Hereditary TP53 Codon 292 and Somatic P16INK4A Codon 94 Mutations in a Li-Fraumeni Syndrome Family

Abstract

Li-Fraumeni syndrome is an autosomal dominant disorder that is characterized by various types of cancer in childhood and adult cases. Although hereditary TP53 mutation is very rare in different human cancers, it has been frequently reported in Li-Fraumeni syndrome. On the other hand, hereditary mutations of TP57 KIP2, P15 INK4B, and P16 INK4A, which affect the cell cycle similar to TP53, were observed in some types of cancer. In a Turkish family with the diagnosis of Li-Fraumeni syndrome, we analyzed the mutation pattern of TP53, P57 KIP2, P15 INK4B, and P16 INK4A in the peripheral blood, and loss of heterozygosity (homo/hemizygous deletion) pattern of TP53 and P15 INK4B/ P16 INK4A in two tumor tissues. The propositus had a seminoma, his daughter a medulloblastoma, and one of his healthy cousins, a TP53 codon 292 missense point mutation (AAA→ATA; Lys→Ile) in the peripheral blood cells. Tumor tissue obtained from the propositus with the seminoma revealed loss of heterozygosity in the TP53 gene. In the analyses of tumor tissues from the propositus and his daughter, a P16 INK4A codon 94 missense point mutation (GCG→GAG; Ala→Glu) was observed with the hereditary TP53 mutation. P16 INK4A codon 94 mutation observed in our family is a novel mutation in Li-Fraumeni syndrome. No other gene alteration in TP53, P57 KIP2, P15 INK4B, and P16 INK4A was observed. Existence of the P16 INK4A mutation and the hereditary TP53 mutation with or without loss of heterozygosity in the TP53 gene (seminoma/medulloblastoma) may be evidence for a common mechanism involved in tumorogenesis. The gene alterations in TP53 and P16 INK4A genes may be used as tumor markers in our family.