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Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility.

Martinez R, Blasina A, Hallin JF, Hu W, Rymer I, Fan J, Hoffman RL, Murphy S, Marx M, Yanochko G, Trajkovic D, Dinh D, Timofeevski S, Zhu Z, Sun P, Lappin PB, Murray BW - PLoS ONE (2015)

Bottom Line: Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated.Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment.Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.

View Article: PubMed Central - PubMed

Affiliation: Oncology Research Unit, Pfizer Worldwide Research and Development, 10724 Science Center Drive, San Diego, CA, 92121, United States of America.

ABSTRACT
Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; Ki<0.5 nM; cellular IC50 2-6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser10 levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser10). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G1 cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment. Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.

No MeSH data available.


Related in: MedlinePlus

Effect of Mps1 inhibitor on duration of mitosis.Duration of mitosis timed from nuclear envelope breakdown to initiation of cytokinesis in three cell lines exposed to vehicle (0.1% DMSO) or an Mps1 inhibitor (50 nM PF-3837) using live-cell imaging (n = 3). The effect of PF-3837 on mitosis duration for tumor cells are highly-significant for T47D (p = 0.001) and MDA-MB-468 (p = 0.0002).
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pone.0138616.g002: Effect of Mps1 inhibitor on duration of mitosis.Duration of mitosis timed from nuclear envelope breakdown to initiation of cytokinesis in three cell lines exposed to vehicle (0.1% DMSO) or an Mps1 inhibitor (50 nM PF-3837) using live-cell imaging (n = 3). The effect of PF-3837 on mitosis duration for tumor cells are highly-significant for T47D (p = 0.001) and MDA-MB-468 (p = 0.0002).

Mentions: Phenotypic consequences of specific inhibition of Mps1 catalytic activity in a TNBC/basal-a breast cancer model (HCC1806 tumor cell line) were evaluated at multiple concentrations of PF-7006 as a function of time. To minimize the possible contribution of off-target effects, low concentrations of PF-7006 and PF-3837 were used. Flow cytometric analysis quantitated the cell cycle distribution with altered distributions (increased >4n DNA content and sub-G1 fractions) apparent after 24–48 hour treatment with a low concentration of PF-7006 (25 nM) (Fig 1A, S6A Fig). Longer Mps1 inhibitor exposures (48–96 h) further increases the >4n DNA fraction. Similar trends are observed following exposure to 50 nM of PF-7006. Flow cytometric analysis in a second basal-a tumor cell line (HCC70) produced results similar to HCC1806 (Fig 1B, S6B Fig). To visualize chromosome dynamics by fluorescent live-cell video microscopy, basal-a tumor cells (MDA-MB-468) were engineered to constitutively express the fluorescent reporter histone-2B green fluorescent protein (H2B-GFP). The acceleration of mitosis induced by Mps1 inhibition was quantitated using the Mps1 inhibitor PF-3837 in two tumor lines (T47D, MDA-MB-458) and one premalignant breast cell line (MCF10A) by measuring the time from nuclear envelope breakdown to the initiation of cytokinesis (Fig 2). Statistically significant decreases in the duration of mitosis was observed with low concentrations of PF-3837 (50 nM). Taken together, the inhibitors display mitotic functional properties consistent with Mps1 inhibition.


Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility.

Martinez R, Blasina A, Hallin JF, Hu W, Rymer I, Fan J, Hoffman RL, Murphy S, Marx M, Yanochko G, Trajkovic D, Dinh D, Timofeevski S, Zhu Z, Sun P, Lappin PB, Murray BW - PLoS ONE (2015)

Effect of Mps1 inhibitor on duration of mitosis.Duration of mitosis timed from nuclear envelope breakdown to initiation of cytokinesis in three cell lines exposed to vehicle (0.1% DMSO) or an Mps1 inhibitor (50 nM PF-3837) using live-cell imaging (n = 3). The effect of PF-3837 on mitosis duration for tumor cells are highly-significant for T47D (p = 0.001) and MDA-MB-468 (p = 0.0002).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4580473&req=5

pone.0138616.g002: Effect of Mps1 inhibitor on duration of mitosis.Duration of mitosis timed from nuclear envelope breakdown to initiation of cytokinesis in three cell lines exposed to vehicle (0.1% DMSO) or an Mps1 inhibitor (50 nM PF-3837) using live-cell imaging (n = 3). The effect of PF-3837 on mitosis duration for tumor cells are highly-significant for T47D (p = 0.001) and MDA-MB-468 (p = 0.0002).
Mentions: Phenotypic consequences of specific inhibition of Mps1 catalytic activity in a TNBC/basal-a breast cancer model (HCC1806 tumor cell line) were evaluated at multiple concentrations of PF-7006 as a function of time. To minimize the possible contribution of off-target effects, low concentrations of PF-7006 and PF-3837 were used. Flow cytometric analysis quantitated the cell cycle distribution with altered distributions (increased >4n DNA content and sub-G1 fractions) apparent after 24–48 hour treatment with a low concentration of PF-7006 (25 nM) (Fig 1A, S6A Fig). Longer Mps1 inhibitor exposures (48–96 h) further increases the >4n DNA fraction. Similar trends are observed following exposure to 50 nM of PF-7006. Flow cytometric analysis in a second basal-a tumor cell line (HCC70) produced results similar to HCC1806 (Fig 1B, S6B Fig). To visualize chromosome dynamics by fluorescent live-cell video microscopy, basal-a tumor cells (MDA-MB-468) were engineered to constitutively express the fluorescent reporter histone-2B green fluorescent protein (H2B-GFP). The acceleration of mitosis induced by Mps1 inhibition was quantitated using the Mps1 inhibitor PF-3837 in two tumor lines (T47D, MDA-MB-458) and one premalignant breast cell line (MCF10A) by measuring the time from nuclear envelope breakdown to the initiation of cytokinesis (Fig 2). Statistically significant decreases in the duration of mitosis was observed with low concentrations of PF-3837 (50 nM). Taken together, the inhibitors display mitotic functional properties consistent with Mps1 inhibition.

Bottom Line: Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated.Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment.Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.

View Article: PubMed Central - PubMed

Affiliation: Oncology Research Unit, Pfizer Worldwide Research and Development, 10724 Science Center Drive, San Diego, CA, 92121, United States of America.

ABSTRACT
Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; Ki<0.5 nM; cellular IC50 2-6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser10 levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser10). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G1 cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment. Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.

No MeSH data available.


Related in: MedlinePlus