Senescent cells affect many physiological and pathophysiological processes. While select genetic and epigenetic elements for senescence induction have been identified, the dynamics, epigenetic ...mechanisms and regulatory networks defining senescence competence, induction and maintenance remain poorly understood, precluding the deliberate therapeutic targeting of senescence for health benefits. Here, we examined the possibility that the epigenetic state of enhancers determines senescent cell fate. We explored this by generating time-resolved transcriptomes and epigenome profiles during oncogenic RAS-induced senescence and validating central findings in different cell biology and disease models of senescence. Through integrative analysis and functional validation, we reveal links between enhancer chromatin, transcription factor recruitment and senescence competence. We demonstrate that activator protein 1 (AP-1) 'pioneers' the senescence enhancer landscape and defines the organizational principles of the transcription factor network that drives the transcriptional programme of senescent cells. Together, our findings enabled us to manipulate the senescence phenotype with potential therapeutic implications.
Cellular senescence is a stress-responsive cell-cycle arrest program that terminates the further expansion of (pre-)malignant cells. Key signalling components of the senescence machinery, such as p16
..., p21
and p53, as well as trimethylation of lysine 9 at histone H3 (H3K9me3), also operate as critical regulators of stem-cell functions (which are collectively termed 'stemness'). In cancer cells, a gain of stemness may have profound implications for tumour aggressiveness and clinical outcome. Here we investigated whether chemotherapy-induced senescence could change stem-cell-related properties of malignant cells. Gene expression and functional analyses comparing senescent and non-senescent B-cell lymphomas from Eμ-Myc transgenic mice revealed substantial upregulation of an adult tissue stem-cell signature, activated Wnt signalling, and distinct stem-cell markers in senescence. Using genetically switchable models of senescence targeting H3K9me3 or p53 to mimic spontaneous escape from the arrested condition, we found that cells released from senescence re-entered the cell cycle with strongly enhanced and Wnt-dependent clonogenic growth potential compared to virtually identical populations that had been equally exposed to chemotherapy but had never been senescent. In vivo, these previously senescent cells presented with a much higher tumour initiation potential. Notably, the temporary enforcement of senescence in p53-regulatable models of acute lymphoblastic leukaemia and acute myeloid leukaemia was found to reprogram non-stem bulk leukaemia cells into self-renewing, leukaemia-initiating stem cells. Our data, which are further supported by consistent results in human cancer cell lines and primary samples of human haematological malignancies, reveal that senescence-associated stemness is an unexpected, cell-autonomous feature that exerts its detrimental, highly aggressive growth potential upon escape from cell-cycle blockade, and is enriched in relapse tumours. These findings have profound implications for cancer therapy, and provide new mechanistic insights into the plasticity of cancer cells.
Derailed cytokine and immune cell networks account for the organ damage and the clinical severity of COVID-19 (refs.
). Here we show that SARS-CoV-2, like other viruses, evokes cellular senescence as ...a primary stress response in infected cells. Virus-induced senescence (VIS) is indistinguishable from other forms of cellular senescence and is accompanied by a senescence-associated secretory phenotype (SASP), which comprises pro-inflammatory cytokines, extracellular-matrix-active factors and pro-coagulatory mediators
. Patients with COVID-19 displayed markers of senescence in their airway mucosa in situ and increased serum levels of SASP factors. In vitro assays demonstrated macrophage activation with SASP-reminiscent secretion, complement lysis and SASP-amplifying secondary senescence of endothelial cells, which mirrored hallmark features of COVID-19 such as macrophage and neutrophil infiltration, endothelial damage and widespread thrombosis in affected lung tissue
. Moreover, supernatant from VIS cells, including SARS-CoV-2-induced senescence, induced neutrophil extracellular trap formation and activation of platelets and the clotting cascade. Senolytics such as navitoclax and a combination of dasatinib plus quercetin selectively eliminated VIS cells, mitigated COVID-19-reminiscent lung disease and reduced inflammation in SARS-CoV-2-infected hamsters and mice. Our findings mark VIS as a pathogenic trigger of COVID-19-related cytokine escalation and organ damage, and suggest that senolytic targeting of virus-infected cells is a treatment option against SARS-CoV-2 and perhaps other viral infections.
