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The pharmacodynamics of the p53-Mdm2 targeting drug Nutlin: the role of gene-switching noise.

Puszynski K, Gandolfi A, d'Onofrio A - PLoS Comput. Biol. (2014)

Bottom Line: The fate of the individual cell is assumed to be decided by the rising of nuclear-phosphorylated p53 over a certain threshold.Our results suggest that dose-splitting may be ineffective at low doses and effective at high doses.This complex behavior can be due to the interplay among the existence of a threshold on the p53 level for its cell activity, the nonlinearity of the relationship between the bolus dose and the peak of active p53, and the relatively fast elimination of the drug.

View Article: PubMed Central - PubMed

Affiliation: Silesian University of Technology, Institute of Automatic Control, Gliwice, Poland.

ABSTRACT
In this work we investigate, by means of a computational stochastic model, how tumor cells with wild-type p53 gene respond to the drug Nutlin, an agent that interferes with the Mdm2-mediated p53 regulation. In particular, we show how the stochastic gene-switching controlled by p53 can explain experimental dose-response curves, i.e., the observed inter-cell variability of the cell viability under Nutlin action. The proposed model describes in some detail the regulation network of p53, including the negative feedback loop mediated by Mdm2 and the positive loop mediated by PTEN, as well as the reversible inhibition of Mdm2 caused by Nutlin binding. The fate of the individual cell is assumed to be decided by the rising of nuclear-phosphorylated p53 over a certain threshold. We also performed in silico experiments to evaluate the dose-response curve after a single drug dose delivered in mice, or after its fractionated administration. Our results suggest that dose-splitting may be ineffective at low doses and effective at high doses. This complex behavior can be due to the interplay among the existence of a threshold on the p53 level for its cell activity, the nonlinearity of the relationship between the bolus dose and the peak of active p53, and the relatively fast elimination of the drug.

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Single-dose vs. split delivery of a total dose of 400 mg/kg of Nutlin: Effects on the RKO cell line.Left panels: dynamics of Nutlin. Extra-cellular free concentration (blue, on the log scale), total intra-cellular amount (green), free intra-cellular amount (red). Right panels: time-course of p53 (green) and Mdm2 (red). Upper panels: single dose. Central panels: the dose is split in four doses delivered with an interval of 24 hours in between. Lower panels: again the dose is split in four doses, but here the time between two doses is 6 hours. Solid lines represent medians, and dotted lines first and third quartiles.
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pcbi-1003991-g008: Single-dose vs. split delivery of a total dose of 400 mg/kg of Nutlin: Effects on the RKO cell line.Left panels: dynamics of Nutlin. Extra-cellular free concentration (blue, on the log scale), total intra-cellular amount (green), free intra-cellular amount (red). Right panels: time-course of p53 (green) and Mdm2 (red). Upper panels: single dose. Central panels: the dose is split in four doses delivered with an interval of 24 hours in between. Lower panels: again the dose is split in four doses, but here the time between two doses is 6 hours. Solid lines represent medians, and dotted lines first and third quartiles.

Mentions: Some insights into the above behavior can be obtained by analyzing the dynamics of extra-cellular free Nutlin and intra-cellular Nutlin, both total and free, and the time-courses of nuclear p53/Mdm2. Figs. 7 and 8 report such profiles in RKO cells when the total Nutlin dose is 50 mg/Kg and 400 mg/Kg, respectively. In Figs. 7B and 8B, the response to the single doses is shown by plotting the profiles of nuclear-phosphorylated p53 and of nuclear-phosphorylated Mdm2. Note that although immediately after the dose delivery the Mdm2 amount reduces close to zero, after a short time-lag the number of molecules rapidly recovers and a high peak is reached 10 hours after the drug administration. Concerning p53, the peak is reached before Mdm2 regrows over the baseline value, and ultimately also p53 is restored to its pre-delivery value. Note, moreover, that the p53/Mdm2 response is initiated by the first small peak of the total intra-cellular Nutlin amount (well visible in Fig. 8A) corresponding to the peak of extra-cellular free Nutlin concentration, and not by the delayed and dominant peak of intra-cellular Nutlin. Due to the rapid drug elimination, the splitting with 24 h breaks results in four almost independent dynamics. In such a case, there is only a slight accumulation of the total intra-cellular Nutlin, more visible at 400 mg/kg (see Fig. 8C), which is mirrored in the nuclear p53 peaks (see Fig. 8D). When the interval among split doses is 6 h, instead, there is a clear accumulation of the total intra-cellular Nutlin both at doses of 50 and 400 mg/Kg. Quite surprisingly, the p53 peaks, although rather merged together, have heights on average smaller than the peaks achieved by 24 h breaks (compare Fig. 7D and F, and Fig. 8D and F).


