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Kinetics of MDR transport in tumor-initiating cells.

Koshkin V, Yang BB, Krylov SN - PLoS ONE (2013)

Bottom Line: In this way it was shown that activation of MDR in TICs occurs in two ways: through the increase of V max in one fraction of cells, and through decrease of K M in another fraction.In addition, kinetic data showed that heterogeneity of MDR parameters in TICs significantly exceeds that of bulk cells.Potential consequences of these findings for chemotherapy are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario, Canada.

ABSTRACT
Multidrug resistance (MDR) driven by ABC (ATP binding cassette) membrane transporters is one of the major causes of treatment failure in human malignancy. MDR capacity is thought to be unevenly distributed among tumor cells, with higher capacity residing in tumor-initiating cells (TIC) (though opposite finding are occasionally reported). Functional evidence for enhanced MDR of TICs was previously provided using a "side population" assay. This assay estimates MDR capacity by a single parameter - cell's ability to retain fluorescent MDR substrate, so that cells with high MDR capacity ("side population") demonstrate low substrate retention. In the present work MDR in TICs was investigated in greater detail using a kinetic approach, which monitors MDR efflux from single cells. Analysis of kinetic traces obtained allowed for the estimation of both the velocity (V max) and affinity (K M) of MDR transport in single cells. In this way it was shown that activation of MDR in TICs occurs in two ways: through the increase of V max in one fraction of cells, and through decrease of K M in another fraction. In addition, kinetic data showed that heterogeneity of MDR parameters in TICs significantly exceeds that of bulk cells. Potential consequences of these findings for chemotherapy are discussed.

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Related in: MedlinePlus

Cells grown in monolayers (a, left image) and tumorspheres (a, right image) show different ability to form secondary tumorspheres (b), resistance to doxorubicin (c), expression of MRP1 (d), and similar ability to retain BCECF and exclude PI (e).Bars represent means ± SE, *p < 0.05.
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pone-0079222-g001: Cells grown in monolayers (a, left image) and tumorspheres (a, right image) show different ability to form secondary tumorspheres (b), resistance to doxorubicin (c), expression of MRP1 (d), and similar ability to retain BCECF and exclude PI (e).Bars represent means ± SE, *p < 0.05.

Mentions: Monolayers (Figure 1a, left image) and tumorspheres (Figure 1a, right image) were dissociated and subjected to tumorsphere formation efficiency assay (see Materials and methods). Figure 1b indicates that cells originating from tumorspheres showed a significantly higher ability to undergo anchorage-independent growth compared to monolayer cells (p < 0.05, n = 3).


Kinetics of MDR transport in tumor-initiating cells.

Koshkin V, Yang BB, Krylov SN - PLoS ONE (2013)

Cells grown in monolayers (a, left image) and tumorspheres (a, right image) show different ability to form secondary tumorspheres (b), resistance to doxorubicin (c), expression of MRP1 (d), and similar ability to retain BCECF and exclude PI (e).Bars represent means ± SE, *p < 0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815210&req=5

pone-0079222-g001: Cells grown in monolayers (a, left image) and tumorspheres (a, right image) show different ability to form secondary tumorspheres (b), resistance to doxorubicin (c), expression of MRP1 (d), and similar ability to retain BCECF and exclude PI (e).Bars represent means ± SE, *p < 0.05.
Mentions: Monolayers (Figure 1a, left image) and tumorspheres (Figure 1a, right image) were dissociated and subjected to tumorsphere formation efficiency assay (see Materials and methods). Figure 1b indicates that cells originating from tumorspheres showed a significantly higher ability to undergo anchorage-independent growth compared to monolayer cells (p < 0.05, n = 3).

Bottom Line: In this way it was shown that activation of MDR in TICs occurs in two ways: through the increase of V max in one fraction of cells, and through decrease of K M in another fraction.In addition, kinetic data showed that heterogeneity of MDR parameters in TICs significantly exceeds that of bulk cells.Potential consequences of these findings for chemotherapy are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario, Canada.

ABSTRACT
Multidrug resistance (MDR) driven by ABC (ATP binding cassette) membrane transporters is one of the major causes of treatment failure in human malignancy. MDR capacity is thought to be unevenly distributed among tumor cells, with higher capacity residing in tumor-initiating cells (TIC) (though opposite finding are occasionally reported). Functional evidence for enhanced MDR of TICs was previously provided using a "side population" assay. This assay estimates MDR capacity by a single parameter - cell's ability to retain fluorescent MDR substrate, so that cells with high MDR capacity ("side population") demonstrate low substrate retention. In the present work MDR in TICs was investigated in greater detail using a kinetic approach, which monitors MDR efflux from single cells. Analysis of kinetic traces obtained allowed for the estimation of both the velocity (V max) and affinity (K M) of MDR transport in single cells. In this way it was shown that activation of MDR in TICs occurs in two ways: through the increase of V max in one fraction of cells, and through decrease of K M in another fraction. In addition, kinetic data showed that heterogeneity of MDR parameters in TICs significantly exceeds that of bulk cells. Potential consequences of these findings for chemotherapy are discussed.

Show MeSH
Related in: MedlinePlus