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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

CREB is required for efficient human glioma cell line proliferation. (a) T98G cells were transfected with either CREB1-specific siRNA (siCREB) or scramble siRNA and then lysate analysed by western blotting for efficiency of CREB knockdown. *P=0.05, **P=0.005, ***P=0.0005. (b, c) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and proliferation was analysed every 24 h using an MTT assay. (d, e) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and apoptosis was determined by FACs determination of AnnexinV uptake.
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fig4: CREB is required for efficient human glioma cell line proliferation. (a) T98G cells were transfected with either CREB1-specific siRNA (siCREB) or scramble siRNA and then lysate analysed by western blotting for efficiency of CREB knockdown. *P=0.05, **P=0.005, ***P=0.0005. (b, c) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and proliferation was analysed every 24 h using an MTT assay. (d, e) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and apoptosis was determined by FACs determination of AnnexinV uptake.

Mentions: To link the specificity of AKT and MAPK activation with CREB activation, the PI3K pathway inhibitor LY294002 and the MAPK pathway inhibitor U0126 were used on T98G and U118 (Figures 3b and c). These cell lines were chosen for further analysis for two reasons. First, they showed the greatest CREB-dependent change in proliferation (Figures 4b and c), and second, these cell lines differ in the tumour-suppressor PTEN status, where T98G has intact PTEN function and U118 is PTEN deficient. One of the PTEN's major functions is to act as the major phosphatase that inhibits the activation of the PI3K pathway24 Significant variability was seen between the cell lines tested with respect to the contribution of either the PI3K or MAPK pathways on CREB activation. In U118 cells, inhibition of the PI3K pathway resulted in no change in CREB activation, while inhibition of the MAPK pathway resulted in knockdown of CREB activation to basal ‘serum-deprived' levels, suggesting that MAPK signalling is the predominant CREB activation pathway in U118 cells (Figures 3c and e). By contrast, inhibition of either or both the PI3K or MAPK pathways in T98G cells did not result in significant changes in CREB activation (Figures 3b and d), highlighting the diversity and complex interdependence between signalling pathways involved in CREB activation in GBM cells.


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)

CREB is required for efficient human glioma cell line proliferation. (a) T98G cells were transfected with either CREB1-specific siRNA (siCREB) or scramble siRNA and then lysate analysed by western blotting for efficiency of CREB knockdown. *P=0.05, **P=0.005, ***P=0.0005. (b, c) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and proliferation was analysed every 24 h using an MTT assay. (d, e) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and apoptosis was determined by FACs determination of AnnexinV uptake.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: CREB is required for efficient human glioma cell line proliferation. (a) T98G cells were transfected with either CREB1-specific siRNA (siCREB) or scramble siRNA and then lysate analysed by western blotting for efficiency of CREB knockdown. *P=0.05, **P=0.005, ***P=0.0005. (b, c) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and proliferation was analysed every 24 h using an MTT assay. (d, e) Scrambled or siCREB was transfected into GBM cell lines T98G and U118, and apoptosis was determined by FACs determination of AnnexinV uptake.
Mentions: To link the specificity of AKT and MAPK activation with CREB activation, the PI3K pathway inhibitor LY294002 and the MAPK pathway inhibitor U0126 were used on T98G and U118 (Figures 3b and c). These cell lines were chosen for further analysis for two reasons. First, they showed the greatest CREB-dependent change in proliferation (Figures 4b and c), and second, these cell lines differ in the tumour-suppressor PTEN status, where T98G has intact PTEN function and U118 is PTEN deficient. One of the PTEN's major functions is to act as the major phosphatase that inhibits the activation of the PI3K pathway24 Significant variability was seen between the cell lines tested with respect to the contribution of either the PI3K or MAPK pathways on CREB activation. In U118 cells, inhibition of the PI3K pathway resulted in no change in CREB activation, while inhibition of the MAPK pathway resulted in knockdown of CREB activation to basal ‘serum-deprived' levels, suggesting that MAPK signalling is the predominant CREB activation pathway in U118 cells (Figures 3c and e). By contrast, inhibition of either or both the PI3K or MAPK pathways in T98G cells did not result in significant changes in CREB activation (Figures 3b and d), highlighting the diversity and complex interdependence between signalling pathways involved in CREB activation in GBM cells.

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