title: Induction of DNA damage and p21-dependent senescence by Riccardin D is a novel mechanism contributing to its growth suppression in prostate cancer cells in vitro and in vivo.
abstract: OBJECTIVE
  Our previous studies had shown that Riccardin D (RD) exhibited cytotoxic effects by induction of apoptosis and inhibition of angiogenesis and topoisomerase II. Here, we reported that apoptosis is not the sole mechanism by which RD inhibits tumor cell growth because low concentrations of RD caused cellular senescence in prostate cancer (PCa) cells.
  
  
  METHODS
  Low concentrations of RD were used to treat PCa cells in vitro and in vivo, and senescence-associated β-galactosidase activity, DNA damage response markers, and/or colony-forming ability, cell cycle were analyzed, respectively. We then used siRNA knockdown to identify key factor in RD-triggered cellular senescence.
  
  
  RESULTS
  RD treatment caused growth arrest at G0/G1 phase with features of cellular senescence phenotype such as enlarged and flattened morphology, increased senescence-associated-beta-galactosidase staining cells, and decreased cell proliferation in PCa cells. Induction of cellular senescence by RD occurred through activation of DNA damage response including increases in the phosphor-H2AX, inactivation of Chk1/2, and suppression of repair-related Ku70/86 and phosphor-BRCA1 in PCa cells in vitro and in vivo. Analysis of expression levels of p53, p21(CIP1), p16(INK4a), p27(KIP1), pRb and E2F1 and genetic knockdown of p21(CIP1) demonstrated an important role of p21(CIP1) in RD-triggered cellular senescence.
  
  
  CONCLUSIONS
  Involvement of the DNA damage response and p21(CIP1) defines a novel mechanism of RD action and indicates that RD could be further developed as a promising anticancer agent for cancer therapy.
authors: Department of Biochemistry and Molecular Biology, Shandong University School of Medicine, 44 Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China.
authors: Zhongyi
authors: Z
authors: Hu
authors: Denglu
authors: D
authors: Zhang
authors: Jianrong
authors: J
authors: Hao
authors: Keli
authors: K
authors: Tian
authors: Wei
authors: W
authors: Wang
authors: Hongxiang
authors: H
authors: Lou
authors: Huiqing
authors: H
authors: Yuan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D004249:DNA Damage; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010647:Phenyl Ethers / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011897:Random Allocation; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D013267:Stilbenes / Q000494:pharmacology*; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D010647:Phenyl Ethers; D013267:Stilbenes; C547185:riccardin D