title: Mechanism of Action of Nigella sativa on Human Colon Cancer Cells: the Suppression of AP-1 and NF-κB Transcription Factors and the Induction of Cytoprotective Genes.
abstract: OBJECTIVE
  Colorectal cancer is one of the leading causes of death in the world. The aim of this study was to investigate the growth-suppression potentiality of a crude saponin extract (CSENS) prepared from medicinal herb, Nigella sativa, on human colon cancer cells, HCT116.
  
  
  METHODS
  HCT116 cells were subjected to increasing doses of CSENS for 24, 48 and 72 h, and then harvested and assayed for cell viability by WST-1. Flow cytometry analyses, cell death detection ELISA, fluorescent stains (Hoechst 33342 and acridine orange/ethidium bromide), DNA laddering and comet assays were carried out to confirm the apoptogenic effects of CSENS. Luciferase reporter gene assays, quantitative reverse transcription-polymerase chain reaction and Western blot analyses were performed to assess the impact of CAERS and CFEZO on the expression levels of key regulatory proteins in HCT116 cells.
  
  
  RESULTS
  The results demonstrated that CSENS inhibited proliferation and induced apoptosis. Apoptosis was confirmed by flow cytometry analyses, while CSENS-treated cells exhibited morphological hallmarks of apoptosis including cell shrinkage, irregularity in cellular shape, cellular detachment and chromatin condensation. Biochemical signs of apoptosis, such as DNA degradation, were observed by comet assay and gel electrophoresis. The pro-apoptotic effect of CSENS was caspase-3-independent and associated with increase of the Bax/Bcl-2 ratio. CSENS treatment down-regulated transcriptional and DNA-binding activities of NF-κB and AP-1 proteins, associated with down-regulation of their target oncogenes, c-Myc, cyclin D1 and survivin. On the other hand, CSENS up-regulated transcriptional and DNA-binding activities of Nrf2 and expression of cytoprotective genes. In addition, CSENS modulated the expression levels of ERK1/2 MAPK, p53 and p21.
  
  
  CONCLUSIONS
  These findings suggest that CSENS may be a valuable agent for treatment of colon cancer.
authors.affiliation: Department of Biological Sciences, Faculty of Sciences, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia E-mail : aielkady@yahoo.co.uk.
authors.forename: Ayman I
authors.initials: AI
authors.lastname: Elkady
authors.forename: Rania A
authors.initials: RA
authors.lastname: Hussein
authors.forename: Sufian M
authors.initials: SM
authors.lastname: El-Assouli
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy*; D019938:Cyclin D1 / Q000096:biosynthesis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis; D019610:Cytoprotection / Q000235:genetics*; D053960:DNA Breaks / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000096:biosynthesis; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D056945:Hep G2 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000096:biosynthesis; D061986:MCF-7 Cells; D051267:NF-E2-Related Factor 2 / Q000096:biosynthesis; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D031881:Nigella sativa / Q000378:metabolism*; D010936:Plant Extracts / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012503:Saponins / Q000494:pharmacology; D000077022:Survivin; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494826:BAX protein, human; C107489:BIRC5 protein, human; C530104:CCND1 protein, human; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D051034:Inhibitor of Apoptosis Proteins; C489427:MYC protein, human; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495635:NFE2L2 protein, human; D010936:Plant Extracts; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D012503:Saponins; D000077022:Survivin; C495901:TP53 protein, human; D018808:Transcription Factor AP-1; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D019938:Cyclin D1; D048049:Extracellular Signal-Regulated MAP Kinases