Prognostic value of P-glycoprotein expression in bone and soft-tissue sarcoma

Abstract

Background. The purpose of this study was to investigate the correlation between P-glycoprotein status and outcome in adult patients with high-grade osteosarcomas and soft-tissue sarcomas. Methods. P-glycoprotein status was determined im-munohistochemically in specimens from 28 patients with osteosarcoma and 34 patients with soft-tissue sarcoma. The polyclonal antibody mdr(Ab-1) was used for either decalcified or undecalcified tissue samples which were formalin-fixed and paraffin-embedded. The expression of P-glycoprotein mRNA was also determined by the polymerase chain reaction in 23 fresh sarcoma specimens. P-glycoprotein status was analyzed in relation to the duration of event-free survival. Results. Positivity for P-glycoprotein was found in 29% of the osteosarcomas and 34% of the soft-tissue sarcomas. Consistent results were obtained at both the immunohistochemical and reverse transcriptase-polymerase chain reaction (RT-PCR) levels in 19 of 23 sarcomas (83%). In patients with osteosarcoma, the presence of increased levels of P-glycoprotein was significantly associated with a decreased probability of event-free survival after diagnosis (P = 0.022). In contrast, in patients with soft-tissue sarcoma there was no correlation between the level of P-glycoprotein and prognosis. Conclusions. In patients with high-grade osteosarcomas, the presence of increased levels of P-glycoprotein detected by polyclonal antibody mdr(Ab-1) was associated with a significantly increased risk of adverse events. This association was not found in patients with soft-tissue sarcomas.