Fludarabine-mediated suppression of the excision repair enzyme ERCC1 contributes to the cytotoxic synergy with the DNA minor groove crosslinking agent SJG-136 (NSC 694501) in chronic lymphocytic leukaemia cells.
In this study, we set out to establish whether fludarabine could enhance the DNA interstrand crosslinking capacity of SJG-136 in primary human chronic lymphocytic leukaemia (CLL) cells and thereby offer a rationale for its clinical use in combination with SJG-136. SJG-136 rapidly induced DNA crosslinking in primary CLL cells which was concentration-dependent. Further, the level of crosslinking correlated with sensitivity to SJG-136-induced apoptosis (P=0.001) and higher levels of crosslinking were induced by the combination of SJG-136 and fludarabine (P=0.002). All of the samples tested (n=40) demonstrated synergy between SJG-136 and fludarabine (mean combination index (CI)=0.54+/-0.2) and this was even retained in samples derived from patients with fludarabine resistance (mean CI=0.62+/-0.3). Transcription of the excision repair enzyme, ERCC1, was consistently increased (20/20) in response to SJG-136 (P<0.0001). In contrast, fludarabine suppressed ERCC1 transcription (P=0.04) and inhibited SJG-136-induced ERCC1 transcription when used in combination (P=0.001). Importantly, the ability of fludarabine to suppress ERCC1 transcription correlated with the degree of synergy observed between SJG-136 and fludarabine (r(2)=0.28; P=0.017) offering a mechanistic rationale for the synergistic interaction. The data presented here provides a clear indication that this combination of drugs may have clinical utility as salvage therapy in drug-resistant CLL.
Pepper
C
C
Department of Haematology, School of Medicine, Cardiff University, Heath Park, Cardiff, UK. peppercj@cf.ac.uk
Lowe
H
H
Fegan
C
C
Thurieau
C
C
Thurston
D E
DE
Hartley
J A
JA
Delavault
P
P
D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols; D001570:Benzodiazepinones / Q000494:pharmacology* / Q000627:therapeutic use; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D004357:Drug Synergism; D004720:Endonucleases / Q000037:antagonists & inhibitors* / Q000235:genetics; D005260:Female; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D011758:Pyrroles / Q000494:pharmacology* / Q000627:therapeutic use; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use
C423343:1,1'-((propane-1,3-diyl)dioxy)bis(7-methoxy-2-methylidene-1,2,3,10,11,11a-hexahydro-5H-pyrrolo(2,1-c)(1,4)benzodiazepin-5,11-dione); D000970:Antineoplastic Agents; D001570:Benzodiazepinones; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D011758:Pyrroles; D004247:DNA; C071447:ERCC1 protein, human; D004720:Endonucleases; D014740:Vidarabine; C024352:fludarabine