Specific killing of BRCA2-deficient tumours with inhibitors of poly(ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (PARP1) facilitates DNA repair by binding to DNA breaks and attracting DNA repair proteins to the site of damage. Nevertheless, PARP1-/- mice are viable, fertile and do not develop early onset tumours. Here, we show that PARP inhibitors trigger γ-H2AX and RAD51 foci formation. We propose that, in the absence of PARP1, spontaneous single-strand breaks collapse replication forks and trigger homologous recombination for repair. Furthermore, we show that BRCA2-deficient cells, as a result of their deficiency in homologous recombination, are acutely sensitive to PARP inhibitors, presumably because resultant collapsed replication forks are no longer repaired. Thus, PARP1 activity is essential in homologous recombination-deficient BRCA2 mutant cells. We exploit this requirement in order to kill BRCA2-deficient tumours by PARP inhibition alone. Treatment with PARP inhibitors is likely to be highly tumour specific, because only the tumours (which are BRCA2-/-) in BRCA2+/- patients are defective in homologous recombination. The use of an inhibitor of a DNA repair enzyme alone to selectively kill a tumour, in the absence of an exogenous DNA-damaging agent, represents a new concept in cancer treatment.

[1]  J. Hoeijmakers,et al.  Overproduction of the poly(ADP‐ribose) polymerase DNA‐binding domain blocks alkylation‐induced DNA repair synthesis in mammalian cells. , 1993, The EMBO journal.

[2]  P. Chambon,et al.  Requirement of poly(ADP-ribose) polymerase in recovery from DNA damage in mice and in cells. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[3]  N. Curtin,et al.  Differential effects of the poly (ADP-ribose) polymerase (PARP) inhibitor NU1025 on topoisomerase I and II inhibitor cytotoxicity in L1210 cells in vitro , 2001, British Journal of Cancer.

[4]  D. Gray,et al.  Poly(ADP‐ribose) polymerase activity in nucleotide permeable cells , 1978, FEBS letters.

[5]  R. Tebbs,et al.  Correction of chromosomal instability and sensitivity to diverse mutagens by a cloned cDNA of the XRCC3 DNA repair gene. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[6]  M. Mark,et al.  Loss of poly(ADP‐ribose) polymerase‐1 causes increased tumour latency in p53‐deficient mice , 2001, The EMBO journal.

[7]  N. Curtin,et al.  Tricyclic benzimidazoles as potent poly(ADP-ribose) polymerase-1 inhibitors. , 2003, Journal of medicinal chemistry.

[8]  R. Kanaar,et al.  Brca2 (XRCC11) Deficiency Results in Radioresistant DNA Synthesis and a Higher Frequency of Spontaneous Deletions , 2002, Molecular and Cellular Biology.

[9]  Alan Ashworth,et al.  Targeting the DNA repair defect in BRCA mutant cells as a therapeutic strategy , 2005, Nature.

[10]  V. Yamazaki,et al.  A critical role for histone H2AX in recruitment of repair factors to nuclear foci after DNA damage , 2000, Current Biology.

[11]  P. Chambon,et al.  Functional interaction between PARP‐1 and PARP‐2 in chromosome stability and embryonic development in mouse , 2003, The EMBO journal.

[12]  T. Lindahl.  Instability and decay of the primary structure of DNA , 1993, Nature.

[13]  B. Preston,et al.  Defects in homologous recombination repair in mismatch-repair-deficient tumour cell lines. , 2002, Human molecular genetics.

[14]  T. Helleday,et al.  Poly(ADP-ribose) polymerase (PARP-1) has a controlling role in homologous recombination. , 2003, Nucleic acids research.

[15]  T. Lindahl,et al.  Post-translational modification of poly(ADP-ribose) polymerase induced by DNA strand breaks. , 1995, Trends in biochemical sciences.

[16]  E. Wagner,et al.  PARP is important for genomic stability but dispensable in apoptosis. , 1997, Genes & development.

[17]  Robert Almassy,et al.  Anticancer chemosensitization and radiosensitization by the novel poly(ADP-ribose) polymerase-1 inhibitor AG14361. , 2004, Journal of the National Cancer Institute.

[18]  A. Bürkle,et al.  Direct stimulation of poly(ADP ribose) polymerase in permeabilized cells by double-stranded DNA oligomers. , 1991, Analytical biochemistry.

[19]  T. Helleday,et al.  DNA double-strand breaks associated with replication forks are predominantly repaired by homologous recombination involving an exchange mechanism in mammalian cells. , 2001, Journal of molecular biology.

[20]  Ashok R Venkitaraman,et al.  Cancer Susceptibility and the Functions of BRCA1 and BRCA2 , 2002, Cell.

[21]  Mitsuko Masutani,et al.  A requirement for PARP-1 for the assembly or stability of XRCC1 nuclear foci at sites of oxidative DNA damage. , 2003, Nucleic acids research.

[22]  G. Poirier,et al.  Poly(ADP-ribosyl)ation reactions in the regulation of nuclear functions. , 1999, The Biochemical journal.

[23]  C. Wilson,et al.  Mammalian recombination-repair genes XRCC2 and XRCC3 promote correct chromosome segregation , 2000, Nature Cell Biology.

[24]  L. Thompson,et al.  Construction of human XRCC1 minigenes that fully correct the CHO DNA repair mutant EM9. , 1992, Nucleic acids research.

[25]  T. Helleday,et al.  RAD51 is involved in repair of damage associated with DNA replication in mammalian cells. , 2003, Journal of molecular biology.

[26]  Zhao-Qi Wang,et al.  Ablation of PARP-1 does not interfere with the repair of DNA double-strand breaks, but compromises the reactivation of stalled replication forks , 2004, Oncogene.