Bcl-2 and mdr-1 gene expression during doxorubicin-induced apoptosis in murine leukemic P388 and P388/R84 cells

Cheppail Ramachandran, Wei You, Awtar Krishan

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The induction of apoptosis by doxorubicin (DOX) alone or in the presence of efflux blockers, verapamil (VPL) or trifluoperazine (TFP), and of bcl-2 and mdr-1 gene expression was analysed in murine leukaemic P388 and doxorubicin resistant P388/R84 cells. Incubation with DOX (0.1-1 μM) for 24 hours induced apoptosis in sensitive cells but not in the resistant P388/R84 cells. Flow cytometric analysis of apoptosis by terminal dideoxynucleotidyl (TdT) assay showed that 1 μM DOX induced apoptosis in 70% of P388 cells and in less than 5% of P388/R84 cells. When P388/R84 resistant cells were co-incubated with DOX and efflux blockers (10 μM VPL or 15 μM TFP), enhanced cellular DOX accumulation was accompanied by apoptosis. Quantitative analysis of DNA fragmentation by 14C-thymidine incorporation and gel electrophoresis of fragmented DNA confirmed the results from TdT assay and showed enhancement of DOX-induced DNA fragmentation in the presence of efflux blockers (VPL or TFP). DOX + VPL and DOX + TFP combination treatments induced apoptosis in upto 55% and 83% of P388/R84 cells, respectively. mdr-1 mRNA and P-gp expression were not altered during DOX-induced apoptosis. The results suggest that in murine leukemic cells, down-regulation of bcl-2 mRNA expression occurs during DOX-induced apoptosis and it depends on the cellular drug retention determined by mdr-1/P-gp drug efflux.

Original languageEnglish (US)
Pages (from-to)3369-3376
Number of pages8
JournalAnticancer research
Issue number5 A
StatePublished - Sep 1997
Externally publishedYes


  • Apoptosis
  • bcl-2 and mdr-1
  • Doxorubicin
  • Drug resistance

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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