Induction of Senescence in Diterpene Ester-Treated Melanoma Cells via PKC-dependent Hyperactivation of the MAPK Pathway
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE3484 | GEO | 2006/01/20
SECONDARY ACCESSION(S): PRJNA93301
REPOSITORIES: GEO
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Project description:The diterpene ester PEP005 is a novel anticancer agent that activates PKC and cures subcutaneous murine melanoma by topical application. We now describe the in vitro cytostatic effects of PEP005 and the diterpene ester TPA, observed in 20% of human melanoma cell lines. Primary cultures of normal human neonatal fibroblasts were uniformly resistant to growth arrest, indicating a potential for tumor selectivity. Sensitive cells were induced to senesce and exhibited a G1 and G2/M arrest. There was sustained expression of p21WAF1/CIP1, irreversible dephosphorylation of the retinoblastoma gene product (Rb) and transcriptional silencing of E2F-responsive genes in sensitive cell lines. Activation of MEK1/2 by PKC was required for diterpene ester-induced senescence. Expression profiling revealed that the MAPK inhibitor HREV107 was expressed at a higher transcript level in resistant compared to sensitive cell lines. We propose that activation of PKC over-stimulates the Ras/Raf/MEK/ERK pathway, resulting in sustained induction of p21WAF1/CIP1, dephosphorylation of Rb and transcriptional silencing of E2F-responsive genes required for DNA synthesis and mitosis. To investigate the molecular changes associated with the senescent phenotype, we examined the unique transcriptional changes occurring in sensitive melanoma cell lines treated with TPA or PEP005. Initially a time-course cDNA microarray analysis was conducted on one sensitive and one resistant cell line treated with 1 µg/ml of TPA for 6, 24 h and 24 h recovery following 24 h treatment, to determine the earliest time point at which the most significant changes in transcription occurred. The results provided support for conducting array experiments with 24 h treatment, in which three sensitive and four resistant melanoma cell lines were treated with 1 µg/ml of either diterpene ester. Our primary objective was to identify those genes which were uniquely up or down-regulated in sensitive or resistant cell lines in response to treatment, which could reflect the phenotypic outcome. Through applying a series of stringent selective criteria (see Material and Methods) we found that the most significant changes occurred in the transcriptional repression of genes required for DNA synthesis and mitosis in cell lines sensitive to treatment (Table 1). To confirm that these changes were reflected at the protein level, western blot analysis was conducted on three sensitive and three resistant cell lines following 6 and 24 h treatment with TPA or PEP005. We also included a 24 h recovery time point to determine the irreversibility of the change.
2010-07-01 | E-GEOD-3484 | biostudies-arrayexpress
Project description:We previously identified the induction of growth arrest with phenotypic characteristics of senescence in melanoma cell lines sensitive to diterpene esters, indicating a therapeutic potential. Here we compared the cytostatic effects of two diterpene esters namely TPA (12-O-tetradecanoylphorbol-13-acetate) and PEP008 (20-O-acetyl-ingenol-3-angelate) in sensitive and resistant cell lines derived from melanoma, breast cancer and colon cancer. We showed the diterpene esters to induce senescence-like growth arrest in the sensitive cells at 100-1000 ng/ml. Use of the pan-PKC inhibitor bisindolylmaleimide-l demonstrated that activation of PKC was required for growth arrest. Full genome expression profiling revealed that pivotal genes involved in DNA synthesis and cell cycle control were down-regulated by treatment in all three sensitive solid tumor models. At the protein level, prolonged down-regulation of E2F-1 and proliferating cell nuclear antigen (PCNA), sustained expression of p21WAF1/CIP1 and dephosphorylation of retinoblastoma (Rb) occurred in the sensitive cells. Although activation of extracellular signal-related kinase (ERK) 1/2 by the diterpene esters occurred in both sensitive and resistant cell lines, the HRASLS3 type II tumor suppressor, which appears to have a role in MAPK pathway suppression, was constitutively elevated in the resistant cell lines compared to their sensitive counterparts. Together, these results demonstrate the ability of the PKC activating drugs TPA and PEP008 to induce growth arrest with characteristics of senescence in solid tumor cell lines derived from a variety of tissue types through a similar mechanism. PKC-activating diterpene esters may therefore have therapeutic potential in a range of solid tumors. Experiment Overall Design: We analyzed the transcriptional profiles of the diterpene ester sensitive cell lines MCF7, COLO-205 and SK-MEL-5 following treatment with PEP008 using full genome expression profiling (Affymetrix, U133 Plus 2.0). Cells were treated for 24 h and 24 h plus 72 h recovery with 1000 ng/ml of the drug, before harvesting RNA for analysis. From the cell growth assays, all three cell lines demonstrated permanent growth arrest with diterpene ester treatments at the 1000 ng/ml dose. Mock controls were treated with solvent alone for 24 h. SK-MEL-5 cells were also treated with 1000 ng/ml TPA for 24 h.
2008-06-16 | E-GEOD-8742 | biostudies-arrayexpress
Project description:We previously identified the induction of growth arrest with phenotypic characteristics of senescence in melanoma cell lines sensitive to diterpene esters, indicating a therapeutic potential. Here we compared the cytostatic effects of two diterpene esters namely TPA (12-O-tetradecanoylphorbol-13-acetate) and PEP008 (20-O-acetyl-ingenol-3-angelate) in sensitive and resistant cell lines derived from melanoma, breast cancer and colon cancer. We showed the diterpene esters to induce senescence-like growth arrest in the sensitive cells at 100-1000 ng/ml. Use of the pan-PKC inhibitor bisindolylmaleimide-l demonstrated that activation of PKC was required for growth arrest. Full genome expression profiling revealed that pivotal genes involved in DNA synthesis and cell cycle control were down-regulated by treatment in all three sensitive solid tumor models. At the protein level, prolonged down-regulation of E2F-1 and proliferating cell nuclear antigen (PCNA), sustained expression of p21WAF1/CIP1 and dephosphorylation of retinoblastoma (Rb) occurred in the sensitive cells. Although activation of extracellular signal-related kinase (ERK) 1/2 by the diterpene esters occurred in both sensitive and resistant cell lines, the HRASLS3 type II tumor suppressor, which appears to have a role in MAPK pathway suppression, was constitutively elevated in the resistant cell lines compared to their sensitive counterparts. Together, these results demonstrate the ability of the PKC activating drugs TPA and PEP008 to induce growth arrest with characteristics of senescence in solid tumor cell lines derived from a variety of tissue types through a similar mechanism. PKC-activating diterpene esters may therefore have therapeutic potential in a range of solid tumors. Keywords: time course
2007-10-10 | GSE8742 | GEO
Project description:The cyclin-dependent kinase inhibitor p21WAF1/Cip1 is the prototype downstream effector of the tumor suppressor protein p53. Yet, evidence from human cancer and mice models, imply that p21WAF1/Cip1, under certain conditions, can exercise oncogenic activity. The mechanism behind this behavior is still obscure. Within this context we unexpectedly noticed, predominantly in p53 mutant human cancers, that a subset of highly atypical cancerous cells expressing strongly p21WAF1/Cip1 demonstrated also signs of proliferation. This finding suggests either tolerance to high p21WAF1/Cip1 levels or that p21WAF1/Cip1 per se guided a selective process that led to more aggressive off-springs. To address the latter scenario we employed p21WAF1/Cip1-inducible p53-null cellular models and monitored them over a prolonged time period, using high-throughput screening means. After an initial phase characterized by stalled growth, mainly due to senescence, a subpopulation of p21WAF1/Cip1 cells emerged, demonstrating increased genomic instability, aggressiveness and chemo-resistance. At the mechanistic level unremitted p21WAF1/Cip1 production “saturates” the CRL4CDT2 and SCFSkp2 ubiquitin ligase complexes reducing the turn-over of the replication licensing machinery. Deregulation of replication licensing triggered replication stress fuelling genomic instability. Conceptually, the above notion should be considered when anti-tumor strategies are designed, since p21WAF1/Cip1 responds also to p53-independent signals, including various chemotherapeutic compounds.
2016-05-15 | GSE62166 | GEO
Project description:The cyclin-dependent kinase inhibitor p21WAF1/Cip1 is the prototype downstream effector of the tumor suppressor protein p53. Yet, evidence from human cancer and mice models, imply that p21WAF1/Cip1, under certain conditions, can exercise oncogenic activity. The mechanism behind this behavior is still obscure. Within this context we unexpectedly noticed, predominantly in p53 mutant human cancers, that a subset of highly atypical cancerous cells expressing strongly p21WAF1/Cip1 demonstrated also signs of proliferation. This finding suggests either tolerance to high p21WAF1/Cip1 levels or that p21WAF1/Cip1 per se guided a selective process that led to more aggressive off-springs. To address the latter scenario we employed p21WAF1/Cip1-inducible p53-null cellular models and monitored them over a prolonged time period, using high-throughput screening means. After an initial phase characterized by stalled growth, mainly due to senescence, a subpopulation of p21WAF1/Cip1 cells emerged, demonstrating increased genomic instability, aggressiveness and chemo-resistance. At the mechanistic level unremitted p21WAF1/Cip1 production â??saturatesâ?? the CRL4CDT2 and SCFSkp2 ubiquitin ligase complexes reducing the turn-over of the replication licensing machinery. Deregulation of replication licensing triggered replication stress fuelling genomic instability. Conceptually, the above notion should be considered when anti-tumor strategies are designed, since p21WAF1/Cip1 responds also to p53-independent signals, including various chemotherapeutic compounds. We used microarrays to compare the non-induced and â??escapedâ?? Saos2-p21WAF1/Cip1 Tet-ON cells gene expression profile Multiple arrays for non-induced and â??escapedâ?? Saos2-p21WAF1/Cip1 Tet-ON cells
2016-05-15 | E-GEOD-62166 | biostudies-arrayexpress
Project description:Most E2F-binding sites repress transcription through the recruitment of Retinoblasoma (RB) family members until the end of the G1 cell-cycle phase. Although the MYB promoter contains an E2F-binding site, its transcription is activated shortly after the exit from quiescence, before RB family members inactivation, by unknown mechanisms. We had previously uncovered a nuclear factor distinct from E2F, Myb-sp, whose DNA-binding site overlapped the E2F element and had hypothesized that this factor might overcome the transcriptional repression of MYB by E2F-RB family members. We have purified Myb-sp and discovered that Myc-associated zinc finger proteins (MAZ) are major components. We show that various MAZ isoforms are present in Myb-sp and activate transcription via the MYB-E2F element. Moreover, while forced RB or p130 expression repressed the activity of a luciferase reporter driven by the MYB-E2F element, co-expression of MAZ proteins not only reverted repression, but also activated transcription. Finally, we show that MAZ binds the MYB promoter in vivo, that its binding site is critical for MYB transactivation, and that MAZ knockdown inhibits MYB expression during the exit from quiescence. Together, these data indicate that MAZ is essential to bypass MYB promoter repression by RB family members and to induce MYB expression.
2017-10-04 | PXD006857 | Pride
Project description:Induction of Senescence in Diterpene Ester-Treated Melanoma Cells via PKC-dependent Hyperactivation of the MAPK Pathway
| PRJNA93301 | ENA
Project description:Epithelial to mesenchymal transition (EMT) is activated during cancer invasion and metastasis, enriches for cancer stem cells (CSCs), and contributes to therapeutic resistance and disease recurrence. Signal transduction kinases play a pivotal role as chromatin-anchored proteins in eukaryotes. Here we report for the first time that protein kinase C-theta (PKC-θ) regulates EMT by acting as a critical chromatin-anchored switch for inducible genes. Genome-wide transcriptome analysis identifies a unique cohort of inducible PKC-θ-sensitive genes in MCF7 cells stimulated with phorbol ester.
2014-06-22 | GSE53267 | GEO
Project description:Epithelial to mesenchymal transition (EMT) is activated during cancer invasion and metastasis, enriches for cancer stem cells (CSCs), and contributes to therapeutic resistance and disease recurrence. Signal transduction kinases play a pivotal role as chromatin-anchored proteins in eukaryotes. Here we report for the first time that protein kinase C-theta (PKC-θ) regulates EMT by acting as a critical chromatin-anchored switch for inducible genes. Genome-wide transcriptome analysis identifies a unique cohort of inducible PKC-θ-sensitive genes in MCF7 cells stimulated with phorbol ester. MCF7 Cells treated with mock or siRNA against PKCtheta were left unstimulated or stimulated with PMA. No replicates.
2014-06-22 | E-GEOD-53267 | biostudies-arrayexpress
Project description:Mutations in cancer are due in part to DNA cytosine deamination by APOBEC3B (A3B). While low in healthy tissues, A3B expression and activity are elevated in tumors and further increase in metastases. However, molecular mechanisms responsible for A3B transcriptional regulation are poorly understood. Here, we address whether the RB/E2F pathway, which is often dysregulated in breast cancer, is a molecular trigger of A3B overexpression. First, an A3B promoter-driven luciferase reporter was used to demonstrate reporter activation by disruption of only one out of five predicted E2F binding sites. Second, A3B-luciferase reporter activation was also triggered by expressing the BK polyomavirus T-antigen, which inactivates RB and thereby alleviates repression of E2F regulated genes. Importantly, A3B-luciferase reporter induction by BK polyomavirus T-antigen could not be further increased by mutating the functional E2F binding site. Third, both CRISPR disruption and targeted base substitutions in the endogenous E2F binding site caused strong A3B upregulation and confirmed importance of this regulatory element. Fourth, proteomics experiments showed that members of the DREAM and PRC1.6-complexes including multiple E2F family members are able to bind to wild-type but not E2F mutant promoter sequences. Finally, a combination of genetic and biochemical studies implicated E2F4 and E2F6 in endogenous A3B gene repression. Altogether, our studies demonstrate that A3B expression is suppressed in normal cells by the RB/E2F axis and that viral or mutational disruption of this pathway causes overexpression of this DNA deaminase in cancer and contributes mutational fuel to tumor evolution.
2020-10-19 | PXD020473 | Pride