p53 gene mutations in soft-tissue sarcomas-correlations with p53 immunohistochemistry and DNA ploidy

The significance ofp53 mutations in a group of 67 soft-tissue tumors was examined using single-strand conformation polymorphism and direct sequencing analysis. Molecular findings were correlated with immunohistochemical detection of thep53 protein and DNA ploidy status. Mutations of thep53 gene were detected in 13 (19.5%) out of 67 cases of soft-tissue tumors. Only there were localized outside the conservative regions of thep53 gene. Six mutations were described for the first time in these tumors. Most of the mutations were point mutations in exons 5–8 and, in one case, a deletion at the 3′-splice site of exon 5 could be demonstrated. There was no significant correlation between the occurrence ofp53 mutations and the histological grade, although a high number of mutations were defined in poorly differentiated tumors (grade 3). Molecular finding of ap53 gene mutation and immunohistochemical detection ofp53 expression did not correlate, which may be due to the high percentage of nonsense mutations in our study (50%). We confirm that only DNA sequencing allows a unique identification and differentiation of mutations in thep53 gene. Other factors may be responsible for the detection ofp53 protein in many cases. Histological grade correlated with aneuploidy. The frequency of mutations observed was in accordance with values quoted in the literature. Generally,p53 mutations andp53 overexpression are more likely to represent a late event in the oncogenesis of soft-tissue tumors.