An inherited p53 mutation that contributes in a tissue-specific manner to pediatric adrenal cortical carcinoma

Abstract

The incidence of pediatric adrenal cortical carcinoma (ACC) in southern Brazil is 10-15 times higher than that of pediatric ACC worldwide. Because childhood ACC is associated with Li-Fraumeni syndrome, we examined the cancer history and p53 status of 36 Brazilian patients and their families. Remarkably, 35 of 36 patients had an identical germ-line point mutation of p53 encoding an R337H amino acid substitution. Differences within intragenic polymorphic markers demonstrated that at least some mutant alleles arose independently, thus eliminating a founder effect. In tumor cells, the wild-type allele was deleted, and mutant p53 protein accumulated within the nuclei. Although these features are consistent with Li-Fraumeni syndrome-associated adrenal tumors, there was no history of increased cancer incidence among family members. Therefore, this inherited R337H p53 mutation represents a low-penetrance p53 allele that contributes in a tissue-specific manner to the development of pediatric ACC.

Figure 1

Pedigree of family with five cases of ACC. Five generations are represented. Two of the children with ACC (closed arrows) were index cases; their ages at diagnosis are noted in parentheses. The three others are indicated by open arrows. There were two additional cases of cancer in the family: an unspecified intraabdominal carcinoma (I-1) and an astrocytoma (III-29). Deceased individuals are indicated by an oblique bar.

Figure 2

Identification of germ-line R337H p53 mutation in patients with ACC. p53 was sequenced in genomic DNA prepared from peripheral blood cells. A representative sequence from a patient with ACC is shown. Sequences correspond to the p53 sense strands between codons 336 and 338 of exon 10. The G at position 1010 (codon 337) in the wild-type strand is replaced by A in the mutated strand (arrow).

Figure 3

Analysis of p53 polymorphisms in patients with ACC. Genotypes were determined by using four markers, including two intragenic p53 polymorphisms. Their positions relative to the p53 gene and their order on chromosome 17 are shown next to an ideogram of chromosome 17. Allelic order of the boxed markers was determined by studies of at least one parent or sibling. Because the markers clearly differed even among patients for whom the allelic order could not be confirmed, a founder effect is highly unlikely to account for the presence of the mutation. D17S1832 and D17S786 = dinucleotide repeat markers; p53(AAAAT)_n = intragenic p53 pentanucleotide polymorphism located in intron 1; p53(CA)_n = intragenic p53 dinucleotide polymorphism located in codon 213.

Figure 4

The R337H mutant retains transactivation function when overexpressed. (A) Wild-type p53 and the R337H mutant showed comparable relative transactivation of a wild-type p53-responsive promoter. (B) Western blot analysis showed that the wild-type and R337H p53 proteins were equally expressed in this assay. WT = wild type; 337H = R337H p53 mutant; Neo = neomycin; 248 = R248W p53 mutant associated with Li-Fraumeni syndrome.