p53 mutation at codons 175 and 273, respectively. In patient 1, the normal p53 gene was lost while the mutant p53 allele was reduced to homozygosity in the RMS. Both normal and mutant genes were maintained in the CPC. In patient 2, normal and mutant p53 alleles were retained in both the CPC and RCC. Both specific PCR and immunostaining detected SV40 T-antigen in both CPCs and the RCC. In addition to chromosomal alterations, epigenetic mechanisms may disrupt p53 function during tumorigenesis. In two LFS patients, we found SV40 DNA sequences and viral T-antigen expression that could account for inactivation of the normal p53 protein. Inactivation of p53 or other tumor suppressors by viral proteins may contribute to tumor formation in specific tissues of genetically susceptible individuals.
UI - 21411575
AU - Varley JM; McGown G; Thorncroft M; Kelsey AM; Birch JM
TI - Significance of intron 6 sequence variations in the TP53 gene in Li-Fraumeni syndrome.
SO - Cancer Genet Cytogenet 2001 Aug;129(1):85-7
AD - CRC Cancer Genetics Group, Paterson Institute for Cancer Research, Wilmslow Road, M20 4BX, Manchester, UK. email@example.com
Many polymorphisms have been reported in the TP53 gene. Some of these are within the coding region, and may affect the function of the p53 protein, others are within introns or non-coding regions, and their significance is unclear. Recently, a number of publications have claimed that polymorphisms within intron 6 are responsible for inherited predisposition to childhood malignancies, familial breast cancer, and Li-Fraumeni syndrome (LFS). We find no evidence for intron 6 sequence variants predisposing to LFS in our cohort of families and, furthermore, we show that some of the conclusions of other groups cannot be supported by data from our analysis.