title: Collateral sensitivity to gemcitabine (2',2'-difluorodeoxycytidine) and cytosine arabinoside of daunorubicin- and VM-26-resistant variants of human small cell lung cancer cell lines.
abstract: Multidrug resistance (MDR), characterized by a cross-resistance to many natural toxin-related compounds, may be caused either by overexpression of a drug efflux pump such as P-glycoprotein, (P-gP), multidrug resistance proteins MRP1-3, or BCRP/MXR or, in the case of DNA topoisomerase II active drugs, by a decrease in the enzymatic activity of the target molecule termed altered topoisomerase MDR (at-MDR). However, human small cell lung carcinoma (SCLC) cell lines showed a collateral sensitivity to 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) and 1-beta-D-arabinofuranosylcytosine (ara-C). H69/DAU, a daunorubicin (DAU)-resistant variant of H69 with a P-gP overexpression, and NYH/VM, a VM-26 (teniposide)-resistant variant of NYH with an at-MDR, were both 2-fold more sensitive to gemcitabine and 7- and 2-fold more sensitive to ara-C, respectively. MDR variants had a 4.3- and 2.0-fold increased activity of deoxycytidine kinase (dCK), respectively. dCK catalyzes the first rate-limiting activation step of both gemcitabine and ara-C. In addition, deoxycytidine deaminase, responsible for inactivation of dFdC and ara-C, was 9.0-fold lower in H69/DAU cells. The level of thymidine kinase 2, a mitochondrial enzyme that can also phosphorylate deoxycytidine and gemcitabine, was not significantly different between the variants. These differences most likely caused an increased accumulation of the active metabolites (dFdCTP, 2.1- and 1.6-fold in NYH/VM and H69/DAU cells, respectively) and of ara-CTP (1.3-fold in NYH/VM cells). Ara-CTP accumulation was not detectable in either H69 variant. The pools of all ribonucleoside and deoxyribonucleoside triphosphates were at least 3- to 4-fold higher in the NYH variants compared to the H69 variants; for dCTP and dGTP this difference was even larger. The higher ribonucleotide pools might explain the >10-fold higher accumulation of dFdCTP in NYH compared to H69 variants. Since dCTP is low, H69 cells might not need a high ara-CTP accumulation to inhibit DNA polymerase. This might be related to the lack of ara-CTP in H69 variants. In addition, the increased CTP, ATP, and UTP pools in the MDR variants might explain the increased ara-CTP and dFdCTP accumulation. In conclusion, the MDR variants of the human SCLC cell lines were collaterally sensitive due to an increased dCK activity, and consequently an increased ara-CTP and dFdCTP accumulation.
authors.affiliation: Department of Oncology, University Hospital VU, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: A M
authors.initials: AM
authors.lastname: Bergman
authors.forename: B
authors.initials: B
authors.lastname: Munch-Petersen
authors.forename: P B
authors.initials: PB
authors.lastname: Jensen
authors.forename: M
authors.initials: M
authors.lastname: Sehested
authors.forename: G
authors.initials: G
authors.lastname: Veerman
authors.forename: D A
authors.initials: DA
authors.lastname: Voorn
authors.forename: K
authors.initials: K
authors.lastname: Smid
authors.forename: H M
authors.initials: HM
authors.lastname: Pinedo
authors.forename: G J
authors.initials: GJ
authors.lastname: Peters
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001085:Arabinofuranosylcytosine Triphosphate / Q000378:metabolism; D018288:Carcinoma, Small Cell; D002470:Cell Survival / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D003564:Cytidine Deaminase; D003630:Daunorubicin / Q000494:pharmacology; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology*; D003842:Deoxycytidine Kinase / Q000378:metabolism; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms; D009700:Nucleoside Deaminases / Q000378:metabolism; D013713:Teniposide / Q000494:pharmacology; D013937:Thymidine Kinase / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014544:Uridine Triphosphate / Q000378:metabolism; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D003561:Cytarabine; D003841:Deoxycytidine; D001085:Arabinofuranosylcytosine Triphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D013713:Teniposide; D013937:Thymidine Kinase; D003842:Deoxycytidine Kinase; D009700:Nucleoside Deaminases; D003564:Cytidine Deaminase; C011530:deoxycytidine deaminase; D014544:Uridine Triphosphate; D003630:Daunorubicin; D000093542:Gemcitabine