Transcriptional functionality of germ line p53 mutants influences cancer phenotype

Purpose: The TP53 tumor suppressor gene encodes a sequence-specific transcription factor that is able to transactivate several sets of genes, the promoters of which include appropriate response elements. Although human cancers frequently contain mutated p53, the alleles as well as the clinical expression are often heterogeneous. Germ line mutations of TP53 result in cancer proneness syndromes known as Li-Fraumeni, Li-Fraumeni - like, and nonsyndromic predisposition with or without family history. p53 mutants can be classified as partial deficiency alleles or severe deficiency alleles depending on their ability to transactivate a set of human target sequences, as measured using a standardized yeast-based assay (see http://www.umd.be:2072/ index.html). We have investigated the extent to which the functional features of p53 mutant alleles determine clinical features in patients who have inherited these alleles and have developed cancer. Experimental Design: We retrieved clinical data from the IARC database (see http:// www.p53.iarc.fr/Germline.html) for all cancer patients with germline p53 mutations and applied stringent statistical evaluations to compare the functional classification of p53 alleles with clinical phenotypes. Results: Our analyses reveal that partial deficiency alleles are associated with a milder family history (P = 0.007), a lower numbers of tumors (P = 0.007), and a delayed disease onset (median, 31 versus 15 years; P = 0.007) which could be related to distinct tumor spectra. Conclusions: These findings establish for the first time significant correlations between the residual transactivation function of individual TP53 alleles and clinical variables in patients with inherited p53 mutations who develop cancer.