Impact of DNA repair pathways on the cytotoxicity of piperlongumine in chicken DT40 cell-lines.
Saki Okamoto1, Takeo Narita2, Hiroyuki Sasanuma2, Shunichi Takeda2, Shin-ichiro Masunaga1, Tadayoshi Bessho3 and Keizo Tano1
1 Division of Radiation Life Science, Research Reactor Institute, Kyoto University, Kumatori, Osaka Japan
2 Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Sakyo-Ku, Kyoto, Japan
3 Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska, USA.
Correspondence:
Tadayoshi Bessho, email:
Correspondence:
Keizo Tano, email:
Keywords: BRCA1, BRCA2, piperlongumine, oxidative stress, homologous recombination, chemotherapy
Received: July 7, 2014 Accepted: August 8, 2014 Published: August 10, 2014
Abstract
Piperlongumine is a naturally-occurring small molecule with various biological activities. Recent studies demonstrate that piperlongumine selectively kills various types of transformed cells with minimal toxicity to non-transformed cells by inducing a high level of reactive oxygen species (ROS). ROS generates various types of DNA lesions, including base modifications and single strand breaks. In order to examine the contribution of ROS-induced DNA damage to the cytotoxicity by piperlongumine, various DNA repair-deficient chicken DT40 cell-lines with a single DNA repair gene deletion were tested for cellular sensitivity to piperlongumine. The results showed that cell lines defective in homologous recombination (HR) display hyper-sensitivity to piperlongumine, while other cell lines with a deficiency in non-homologous end joining (NHEJ), base excision repair (BER), nucleotide excision repair (NER), Fanconi anemia (FA) pathway, or translesion DNA synthesis (TLS) polymerases, show no sensitivity to piperlongumine. The results strongly implicate that double strand breaks (DSBs) generated by piperlongumine are major cytotoxic DNA lesions. Furthermore, a deletion of 53BP1 or Ku70 in the BRCA1-deficient cell line restored cellular resistance to piperlongumine. This strongly supports the idea that piperlongumine induces DSB- mediated cell death. Interestingly, piperlongumine makes the wild type DT40 cell line hypersensitive to a PARP-inhibitor, Olaparib. The results implicate that piperlongumine inhibits HR. Further analysis with cell-based HR assay and the kinetic study of Rad51 foci formation confirmed that piperlongumine suppresses HR activity. Altogether, we revealed novel mechanisms of piperlongumine-induced cytotoxicity.
