Ependymomas in children express the multidrug resistance gene: immunohistochemical and molecular biologic study

In view of the poor response of ependymomas to chemotherapy, it may be hypothesized that these tumors have intrinsic drug resistance to some chemotherapeutic agents. The expression of drug resistance may be specific to a single agent or may involve multiple drugs. Among several mechanisms of drug resistance, P-glycoprotein (Pgp) has been the subject of considerable attention in clinical practice. In order to assess the possible participation of Pgp in the chemotherapeutic resistance of ependymomas, 42 biopsy specimens from 35 patients with ependymoma seen at our institutions were studied by immunohistochemistry with two monoclonal antibodies: C219 (Signet) and UIC-2 (Dr. Roninson's gift). In addition, four cases were studied by polymerase chain reaction after reverse transcription to detect transcripts of Pgp. Our results showed that in 35 samples there was a positive reaction for Pgp with both antibodies; two biopsy samples were positive only with C219 and three others with UIC-2; the remaining two samples were negative with both antibodies. Of the four cases studied by RT-PCR, three showed MDR1 transcripts. These results support our hypothesis of Pgp-mediated intrinsic multidrug resistance in these tumors.