title: Quercetin induces cytochrome-c release and ROS accumulation to promote apoptosis and arrest the cell cycle in G2/M, in cervical carcinoma: signal cascade and drug-DNA interaction.
abstract: OBJECTIVE
  Small aromatic compounds like flavonoids can intercalate with DNA molecules bringing about conformational changes leading to reduced replication and transcription. Here, we have examined one dietary flavonoid, quercetin (found in many fruit and vegetables), for possible anti-cancer effects, on HeLa cells originally derived from a case of human cervical cancer.
  
  
  METHODS
  By circular dichroism spectroscopy we tested whether quercetin effectively interacted with DNA to bring about conformational changes that would strongly inhibit proliferation and migration of the HeLa cells. Cytotoxic effects of quercetin on cancer/normal cells, if any, were determined by MTT assay and such depolarization of mitochondrial membrane potential, as a consequence of quercetin treatment, and accumulation of reactive oxygen species (ROS) also were studied, by FACS analysis and expression profiles of different anti- and pro-apoptotic genes and their products were determined.
  
  
  RESULTS
  Quercetin intercalated with calf thymus cell DNA and HeLa cell DNA and inhibition of anti-apoptotic AKT and Bcl-2 expression were observed. Levels of mitochondrial cytochrome-c were elevated and depolarization of mitochondrial membrane potential occurred with increase of ROS; upregulation of expression of p53 and caspase-3 activity were also noted. These alterations in signalling proteins and externalization of phosphotidyl serine residues were involved with initiation of apoptosis. Reduced AKT expression suggested reduction in cell proliferation and metastasis potential, with arrest of the cell cycle at G2/M.
  
  
  CONCLUSIONS
  Quercetin would have potential for use in cervical cancer chemotherapy.
authors.affiliation: Department of Zoology, Cytogenetics and Molecular Biology Laboratory, University of Kalyani, Kalyani, 741235, West Bengal, India.
authors.forename: K
authors.initials: K
authors.lastname: Bishayee
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: A
authors.initials: A
authors.lastname: Mukherjee
authors.forename: R
authors.initials: R
authors.lastname: Sadhukhan
authors.forename: J
authors.initials: J
authors.lastname: Mondal
authors.forename: A R
authors.initials: AR
authors.lastname: Khuda-Bukhsh
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002942:Circular Dichroism; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D053938:DNA Fragmentation; D004273:DNA, Neoplasm / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints; D015972:Gene Expression Regulation, Neoplastic; D019254:Genes, bcl-2; D006367:HeLa Cells; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints; D053078:Membrane Potential, Mitochondrial; D009707:Nucleosomes / Q000473:pathology; D011794:Quercetin / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D059467:Transcriptome; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004273:DNA, Neoplasm; D009707:Nucleosomes; D017382:Reactive Oxygen Species; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D045304:Cytochromes c; D004247:DNA; C427203:calf thymus DNA; D011794:Quercetin; C505407:CASP3 protein, human; D053148:Caspase 3