Limits...
Selective CREB-dependent cyclin expression mediated by the PI3K and MAPK pathways supports glioma cell proliferation.

Daniel P, Filiz G, Brown DV, Hollande F, Gonzales M, D'Abaco G, Papalexis N, Phillips WA, Malaterre J, Ramsay RG, Mantamadiotis T - Oncogenesis (2014)

Bottom Line: CREB overexpression in transgenic animals imparts oncogenic properties on cells in various tissues, and aberrant CREB expression is associated with tumours.Cyclin D1 is highly CREB-dependent, whereas cyclin B1 and PCNA are co-regulated by both CREB-dependent and -independent mechanisms.The precise regulatory network involved appears to differ depending on the tumour-suppressor phosphatase and tensin homolog status of the GBM cells, which in turn allows CREB to regulate the activity of the PI3K itself.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, The University of Melbourne, Parkville, Victoria, Australia.

ABSTRACT
The cyclic-AMP response element binding (CREB) protein has been shown to have a pivotal role in cell survival and cell proliferation. Transgenic rodent models have revealed a role for CREB in higher-order brain functions, such as memory and drug addiction behaviors. CREB overexpression in transgenic animals imparts oncogenic properties on cells in various tissues, and aberrant CREB expression is associated with tumours. It is the central position of CREB, downstream from key developmental and growth signalling pathways, which gives CREB this ability to influence a spectrum of cellular activities, such as cell survival, growth and differentiation, in both normal and cancer cells. We show that CREB is highly expressed and constitutively activated in patient glioma tissue and that this activation closely correlates with tumour grade. The mechanism by which CREB regulates glioblastoma (GBM) tumour cell proliferation involves activities downstream from both the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways that then modulate the expression of three key cell cycle factors, cyclin B, D and proliferating cell nuclear antigen (PCNA). Cyclin D1 is highly CREB-dependent, whereas cyclin B1 and PCNA are co-regulated by both CREB-dependent and -independent mechanisms. The precise regulatory network involved appears to differ depending on the tumour-suppressor phosphatase and tensin homolog status of the GBM cells, which in turn allows CREB to regulate the activity of the PI3K itself. Given that CREB sits at the hub of key cancer cell signalling pathways, understanding the role of glioma-specific CREB function may lead to improved novel combinatorial anti-tumour therapies, which can complement existing PI3K-specific drugs undergoing early phase clinical trials.

No MeSH data available.


Related in: MedlinePlus

The PI3K and MAPK-dependent signalling pathways but not the PKA pathway activate nuclear CREB in glioma cells. (a) GBM cell lines T98G, LN18 and U118 were serum starved for 24 h then exposed to serum and protein lysate immunoblotted for the indicated antibodies. (b, c) GBM cell lines T98G and U118 were pretreated with a PI3K inhibitor LY294002, a MAPK inhibitor U0126 or both inhibitors, and then exposed to serum, protein lysate collected after 4 h and analysed for the presence of the indicated antibodies (d, e) Quantification of the effects of inhibitor combinations on pCREB levels in T98G and U118 GBM cells. *P<0.05, **P<0.005. (f) Western blotting showing the level of pCREB and pAKT in mouse NSPCs grown as neurospheres, with an activated Pik3caH1047R mutation and PTEN deletion (M) or parental NSPCs with ‘wild-type' Pik3ca and PTEN (C). All western blottings were performed at least three times, and where applicable, total CREB, AKT and MAPK were imaged, then membranes were stripped and reprobed for pCREB, pAKT and pMAPK detection.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4150215&req=5

fig3: The PI3K and MAPK-dependent signalling pathways but not the PKA pathway activate nuclear CREB in glioma cells. (a) GBM cell lines T98G, LN18 and U118 were serum starved for 24 h then exposed to serum and protein lysate immunoblotted for the indicated antibodies. (b, c) GBM cell lines T98G and U118 were pretreated with a PI3K inhibitor LY294002, a MAPK inhibitor U0126 or both inhibitors, and then exposed to serum, protein lysate collected after 4 h and analysed for the presence of the indicated antibodies (d, e) Quantification of the effects of inhibitor combinations on pCREB levels in T98G and U118 GBM cells. *P<0.05, **P<0.005. (f) Western blotting showing the level of pCREB and pAKT in mouse NSPCs grown as neurospheres, with an activated Pik3caH1047R mutation and PTEN deletion (M) or parental NSPCs with ‘wild-type' Pik3ca and PTEN (C). All western blottings were performed at least three times, and where applicable, total CREB, AKT and MAPK were imaged, then membranes were stripped and reprobed for pCREB, pAKT and pMAPK detection.

Mentions: Many signalling pathways relevant to GBM converge onto CREB, suggesting that constitutive CREB activation as observed in GBM is the result of cooperation between multiple upstream factors. To determine which pathways activate CREB, we evaluated cells grown in stimulatory and non-stimulatory conditions for differences in kinase activation. Several serine/threonine kinases that are known to phosphorylate CREB at Serine133 were investigated. Analysis of cell lines T98G, LN18 and U118 demonstrated activation of CREB, AKT and MAPK upon serum stimulation. By contrast, we did not observe activation of PKA, an activator of CREB in other cell types (Figure 3a), showing that there is a selective use of upstream components regulating CREB activity.


