title: Epigenetic-based combinatorial resveratrol and pterostilbene alters DNA damage response by affecting SIRT1 and DNMT enzyme expression, including SIRT1-dependent γ-H2AX and telomerase regulation in triple-negative breast cancer.
abstract: BACKGROUND
  Nutrition is believed to be a primary contributor in regulating gene expression by affecting epigenetic pathways such as DNA methylation and histone modification. Resveratrol and pterostilbene are phytoalexins produced by plants as part of their defense system. These two bioactive compounds when used alone have been shown to alter genetic and epigenetic profiles of tumor cells, but the concentrations employed in various studies often far exceed physiologically achievable doses. Triple-negative breast cancer (TNBC) is an often fatal condition that may be prevented or treated through novel dietary-based approaches.
  
  
  METHODS
  HCC1806 and MDA-MB-157 breast cancer cells were used as TNBC cell lines in this study. MCF10A cells were used as control breast epithelial cells to determine the safety of this dietary regimen. CompuSyn software was used to determine the combination index (CI) for drug combinations.
  
  
  RESULTS
  Combinatorial resveratrol and pterostilbene administered at close to physiologically relevant doses resulted in synergistic (CI <1) growth inhibition of TNBCs. SIRT1, a type III histone deacetylase (HDAC), was down-regulated in response to this combinatorial treatment. We further explored the effects of this novel combinatorial approach on DNA damage response by monitoring γ-H2AX and telomerase expression. With combination of these two compounds there was a significant decrease in these two proteins which might further resulted in significant growth inhibition, apoptosis and cell cycle arrest in HCC1806 and MDA-MB-157 breast cancer cells, while there was no significant effect on cellular viability, colony forming potential, morphology or apoptosis in control MCF10A breast epithelial cells. SIRT1 knockdown reproduced the effects of combinatorial resveratrol and pterostilbene-induced SIRT1 down-regulation through inhibition of both telomerase activity and γ-H2AX expression in HCC1806 breast cancer cells. As a part of the repair mechanisms and role of SIRT1 in recruiting DNMTs, the effects of this combination treatment was also explored on DNA methyltransferases (DNMTs) expression. Interestingly, the compounds resulted in a significant down-regulation of DNMT enzymes with no significant effects on DNMT enzyme expression in MCF10A control cells.
  
  
  CONCLUSIONS
  Collectively, these results provide new insights into the epigenetic mechanisms of a novel combinatorial nutrient control strategy that exhibits synergy and may contribute to future recalcitrant TNBC prevention and/or therapy.
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL, 35294, USA. rishabh@uab.edu.
authors.forename: Rishabh
authors.initials: R
authors.lastname: Kala
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL, 35294, USA. hnshah@uab.edu.
authors.forename: Harsh N
authors.initials: HN
authors.lastname: Shah
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL, 35294, USA. jcvessel@uab.edu.
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Martin
authors.affiliation: Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL, 35294, USA. trygve@uab.edu.|Comprehensive Center for Healthy Aging, University of Alabama at Birmingham, 1530 3rd Avenue South, Birmingham, AL, 35294, USA. trygve@uab.edu.|Comprehensive Cancer Center, University of Alabama at Birmingham, 1802 6th Avenue South, Birmingham, AL, 35294, USA. trygve@uab.edu.|Nutrition Obesity Research Center, University of Alabama at Birmingham, 1675 University Boulevard, Birmingham, AL 35294, USA. trygve@uab.edu.|Comprehensive Diabetes Center, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL, 35294, USA. trygve@uab.edu.
authors.forename: Trygve O
authors.initials: TO
authors.lastname: Tollefsbol
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics* / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D044127:Epigenesis, Genetic / Q000187:drug effects; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006657:Histones / Q000378:metabolism*; D006801:Humans; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D000077185:Resveratrol; D056564:Sirtuin 1 / Q000235:genetics* / Q000378:metabolism; D013267:Stilbenes / Q000008:administration & dosage / Q000494:pharmacology; D019098:Telomerase / Q000378:metabolism*; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases; D006657:Histones; D018719:Erb-b2 Receptor Tyrosine Kinases; D000077185:Resveratrol; D056564:Sirtuin 1; D013267:Stilbenes; D019098:Telomerase; C107773:pterostilbene