title: Biological characterization of MLN944: a potent DNA binding agent.
abstract: MLN944 (XR5944) is a novel bis-phenazine that has demonstrated exceptional efficacy against a number of murine and human tumor models. The drug was reported originally as a dual topoisomerase I/II poison, but a precise mechanism of action for this compound remains to be determined. Several lines of evidence, including the marginal ability of MLN944 to stabilize topoisomerase-dependent cleavage, and the sustained potency of MLN944 in mammalian cells with reduced levels of both topoisomerases, suggest that other activities of the drug exist. In this study, we show that MLN944 intercalates into DNA, but has no effect on the catalytic activity of either topoisomerase I or II. MLN944 displays no significant ability to stimulate DNA scission mediated by either topoisomerase I or II compared with camptothecin or etoposide, respectively. In addition, yeast genetic models also point toward a topoisomerase-independent mechanism of action. To examine cell cycle effects, synchronized human HCT116 cells were treated with MLN944, doxorubicin, camptothecin, or a combination of the latter two to mimic a dual topoisomerase poison. MLN944 treatment was found to induce a G(1) and G(2) arrest in cells that is unlike the typical G(2)-M arrest noted with known topoisomerase poisons. Finally, transcriptional profiling analysis of xenograft tumors treated with MLN944 revealed clusters of regulated genes distinct from those observed in irinotecan hydrochloride (CPT-11)-treated tumors. Taken together, these findings suggest that the primary mechanism of action of MLN944 likely involves DNA binding and intercalation, but does not appear to involve topoisomerase inhibition.
authors.affiliation: Department of Molecular and Cellular Oncology, Millennium Pharmaceuticals, Inc., Cambridge, MA 02140, USA. darshan.sappal@mpi.com
authors.forename: Darshan S
authors.initials: DS
authors.lastname: Sappal
authors.forename: A Kathleen
authors.initials: AK
authors.lastname: McClendon
authors.forename: James A
authors.initials: JA
authors.lastname: Fleming
authors.forename: Vala
authors.initials: V
authors.lastname: Thoroddsen
authors.forename: Kelly
authors.initials: K
authors.lastname: Connolly
authors.forename: Corinne
authors.initials: C
authors.lastname: Reimer
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Blackman
authors.forename: Christine E
authors.initials: CE
authors.lastname: Bulawa
authors.forename: Neil
authors.initials: N
authors.lastname: Osheroff
authors.forename: Peter
authors.initials: P
authors.lastname: Charlton
authors.forename: Laura A
authors.initials: LA
authors.lastname: Rudolph-Owen
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002384:Catalysis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D016000:Cluster Analysis; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D020869:Gene Expression Profiling; D045325:HCT116 Cells; D006801:Humans; D007364:Intercalating Agents / Q000737:chemistry / Q000494:pharmacology*; D000077146:Irinotecan; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008938:Mitosis / Q000187:drug effects; D009154:Mutation; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D010619:Phenazines / Q000737:chemistry / Q000494:pharmacology*; D014183:Transplantation, Heterologous; D023041:Xenograft Model Antitumor Assays; D015003:Yeasts / Q000187:drug effects / Q000201:enzymology / Q000235:genetics
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D007364:Intercalating Agents; D010619:Phenazines; C434883:XR5944; D000077146:Irinotecan; D004247:DNA; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D002166:Camptothecin