title: Downregulation of deoxycytidine kinase in cytarabine-resistant mantle cell lymphoma cells confers cross-resistance to nucleoside analogs gemcitabine, fludarabine and cladribine, but not to other classes of anti-lymphoma agents.
abstract: BACKGROUND
  Mantle cell lymphoma (MCL) is an aggressive type of B-cell non-Hodgkin lymphoma associated with poor prognosis. Implementation of high-dose cytarabine (araC) into induction therapy became standard-of-care for all newly diagnosed younger MCL patients. However, many patients relapse even after araC-based regimen. Molecular mechanisms responsible for araC resistance in MCL are unknown and optimal treatment strategy for relapsed/refractory MCL patients remains elusive.
  
  
  METHODS
  Five araC-resistant (R) clones were derived by long-term culture of five MCL cell lines (CTRL) with increasing doses of araC up to 50 microM. Illumina BeadChip and 2-DE proteomic analysis were used to identify gene and protein expression changes associated with araC resistance in MCL. In vitro cytotoxicity assays and experimental therapy of MCL xenografts in immunodeficient mice were used to analyze their relative responsiveness to a set of clinically used anti-MCL drugs. Primary MCL samples were obtained from patients at diagnosis and after failure of araC-based therapies.
  
  
  RESULTS
  Marked downregulation of deoxycytidine-kinase (DCK) mRNA and protein expression was identified as the single most important molecular event associated with araC-resistance in all tested MCL cell lines and in 50% primary MCL samples. All R clones were highly (20-1000x) cross-resistant to all tested nucleoside analogs including gemcitabine, fludarabine and cladribine. In vitro sensitivity of R clones to other classes of clinically used anti-MCL agents including genotoxic drugs (cisplatin, doxorubicin, bendamustine) and targeted agents (bortezomib, temsirolimus, rituximab) remained unaffected, or was even increased (ibrutinib). Experimental therapy of immunodeficient mice confirmed the anticipated loss of anti-tumor activity (as determined by overall survival) of the nucleoside analogs gemcitabine and fludarabine in mice transplanted with R clone compared to mice transplanted with CTRL cells, while the anti-tumor activity of cisplatin, temsirolimus, bortezomib, bendamustine, cyclophosphamide and rituximab remained comparable between the two cohorts.
  
  
  CONCLUSIONS
  Acquired resistance of MCL cells to araC is associated with downregulation of DCK, enzyme of the nucleotide salvage pathway responsible for the first phosphorylation (=activation) of most nucleoside analogs used in anti-cancer therapy. The data suggest that nucleoside analogs should not be used in the therapy of MCL patients, who relapse after failure of araC-based therapies.
authors: Magdalena
authors: M
authors: Klanova
authors: Lucie
authors: L
authors: Lorkova
authors: Ondrej
authors: O
authors: Vit
authors: Bokang
authors: B
authors: Maswabi
authors: Jan
authors: J
authors: Molinsky
authors: Jana
authors: J
authors: Pospisilova
authors: Petra
authors: P
authors: Vockova
authors: Cory
authors: C
authors: Mavis
authors: Lucie
authors: L
authors: Lateckova
authors: Vojtech
authors: V
authors: Kulvait
authors: Dana
authors: D
authors: Vejmelkova
authors: Radek
authors: R
authors: Jaksa
authors: Francisco
authors: F
authors: Hernandez
authors: Marek
authors: M
authors: Trneny
authors: Martin
authors: M
authors: Vokurka
authors: Jiri
authors: J
authors: Petrak
authors: Institute of Pathological Physiology, Charles University in Prague, First Faculty of Medicine, Prague, Czech Republic. pavel.klener@gmail.com.
authors: Pavel
authors: P
authors: Klener
mesh_terms: D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000494:pharmacology / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D015153:Blotting, Western; D045744:Cell Line, Tumor; D017338:Cladribine / Q000494:pharmacology*; D002999:Clone Cells; D003561:Cytarabine / Q000494:pharmacology*; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003842:Deoxycytidine Kinase / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D015180:Electrophoresis, Gel, Two-Dimensional; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020522:Lymphoma, Mantle-Cell / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D013058:Mass Spectrometry; D051379:Mice; D040901:Proteomics; D000069283:Rituximab; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents; D003561:Cytarabine; D003841:Deoxycytidine; D017338:Cladribine; D000069283:Rituximab; D003842:Deoxycytidine Kinase; D014740:Vidarabine; C024352:fludarabine; D000093542:Gemcitabine