Expression of P-glycoprotein in human glioma cell lines and surgical glioma specimens

Abstract

✓ The expression of P-glycoprotein, a product of multidrug resistance gene 1, was studied by Western blotting and immunohistochemistry in five human glioma cell lines. One glioma cell line was resistant to vincristine, Adriamycin (doxorubicin), and etoposide, and the other four glioma cell lines were sensitive to each drug. The multidrug-resistant cell line showed a high expression of P-glycoprotein in Western blot analysis and a positive immunostaining for P-glycoprotein mainly along the cell membrane, whereas all multidrug-sensitive glioma cell lines demonstrated no expression of P-glycoprotein in Western blotting and no immunostaining for P-glycoprotein, thus showing a good correlation between the expression level of P-glycoprotein and the extent of multidrug resistance. In 18 human surgical glioma specimens, there was no evidence of complete absence of immunostaining for P-glycoprotein. With a definition of more than 20% of P-glycoprotein-positive cells as positive, from 10% to 20% as intermediate, and less than 10% as negative, immunostaining for P-glycoprotein was positive in one specimen and intermediate in six of 15 specimens taken from virgin gliomas, and positive in two specimens and intermediate in one of three recurrent gliomas treated previously with irradiation, ACNU (1-(4-amino-2-methyl-pyrimidine-5-yl)-methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride), cisplatin, vincristine, and/or procarbazine.