Expression of multidrug-resistance P-glycoprotein (MDR1) in human brain tumors

Abstract

Multidrug resistance (MDR) is associated with the expression of P‐glycoprotein (P‐gp), an ATP‐dependent transporter which expels anti‐cancer drugs from cells. In the present study, MDR1 P‐gp was immunodetected by Western blot analysis in 60 human brain tumors, including meningiomas, schwannomas, low‐grade gliomas (astrocytomas, pilocytic astrocytomas) and high‐grade gliomas (anaplastic astrocytomas, glioblastomas and anaplastic oligodendrogliomas). Most samples from primary tumors expressed P‐gp at the same levels as normal brain tissue except for schwannomas, in which levels were reduced by 65%, and meningiomas, in which levels were more than 10‐fold higher in 7 of 10 samples. P‐gp levels were 70% and 95% lower in brain metastases from melanomas and lung adenocarcinomas, respectively, than in normal brain tissue. These results indicate that the majority of primary brain tumors express MDR1 P‐gp and that its high expression levels in meningiomas may be a marker for this type of brain tumor.