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

Abstract

The significance of p53 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 the p53 protein and DNA ploidy status. Mutations of the p53 gene were detected in 13 (19.5%) out of 67 cases of soft-tissue tumors. Only three were localized outside the conservative regions of the p53 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 of p53 mutations and the histological grade, although a high number of mutations were defined in poorly differentiated tumors (grade 3). Molecular finding of a p53 gene mutation and immunohistochemical detection of p53 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 the p53 gene. Other factors may be responsible for the detection of p53 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 and p53 overexpression are more likely to represent a late event in the oncogenesis of soft-tissue tumors.

Immunohistochemical and molecular analysis of p53, RB, and PTEN in malignant peripheral nerve sheath tumors

“…In our series, among 12 tumors, we identified one mutation (8%) of the p53 gene in a sporadic MPNST. This is a much lower frequency than with the recent observations of Schneider-Stock et al [31] who identified four mutations among 12 sporadic MPNSTs (33%), although in two other single cases [36,38] no mutations in sporadic MPNSTs were found. In the setting of NF1, the reported frequency of p53 mutations in these tumors ranged from three of four (75%, [15]) and two of seven (29%, [23]) to no detectable mutation in five MPNSTs [27] and in the two NF 1 cases in the present study.…”

“…A methodological description and primer sequences are given in detail by Schneider-Stock et al [30,31]. In brief, for SSCP analysis, an aliquot of the PCR product (7 µl) was denatured in formamide buffer at 95 C for 5 min, chilled on ice, and loaded onto ultrathin mutation detection enhancement (MDE) gels (AT Biochem, Malvern, Pa.).…”

“…We wanted to contribute to a growing number of MPNST cases screened for p53 mutations and immunohistochemical expression, since only conflicting results have so far been reported in the literature, ranging from no mutations to high frequencies in NF1-associated as well as in sporadic cases [16,23,27,31,36,38]. The molecular analysis of loss of heterozygosity (LOH) in the Rb gene region was motivated by a few reports suggesting a role of the RB pathway in MPNSTs, but leaving open the question of direct allelic losses of the gene.…”

Prognostic significance of p53 gene mutations and p53 protein expression in synovial sarcomas

“…Taubert et al [30] failed to detect p53 mutation in four synovial sarcomas. In our previous study no p53 mutation was noted in three synovial sarcomas [24], nor did we see p16 gene alterations in a group of 11 synovial sarcomas [25]. According to the database of Hainaut et al [14], no p53 gene mutations have been reported in synovial sarcomas.…”

“…The oligonucleotide primers and annealing temperatures are described elsewhere [24]. The PCR products were detected on ultrathin polyacrylamide gels (0.3-0.45 mm thick, and 8%-15%, depending on the fragment length to be separated) at 15°C for approximately 2.5 h in horizontal electrophoresis (Multiphor, Pharmacia/Biotech).…”