Mutational analysis of p53 and PTEN in soft tissue sarcoma

Abstract

p53 and PTEN are the two most frequently mutated tumor suppressors in human cancer. However, literature on the effect of the joint inactivation of tumor-suppressor genes in soft tissue sarcoma (STS) is lacking. The purpose of this study was to investigate whether p53 and PTEN mutations play a role in the carcinogenesis of STS, as well as to evaluate their mutual role in STS pathogenesis. We screened mutations of p53 and PTEN in 86 human STSs using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing, respectively. p53 mutations were detected in 25.6% (22 out of 86) of STSs: 6 cases of p53 mutations were detected in 46 cases of specific reciprocal translocations in STSs (13.0%), 16 cases were detected in 40 cases of nonspecific reciprocal translocations in STSs (40.0%); the majority of the mutations were point mutations in exon 6-7. Furthermore, PTEN mutations were observed in 2 out of 86 STSs (2.3%). Two out of 86 cases revealed a 130th codon G>A missense mutation in exon 8 of PTEN which resulted in an Arg change to Gln in the PTEN protein structure; and a 334th codon A>T missense mutation in exon 8 of PTEN, which resulted in an Asn change to Lys in the PTEN protein structure. All subjects were examined for p53 exon 5-9 mutations and for PTEN exon 5-9 mutations. However, no tumors contained an alteration of the two genes. The findings indicate that p53 mutations may be involved in the oncogenesis of STS and also suggest that p53 may function as a potential molecular marker for distinguishing between STSs with specific reciprocal translocations and nonspecific reciprocal translocations. Although the existence of PTEN mutations in STS was detected, the PTEN mutation frequency was quite low. We conclude that PTEN may have played a less prognostic role than p53 in the development and malignant transformation of STS in the patients examined.