DNA double strand break repair in human bladder cancer is error prone and involves microhomology-associated end-joining

Nucleic Acids Res. 2004 Oct 5;32(17):5249-59. doi: 10.1093/nar/gkh842. Print 2004.


In human cells DNA double strand breaks (DSBs) can be repaired by the non-homologous end-joining (NHEJ) pathway. In a background of NHEJ deficiency, DSBs with mismatched ends can be joined by an error-prone mechanism involving joining between regions of nucleotide microhomology. The majority of joins formed from a DSB with partially incompatible 3' overhangs by cell-free extracts from human glioblastoma (MO59K) and urothelial (NHU) cell lines were accurate and produced by the overlap/fill-in of mismatched termini by NHEJ. However, repair of DSBs by extracts using tissue from four high-grade bladder carcinomas resulted in no accurate join formation. Junctions were formed by the non-random deletion of terminal nucleotides and showed a preference for annealing at a microhomology of 8 nt buried within the DNA substrate; this process was not dependent on functional Ku70, DNA-PK or XRCC4. Junctions were repaired in the same manner in MO59K extracts in which accurate NHEJ was inactivated by inhibition of Ku70 or DNA-PK(cs). These data indicate that bladder tumour extracts are unable to perform accurate NHEJ such that error-prone joining predominates. Therefore, in high-grade tumours mismatched DSBs are repaired by a highly mutagenic, microhomology-mediated, alternative end-joining pathway, a process that may contribute to genomic instability observed in bladder cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Nuclear / physiology
  • Base Sequence
  • Cell Line, Tumor
  • DNA Damage*
  • DNA Repair*
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins / physiology
  • Humans
  • Ku Autoantigen
  • Nuclear Proteins
  • Protein-Serine-Threonine Kinases / physiology
  • Recombination, Genetic
  • Sequence Homology
  • Ureteral Neoplasms / genetics
  • Ureteral Neoplasms / metabolism
  • Urinary Bladder Neoplasms / genetics*
  • Urinary Bladder Neoplasms / metabolism


  • Antigens, Nuclear
  • DNA-Binding Proteins
  • Nuclear Proteins
  • XRCC4 protein, human
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein-Serine-Threonine Kinases
  • Xrcc6 protein, human
  • Ku Autoantigen