Investigation of chemoresistance-related genes mRNA expression for selecting anticancer agents in successful adjuvant chemotherapy for a case of recurrent glioblastoma

BACKGROUND Glioblastoma multiforme represents one of the most malignant forms of primary intracranial tumors, often intractable to multimodality of treatment including chemotherapy. The unsatisfactory results of chemotherapy are chiefly attributed to chemoresistance. Since various molecules that could confer drug resistance have been elucidated, screening of the amount of such molecules in the tumor cells could provide possibilities for predicting their chemoresistance beforehand and help select more effective drugs. METHODS We present a 45-year-old woman with recurrent glioblastoma multiforme in the cerebellum and invading the brain stem, treated successfully by postoperative chemotherapy, In this patient, anticancer drugs were determined by measurements of mRNA expression of chemoresistance-related genes, such as O-6-methylguanine-DNA methyltransferase (MGMT), mdr1, glutathione S-transferase (GST)-pi, and metallothionein (MT) in the resected tumor. RESULTS Northern blot analysis demonstrated the moderate mRNA level of MGMT, a major molecule causing ACNU (1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride) resistance. On the other hand, expression levels of mdr1 which codes the P-glycoprotein responsible for multidrug resistance, and GST-pi, a detoxification enzyme, were low. Transcript of MT, another thiol containing molecule for dcellular detoxification possibly associated with cisdiamminedichloroplatinum(II) (CDDP) resistance, was only faintly detectable. Postoperatively, the patient was treated initially with intravenous administration of ACNU and etoposide (VP16), resulting in a minor response of tumor regression. For maintenance therapy, we changed ACNU to CDDP according to the findings of the Northern blot analysis. Consequently, the residual tumor showed a marked response and almost disappeared after two courses of systemic chemotherapy with CDDP and VP16. CONCLUSIONS The successful tumor regression in this case suggests that Northern blot analysis on expression of these chemoresistance-related genes in tumor tissues could provide beneficial information for determination of optimal anticancer agents to improve the efficacy of chemotherapy.