Colorectal tumors are continuously exposed to an inflammatory environment, which together with mitogenic signals sustain several cancer hallmarks. Nuclear factor-kappa B (NFκB) is a major regulator ...of inflammation and variation in NFκB-associated genes could potentially be used as biomarkers to identify patients with increased risk of colorectal cancer (CRC) development, and/or a rapidly progressing disease. In this study, 348 CRC cases and 806 randomly selected healthy individuals from southeastern Sweden were examined with regard to seven polymorphisms in NFκB pathway-associated genes. Log-rank-tests and Cox proportional hazard regression analysis examined the association between the polymorphisms and CRC-specific survival, whereas chi-square tests and logistic regression analysis were used to test for associations between the polymorphisms and CRC susceptibility. Gene expression and loss of heterozygosity analyses of TNFAIP3 were carried out in a subset of tumors to assess its role as a tumor suppressor in CRC. Heterozygous and polymorphic TNFAIP3 (rs6920220), heterozygous NLRP3 (Q705K) and polymorphic NFκB -94 ATTG ins/del genotypes were found to be associated with poorer survival in patients diagnosed with invasive CRC (aHR = 5.2, 95% CI: 2.5-10.9, P < 0.001). TNFAIP3 mRNA levels were significantly decreased in tumors compared with adjacent non-neoplastic mucosa (P < 0.0001) and loss of heterozygosity of 6q23.3 (TNFAIP3) was detected in 17% of cases, whereas only 2.5% of the investigated specimens displayed TNFAIP3 gene mutations. We propose that TNFAIP3 (rs6920220), NLRP3 (Q705K) and NFκB -94 ATTG ins/del polymorphisms are associated with poor survival in patients with advanced CRC and may be used as prognostic markers. Experimental results indicate that TNFAIP3 may act as a tumor suppressor in CRC.
Zelluläre Seneszenz wird als terminaler Zellzyklusarrest definiert, der mit dem Altern und funktionellen Verlust von Geweben verknüpft ist. Eine Seneszenzreaktion wird ebenso durch Onkogene und ...zytotoxischen Stress verursacht. Die Ausführung des Seneszenzprogramms wird durch eine zeitlich hochdynamische Aktivität von Transkriptionsfaktoren (TF) bedingt. Interessanterweise kann die Zelllinienzugehörigkeit einer Zelle durch die Expression von linien-aberranten TF überschrieben werden. ;
Die vorliegende Arbeit untersucht Chemotherapie-induzierte Seneszenz (TIS) in Bcl-2 überexprimierenden, deshalb vor Apoptose geschützten, murinen Eµ-Myc B-Zell Lymphomen in An- oder Abwesenheit der Seneszenz-essentiellen Histonmethyltransferase Suv39h1. Analysen auf Transkriptom- und auf Proteinebene ergeben dabei, dass in einer Seneszenz-spezifischen Weise die TF AP-1, PU.1 und C/EBPβ induziert werden, welche normalerweise für die Funktion und Entwicklung myeloischer Zelllinien bedeutend sind. Dementsprechend korreliert der Seneszenzzustand mit Transkripten, Oberflächenmarkern und einer enzymatischen Funktion der myeloischen Linie. Indem die identifizierten TFs heruntergeschaltet oder überexprimiert werden, wird ihre direkte Beteiligung an der Linienuntreue der TIS Lymphome demonstriert. ;
TIS-Kapazität wird als für den Erfolg von Krebstherapie günstige Eigenschaft betrachtet, da sie zu einem Wachstumsblock führt. Nichtsdestotrotz können sich verweilende TIS Zellen krebsbiologisch auch nachteilig auswirken. Anhand von murinen und humanen, klinisch annotieren Transkriptomdatensätzen kann hier in beiden Spezies ein myeloisch verschobenes, Linienuntreue anzeigendes Genexpressionsprofil mit einer besseren Überlebensprognose korreliert werden. Die vorliegenden Befunde legen nahe, dass die Modulation von TF Aktivitäten in Seneszenz einen potentiellen therapeutischen Angriffspunkt darstellt, um den für den Therapieerfolg nützlichen Zweig des TIS Phänotyps zu befördern.
