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A dynamical systems model for combinatorial cancer therapy enhances oncolytic adenovirus efficacy by MEK-inhibition.

Bagheri N, Shiina M, Lauffenburger DA, Korn WM - PLoS Comput. Biol. (2011)

Bottom Line: Specifically, we fit a nonlinear differential equation system to dedicated experimental data and analyzed the resulting simulations for favorable treatment strategies.Simulations predicted enhanced combinatorial therapy when both treatments were applied simultaneously; we successfully validated these predictions in an ensuing explicit test study.We conclude that integrated computational and experimental analysis of combinatorial therapy provides a useful means to identify treatment/infection protocols that yield clinically significant oncolysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.

ABSTRACT
Oncolytic adenoviruses, such as ONYX-015, have been tested in clinical trials for currently untreatable tumors, but have yet to demonstrate adequate therapeutic efficacy. The extent to which viruses infect targeted cells determines the efficacy of this approach but many tumors down-regulate the Coxsackievirus and Adenovirus Receptor (CAR), rendering them less susceptible to infection. Disrupting MAPK pathway signaling by pharmacological inhibition of MEK up-regulates CAR expression, offering possible enhanced adenovirus infection. MEK inhibition, however, interferes with adenovirus replication due to resulting G1-phase cell cycle arrest. Therefore, enhanced efficacy will depend on treatment protocols that productively balance these competing effects. Predictive understanding of how to attain and enhance therapeutic efficacy of combinatorial treatment is difficult since the effects of MEK inhibitors, in conjunction with adenovirus/cell interactions, are complex nonlinear dynamic processes. We investigated combinatorial treatment strategies using a mathematical model that predicts the impact of MEK inhibition on tumor cell proliferation, ONYX-015 infection, and oncolysis. Specifically, we fit a nonlinear differential equation system to dedicated experimental data and analyzed the resulting simulations for favorable treatment strategies. Simulations predicted enhanced combinatorial therapy when both treatments were applied simultaneously; we successfully validated these predictions in an ensuing explicit test study. Further analysis revealed that a CAR-independent mechanism may be responsible for amplified virus production and cell death. We conclude that integrated computational and experimental analysis of combinatorial therapy provides a useful means to identify treatment/infection protocols that yield clinically significant oncolysis. Enhanced oncolytic therapy has the potential to dramatically improve non-surgical cancer treatment, especially in locally advanced or metastatic cases where treatment options remain limited.

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G1 arrested cells show more potent cell killing effect and virus production.HCT116 cells were density arrested and released from synchronization. (A) Cell cycle distribution was quantified upon release at 0, 7, 16, and 24-hours. (B) The effect of cell cycle synchronization on CAR expression was analyzed. (C) Cell viability and (D) virus production were measured 3 days after infection (MOI = 1) with WtD, ONYX-014, Delta-24, and Delta-24RGD (denoted as RGD) at 7, 16, and 24-hours after release from density arrest. Error bars represent the standard deviation of triplicate measurements for cell viability and duplicate measurements for virus production.
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pcbi-1001085-g006: G1 arrested cells show more potent cell killing effect and virus production.HCT116 cells were density arrested and released from synchronization. (A) Cell cycle distribution was quantified upon release at 0, 7, 16, and 24-hours. (B) The effect of cell cycle synchronization on CAR expression was analyzed. (C) Cell viability and (D) virus production were measured 3 days after infection (MOI = 1) with WtD, ONYX-014, Delta-24, and Delta-24RGD (denoted as RGD) at 7, 16, and 24-hours after release from density arrest. Error bars represent the standard deviation of triplicate measurements for cell viability and duplicate measurements for virus production.

Mentions: Model simulations and experimental validation confirm that simultaneous treatment with MEK-inhibitor and infection is most advantageous, suggesting that alternate (CAR-independent) regulatory mechanisms may be responsible for enhanced oncolysis. Given the disproportionate increase in virus replication relative to infection (Figure 1e), we hypothesized that enhanced CAR may not be the key factor involved in amplifying virus replication and cell death; MEK-inhibition might provide an alternate mechanism responsible for greater efficacy of infection. Since MEK inhibitor treatment leads to G1-phase cell cycle arrest in HCT116 cells, we tested the impact of cell cycle distribution on oncolysis and virus production in cells infected with various oncolytic adenoviruses. HCT116 cells were arrested in the G1-phase of the cell cycle by contact inhibition and released by re-seeding at sub-confluent densities. We then quantified the change in cell cycle distribution as cells transitioned from the G1-phase. At 7-hours after re-seeding, 80% of the cell population remained in G1-phase. At 16-hours, 80% of cells reached S-phase (Figure 6a). Meanwhile, CAR expression remained unchanged throughout these cell cycle phase transitions (Figure 6b). Despite constant CAR, we observed significant differences in cell killing when infection occurred at 7-hours, 16-hours, and 24-hours after re-seeding. The greatest lytic effect occurred when infection took place 7-hours after re-seeding (Figure 6c), which coincided with greatest virus production (Figure 6d). The marked increase in cell death and adenovirus replication suggests that the G1-S phase transition mediates adenovirus replication. These observations were confirmed with a variety of oncolytic adenoviruses, including Delta-24RGD, which is characterized by an RGD motif on the fiber knob of the adenovirus allowing for CAR-independent infection [20]. Therefore, the expression of CAR molecules on the cell surface at the time of infection does not appear to be the sole regulatory mechanism governing the efficacy of oncolytic adenovirus therapy. The detailed molecular mechanisms by which cell cycle distribution influences viral replication are currently under investigation.


