title: Purine analog-like properties of bendamustine underlie rapid activation of DNA damage response and synergistic effects with pyrimidine analogues in lymphoid malignancies.
abstract: Bendamustine has shown considerable clinical activity against indolent lymphoid malignancies as a single agent or in combination with rituximab, but combination with additional anti-cancer drugs may be required for refractory and/or relapsed cases as well as other intractable tumors. In this study, we attempted to determine suitable anti-cancer drugs to be combined with bendamustine for the treatment of mantle cell lymphoma, diffuse large B-cell lymphoma, aggressive lymphomas and multiple myeloma, all of which are relatively resistant to this drug, and investigated the mechanisms underlying synergism. Isobologram analysis revealed that bendamustine had synergistic effects with alkylating agents (4-hydroperoxy-cyclophosphamide, chlorambucil and melphalan) and pyrimidine analogues (cytosine arabinoside, gemcitabine and decitabine) in HBL-2, B104, Namalwa and U266 cell lines, which represent the above entities respectively. In cell cycle analysis, bendamustine induced late S-phase arrest, which was enhanced by 4-hydroperoxy-cyclophosphamide, and potentiated early S-phase arrest by cytosine arabinoside (Ara-C), followed by a robust increase in the size of sub-G1 fractions. Bendamustine was able to elicit DNA damage response and subsequent apoptosis faster and with shorter exposure than other alkylating agents due to rapid intracellular incorporation via equilibrative nucleoside transporters (ENTs). Furthermore, bendamustine increased the expression of ENT1 at both mRNA and protein levels and enhanced the uptake of Ara-C and subsequent increase in Ara-C triphosphate (Ara-CTP) in HBL-2 cells to an extent comparable with the purine analog fludarabine. These purine analog-like properties of bendamustine may underlie favorable combinations with other alkylators and pyrimidine analogues. Our findings may provide a theoretical basis for the development of more effective bendamustine-based combination therapies.
authors.affiliation: Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Nobuya
authors.initials: N
authors.lastname: Hiraoka
authors.affiliation: Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Kikuchi
authors.affiliation: Division of Hematology and Oncology, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamauchi
authors.affiliation: Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koyama
authors.affiliation: Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Taeko
authors.initials: T
authors.lastname: Wada
authors.affiliation: Department of Hematology, Tochigi Cancer Center, Utsunomiya, Tochigi, Japan.
authors.forename: Mitsuyo
authors.initials: M
authors.lastname: Uesawa
authors.affiliation: Department of Hematology, Tochigi Cancer Center, Utsunomiya, Tochigi, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Akutsu
authors.affiliation: Medical Education Center, Saitama Medical University, Moroyama, Saitama, Japan.
authors.forename: Shigehisa
authors.initials: S
authors.lastname: Mori
authors.affiliation: Department of Hematology, Saitama Medical University, Moroyama, Saitama, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Division of Hematology and Oncology, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Ueda
authors.affiliation: Department of Hematology, Tochigi Cancer Center, Utsunomiya, Tochigi, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kano
authors.affiliation: Division of Stem Cell Regulation, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Furukawa
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage / Q000737:chemistry*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000737:chemistry; D000069461:Bendamustine Hydrochloride / Q000008:administration & dosage / Q000737:chemistry*; D002453:Cell Cycle; D045744:Cell Line, Tumor / Q000187:drug effects; D049109:Cell Proliferation; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000031:analogs & derivatives; D003561:Cytarabine / Q000008:administration & dosage; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D006801:Humans; D020128:Inhibitory Concentration 50; D008223:Lymphoma / Q000473:pathology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000473:pathology; D020522:Lymphoma, Mantle-Cell / Q000473:pathology; D009101:Multiple Myeloma / Q000473:pathology; D011743:Pyrimidines / Q000737:chemistry*; D000069283:Rituximab / Q000008:administration & dosage
chemical_list: D018906:Antineoplastic Agents, Alkylating; D011743:Pyrimidines; D003561:Cytarabine; D000069283:Rituximab; D003520:Cyclophosphamide; D000069461:Bendamustine Hydrochloride; C030986:pyrimidine; C011272:perfosfamide