title: P-glycoprotein expression does not change the apoptotic pathway induced by curcumin in HL-60 cells.
abstract: OBJECTIVE
  One of the mechanisms responsible for the multidrug resistance (MDR) phenotype of cancer cells is overexpression of so-called ATP-dependent drug efflux proteins: the 170-kDa P-glycoprotein (P-gp) encoded by the MDR1 gene and the 190-kDa multidrug resistance-associated protein 1 encoded by the MRP1 gene. The purpose of the present study was to verify the hypothesis postulating that P-gp expression, apart from enabling drug efflux, confers on the cells resistance to apoptosis by inhibiting caspase-8 and caspase-3.
  
  
  METHODS
  Human HL-60 cells, either drug-sensitive or with the MDR phenotype caused by overexpression of P-gp (HL-60/Vinc) or MRP1 (HL-60/Adr), were treated with the natural dye curcumin at 50 micro M or with UVC to induce apoptosis. Symptoms of cell death were assessed by morphological observation after Hoechst staining, DNA fragmentation was measured by flow cytometry and the TUNEL method, and caspase-8 and caspase-3 activation and cytochrome c release from mitochondria were measured by Western blotting.
  
  
  RESULTS
  Curcumin induced cell death in HL-60 cells, both sensitive and with the MDR phenotype, which could be classified as caspase-3-dependent apoptosis, together with cytochrome c release, activation of caspase-3 and oligonucleosomal DNA fragmentation. No active caspase-8 was detected. Also UVC caused caspase-3 activation in both the sensitive and the MDR HL-60 cells.
  
  
  CONCLUSIONS
  Our findings show that there was no correlation between P-gp expression and resistance to caspase-3-dependent apoptosis induced by curcumin and UVC, at least in HL-60 cells. However, we cannot exclude the possibility of parallel P-gp expression and caspase-3 inhibition in some other cell lines, as cancer cells can acquire many different apoptosis-resistance mechanisms.
authors.affiliation: Laboratory of Molecular Bases of Aging, Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093 Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Bielak-Mijewska
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Piwocka
authors.forename: Adriana
authors.initials: A
authors.lastname: Magalska
authors.forename: Ewa
authors.initials: E
authors.lastname: Sikora
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000096:biosynthesis; D003474:Curcumin / Q000494:pharmacology*; D045304:Cytochromes c / Q000096:biosynthesis / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D019450:Genes, MDR / Q000235:genetics; D018922:HL-60 Cells; D006801:Humans; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D011506:Proteins; D012333:RNA, Messenger; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases; D003474:Curcumin