title: Influence of combinations of digitonin with selected phenolics, terpenoids, and alkaloids on the expression and activity of P-glycoprotein in leukaemia and colon cancer cells.
abstract: P-glycoprotein (P-gp or MDR1) is an ATP-binding cassette (ABC) transporter. It is involved in the efflux of several anticancer drugs, which leads to chemotherapy failure and multidrug resistance (MDR) in cancer cells. Representative secondary metabolites (SM) including phenolics (EGCG and thymol), terpenoids (menthol, aromadendrene, β-sitosterol-O-glucoside, and β-carotene), and alkaloids (glaucine, harmine, and sanguinarine) were evaluated as potential P-gp inhibitors (transporter activity and expression level) in P-gp expressing Caco-2 and CEM/ADR5000 cancer cell lines. Selected SM increased the accumulation of the rhodamine 123 (Rho123) and calcein-AM (CAM) in a dose dependent manner in Caco-2 cells, indicating that they act as competitive inhibitors of P-gp. Non-toxic concentrations of β-carotene (40μM) and sanguinarine (1μM) significantly inhibited Rho123 and CAM efflux in CEM/ADR5000 cells by 222.42% and 259.25% and by 244.02% and 290.16%, respectively relative to verapamil (100%). Combination of the saponin digitonin (5μM), which also inhibits P-gp, with SM significantly enhanced the inhibition of P-gp activity. The results were correlated with the data obtained from a quantitative analysis of MDR1 expression. Both compounds significantly decreased mRNA levels of the MDR1 gene to 48% (p<0.01) and 46% (p<0.01) in Caco-2, and to 61% (p<0.05) and 1% (p<0.001) in CEM/ADR5000 cells, respectively as compared to the untreated control (100%). Combinations of digitonin with SM resulted in a significant down-regulation of MDR1. Our findings provide evidence that the selected SM interfere directly and/or indirectly with P-gp function. Combinations of different P-gp substrates, such as digitonin alone and together with the set of SM, can mediate MDR reversal in cancer cells.
authors.affiliation: Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany. Electronic address: S.Eid@stud.uni-heidelberg.de.
authors.forename: Safaa Yehia
authors.initials: SY
authors.lastname: Eid
authors.forename: Mahmoud Zaki
authors.initials: MZ
authors.lastname: El-Readi
authors.forename: Essam Eldin Mohamed Nour
authors.initials: EE
authors.lastname: Eldin
authors.forename: Sameer Hassan
authors.initials: SH
authors.lastname: Fatani
authors.forename: Michael
authors.initials: M
authors.lastname: Wink
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000470:Alkaloids / Q000494:pharmacology / Q000627:therapeutic use; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology* / Q000627:therapeutic use; D053119:Benzophenanthridines / Q000494:pharmacology / Q000627:therapeutic use; D018938:Caco-2 Cells; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D004072:Digitonin / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology / Q000627:therapeutic use; D007938:Leukemia / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D010636:Phenols / Q000494:pharmacology / Q000627:therapeutic use; D064209:Phytochemicals / Q000494:pharmacology* / Q000627:therapeutic use; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology* / Q000627:therapeutic use; D012333:RNA, Messenger / Q000378:metabolism; D020112:Rhodamine 123 / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology / Q000627:therapeutic use; D019207:beta Carotene / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000470:Alkaloids; D000972:Antineoplastic Agents, Phytogenic; D053119:Benzophenanthridines; D004338:Drug Combinations; D005452:Fluoresceins; D007546:Isoquinolines; D010636:Phenols; D064209:Phytochemicals; D010936:Plant Extracts; D012333:RNA, Messenger; D013729:Terpenes; D019207:beta Carotene; C085925:calcein AM; D020112:Rhodamine 123; C005705:sanguinarine; D004072:Digitonin
keywords: Colon cells; Digitonin; Leukaemia; Multidrug resistance; Sanguinarine; β-Carotene