title: A non-apoptotic function of caspase-3 in pharmacologically-induced differentiation of K562 cells.
abstract: OBJECTIVE
  Several anticancer drugs with diverse chemical structures can induce differentiation of cancer cells. This study was undertaken to explore the potential contribution of caspase-3 to pharmacologically-induced differentiation of K562 cells.
  
  
  METHODS
  We assessed differentiation by measuring the expression of glycophorin A and haemoglobin synthesis in K562 cells treated with low concentrations of doxorubicin, hydroxyurea, cytosine arabinoside, cisplatin and haemin. Caspase-3 activation, mitochondrial membrane potential dissipation and viability were assessed by FACS. GATA-1-binding activity was evaluated by EMSA.
  
  
  RESULTS
  Treatment of K562 cells with low concentrations of the tested drugs activated caspase-3 but did not trigger detectable apoptosis. Instead, elevated levels of haemoglobin-positive and glycophorin A/caspase-3-double-positive cells were observed, suggesting involvement of caspase-3 in drug-induced differentiation. Inhibition of caspase-3 activity significantly reduced the ability of K562 cells to execute the differentiation programme. Mitochondrial membrane potential dissipation was observed, indicating involvement of the mitochondrial pathway. Binding activity of GATA-1, transcription factor responsible for differentiation and cell survival, was not diminished by increased caspase-3 activity during drug-stimulated differentiation.
  
  
  CONCLUSIONS
  Our results could explain how anticancer drugs, with diverse structures and modes of action, can stimulate erythroid differentiation in leukaemic cells with appropriate genetic backgrounds. Our findings imply that some similarities exist between pharmacologically-induced differentiation of erythroleukaemic cells and normal erythropoiesis, both involving caspase-3 activation at high levels of anti-apoptotic protein Bcl-X(L) and chaperone protein Hsp70 (heat shock protein 70). Therefore, the functions of caspase-3, unrelated to cell death, can be extended to pharmacologically-induced differentiation of some cancer cells.
authors.affiliation: Department of Molecular Biology of Cancer, Medical University of Lodz, Lodz, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Sztiller-Sikorska
authors.forename: J
authors.initials: J
authors.lastname: Jakubowska
authors.forename: M
authors.initials: M
authors.lastname: Wozniak
authors.forename: M
authors.initials: M
authors.lastname: Stasiak
authors.forename: M
authors.initials: M
authors.lastname: Czyz
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D050982:GATA1 Transcription Factor / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D020014:K562 Cells; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D013329:Structure-Activity Relationship; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D018840:HSP70 Heat-Shock Proteins; D051020:bcl-X Protein; D003561:Cytarabine; D004317:Doxorubicin; D053148:Caspase 3; D002945:Cisplatin; D006918:Hydroxyurea