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Distinct gene regulatory programs define the inhibitory effects of liver X receptors and PPARG on cancer cell proliferation.

Savic D, Ramaker RC, Roberts BS, Dean EC, Burwell TC, Meadows SK, Cooper SJ, Garabedian MJ, Gertz J, Myers RM - Genome Med (2016)

Bottom Line: PPARG generated a rapid and short-term response while maintaining a gene activator role.By contrast, LXR signaling was prolonged, with initial, predominantly activating functions that transitioned to repressive gene regulatory activities at late time points.Through the use of a multi-tiered strategy that integrated various genomic datasets, our data illustrate that distinct gene regulatory programs elicit common phenotypic effects, highlighting the complexity of the genome.

View Article: PubMed Central - PubMed

Affiliation: HudsonAlpha Institute for Biotechnology, Huntsville, AL, 35806, USA.

ABSTRACT

Background: The liver X receptors (LXRs, NR1H2 and NR1H3) and peroxisome proliferator-activated receptor gamma (PPARG, NR1C3) nuclear receptor transcription factors (TFs) are master regulators of energy homeostasis. Intriguingly, recent studies suggest that these metabolic regulators also impact tumor cell proliferation. However, a comprehensive temporal molecular characterization of the LXR and PPARG gene regulatory responses in tumor cells is still lacking.

Methods: To better define the underlying molecular processes governing the genetic control of cellular growth in response to extracellular metabolic signals, we performed a comprehensive, genome-wide characterization of the temporal regulatory cascades mediated by LXR and PPARG signaling in HT29 colorectal cancer cells. For this analysis, we applied a multi-tiered approach that incorporated cellular phenotypic assays, gene expression profiles, chromatin state dynamics, and nuclear receptor binding patterns.

Results: Our results illustrate that the activation of both nuclear receptors inhibited cell proliferation and further decreased glutathione levels, consistent with increased cellular oxidative stress. Despite a common metabolic reprogramming, the gene regulatory network programs initiated by these nuclear receptors were widely distinct. PPARG generated a rapid and short-term response while maintaining a gene activator role. By contrast, LXR signaling was prolonged, with initial, predominantly activating functions that transitioned to repressive gene regulatory activities at late time points.

Conclusions: Through the use of a multi-tiered strategy that integrated various genomic datasets, our data illustrate that distinct gene regulatory programs elicit common phenotypic effects, highlighting the complexity of the genome. These results further provide a detailed molecular map of metabolic reprogramming in cancer cells through LXR and PPARG activation. As ligand-inducible TFs, these nuclear receptors can potentially serve as attractive therapeutic targets for the treatment of various cancers.

No MeSH data available.


Related in: MedlinePlus

Effects of LXRs and PPARG on cellular phenotypes and metabolites. a Proliferation assays using DNA content after 24, 48, and 96 h of drug treatment (24-h n = 10 for each treatment; 48/96-h n = 12 for each treatment). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. b Proliferation assays using ATP levels after 24, 48, and 96 h of drug treatment (24-h n = 15 DMSO, n = 8 rosiglitazone, n = 7 GW3965; 48/96-h n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. c Oxidative stress assays after 48 and 96 h of drug treatment (n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Glutathione concentrations are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. d The carbohydrate metabolism pathway illustrating key metabolites. e Relative metabolite abundance after 24 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. f Relative metabolite abundance after 48 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. Error bars represent standard deviation
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Fig1: Effects of LXRs and PPARG on cellular phenotypes and metabolites. a Proliferation assays using DNA content after 24, 48, and 96 h of drug treatment (24-h n = 10 for each treatment; 48/96-h n = 12 for each treatment). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. b Proliferation assays using ATP levels after 24, 48, and 96 h of drug treatment (24-h n = 15 DMSO, n = 8 rosiglitazone, n = 7 GW3965; 48/96-h n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. c Oxidative stress assays after 48 and 96 h of drug treatment (n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Glutathione concentrations are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. d The carbohydrate metabolism pathway illustrating key metabolites. e Relative metabolite abundance after 24 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. f Relative metabolite abundance after 48 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. Error bars represent standard deviation

Mentions: We evaluated the proliferative and metabolic effects of LXRs and PPARG in HT29 colorectal cancer cells with several cellular assays. First, we assayed cellular proliferation by measuring DNA and ATP content in cells after 24, 48, and 96 h of treatment with the LXR agonist GW3965 and the PPARG agonist rosiglitazone (Fig. 1a, b) and by comparing the resulting cellular responses to control culture conditions containing the carrier DMSO. The evaluation of both DNA and ATP confirmed an inhibitory effect on colorectal cancer cell proliferation, supporting conclusions of previous reports [32, 46]. Notably, these anti-proliferative effects became more pronounced over time. In light of the functions of LXRs and PPARG as regulators of energy homeostasis, we also measured glutathione levels in drug-treated cells (Fig. 1c). LXR and PPARG activation significantly decreased glutathione levels, highlighting a potential inhibitory effect on proliferation through increased oxidative stress, a finding that has been reported for PPARG in lung cancer cells [31].Fig. 1


Distinct gene regulatory programs define the inhibitory effects of liver X receptors and PPARG on cancer cell proliferation.

