title: ERK mediated upregulation of death receptor 5 overcomes the lack of p53 functionality in the diaminothiazole DAT1 induced apoptosis in colon cancer models: efficiency of DAT1 in Ras-Raf mutated cells.
abstract: BACKGROUND
  p53 is a tumour suppressor protein that plays a key role in many steps of apoptosis, and malfunctioning of this transcription factor leads to tumorigenesis. Prognosis of many tumours also depends upon the p53 status. Most of the clinically used anticancer compounds activate p53 dependent pathway of apoptosis and hence require p53 for their mechanism of action. Further, Ras/Raf/MEK/ERK axis is an important signaling pathway activated in many cancers. Dependence of diaminothiazoles, compounds that have gained importance recently due to their anticancer and anti angiogenic activities, were tested in cancer models with varying p53 or Ras/Raf mutational status.
  
  
  METHODS
  In this study we have used p53 mutated and knock out colon cancer cells and xenograft tumours to study the role of p53 in apoptosis mediated by diaminothiazoles. Colon cancer cell lines with varying mutational status for Ras or Raf were also used. We have also examined the toxicity and in vivo efficacy of a lead diaminothiazole 4-Amino-5-benzoyl-2-(4-methoxy phenylamino)thiazole (DAT1) in colon cancer xenografts.
  
  
  RESULTS
  We have found that DAT1 is active in both in vitro and in vivo models with nonfunctional p53. Earlier studies have shown that extrinsic pathway plays major role in DAT1 mediated apoptosis. In this study, we have found that DAT1 is causing p53 independent upregulation of the death receptor 5 by activating the Ras/Raf/MEK/ERK signaling pathway both in wild type and p53 suppressed colon cancer cells. These findings are also confirmed by the in vivo results. Further, DAT1 is more efficient to induce apoptosis in colon cancer cells with mutated Ras or Raf.
  
  
  CONCLUSIONS
  Minimal toxicity in both acute and subacute studies along with the in vitro and in vivo efficacy of DAT1 in cancers with both wild type and nonfunctional p53 place it as a highly beneficial candidate for cancer chemotherapy. Besides, efficiency in cancer cells with mutations in the Ras oncoprotein or its downstream kinase Raf raise interest in diaminothiazole class of compounds for further follow-up.
authors.affiliation: Cancer Research Program - 3, Rajiv Gandhi Centre for Biotechnology, Trivandrum, 695014, India.
authors.forename: Reshma
authors.initials: R
authors.lastname: Thamkachy
authors.affiliation: Cancer Research Program - 3, Rajiv Gandhi Centre for Biotechnology, Trivandrum, 695014, India.
authors.forename: Rohith
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Chemistry, University of Kerala, Trivandrum, India.
authors.forename: K N
authors.initials: KN
authors.lastname: Rajasekharan
authors.affiliation: Cancer Research Program - 3, Rajiv Gandhi Centre for Biotechnology, Trivandrum, 695014, India. sengupta_suparna@hotmail.com.
authors.forename: Suparna
authors.initials: S
authors.lastname: Sengupta
mesh_terms: D000818:Animals; D050256:Antimitotic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D020128:Inhibitory Concentration 50; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013844:Thiazoles / Q000494:pharmacology* / Q000633:toxicity; D023382:Toxicity Tests, Acute; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects*; D048490:raf Kinases / Q000235:genetics; D018631:ras Proteins / Q000235:genetics*
chemical_list: C496402:4-amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole; D050256:Antimitotic Agents; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D048490:raf Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins