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Retinoblastoma loss modulates DNA damage response favoring tumor progression.

Seoane M, Iglesias P, Gonzalez T, Dominguez F, Fraga M, Aliste C, Forteza J, Costoya JA - PLoS ONE (2008)

Bottom Line: It has been described in premalignant lesions that OIS requires DNA damage response (DDR) activation, safeguard of the integrity of the genome.In human gliomas most of the genetic alterations that have been previously identified result in abnormal activation of cell growth signaling pathways and deregulation of cell cycle, features recapitulated in our model by oncogenic Ras expression and retinoblastoma (Rb) inactivation respectively.Moreover, Rb loss inactivates the stress kinase DDR-associated p38MAPK by specific Wip1-dependent dephosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Molecular Oncology Lab, Departamento de Fisioloxia, Facultade de Medicina, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.

ABSTRACT
Senescence is one of the main barriers against tumor progression. Oncogenic signals in primary cells result in oncogene-induced senescence (OIS), crucial for protection against cancer development. It has been described in premalignant lesions that OIS requires DNA damage response (DDR) activation, safeguard of the integrity of the genome. Here we demonstrate how the cellular mechanisms involved in oncogenic transformation in a model of glioma uncouple OIS and DDR. We use this tumor type as a paradigm of oncogenic transformation. In human gliomas most of the genetic alterations that have been previously identified result in abnormal activation of cell growth signaling pathways and deregulation of cell cycle, features recapitulated in our model by oncogenic Ras expression and retinoblastoma (Rb) inactivation respectively. In this scenario, the absence of pRb confers a proliferative advantage and activates DDR to a greater extent in a DNA lesion-independent fashion than cells that express only HRas(V12). Moreover, Rb loss inactivates the stress kinase DDR-associated p38MAPK by specific Wip1-dependent dephosphorylation. Thus, Rb loss acts as a switch mediating the transition between premalignant lesions and cancer through DDR modulation. These findings may have important implications for the understanding the biology of gliomas and anticipate a new target, Wip1 phosphatase, for novel therapeutic strategies.

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Wip1 inhibition enables senescence in cRb−/−/RasV12 astrocytes.a, All the experimental groups were treated with the Wip1 chemical inhibitors CCT007093 and Arsenic Trioxide (ATO). Levels of p-p38MAPK were assessed by Western blot analysis as a readout of Wip1 phosphatase activity inhibition. b, SA-β-galactosidase assays in all groups (without treatment, ATO treatment, CCT007093 treatment). The y-axis represents the percentage of-positive cells (mean and s.d.).
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pone-0003632-g005: Wip1 inhibition enables senescence in cRb−/−/RasV12 astrocytes.a, All the experimental groups were treated with the Wip1 chemical inhibitors CCT007093 and Arsenic Trioxide (ATO). Levels of p-p38MAPK were assessed by Western blot analysis as a readout of Wip1 phosphatase activity inhibition. b, SA-β-galactosidase assays in all groups (without treatment, ATO treatment, CCT007093 treatment). The y-axis represents the percentage of-positive cells (mean and s.d.).

Mentions: Also, to test our hypothesis regarding the Ras-pRb loss cooperation mediated by Wip1 all experimental groups were treated with two chemical inhibitors upon infection, CCT007093 [57] and Arsenic Trioxide [58]. As a result, dephosphorylation of p38MAPK by Wip1 was blocked as demonstrated by the increased level of phosphorylated p38MAPK, especially in the cRb−/−/RasV12 group (Figure 5A). This biochemical outcome correlates with the positive staining observed in SA-β-Galactosidase assays (Figure 5B). In addition, proliferation rates observed in cRbloxP/loxP/RasV12 and cRb−/−/RasV12 treated groups were significantly lower that the same cells without treatments (Figure S4), confirming previous reports where Ppm1d−/− MEFs showed reduced proliferation rate with features of early senescence [52].