Selective CREB-dependent cyclin expression mediated by the PI3K and MAPK pathways supports glioma cell proliferation.

Daniel P, Filiz G, Brown DV, Hollande F, Gonzales M, D'Abaco G, Papalexis N, Phillips WA, Malaterre J, Ramsay RG, Mantamadiotis T - Oncogenesis (2014)

The PI3K and MAPK-dependent signalling pathways but not the PKA pathway activate nuclear CREB in glioma cells. (a) GBM cell lines T98G, LN18 and U118 were serum starved for 24 h then exposed to serum and protein lysate immunoblotted for the indicated antibodies. (b, c) GBM cell lines T98G and U118 were pretreated with a PI3K inhibitor LY294002, a MAPK inhibitor U0126 or both inhibitors, and then exposed to serum, protein lysate collected after 4 h and analysed for the presence of the indicated antibodies (d, e) Quantification of the effects of inhibitor combinations on pCREB levels in T98G and U118 GBM cells. *P<0.05, **P<0.005. (f) Western blotting showing the level of pCREB and pAKT in mouse NSPCs grown as neurospheres, with an activated Pik3caH1047R mutation and PTEN deletion (M) or parental NSPCs with ‘wild-type' Pik3ca and PTEN (C). All western blottings were performed at least three times, and where applicable, total CREB, AKT and MAPK were imaged, then membranes were stripped and reprobed for pCREB, pAKT and pMAPK detection.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150215&req=5

fig3: The PI3K and MAPK-dependent signalling pathways but not the PKA pathway activate nuclear CREB in glioma cells. (a) GBM cell lines T98G, LN18 and U118 were serum starved for 24 h then exposed to serum and protein lysate immunoblotted for the indicated antibodies. (b, c) GBM cell lines T98G and U118 were pretreated with a PI3K inhibitor LY294002, a MAPK inhibitor U0126 or both inhibitors, and then exposed to serum, protein lysate collected after 4 h and analysed for the presence of the indicated antibodies (d, e) Quantification of the effects of inhibitor combinations on pCREB levels in T98G and U118 GBM cells. *P<0.05, **P<0.005. (f) Western blotting showing the level of pCREB and pAKT in mouse NSPCs grown as neurospheres, with an activated Pik3caH1047R mutation and PTEN deletion (M) or parental NSPCs with ‘wild-type' Pik3ca and PTEN (C). All western blottings were performed at least three times, and where applicable, total CREB, AKT and MAPK were imaged, then membranes were stripped and reprobed for pCREB, pAKT and pMAPK detection.
Mentions: Many signalling pathways relevant to GBM converge onto CREB, suggesting that constitutive CREB activation as observed in GBM is the result of cooperation between multiple upstream factors. To determine which pathways activate CREB, we evaluated cells grown in stimulatory and non-stimulatory conditions for differences in kinase activation. Several serine/threonine kinases that are known to phosphorylate CREB at Serine133 were investigated. Analysis of cell lines T98G, LN18 and U118 demonstrated activation of CREB, AKT and MAPK upon serum stimulation. By contrast, we did not observe activation of PKA, an activator of CREB in other cell types (Figure 3a), showing that there is a selective use of upstream components regulating CREB activity.

Bottom Line: CREB overexpression in transgenic animals imparts oncogenic properties on cells in various tissues, and aberrant CREB expression is associated with tumours.Cyclin D1 is highly CREB-dependent, whereas cyclin B1 and PCNA are co-regulated by both CREB-dependent and -independent mechanisms.The precise regulatory network involved appears to differ depending on the tumour-suppressor phosphatase and tensin homolog status of the GBM cells, which in turn allows CREB to regulate the activity of the PI3K itself.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, The University of Melbourne, Parkville, Victoria, Australia.

ABSTRACT
The cyclic-AMP response element binding (CREB) protein has been shown to have a pivotal role in cell survival and cell proliferation. Transgenic rodent models have revealed a role for CREB in higher-order brain functions, such as memory and drug addiction behaviors. CREB overexpression in transgenic animals imparts oncogenic properties on cells in various tissues, and aberrant CREB expression is associated with tumours. It is the central position of CREB, downstream from key developmental and growth signalling pathways, which gives CREB this ability to influence a spectrum of cellular activities, such as cell survival, growth and differentiation, in both normal and cancer cells. We show that CREB is highly expressed and constitutively activated in patient glioma tissue and that this activation closely correlates with tumour grade. The mechanism by which CREB regulates glioblastoma (GBM) tumour cell proliferation involves activities downstream from both the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways that then modulate the expression of three key cell cycle factors, cyclin B, D and proliferating cell nuclear antigen (PCNA). Cyclin D1 is highly CREB-dependent, whereas cyclin B1 and PCNA are co-regulated by both CREB-dependent and -independent mechanisms. The precise regulatory network involved appears to differ depending on the tumour-suppressor phosphatase and tensin homolog status of the GBM cells, which in turn allows CREB to regulate the activity of the PI3K itself. Given that CREB sits at the hub of key cancer cell signalling pathways, understanding the role of glioma-specific CREB function may lead to improved novel combinatorial anti-tumour therapies, which can complement existing PI3K-specific drugs undergoing early phase clinical trials.

No MeSH data available.


Related in: MedlinePlus