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Protracted p53-independent stimulation of p21WAF1/Cip1 fuels genomic instability by deregulating the replication licensing machinery

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE62166 | GEO | 2016/05/15

SECONDARY ACCESSION(S): PRJNA263336

REPOSITORIES: GEO

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Protracted p53-independent stimulation of p21WAF1/Cip1 fuels genomic instability by deregulating the replication licensing machinery

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

Homo sapiens

Project description:Protracted p53-independent stimulation of p21WAF1/Cip1 fuels genomic instability by deregulating the replication licensing machinery

| PRJNA263336 | ENA

Chronic p53-independent p21 expression deregulates replication licensing, leading to genomic instability II

Project description:The cyclin-dependent kinase inhibitor p21WAF1/Cip1 (p21) is a cell-cycle checkpoint effector and inducer of senescence, regulated by p53. Yet, evidence suggests that, through a so-far obscure mechanism, p21 could also be oncogenic. We report that a subset of atypical cancerous cells strongly expressing p21 showed proliferation features. This occurred predominantly in p53-mutant human cancers suggesting p53-independent upregulation of p21 selectively in more aggressive tumour cells. Multifaceted phenotypic and genomic analyses of p21-inducible, p53-null, cancerous and near-normal cellular models showed that after an initial senescence-like phase, a subpopulation of p21-expressing proliferating cells emerged, featuring increased genomic instability, aggressiveness and chemo-resistance. Mechanistically, sustained p21-accumulation inhibited mainly the CRL4CDT2 ubiquitin-ligase, leading to deregulated origin licensing and replication stress. Collectively, our data reveal tumour-promoting ability of p21 through deregulation of DNA replication licensing machinery, an unorthodox role to be considered in cancer treatment, since p21 responds to various stimuli including some chemotherapy drugs.

2016-05-24 | GSE81753 | GEO

Chronic p53-independent p21 expression deregulates replication licensing, leading to genomic instability I

2016-05-24 | GSE81752 | GEO

Chronic p53-independent p21 expression deregulates replication licensing, leading to genomic instability

Project description:P53 independent P21 expression deregulates replication licensing , leading to genomic instability

2016-05-17 | PXD004140 | Pride

Metformin reverses a precancerous niche featuring cytoplasmic p21WAF1/CIP1-expressing hepatocytes and prevents hepatocellular carcinoma development

Project description:Prevention and treatment options for hepatocellular carcinoma (HCC) are presently limited, underscoring the necessity for elucidating molecular mechanisms underlying HCC development and identifying new prevention and therapeutic targets. We demonstrate a unique precancerous niche that features enhanced p53 pathway, aberrant cytoplasmic p21WAF1/CIP1-expressing hepatocytes, and increased CD8+ T lymphocyte and macrophage infiltration in the livers of Ncoa5+/- mouse model of HCC. Metformin treatment reverses these precancerous features and profoundly reduces tumor incidence. Our data also reveal that a subset of HCC patients with a similar precancerous niche in the adjacent noncancerous livers had a relatively poor prognosis. Our study suggests a perceptible hepatic niche predisposing to HCC development and uncovers new actions of metformin in the prevention and treatment of HCC.

2020-03-28 | GSE110524 | GEO

Oncogenic Potential of SIRT7 in Human Hepatocellular Carcinoma and its Regulation by the Tumor Suppressors MiR-125a-5p and MiR-125b

Project description:Sirtuins (SIRT) are NAD-dependent protein deacteylases and function in cellular metabolism, stress resistance, proliferation and disease. For SIRT7, a role in ribosomal gene transcription is proposed, but its function in cancer is currently unknown. In this study, we showed that SIRT7 expression was up-regulated in a large cohort of human hepatocellular carcinoma (HCC) patients, and that high expression of SIRT7 was associated with poor prognosis of HCC patients. Notably, inactivation of SIRT7 by siRNA suppressed tumor cell growth and caused G1/S cell cycle arrest in liver cancer cells. This treatment restored p21WAF1/Cip1 activity, induced Beclin-1 and autophagic gene expression and repressed cyclin D1. To explore mechanisms in SIRT7 regulation, microRNA (miRNA) profiling was carried out. This identified five significantly down-regulated miRNAs in HCC. Bioinformatic analysis of target sites and ectopic expression in HCC cells evidenced miR-125a-5p and miR-125b to suppress SIRT7 and cyclin D1 expression and to induce p21WAF1/Cip1-dependent G1 cell cycle arrest. Furthermore, treatment of HCC cells with 5-aza-2’-deoxycytidine or ectopic expression of wild-type but not mutated p53 restored miR-125a-5p and miR-125b expression and inhibited tumor cell growth to suggest their regulation by promoter methylation and p53 activity. To evidence clinical significance of these findings, mutations in the DNA binding domain of p53 and promoter methylation of miR-125b were investigated. Four out of nine patients with induced SIRT7 carried mutations in p53 gene and one patient showed hypermethylation of miR-125b promoter region. Conclusion: Our findings suggest that oncogenic potential of SIRT in hepatocarcinogenesis and that a regulatory loop is proposed whereby SIRT7 inhibits transcriptional activation of p21WAF1/Cip1 via repression of miR-125a-5p and miR-125b. This makes SIRT7 a promising target in cancer therapy.

2012-09-30 | GSE39678 | GEO

Chronic p53-independent p21 expression deregulates replication licensing, leading to genomic instability

Project description:Chronic p53-independent p21 expression deregulates replication licensing, leading to genomic instability

| PRJNA322497 | ENA

Intestinal ablation of CKIalpha highlights invasiveness control

Project description:Wnt signaling, which drives the rapid self-renewal of the gut epithelium is causally associated with intestinal neoplasia. Here we show that CKIalpha is a activation depends on p53 and p21Waf1/Cip1: CKIα ablation provokes activation of p53 and p21, which assume a pivotal role in suppressing invasive cancer. Dual loss of CKIalpha and either p53 or p21 results in rapid, rampant malignant signature denoted p53supinv (p53-suppressed invasiveness) that is conditionally induction of invasiveness. Like invasiveness control, the transcriptional suppression of p53supinv genes is largely mediated by p21, independently of cell cycle control, representing a novel tumor suppressor function of wild-type p53.

2010-10-23 | GSE24760 | GEO

Intestinal ablation of CKIalpha highlights invasiveness control

Project description:Wnt signaling, which drives the rapid self-renewal of the gut epithelium is causally associated with intestinal neoplasia. Here we show that CKIalpha is a activation depends on p53 and p21Waf1/Cip1: CKIÎ± ablation provokes activation of p53 and p21, which assume a pivotal role in suppressing invasive cancer. Dual loss of CKIalpha and either p53 or p21 results in rapid, rampant malignant signature denoted p53supinv (p53-suppressed invasiveness) that is conditionally induction of invasiveness. Like invasiveness control, the transcriptional suppression of p53supinv genes is largely mediated by p21, independently of cell cycle control, representing a novel tumor suppressor function of wild-type p53. 13 arrays of mice entrocytes herto or homozygot for gut specific KO of CKI alpha. Crossed with p53 or p21 KO mice.

2010-10-23 | E-GEOD-24760 | biostudies-arrayexpress

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