title: Cellular influx, efflux, and anabolism of 3-carboranyl thymidine analogs: potential boron delivery agents for neutron capture therapy.
abstract: 3-[5-{2-(2,3-Dihydroxyprop-1-yl)-o-carboran-1-yl}pentan-1-yl]thymidine (N5-2OH) is a first generation 3-carboranyl thymidine analog (3CTA) that has been intensively studied as a boron-10 ((10)B) delivery agent for neutron capture therapy (NCT). N5-2OH is an excellent substrate of thymidine kinase 1 and its favorable biodistribution profile in rodents led to successful preclinical NCT of rats bearing intracerebral RG2 glioma. The present study explored cellular influx and efflux mechanisms of N5-2OH, as well as its intracellular anabolism beyond the monophosphate level. N5-2OH entered cultured human CCRF-CEM cells via passive diffusion, whereas the multidrug resistance-associated protein 4 appeared to be a major mediator of N5-2OH monophosphate efflux. N5-2OH was effectively monophosphorylated in cultured murine L929 [thymidine kinase 1 (TK1(+))] cells whereas formation of N5-2OH monophosphate was markedly lower in L929 (TK1(-)) cell variants. Further metabolism to the di- and triphosphate forms was not observed in any of the cell lines. Regardless of monophosphorylation, parental N5-2OH was the major intracellular component in both TK1(+) and TK1(-) cells. Phosphate transfer experiments with enzyme preparations showed that N5-2OH monophosphate, as well as the monophosphate of a second 3-carboranyl thymidine analog [3-[5-(o-carboran-1-yl)pentan-1-yl]thymidine (N5)], were not substrates of thymidine monophosphate kinase. Surprisingly, N5-diphosphate was phosphorylated by nucleoside diphosphate kinase although N5-triphosphate apparently was not a substrate of DNA polymerase. Our results provide valuable information on the cellular metabolism and pharmacokinetic profile of 3-carboranyl thymidine analogs.
authors.affiliation: Department of Anatomy, Physiology, and Biochemistry, The Swedish University of Agricultural Sciences, Biomedical Center, Uppsala, Sweden (E.S., S.E.); Department of Oncology, University of Alberta, Edmonton, Alberta, Canada (V.L.D., D.M., M.B.S., C.E.C); Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, Columbus, Ohio (R.T., H.K.A., A.K., S.H., A.G., W.T.); Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt (A.K.); Division of Pharmaceutical Organic Chemistry, College of Pharmacy, Helwan University, Ain Helwan, Cairo, Egypt (S.H.); Division of Pharmacology, College of Veterinary Medicine, Cairo University, Giza, Egypt (A.G.); and Department of Pathology, The Ohio State University, Columbus, Ohio (R.J.N., R.F.B.).
authors.forename: Elena
authors.initials: E
authors.lastname: Sjuvarsson
authors.forename: Vijaya L
authors.initials: VL
authors.lastname: Damaraju
authors.forename: Delores
authors.initials: D
authors.lastname: Mowles
authors.forename: Michael B
authors.initials: MB
authors.lastname: Sawyer
authors.forename: Rohit
authors.initials: R
authors.lastname: Tiwari
authors.forename: Hitesh K
authors.initials: HK
authors.lastname: Agarwal
authors.forename: Ahmed
authors.initials: A
authors.lastname: Khalil
authors.forename: Sherifa
authors.initials: S
authors.lastname: Hasabelnaby
authors.forename: Ayman
authors.initials: A
authors.lastname: Goudah
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Nakkula
authors.forename: Rolf F
authors.initials: RF
authors.lastname: Barth
authors.forename: Carol E
authors.initials: CE
authors.lastname: Cass
authors.forename: Staffan
authors.initials: S
authors.lastname: Eriksson
authors.forename: Werner
authors.initials: W
authors.lastname: Tjarks
mesh_terms: D000818:Animals; D001692:Biological Transport; D001896:Boron Compounds / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D016754:Boron Neutron Capture Therapy / Q000379:methods; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D051379:Mice; D015394:Molecular Structure; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D033703:Nucleoside Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013379:Substrate Specificity; D013936:Thymidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013937:Thymidine Kinase / Q000378:metabolism*; D014162:Transfection
chemical_list: D001896:Boron Compounds; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D033703:Nucleoside Transport Proteins; D013936:Thymidine; D013937:Thymidine Kinase; C514063:3-(5-(2-(2,3-dihydroxyprop-1-yl)-o-carboran-1-yl)pentan-1-yl)thymidine; C073492:ABCC4 protein, human; C092717:thymidine kinase 1