title: Targeting KRAS Oncogene in Colon Cancer Cells with 7-Carboxylate Indolo[3,2-b]quinoline Tri-Alkylamine Derivatives.
abstract: BACKGROUND
  A guanine-rich strand within the promoter of the KRAS gene can fold into an intra-molecular G-quadruplex structure (G4), which has an important role in the regulation of KRAS transcription. We have previously identified indolo[3,2-b]quinolines with a 7-carboxylate group and three alkylamine side chains (IQ3A) as effective G4 stabilizers and promising selective anticancer leads. Herein we investigated the anticancer mechanism of action of these compounds, which we hypothesized due to stabilization of the G4 sequence in the KRAS promoter and subsequent down-regulation of gene expression.
  
  
  RESULTS
  IQ3A compounds showed greater stabilization of G4 compared to duplex DNA structures and reduced KRAS promoter activity in a dual luciferase reporter assay. Moreover, IQ3A compounds showed high anti-proliferative activity in HCT116 and SW620 colon cancer cells (IC50 < 2.69 μM), without eliciting cell death in non-malignant HEK293T human embryonic kidney, and human colon fibroblasts CCD18co. IQ3A compounds significantly reduced KRAS mRNA and protein steady-state levels at IC50 concentrations, and increased p53 protein steady-state levels and cell death by apoptosis in HCT116 cells (mut KRAS, wt p53). Furthermore, KRAS silencing in HCT116 p53 wild-type (p53(+/+)) and null (p53(-/-)) isogenic cell lines induced a higher level of cell death, and a higher IQ3A-induced cell death in HCT116 p53(+/+) compared to HCT116 p53(-/-).
  
  
  CONCLUSIONS
  Herein we provide evidence that G4 ligands such as IQ3A compounds can target G4 motifs present in KRAS promoter, down-regulate the expression of the mutant KRAS gene through inhibition of transcription and translation, and induce cell death by apoptosis in colon cancer cell lines. Thus, targeting KRAS at the genomic level with G4 ligands may be a new anticancer therapy strategy for colon cancer.
authors.affiliation: Cell Function and Therapeutic Targeting Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Hugo
authors.initials: H
authors.lastname: Brito
authors.affiliation: Medicinal Chemistry Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Martins
authors.affiliation: Medicinal Chemistry Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Lavrado
authors.affiliation: Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Eduarda
authors.initials: E
authors.lastname: Mendes
authors.affiliation: Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Francisco
authors.affiliation: Medicinal Chemistry Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal; Center for Systems Biology, Massachusetts General Hospital, Boston, MA 02114, United States of America.
authors.forename: Sofia A
authors.initials: SA
authors.lastname: Santos
authors.affiliation: UCL School of Pharmacy, University College London, 29/39 Brunswick Square, London WC1N 1AX, United Kingdom.
authors.forename: Stephan A
authors.initials: SA
authors.lastname: Ohnmacht
authors.affiliation: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-333, Republic of Korea.
authors.forename: Nam-Soon
authors.initials: NS
authors.lastname: Kim
authors.affiliation: Cell Function and Therapeutic Targeting Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Cecília M P
authors.initials: CM
authors.lastname: Rodrigues
authors.affiliation: Medicinal Chemistry Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Moreira
authors.affiliation: UCL School of Pharmacy, University College London, 29/39 Brunswick Square, London WC1N 1AX, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Neidle
authors.affiliation: Cell Function and Therapeutic Targeting Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Borralho
authors.affiliation: Medicinal Chemistry Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Paulo
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics; D054856:G-Quadruplexes / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D011905:Genes, ras; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D011401:Promoter Regions, Genetic; D011804:Quinolines / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D011804:Quinolines