Cellular senescence is regarded as an irreversible cell cycle arrest associated with tissue aging and its functional decline. A senescence response is also evoked by oncogenic and cytotoxic stress. The execution of the senescence program relies on a highly dynamic sequence of transcription factor (TF) activities. Interestingly, cell lineage commitment can be overridden by the expression of lineage-aberrant TFs. ;
This thesis examines chemotherapy-induced senescence (TIS) in Bcl-2 overexpressing, thus apoptosis-protected, murine Eμ-Myc B-cell lymphomas with or without the senescence-essential histone methyltransferase Suv39h1. Transcriptome as well as protein level analyses reveal senescence-specific induction of the TFs AP-1, PU.1 and C/EBPβ which are typically crucial for myeloid lineage commitment and function. Correspondingly, the senescent state associates with myeloid lineage transcripts, surface markers and enzymatic function, reminiscent of, but not equal to a transdifferentiation phenotype. By knocking down and overexpressing the identified TFs, we demonstrate their direct involvement in the lineage infidelity of TIS lymphomas.;
TIS-capacity is viewed as beneficial to cancer therapy outcome due to its block on proliferation. However, lingering TIS cells can also be detrimental due to the acquisition of latent stemness properties or tumor-protective remodeling of their microenvironment. By interrogating murine and human, clinical course-annotated transcriptome data sets, an association between a myeloid-skewed, lineage infidelity indicating gene expression profile and better tumor prognosis is established in both species. The presented findings suggest that modulation of the senescent TF activities could be therapeutically exploited to foster the cancer patient-beneficial branch of the TIS phenotype.
Colorectal tumors are continuously exposed to an inflammatory environment, which together with mitogenic signals sustain several cancer hallmarks. Nuclear factor-kappa B (NF Kappa B) is a major ...regulator of inflammation and variation in NF Kappa B-associated genes could potentially be used as biomarkers to identify patients with increased risk of colorectal cancer (CRC) development, and/or a rapidly progressing disease. In this study, 348 CRC cases and 806 randomly selected healthy individuals from southeastern Sweden were examined with regard to seven polymorphisms in NF Kappa B pathway-associated genes. Log-rank-tests and Cox proportional hazard regression analysis examined the association between the polymorphisms and CRC-specific survival, whereas chi-square tests and logistic regression analysis were used to test for associations between the polymorphisms and CRC susceptibility. Gene expression and loss of heterozygosity analyses of TNFAIP3 were carried out in a subset of tumors to assess its role as a tumor suppressor in CRC. Heterozygous and polymorphic TNFAIP3 (rs6920220), heterozygous NLRP3 (Q705K) and polymorphic NF Kappa B -94 ATTG ins/del genotypes were found to be associated with poorer survival in patients diagnosed with invasive CRC (aHR = 5.2, 95% CI: 2.5-10.9, P < 0.001). TNFAIP3 mRNA levels were significantly decreased in tumors compared with adjacent non-neoplastic mucosa (P < 0.0001) and loss of heterozygosity of 6q23.3 (TNFAIP3) was detected in 17% of cases, whereas only 2.5% of the investigated specimens displayed TNFAIP3 gene mutations. We propose that TNFAIP3 (rs6920220), NLRP3 (Q705K) and NF Kappa B -94 ATTG ins/del polymorphisms are associated with poor survival in patients with advanced CRC and may be used as prognostic markers. Experimental results indicate that TNFAIP3 may act as a tumor suppressor in CRC.
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