title: Resveratrol abrogates the temozolomide-induced G2 arrest leading to mitotic catastrophe and reinforces the temozolomide-induced senescence in glioma cells.
abstract: BACKGROUND
  Temozolomide (TMZ) is the most widely used drug to treat glioblastoma (GBM), which is the most common and aggressive primary tumor of the Central Nervous System and one of the hardest challenges in oncotherapy. TMZ is an alkylating agent that induces autophagy, apoptosis and senescence in GBM cells. However, therapy with TMZ increases survival after diagnosis only from 12 to 14.4 months, making the development of combined therapies to treat GBM fundamental. One candidate for GBM therapy is Resveratrol (Rsv), which has additive toxicity with TMZ in several glioma cells in vitro and in vivo. However, the mechanism of Rsv and TMZ additive toxicity, which is the aim of the present work, is not clear, especially concerning cell cycle dynamics and long term effects.
  
  
  METHODS
  Glioma cell lines were treated with Rsv and TMZ, alone or in combinations, and the induction and the role of autophagy, apoptosis, cell cycle dynamics, protein expression and phosphorylation status were measured. We further evaluated the long term senescence induction and clonogenic capacity.
  
  
  RESULTS
  As expected, temozolomide caused a G2 cell cycle arrest and extensive DNA damage response. Rsv did not reduced this response, even increasing pATM, pChk2 and gammaH2Ax levels, but abrogated the temozolomide-induced G2 arrest, increasing levels of cyclin B and pRb(S807/811) and reducing levels of pWee1(S642) and pCdk1(Y15). This suggests a cellular state of forced passage through G2 checkpoint despite large DNA damage, a scenario that may produce mitotic catastrophe. Indeed, the proportion of cells with high nuclear irregularity increased from 6 to 26% in 48 h after cotreatment. At a long term, a reduction in clonogenic capacity was observed, accompanied by a large induction of senescence.
  
  
  CONCLUSIONS
  The presence of Rsv forces cells treated with TMZ through mitosis leading to mitotic catastrophe and senescence, reducing the clonogenic capacity of glioma cells and increasing the chronic effects of temozolomide.
authors.affiliation: Department of Biophysics, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Eduardo C
authors.initials: EC
authors.lastname: Filippi-Chiela
authors.forename: Marcos Paulo
authors.initials: MP
authors.lastname: Thomé
authors.forename: Mardja Manssur
authors.initials: MM
authors.lastname: Bueno e Silva
authors.forename: Alessandra Luíza
authors.initials: AL
authors.lastname: Pelegrini
authors.forename: Pitia Flores
authors.initials: PF
authors.lastname: Ledur
authors.forename: Bernardo
authors.initials: B
authors.lastname: Garicochea
authors.forename: Lauren L
authors.initials: LL
authors.lastname: Zamin
authors.forename: Guido
authors.initials: G
authors.lastname: Lenz
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D016203:CDC2 Protein Kinase / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000187:drug effects*; D064447:Checkpoint Kinase 2 / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004357:Drug Synergism; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D005909:Glioblastoma / Q000188:drug therapy*; D006657:Histones / Q000378:metabolism; D006801:Humans; D008938:Mitosis / Q000187:drug effects; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D000077185:Resveratrol; D013267:Stilbenes / Q000494:pharmacology*; D000077204:Temozolomide; D013997:Time Factors
chemical_list: D018906:Antineoplastic Agents, Alkylating; D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D019926:Cyclin B; C468783:H2AX protein, human; D006657:Histones; D009687:Nuclear Proteins; D013267:Stilbenes; D003606:Dacarbazine; D064447:Checkpoint Kinase 2; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D016203:CDC2 Protein Kinase; D000077185:Resveratrol; D000077204:Temozolomide