A dynamical systems model for combinatorial cancer therapy enhances oncolytic adenovirus efficacy by MEK-inhibition.

Bagheri N, Shiina M, Lauffenburger DA, Korn WM - PLoS Comput. Biol. (2011)

G1 arrested cells show more potent cell killing effect and virus production.HCT116 cells were density arrested and released from synchronization. (A) Cell cycle distribution was quantified upon release at 0, 7, 16, and 24-hours. (B) The effect of cell cycle synchronization on CAR expression was analyzed. (C) Cell viability and (D) virus production were measured 3 days after infection (MOI = 1) with WtD, ONYX-014, Delta-24, and Delta-24RGD (denoted as RGD) at 7, 16, and 24-hours after release from density arrest. Error bars represent the standard deviation of triplicate measurements for cell viability and duplicate measurements for virus production.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3040662&req=5

pcbi-1001085-g006: G1 arrested cells show more potent cell killing effect and virus production.HCT116 cells were density arrested and released from synchronization. (A) Cell cycle distribution was quantified upon release at 0, 7, 16, and 24-hours. (B) The effect of cell cycle synchronization on CAR expression was analyzed. (C) Cell viability and (D) virus production were measured 3 days after infection (MOI = 1) with WtD, ONYX-014, Delta-24, and Delta-24RGD (denoted as RGD) at 7, 16, and 24-hours after release from density arrest. Error bars represent the standard deviation of triplicate measurements for cell viability and duplicate measurements for virus production.
Mentions: Model simulations and experimental validation confirm that simultaneous treatment with MEK-inhibitor and infection is most advantageous, suggesting that alternate (CAR-independent) regulatory mechanisms may be responsible for enhanced oncolysis. Given the disproportionate increase in virus replication relative to infection (Figure 1e), we hypothesized that enhanced CAR may not be the key factor involved in amplifying virus replication and cell death; MEK-inhibition might provide an alternate mechanism responsible for greater efficacy of infection. Since MEK inhibitor treatment leads to G1-phase cell cycle arrest in HCT116 cells, we tested the impact of cell cycle distribution on oncolysis and virus production in cells infected with various oncolytic adenoviruses. HCT116 cells were arrested in the G1-phase of the cell cycle by contact inhibition and released by re-seeding at sub-confluent densities. We then quantified the change in cell cycle distribution as cells transitioned from the G1-phase. At 7-hours after re-seeding, 80% of the cell population remained in G1-phase. At 16-hours, 80% of cells reached S-phase (Figure 6a). Meanwhile, CAR expression remained unchanged throughout these cell cycle phase transitions (Figure 6b). Despite constant CAR, we observed significant differences in cell killing when infection occurred at 7-hours, 16-hours, and 24-hours after re-seeding. The greatest lytic effect occurred when infection took place 7-hours after re-seeding (Figure 6c), which coincided with greatest virus production (Figure 6d). The marked increase in cell death and adenovirus replication suggests that the G1-S phase transition mediates adenovirus replication. These observations were confirmed with a variety of oncolytic adenoviruses, including Delta-24RGD, which is characterized by an RGD motif on the fiber knob of the adenovirus allowing for CAR-independent infection [20]. Therefore, the expression of CAR molecules on the cell surface at the time of infection does not appear to be the sole regulatory mechanism governing the efficacy of oncolytic adenovirus therapy. The detailed molecular mechanisms by which cell cycle distribution influences viral replication are currently under investigation.

Bottom Line: Specifically, we fit a nonlinear differential equation system to dedicated experimental data and analyzed the resulting simulations for favorable treatment strategies.Simulations predicted enhanced combinatorial therapy when both treatments were applied simultaneously; we successfully validated these predictions in an ensuing explicit test study.We conclude that integrated computational and experimental analysis of combinatorial therapy provides a useful means to identify treatment/infection protocols that yield clinically significant oncolysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.

ABSTRACT
Oncolytic adenoviruses, such as ONYX-015, have been tested in clinical trials for currently untreatable tumors, but have yet to demonstrate adequate therapeutic efficacy. The extent to which viruses infect targeted cells determines the efficacy of this approach but many tumors down-regulate the Coxsackievirus and Adenovirus Receptor (CAR), rendering them less susceptible to infection. Disrupting MAPK pathway signaling by pharmacological inhibition of MEK up-regulates CAR expression, offering possible enhanced adenovirus infection. MEK inhibition, however, interferes with adenovirus replication due to resulting G1-phase cell cycle arrest. Therefore, enhanced efficacy will depend on treatment protocols that productively balance these competing effects. Predictive understanding of how to attain and enhance therapeutic efficacy of combinatorial treatment is difficult since the effects of MEK inhibitors, in conjunction with adenovirus/cell interactions, are complex nonlinear dynamic processes. We investigated combinatorial treatment strategies using a mathematical model that predicts the impact of MEK inhibition on tumor cell proliferation, ONYX-015 infection, and oncolysis. Specifically, we fit a nonlinear differential equation system to dedicated experimental data and analyzed the resulting simulations for favorable treatment strategies. Simulations predicted enhanced combinatorial therapy when both treatments were applied simultaneously; we successfully validated these predictions in an ensuing explicit test study. Further analysis revealed that a CAR-independent mechanism may be responsible for amplified virus production and cell death. We conclude that integrated computational and experimental analysis of combinatorial therapy provides a useful means to identify treatment/infection protocols that yield clinically significant oncolysis. Enhanced oncolytic therapy has the potential to dramatically improve non-surgical cancer treatment, especially in locally advanced or metastatic cases where treatment options remain limited.

Show MeSH
Related in: MedlinePlus