HIGH-FREQUENCY OF GERMLINE P53 MUTATIONS IN CHILDHOOD ADRENOCORTICAL CANCER

Background: Adrenocortical carcinoma (ADCC) is a rare childhood cancer, affecting three of 1 million children younger than 16 years old in the United States. ADCC may be found in association with the Li-Fraumeni and Beckwith-Wiedemann syndromes. Children with ADCC are also at substantially increased risk of second primary cancers. Because of these associations, it is believed that the genetic basis for ADCC is stronger than for most childhood malignancies. Germline mutations of the TP53 tumor suppressor gene are associated with cancer predisposition in families with the Li-Fraumeni syndrome as well as in individuals with sporadically occurring component tumors of the syndrome. Purpose: We investigated the possibility that germline TP53 gene alterations existed in children with ADCC. Methods: Sixteen children with ADCC under the age of 18 were identified from searches of medical oncology records at three Canadian hospitals. Eleven of these 16 patients identified were alive. The mean age at diagnosis was 4.8 years (range, 1-17 years). Family histories were obtained for 11 unselected children with ADCC (six girls and five boys). Pathologic confirmation of tumor diagnosis was obtained from the medical records. Using single-strand conformational polymorphism analysis followed by single-strand DNA sequencing, genomic DNA extracted from whole blood was analyzed for the presence of TP53 mutations for six living ADCC patients. Results: Three of six (50%) children were found to carry germline TP53 mutations in exons 5, 6, and 7, respectively. Both wild-type and mutant alwere identified in all three TP53 sequences, indicating that the patients were heterozygous for germline TP53 mutations. None of these children was from a family with the Li-Fraumeni syndrome, The mutation in one child was shown to be inherited from the mother, who subsequently developed breast cancer. A striking excess of cancer was found in one family of a patient carrying wild-type TP53, Conclusions: Our observation of a high frequency of germline TP53 mutations in children with sporadic ADCC suggests that these children may represent probands with which to ascertain Li-Fraumeni syndrome families. It may be reasonable for children with adrenocortical carcinoma to be candidates for germline TP53 analysis. In light of the wealth of information in the Li-Fraumeni literature that associates germline TP53 mutations with a variety of malignancies, this testing may have important consequences for risk assessment for other close relatives, including early-onset breast cancer in the mothers.