The TP53 gene promoter is not methylated in families suggestive of Li-Fraumeni syndrome with no germline TP53 mutations
Abstract
Germline TP53 mutations are found in only 70% of families with the Li-Fraumeni syndrome (LFS), and with an even lower frequency in families suggestive of LFS but not meeting clinical criteria of the syndrome. Despite intense efforts, to date, no other genes have been associated with the disorder in a significant number of TP53 mutation-negative families.
A search for defects in TP53 other than heterozygous missense mutations showed that neither intron variants nor sequence variants in the TP53 promoter are frequent in LFS, and multiexon deletions have been found to be responsible for US only in several cases. Another cancer predisposition syndrome, hereditary non-polyposis colon cancer, has been associated with epigenetic silencing of one allele of the MLH1 or MSH2 genes.
This prompted us to test the methylation of the TP53 gene promoter in a set of 14 families suggestive of LFS using bisulphite sequencing of three DNA fragments from the 5' region of the gene. We found no detectable methylation at any of the CG dinucleotides tested.
Thus, epigenetic silencing of the TP53 promoter is not a frequent cause of the disorder in families suggestive of LFS but with no germline mutations in the coding part of the gene.