Retinoblastoma loss modulates DNA damage response favoring tumor progression.

Seoane M, Iglesias P, Gonzalez T, Dominguez F, Fraga M, Aliste C, Forteza J, Costoya JA - PLoS ONE (2008)

Wip1 inhibition enables senescence in cRb−/−/RasV12 astrocytes.a, All the experimental groups were treated with the Wip1 chemical inhibitors CCT007093 and Arsenic Trioxide (ATO). Levels of p-p38MAPK were assessed by Western blot analysis as a readout of Wip1 phosphatase activity inhibition. b, SA-β-galactosidase assays in all groups (without treatment, ATO treatment, CCT007093 treatment). The y-axis represents the percentage of-positive cells (mean and s.d.).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2573954&req=5

pone-0003632-g005: Wip1 inhibition enables senescence in cRb−/−/RasV12 astrocytes.a, All the experimental groups were treated with the Wip1 chemical inhibitors CCT007093 and Arsenic Trioxide (ATO). Levels of p-p38MAPK were assessed by Western blot analysis as a readout of Wip1 phosphatase activity inhibition. b, SA-β-galactosidase assays in all groups (without treatment, ATO treatment, CCT007093 treatment). The y-axis represents the percentage of-positive cells (mean and s.d.).
Mentions: Also, to test our hypothesis regarding the Ras-pRb loss cooperation mediated by Wip1 all experimental groups were treated with two chemical inhibitors upon infection, CCT007093 [57] and Arsenic Trioxide [58]. As a result, dephosphorylation of p38MAPK by Wip1 was blocked as demonstrated by the increased level of phosphorylated p38MAPK, especially in the cRb−/−/RasV12 group (Figure 5A). This biochemical outcome correlates with the positive staining observed in SA-β-Galactosidase assays (Figure 5B). In addition, proliferation rates observed in cRbloxP/loxP/RasV12 and cRb−/−/RasV12 treated groups were significantly lower that the same cells without treatments (Figure S4), confirming previous reports where Ppm1d−/− MEFs showed reduced proliferation rate with features of early senescence [52].

Bottom Line: It has been described in premalignant lesions that OIS requires DNA damage response (DDR) activation, safeguard of the integrity of the genome.In human gliomas most of the genetic alterations that have been previously identified result in abnormal activation of cell growth signaling pathways and deregulation of cell cycle, features recapitulated in our model by oncogenic Ras expression and retinoblastoma (Rb) inactivation respectively.Moreover, Rb loss inactivates the stress kinase DDR-associated p38MAPK by specific Wip1-dependent dephosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Molecular Oncology Lab, Departamento de Fisioloxia, Facultade de Medicina, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.

ABSTRACT
Senescence is one of the main barriers against tumor progression. Oncogenic signals in primary cells result in oncogene-induced senescence (OIS), crucial for protection against cancer development. It has been described in premalignant lesions that OIS requires DNA damage response (DDR) activation, safeguard of the integrity of the genome. Here we demonstrate how the cellular mechanisms involved in oncogenic transformation in a model of glioma uncouple OIS and DDR. We use this tumor type as a paradigm of oncogenic transformation. In human gliomas most of the genetic alterations that have been previously identified result in abnormal activation of cell growth signaling pathways and deregulation of cell cycle, features recapitulated in our model by oncogenic Ras expression and retinoblastoma (Rb) inactivation respectively. In this scenario, the absence of pRb confers a proliferative advantage and activates DDR to a greater extent in a DNA lesion-independent fashion than cells that express only HRas(V12). Moreover, Rb loss inactivates the stress kinase DDR-associated p38MAPK by specific Wip1-dependent dephosphorylation. Thus, Rb loss acts as a switch mediating the transition between premalignant lesions and cancer through DDR modulation. These findings may have important implications for the understanding the biology of gliomas and anticipate a new target, Wip1 phosphatase, for novel therapeutic strategies.

Show MeSH
Related in: MedlinePlus