Relevance of the Fanconi anemia pathway in the response of human cells to trabectedin

Division of Hematopoiesis and Gene Therapy Program, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avenida Complutense 22, 28040 Madrid, Spain.
Molecular Cancer Therapeutics (Impact Factor: 5.68). 06/2008; 7(5):1309-18. DOI: 10.1158/1535-7163.MCT-07-2432
Source: PubMed


Trabectedin (Yondelis; ET-743) is a potent anticancer drug that binds to DNA by forming a covalent bond with a guanine in one strand and one or more hydrogen bonds with the opposite strand. Using a fluorescence-based melting assay, we show that one single trabectedin-DNA adduct increases the thermal stability of the double helix by >20 degrees C. As deduced from the analysis of phosphorylated H2AX and Rad51 foci, we observed that clinically relevant doses of trabectedin induce the formation of DNA double-strand breaks in human cells and activate homologous recombination repair in a manner similar to that evoked by the DNA interstrand cross-linking agent mitomycin C (MMC). Because one important characteristic of this drug is its marked cytotoxicity on cells lacking a functional Fanconi anemia (FA) pathway, we compared the response of different subtypes of FA cells to MMC and trabectedin. Our data clearly show that human cells with mutations in FANCA, FANCC, FANCF, FANCG, or FANCD1 genes are highly sensitive to both MMC and trabectedin. However, in marked contrast to MMC, trabectedin does not induce any significant accumulation of FA cells in G2-M. The critical relevance of FA proteins in the response of human cells to trabectedin reported herein, together with observations showing the role of the FA pathway in cancer suppression, strongly suggest that screening for mutations in FA genes may facilitate the identification of tumors displaying enhanced sensitivity to this novel anticancer drug.

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    • "A defect in the FA/BRCA pathway induces a hypersensitivity to DNA damaging chemotherapy [16], [23]. However, it remains unknown whether disruption of FA/BRCA pathway is involved in the cytotoxicity of other chemotheraperutic agents such as mitoxantrone. "
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    • "Thus, although these three compounds are covalently bonded to only one strand of the DNA double helix, they have been viewed (8) as functional interstrand crosslinkers insofar as they prevent strand separation very effectively. To compare this action with that elicited by a true interstrand crosslinker, we chose MMC as a prototypical representative because of the similarities detected in cells exposed to all of these drugs regarding (i) phosphorylation of histone H2AX, a surrogate marker of double-strand breaks, (ii) Rad51 foci formation in the nucleus, which is known to facilitate DNA repair via homologous recombination and (iii) participation of the Fanconi anaemia (FA) pathway in the processing of the DNA damage (8). Nonetheless, a notable and yet unexplained difference regarding the effects of MMC and Yondelis® on the cell cycle of FA-deficient cells is that trabectedin, unlike MMC, did not induce any significant accumulation of cells in G2-M. "
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    • "A likely consequence, supported by the DNA melting results reported above, is that one or more PM01183-guanine adducts can hamper or prevent strand separation, thereby blocking replication and transcription forks. As a result, PM01183's behaviour could be akin to that of agents giving rise to true interstrand crosslinks (ICLs), such as mitomycin (Casado et al., 2008). In this respect, it is of interest that ICL resolution is known to occur through the coordinated action of multiple DNA repair pathways, including homologous recombination, a process that gives rise to DSBs because both DNA strands are covalently modified and need to be incised. "
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