Our data suggest that the investigated brain tumors had an intact BBTB, which is impermeable to anticancer drugs, which are dual ABCB1/ABCG2 substrates.
CD133, a putative stem cell marker in normal tissue and malignant brain tumors, enhances multidrug resistant gene 1 (MDR1) expression following chemotherapy in adult malignant glioblastomas.
We investigated the expression of the drug-transporter proteins P-glycoprotein (P-gp) and multidrug-resistance protein 1 (MRP1) in cell lines (N = 24) and primary cell cultures (N = 36) from neuroectodermal tumors, as well as in brain tumor extracts (N = 18) and normal human astrocytes (N = 1).
These results indicate that the majority of primary brain tumors express MDR1P-gp and that its high expression levels in meningiomas may be a marker for this type of brain tumor.
The data indicate that knowledge of the expression levels of MGMT and mdr1 may be particularly useful for a more rational selection of drugs which are not influenced by these resistance genes and which have improved efficacy against human brain tumors.
To examine whether brain tumors overexpress the MDR1 gene, 25 brain-tumor specimens were subjected to Northern blot analysis: 10 gliomas, eight meningiomas, three schwannomas, one malignant lymphoma, and three tumors metastatic to the brain.