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Related Experiment Videos

Pheophorbide a is a specific probe for ABCG2 function and inhibition.

Robert W Robey1, Kenneth Steadman, Orsolya Polgar

  • 1Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 10, Rm. 12C203, 9000 Rockville Pike, Bethesda, MD 20892, USA. robeyr@mail.nih.gov

Cancer Research
|February 20, 2004
PubMed
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Pheophorbide a (PhA) serves as a specific substrate for ABCG2 (ATP-binding cassette sub-family G member 2). This study developed a functional assay using PhA to measure ABCG2 expression and function in cells.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Pharmacology

Background:

  • Pheophorbide a (PhA), a chlorophyll catabolite, has been identified as a substrate for the ATP-binding cassette sub-family G member 2 (ABCG2) transporter.
  • Previous studies using Abcg2 knockout mice indicated PhA's role as an ABCG2 substrate.

Purpose of the Study:

  • To develop a functional assay for ABCG2 using PhA.
  • To evaluate PhA's utility in measuring ABCG2 expression and function.

Main Methods:

  • Development of a functional assay utilizing PhA and the ABCG2 inhibitor fumitremorgin C.
  • Assessment of PhA transport in cell lines expressing ABCG2, P-glycoprotein, or multidrug resistance-associated protein 1.
  • Correlation of PhA transport with cell surface ABCG2 expression using the 5D3 antibody.

Related Experiment Videos

  • Investigation of the effects of UCN-01 and tariquidar on ABCG2-mediated PhA transport and cytotoxicity assays.

    • Main Results:

    • PhA transport was exclusively observed in cell lines expressing ABCG2.
    • Fumitremorgin C-inhibitable PhA transport correlated with cell surface ABCG2 expression.
    • The cyclin-dependent kinase inhibitor UCN-01 and the P-glycoprotein inhibitor tariquidar affected ABCG2-mediated PhA transport.
    • ABCG2-mediated resistance to SN-38 and topotecan was reduced by tariquidar, and ABCG2-transfected cells showed resistance to UCN-01.

    Conclusions:

    • Pheophorbide a is a specific substrate for ABCG2.
    • The developed PhA-based assay can be valuable for assessing ABCG2 function and expression in clinical settings.