Savic D, Ramaker RC, Roberts BS, Dean EC, Burwell TC, Meadows SK, Cooper SJ, Garabedian MJ, Gertz J, Myers RM - Genome Med (2016)

Effects of LXRs and PPARG on cellular phenotypes and metabolites. a Proliferation assays using DNA content after 24, 48, and 96 h of drug treatment (24-h n = 10 for each treatment; 48/96-h n = 12 for each treatment). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. b Proliferation assays using ATP levels after 24, 48, and 96 h of drug treatment (24-h n = 15 DMSO, n = 8 rosiglitazone, n = 7 GW3965; 48/96-h n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. c Oxidative stress assays after 48 and 96 h of drug treatment (n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Glutathione concentrations are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. d The carbohydrate metabolism pathway illustrating key metabolites. e Relative metabolite abundance after 24 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. f Relative metabolite abundance after 48 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. Error bars represent standard deviation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig1: Effects of LXRs and PPARG on cellular phenotypes and metabolites. a Proliferation assays using DNA content after 24, 48, and 96 h of drug treatment (24-h n = 10 for each treatment; 48/96-h n = 12 for each treatment). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. b Proliferation assays using ATP levels after 24, 48, and 96 h of drug treatment (24-h n = 15 DMSO, n = 8 rosiglitazone, n = 7 GW3965; 48/96-h n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Luminescence values are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. c Oxidative stress assays after 48 and 96 h of drug treatment (n = 18 DMSO, n = 9 rosiglitazone, n = 9 GW3965). Glutathione concentrations are presented for GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.01. d The carbohydrate metabolism pathway illustrating key metabolites. e Relative metabolite abundance after 24 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. f Relative metabolite abundance after 48 h of GW3965 (blue, LXR agonist), rosiglitazone (gold, PPARG agonist), and DMSO (gray, vehicle control) treatment. *p < 0.05. Error bars represent standard deviation
Mentions: We evaluated the proliferative and metabolic effects of LXRs and PPARG in HT29 colorectal cancer cells with several cellular assays. First, we assayed cellular proliferation by measuring DNA and ATP content in cells after 24, 48, and 96 h of treatment with the LXR agonist GW3965 and the PPARG agonist rosiglitazone (Fig. 1a, b) and by comparing the resulting cellular responses to control culture conditions containing the carrier DMSO. The evaluation of both DNA and ATP confirmed an inhibitory effect on colorectal cancer cell proliferation, supporting conclusions of previous reports [32, 46]. Notably, these anti-proliferative effects became more pronounced over time. In light of the functions of LXRs and PPARG as regulators of energy homeostasis, we also measured glutathione levels in drug-treated cells (Fig. 1c). LXR and PPARG activation significantly decreased glutathione levels, highlighting a potential inhibitory effect on proliferation through increased oxidative stress, a finding that has been reported for PPARG in lung cancer cells [31].Fig. 1

Bottom Line: PPARG generated a rapid and short-term response while maintaining a gene activator role.By contrast, LXR signaling was prolonged, with initial, predominantly activating functions that transitioned to repressive gene regulatory activities at late time points.Through the use of a multi-tiered strategy that integrated various genomic datasets, our data illustrate that distinct gene regulatory programs elicit common phenotypic effects, highlighting the complexity of the genome.

View Article: PubMed Central - PubMed

Affiliation: HudsonAlpha Institute for Biotechnology, Huntsville, AL, 35806, USA.

ABSTRACT

Background: The liver X receptors (LXRs, NR1H2 and NR1H3) and peroxisome proliferator-activated receptor gamma (PPARG, NR1C3) nuclear receptor transcription factors (TFs) are master regulators of energy homeostasis. Intriguingly, recent studies suggest that these metabolic regulators also impact tumor cell proliferation. However, a comprehensive temporal molecular characterization of the LXR and PPARG gene regulatory responses in tumor cells is still lacking.

Methods: To better define the underlying molecular processes governing the genetic control of cellular growth in response to extracellular metabolic signals, we performed a comprehensive, genome-wide characterization of the temporal regulatory cascades mediated by LXR and PPARG signaling in HT29 colorectal cancer cells. For this analysis, we applied a multi-tiered approach that incorporated cellular phenotypic assays, gene expression profiles, chromatin state dynamics, and nuclear receptor binding patterns.

Results: Our results illustrate that the activation of both nuclear receptors inhibited cell proliferation and further decreased glutathione levels, consistent with increased cellular oxidative stress. Despite a common metabolic reprogramming, the gene regulatory network programs initiated by these nuclear receptors were widely distinct. PPARG generated a rapid and short-term response while maintaining a gene activator role. By contrast, LXR signaling was prolonged, with initial, predominantly activating functions that transitioned to repressive gene regulatory activities at late time points.

Conclusions: Through the use of a multi-tiered strategy that integrated various genomic datasets, our data illustrate that distinct gene regulatory programs elicit common phenotypic effects, highlighting the complexity of the genome. These results further provide a detailed molecular map of metabolic reprogramming in cancer cells through LXR and PPARG activation. As ligand-inducible TFs, these nuclear receptors can potentially serve as attractive therapeutic targets for the treatment of various cancers.

No MeSH data available.


Related in: MedlinePlus