title: The anticancer activity of the substituted pyridone-annelated isoindigo (5'-Cl) involves G0/G1 cell cycle arrest and inactivation of CDKs in the promyelocytic leukemia cell line HL-60.
abstract: OBJECTIVE
  The antileukemic potential of isoindigos make them desired candidates for understanding their mechanism of action. We have recently synthesized a novel group of pyridone-annelated isoindigos and identified the derivative 5'-Cl that is cytotoxic to various cancer cell lines. In the present study, we analyzed the effect of this compound on cell cycle of the promyelocytic leukemia cell line HL-60.
  
  
  METHODS
  HL-60 cells were treated with 5'-Cl and its effect on cell cycle stages were determined by flow cytometry. Expression of cyclins, cyclin dependent kinases (CDKs) and cyclin kinase inhibitors (CKIs) were determined by Western blotting, and activation of CDKs was studied using kinase assays.
  
  
  RESULTS
  5'-Cl remarkably arrested cell cycle in HL-60 cells at the G0/G1 phase in a dose and time-dependent manner. Furthermore, 5'-Cl treatment significantly inhibited expression of D-cyclins, CDK2 and CDK4 and suppressed phosphorylation of the retinoblastoma protein Rb, whereas it increased the level of CKI p21. Molecular modelling experiments show that 5'-Cl may compete with ATP for binding to the catalytic subunit of CDK2 and CDK4 that could lead to inhibition of these enzymes. Indeed, 5'-Cl inhibited the kinase activity of CDK2 and CDK4 both in cell free systems and in treated cells. 5'-Cl also inhibited cell cycle progression in several other tumor cell lines.
  
  
  CONCLUSIONS
  We demonstrate the potent inhibitory effects of 5'-Cl on HL-60 cells could be mediated by arresting cells in the G0/G1 phase.
authors: Department of Basic Medical Sciences, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS), National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia.
authors: Ayman M
authors: AM
authors: Saleh
authors: Ahmad
authors: A
authors: Aljada
authors: Mustafa M
authors: MM
authors: El-Abadelah
authors: Mutasem O
authors: MO
authors: Taha
authors: Salim S
authors: SS
authors: Sabri
authors: Jalal A
authors: JA
authors: Zahra
authors: Mohammad Azhar
authors: MA
authors: Aziz
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004354:Drug Screening Assays, Antitumor; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D018922:HL-60 Cells; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism / Q000473:pathology; D062105:Molecular Docking Simulation; D010766:Phosphorylation; D011728:Pyridones / Q000737:chemistry* / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007211:Indoles; D011728:Pyridones; D016160:Retinoblastoma Protein; C049010:isoindigotin; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases