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Role of MSK1 in the malignant phenotype of Ras-transformed mouse fibroblasts.

ABSTRACT: Activated by the RAS-MAPK signaling pathway, MSK1 is recruited to immediate-early gene (IEG) regulatory regions, where it phosphorylates histone H3 at Ser-10 or Ser-28. Chromatin remodelers and modifiers are then recruited by 14-3-3 proteins, readers of phosphoserine marks, leading to the occupancy of IEG promoters by the initiation-engaged form of RNA polymerase II and the onset of transcription. In this study, we show that this mechanism of IEG induction, initially elucidated in parental 10T1/2 murine fibroblast cells, applies to metastatic Hras1-transformed Ciras-3 cells. As the RAS-MAPK pathway is constitutively activated in Ciras-3 cells, MSK1 activity and phosphorylated H3 steady-state levels are elevated. We found that steady-state levels of the IEG products AP-1 and COX-2 were also elevated in Ciras-3 cells. When MSK1 activity was inhibited or MSK1 expression was knocked down in Ciras-3 cells, the induction of IEG expression and the steady-state levels of COX-2, FRA-1, and JUN were greatly reduced. Furthermore, MSK1 knockdown Ciras-3 cells lost their malignant phenotype, as reflected by the absence of anchorage-independent growth.

SUBMITTER: Perez-Cadahia B

PROVIDER: S-EPMC3013000 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Role of MSK1 in the malignant phenotype of Ras-transformed mouse fibroblasts.

Pérez-Cadahía Beatriz B Drobic Bojan B Espino Paula S PS He Shihua S Mandal Soma S Healy Shannon S Davie James R JR

The Journal of biological chemistry 20101110 1

Activated by the RAS-MAPK signaling pathway, MSK1 is recruited to immediate-early gene (IEG) regulatory regions, where it phosphorylates histone H3 at Ser-10 or Ser-28. Chromatin remodelers and modifiers are then recruited by 14-3-3 proteins, readers of phosphoserine marks, leading to the occupancy of IEG promoters by the initiation-engaged form of RNA polymerase II and the onset of transcription. In this study, we show that this mechanism of IEG induction, initially elucidated in parental 10T1/ ...[more]

PMID: 21071437

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Project description:BackgroundOncogene activation plays a role in metabolic reprogramming of cancer cells. We have previously shown that K-ras transformed fibroblasts have a stronger dependence on glycolysis and a reduced oxidative phosphorylation ability as compared to their normal counterparts. Another metabolic adaptation of cancer cells, that has long been established, is their propensity to exhibit increased glutamine consumption, although the effects induced by glutamine deprivation on cancer cells are still controversial.Methodology and principal findingsHere, by using nutritional perturbations and molecular physiology, we show that reduction or complete depletion of glutamine availability in K-ras transformed fibroblasts causes a strong decrease of proliferation ability and a slower re-entry of synchronized cells into the cell cycle. The reduced proliferation is accompanied by sustained expression of cyclin D and E, abortive S phase entrance and is dependent on Ras signalling deregulation, since it is rescued by expression of a dominant negative guanine nucleotide exchange factor. The growth potential of transformed cells as well as the ability to execute the G(1) to S transition is restored by adding the four deoxyribonucleotides, indicating that the arrest of proliferation of K-ras transformed cells induced by glutamine depletion is largely due to a reduced supply of DNA in the presence of signalling pathways promoting G(1) to S transition.Conclusions and significanceOur results suggest that the differential effects of glutamine and glucose on cell viability are not a property of the transformed phenotype per se, but rather depend on the specific pathway being activated in transformation. For instance, myc-overexpressing cells have been reported to die under glutamine depletion and not under glucose shortage, while the opposite holds for ras-transformed fibroblasts as shown in this paper. These different responses of transformed cells to nutritional stress should be taken into account when designing anti-cancer therapies that aim to exploit metabolic differences between normal and transformed cells.

Project description:BackgroundCancer stem cells (CSCs) are likely critical to carcinogenesis, and, like normal stem cells (NSCs), are affected by microenvironmental factors. Malignant cells release extracellular factors, modifying tumor behavior. Inorganic arsenic, a human carcinogen, is associated with an overproduction of CSCs in various model systems of carcinogenesis.ObjectiveWe aimed to determine if NSCs are influenced by nearby arsenic-transformed malignant epithelial cells (MECs) as a possible factor in arsenic-associated CSC overabundance.MethodsTranswell noncontact co-culture allowed the study of the effects of non-contiguous, arsenic-transformed prostate MECs on the isogenic human prostate NSC line, WPE-stem. Cancer phenotype was assessed by evaluating secreted matrix metalloproteinases (MMPs), invasiveness, colony formation, and spheroid formation. Gene expression was assessed at the protein (Western blot) or mRNA (real-time reverse transcription-polymerase chain reaction) levels.ResultsNoncontact co-culture of MECs and NSCs rapidly (? 3 weeks) caused hypersecretion of MMPs and marked suppression of the tumor suppressor gene PTEN in NSCs. NSCs co-cultured with MECs also showed increased invasiveness and clonogenicity and formed more free-floating spheroids and highly branched ductal-like structures in Matrigel, all typical for CSCs. MEC co-culture caused dysregulated self-renewal and differentiation-related gene expression patterns and epithelial-to-mesenchymal transition in NSCs consistent with an acquired cancer phenotype. Interleukin-6 (IL-6), a cytokine involved in tumor microenvironment control, was hypersecreted by MECs, and IL-6 exposure of NSCs resulted in the duplication of several responses in NSCs of conversion to CSCs via MEC co-culture (e.g., MMP hypersecretion, decreased PTEN).ConclusionsArsenic-transformed MECs recruit nearby NSCs into a cancer phenotype, thereby potentially increasing CSC number. This may be a factor in arsenic-induced CSC overabundance seen in multiple model systems.

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Role of MSK1 in the malignant phenotype of Ras-transformed mouse fibroblasts.

Publications

Role of MSK1 in the malignant phenotype of Ras-transformed mouse fibroblasts.

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