title: Temozolomide competes for P-glycoprotein and contributes to chemoresistance in glioblastoma cells.
abstract: Chemotherapeutic resistance can occur by P-glycoprotein (P-gp), a 12-transmembrane ATP-dependent drug efflux pump. Glioblastoma (GBM) has poor survival rate and uniformly acquired chemoresistance to its frontline agent, Temozolomide (TMZ). Despite much effort, overcoming TMZ resistance remains a challenge. We reported on autonomous induction of TMZ resistance by increased transcription MDR1, the gene for P-gp. This study investigated how P-gp and TMZ interact to gain resistance. Using an experimental model of Adriamycin-resistant DC3F cells (DC3F/Adx), we showed that increased P-gp caused TMZ resistance. Increasing concentrations of TMZ competed with Calcein for P-gp, resulting in reduced efflux in the DC3F/Adx cells. Three different inhibitors of P-gp reversed the resistance to TMZ in two different GBM cell lines, by increasing active Caspase 3. Molecular modeling predicted the binding sites to be the intracellular region of P-gp and also identified specific amino acids and kinetics of energy for the efflux of TMZ. Taken together, we confirmed P-gp targeting of TMZ, a crucial regulator of TMZ resistance in GBM. This study provides insights on the effectiveness by which TMZ competes with other P-gp substrates, thereby opening the door for combined targeted therapies.
authors.affiliation: New Jersey Medical School, Rutgers, Newark, NJ, USA; Graduate School of Biomedical Science, Rutgers School of Biomedical Health Sciences, Newark, NJ, USA.
authors.forename: Jessian L
authors.initials: JL
authors.lastname: Munoz
authors.affiliation: Graduate School of Biomedical Science, Rutgers School of Biomedical Health Sciences, Newark, NJ, USA.
authors.forename: Nykia D
authors.initials: ND
authors.lastname: Walker
authors.affiliation: Robert Wood Johnson Medical School, The Cancer Institute of New Jersey, New Brunswick, NJ, USA.
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Scotto
authors.affiliation: New Jersey Medical School, Rutgers, Newark, NJ, USA; Graduate School of Biomedical Science, Rutgers School of Biomedical Health Sciences, Newark, NJ, USA. Electronic address: rameshwa@njms.rutgers.edu.
authors.forename: Pranela
authors.initials: P
authors.lastname: Rameshwar
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000378:metabolism / Q000494:pharmacology*; D001667:Binding, Competitive; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D006224:Cricetinae; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005452:Fluoresceins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D000077204:Temozolomide; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D015854:Up-Regulation
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D018906:Antineoplastic Agents, Alkylating; D005452:Fluoresceins; D003606:Dacarbazine; C505407:CASP3 protein, human; D053148:Caspase 3; C007740:fluorexon; D000077204:Temozolomide
keywords: Chemoresistance; Glioblastoma; MDR1; P-gp; Temozolomide