Farnesyltransferase inhibitors induce DNA damage via reactive oxygen species in human cancer cells.
Farnesyltransferase inhibitors (FTIs) possess antitumor activity. Based on recent findings, we hypothesized that FTIs induce reactive oxygen species (ROS) that damage DNA, leading to DNA damage responses. To test this hypothesis, we investigated the effects of FTIs on the generation of ROS, DNA double-strand breaks (DSB), DNA damage responses, and RhoB, and the effects of quenching ROS on these FTI effects. We evaluated four FTIs in human cancer cell lines of different tissue origins. We found that FTIs induced ROS and DSBs. Suppressing expression of the beta-subunit of farnesyltransferase with siRNA did not induce ROS, but slightly attenuated the ROS induced by FTIs. N-acetyl-L-cysteine (NAC), but not caspase inhibitors, blocked FTI-induced DSBs, suggesting that the DSBs were caused by ROS and did not result from apoptosis. The DSBs led to DNA damage responses. H2AX became phosphorylated and formed nuclear foci. The DNA-damage-sensing molecules involved were probably ataxia-telangiectasia mutated protein (ATM) and DNA-dependent protein kinase (DNA-PK) but not ATM- and Rad3-related protein (ATR). Key components of the homologous recombination and nonhomologous end joining repair pathways (DNA-PK, BRCA1, and NBS1) underwent phosphorylation and formed nuclear foci. RhoB, a mediator of the antineoplastic effect of FTIs and a protein inducible by DNA damage, was increased by FTIs. This increase was blocked by NAC. We concluded that FTIs induced oxidative DNA damage by inducing ROS and initiated DNA damage responses, including RhoB induction, and there was a complex relationship among FTIs, farnesyltransferase, ROS, and RhoB. Our data also imply that inhibitors of DNA repair may accentuate the clinical efficacy of FTIs.
Pan
Jingxuan
J
Department of Experimental Therapeutics, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
She
Miaorong
M
Xu
Zhi-Xiang
ZX
Sun
Lily
L
Yeung
Sai-Ching Jim
SC
D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051231:Farnesyltranstransferase; D045325:HCT116 Cells; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D009687:Nuclear Proteins; D011090:Polyenes / Q000494:pharmacology*; D053284:Polyunsaturated Alkamides; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000096:biosynthesis / Q000378:metabolism
D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D017382:Reactive Oxygen Species; D025521:Tumor Suppressor Proteins; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D020743:rhoB GTP-Binding Protein; C054474:manumycin