TP53 DNA contact mutations are selectively associated with allelic loss and have a strong clinical impact in head and neck cancer

Recent studies have suggested that different mutation types within the core domain of the tumour suppressor protein p53, i.e. DNA contact mutations and structural mutations, confer different biological properties. We have analysed in 86 head and neck squamous cell carcinomas (HNSCC), whether these p53 mutation types have a differential clinical impact. Thirty-seven missense mutations were identified. Thirteen of these (36%) were DNA contact mutations, occurring in the L3 loop, in the H2 loop sheet helix motif, in the S10 β strand and in Zinc binding residues. Microsatellite marker analysis revealed a selective association between these mutations and the loss of wild-type alleles (100% LOH vs 50% LOH in tumours with structural mutations; P=0.0034, Fisher's exact, 2-tailed). In comparison to structural mutations or to the absence of mutations in the core domain, DNA contact mutations were associated with higher tumour stages (84.6% vs 62%), a higher incidence of lymph node metastasis (91.7% vs 56%; P=0.014, Fisher's exact, 2-tailed), a shortened recurrence-free survival (8.1 months vs 23.7 months, P=0.047, log rank test) and overall survival (11 months vs 29.2 months; P=0.003, log rank test). The latter was also the case when only stage IV tumours were analysed (P=0.0055, log rank test). These data indicate that in HNSCC, TP53 DNA contact mutations confer a strong selection pressure to eliminate wild-type alleles, and that they result in an accelerated tumour progression and reduced therapeutic responsiveness.