title: (99m)Tc-MIBI imaging for prediction of therapeutic effects of second-generation MDR1 inhibitors in malignant brain tumors.
abstract: The aim of this study was to explore whether (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) is suitable to elucidate multidrug resistance and prediction of potentiation of antitumor agents by second-generation MDR1 inhibitors (PSC833, MS-209) in malignant brain tumors in rat. Malignant tumor cells (RG2 and C6 gliomas, Walker 256 carcinoma) were incubated with low dose vincristine (VCR) to induce multidrug resistance. MTT assay demonstrated a significant increase of surviving fractions in VCR-resistant sublines compared to those of drug-naive cells. Reverse transcriptase polymerase chain reaction revealed higher expression of MDR1 mRNA in VCR-resistant cells than drug-naive cells in each line. Volume distribution (V(d)) of (99m)Tc-MIBI was negatively correlated with MDR1 mRNA expression among drug-naive and VCR-resistant cells. MDR1 inhibitors decreased surviving fractions and increased V(d) of (99m)Tc-MIBI significantly in VCR-resistant sublines, whereas MDR1 mRNA expression was unchanged. These findings indicate that (99m)Tc-MIBI efflux was functionally suppressed by MDR1 inhibitors. Autoradiographic images of (99m)Tc-MIBI revealed higher uptake in drug-naive cells at basal ganglia compared with VCR-resistant cells at the opposite basal ganglia of rats. Oral administration of the second-generation MDR1 inhibitors significantly increased (99m)Tc-MIBI accumulation of both tumors. Therapeutic effects of VCR with or without the MDR1 inhibitors were also evaluated autoradiographically using (14)C-methyl-L-methionine ((14)C-Met) and MIB-5 index. (14)C-Met uptake and MIB-5 index of both tumors treated with VCR following the MDR1 inhibitor treatment significantly decreased compared with tumors treated with VCR alone. Analysis of (99m)Tc-MIBI accumulation is considered informative for detecting MDR1-mediated drug resistance and for monitoring the therapeutic effects of MDR1 inhibitors in malignant brain tumors.
authors: Department of Neurosurgery, Akita University School of Medicine, Akita, Japan. sasajima@nsg.med.akita-u.ac.jp
authors: Toshio
authors: T
authors: Sasajima
authors: Naoya
authors: N
authors: Shimada
authors: Yuichiro
authors: Y
authors: Naitoh
authors: Masataka
authors: M
authors: Takahashi
authors: Yi
authors: Y
authors: Hu
authors: Tomo
authors: T
authors: Satoh
authors: Kazuo
authors: K
authors: Mizoi
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001345:Autoradiography; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism; D002279:Carcinoma 256, Walker / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D003524:Cyclosporins / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004357:Drug Synergism; D011237:Predictive Value of Tests; D011804:Quinolines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D019275:Radiopharmaceuticals; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014750:Vincristine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; D003603:Cytotoxins; D011804:Quinolines; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; C087719:dofequidar; D014750:Vincristine; D016572:Cyclosporine; D017256:Technetium Tc 99m Sestamibi; C070272:valspodar