The pharmacodynamics of the p53-Mdm2 targeting drug Nutlin: the role of gene-switching noise.

Puszynski K, Gandolfi A, d'Onofrio A - PLoS Comput. Biol. (2014)

Single-dose vs. split delivery of a total dose of 400 mg/kg of Nutlin: Effects on the RKO cell line.Left panels: dynamics of Nutlin. Extra-cellular free concentration (blue, on the log scale), total intra-cellular amount (green), free intra-cellular amount (red). Right panels: time-course of p53 (green) and Mdm2 (red). Upper panels: single dose. Central panels: the dose is split in four doses delivered with an interval of 24 hours in between. Lower panels: again the dose is split in four doses, but here the time between two doses is 6 hours. Solid lines represent medians, and dotted lines first and third quartiles.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263360&req=5

pcbi-1003991-g008: Single-dose vs. split delivery of a total dose of 400 mg/kg of Nutlin: Effects on the RKO cell line.Left panels: dynamics of Nutlin. Extra-cellular free concentration (blue, on the log scale), total intra-cellular amount (green), free intra-cellular amount (red). Right panels: time-course of p53 (green) and Mdm2 (red). Upper panels: single dose. Central panels: the dose is split in four doses delivered with an interval of 24 hours in between. Lower panels: again the dose is split in four doses, but here the time between two doses is 6 hours. Solid lines represent medians, and dotted lines first and third quartiles.
Mentions: Some insights into the above behavior can be obtained by analyzing the dynamics of extra-cellular free Nutlin and intra-cellular Nutlin, both total and free, and the time-courses of nuclear p53/Mdm2. Figs. 7 and 8 report such profiles in RKO cells when the total Nutlin dose is 50 mg/Kg and 400 mg/Kg, respectively. In Figs. 7B and 8B, the response to the single doses is shown by plotting the profiles of nuclear-phosphorylated p53 and of nuclear-phosphorylated Mdm2. Note that although immediately after the dose delivery the Mdm2 amount reduces close to zero, after a short time-lag the number of molecules rapidly recovers and a high peak is reached 10 hours after the drug administration. Concerning p53, the peak is reached before Mdm2 regrows over the baseline value, and ultimately also p53 is restored to its pre-delivery value. Note, moreover, that the p53/Mdm2 response is initiated by the first small peak of the total intra-cellular Nutlin amount (well visible in Fig. 8A) corresponding to the peak of extra-cellular free Nutlin concentration, and not by the delayed and dominant peak of intra-cellular Nutlin. Due to the rapid drug elimination, the splitting with 24 h breaks results in four almost independent dynamics. In such a case, there is only a slight accumulation of the total intra-cellular Nutlin, more visible at 400 mg/kg (see Fig. 8C), which is mirrored in the nuclear p53 peaks (see Fig. 8D). When the interval among split doses is 6 h, instead, there is a clear accumulation of the total intra-cellular Nutlin both at doses of 50 and 400 mg/Kg. Quite surprisingly, the p53 peaks, although rather merged together, have heights on average smaller than the peaks achieved by 24 h breaks (compare Fig. 7D and F, and Fig. 8D and F).

Bottom Line: The fate of the individual cell is assumed to be decided by the rising of nuclear-phosphorylated p53 over a certain threshold.Our results suggest that dose-splitting may be ineffective at low doses and effective at high doses.This complex behavior can be due to the interplay among the existence of a threshold on the p53 level for its cell activity, the nonlinearity of the relationship between the bolus dose and the peak of active p53, and the relatively fast elimination of the drug.

View Article: PubMed Central - PubMed

Affiliation: Silesian University of Technology, Institute of Automatic Control, Gliwice, Poland.

ABSTRACT
In this work we investigate, by means of a computational stochastic model, how tumor cells with wild-type p53 gene respond to the drug Nutlin, an agent that interferes with the Mdm2-mediated p53 regulation. In particular, we show how the stochastic gene-switching controlled by p53 can explain experimental dose-response curves, i.e., the observed inter-cell variability of the cell viability under Nutlin action. The proposed model describes in some detail the regulation network of p53, including the negative feedback loop mediated by Mdm2 and the positive loop mediated by PTEN, as well as the reversible inhibition of Mdm2 caused by Nutlin binding. The fate of the individual cell is assumed to be decided by the rising of nuclear-phosphorylated p53 over a certain threshold. We also performed in silico experiments to evaluate the dose-response curve after a single drug dose delivered in mice, or after its fractionated administration. Our results suggest that dose-splitting may be ineffective at low doses and effective at high doses. This complex behavior can be due to the interplay among the existence of a threshold on the p53 level for its cell activity, the nonlinearity of the relationship between the bolus dose and the peak of active p53, and the relatively fast elimination of the drug.

Show MeSH
Related in: MedlinePlus