Genomic profiling of TP53 and non-TP53 Li-Fraumeni syndrome tumors reveals hits in the p53 and overlapping pathways

Li-Fraumeni syndrome (LFS) is a rare, clinically and genetically heterogeneous inherited cancer syndrome. Most cases are due to mutations in TP53. CHK2 is a minor predisposing locus; we recently mapped a third locus to 1q23. In both TP53 and non-TP53 LFS, there is evidence for risk heterogeneity within and between kindreds, suggesting additional risk modifiers. Using BAC- and SNP-based microarrays, we performed genomic profiling of primary soft tissue sarcomas, osteosarcomas and matching constitutive samples of 10 LFS patients (6 with and 4 without TP53 mutations), to identify genome-wide patterns of copy number changes and loss-of-heterozygosity (LOH). Our complementing global approaches revealed several interesting patterns for TP53 and non-TP53 LFS tumors, including positive (1q/7, 3p/15, 4q/9q, 8q/19p, 9p/10q, 13/14 and 15q/18q) and negative (2q/9q, 3q/14q and 4q/6q) associations between chromosomal regions. The region containing the oncogene TWIST1 (7p21.1) was the most common gain independent of TP53 status and tumor type, while LOH of 8q11.2 with the tumor suppressor ST18 was the only region exclusively associated with non-TP53 soft tissue sarcomas. We resequenced known mutations in BRAF, KRAS and NRAS and identified somatic NRAS mutations in 2 of 10 tumors. TP53 and non-TP53 LFS tumors shared multiple hits in genes of the p53 and overlapping pathways. Although common dogma in cancer genetics holds that multiple hits in the same pathway are redundant and thus unlikely, we show that different combinations of genetic alterations in both TP53 and non-TP53 LFS tumors appear to act together in the p53 network in LFS tumorigenesis Keywords: Comparative genomic hybridization Using the Spectral Genomics dye-swap BAC arrays we studied 10 Li Fraumeni syndrome tumor cases