title: Targeting DNA repair with aphidicolin sensitizes primary chronic lymphocytic leukemia cells to purine analogs.
abstract: Purine analogs are among the most effective chemotherapeutic drugs for the treatment of chronic lymphocytic leukemia (CLL). However, chemoresistance and toxicity limit their clinical use. Here, we report that the DNA polymerase inhibitor aphidicolin, which displayed negligible cytotoxicity as a single agent in primary CLL cells, markedly synergizes with fludarabine and cladribine via enhanced apoptosis. Importantly, synergy was recorded regardless of CLL prognostic markers. At the molecular level, aphidicolin enhanced purine analog-induced phosphorylation of p53 and accumulation of γH2AX, consistent with increase in DNA damage. In addition, aphidicolin delayed γH2AX disappearance that arises after removal of purine analogs, suggesting that aphidicolin causes an increase in DNA damage by impeding DNA damage repair. Similarly, aphidicolin inhibited UV-induced DNA repair known to occur primarily through the nucleotide excision repair (NER) pathway. Finally, we showed that fludarabine induced nuclear import of XPA, an indispensable factor for NER, and that XPA silencing sensitized cell lines to undergo apoptosis in response to fludarabine. Together, our data indicate that aphidicolin potentiates the cytotoxicity of purine analogs by inhibiting a DNA repair pathway that involves DNA polymerases, most likely NER, and provide a rationale for manipulating it to therapeutic advantage.
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Eliza
authors.initials: E
authors.lastname: Starczewska
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Maxime
authors.initials: M
authors.lastname: Beyaert
authors.affiliation: Department of Hematology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Lucienne
authors.initials: L
authors.lastname: Michaux
authors.affiliation: Department of Hematology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Marie-Christiane
authors.initials: MC
authors.lastname: Vekemans
authors.affiliation: Service de Biologie Clinique, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Pascale
authors.initials: P
authors.lastname: Saussoy
authors.affiliation: Center for Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Experimentale et Clinique (IREC), Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Vanesa
authors.initials: V
authors.lastname: Bol
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Ainhoa
authors.initials: A
authors.lastname: Arana Echarri
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Smal
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.|Department of Hematology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Eric
authors.initials: E
authors.lastname: Van Den Neste
authors.affiliation: de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium.
authors.forename: Françoise
authors.initials: F
authors.lastname: Bontemps
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D016590:Aphidicolin / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D017338:Cladribine / Q000494:pharmacology*; D004249:DNA Damage; D004260:DNA Repair; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000235:genetics*; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D016590:Aphidicolin; D017338:Cladribine; D014740:Vidarabine; C024352:fludarabine
keywords: DNA damage; aphidicolin; chronic lymphocytic leukemia; fludarabine; γH2AX