ABSTRACT: HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. Given the importance of p53, we sought to determine what gene changes were affected if its activation was inhibited. To do this we used the Genetic Suppressor Element (GSE)56 which inhibits the transcriptional activity of p53 (Ossovskaya, 1996). The presence of the GSEp53 delayed the arrest of the HMF3A cells when LT was inactivated. However the cells did arrest. We thus examined the array profiles for 3A-GSEp53 cells after 2 and 7 days of LT inactivation (against 3A-GSEp53 cells at 33°C) and compared these to the profiles for 3A-puro cells. Keywords = p53 Keywords = LT antigen Keywords = fibroblast Keywords = senescence Keywords = Rb Keywords: other
Project description:HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. Given the importance of p53, we sought to determine what gene changes were affected if its activation was inhibited. To do this we used the Genetic Suppressor Element (GSE)56 which inhibits the transcriptional activity of p53 (Ossovskaya, 1996). The presence of the GSEp53 delayed the arrest of the HMF3A cells when LT was inactivated. However the cells did arrest. We thus examined the array profiles for 3A-GSEp53 cells after 2 and 7 days of LT inactivation (against 3A-GSEp53 cells at 33°C) and compared these to the profiles for 3A-puro cells. Keywords = p53 Keywords = LT antigen Keywords = fibroblast Keywords = senescence Keywords = Rb
Project description:HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. HMF3A cells cease proliferating by 4 days at 39°C. We directly compared the gene expression profiles of cells at 33.5°C and after shift up to 39.5°C for 7 days (10 arrays, 3 biological replicates). To eliminate genes that change in response to the temperature shift, we compared the profiles of HMF3Dwt cells at 33°C and those shifted up to 39°C for 7 days (4 arrays, 2 biological replicates). Since HMF3Dwt cells were immortalised with wild type U19 LT antigen, they proliferate at both temperatures. To break up the list of genes obtained with the 7 day shift, we performed several further comparisons on the arrays. HMF3A cells at 33°C were compared to the primary donor fibroblasts (HMF3 passage 8, 4 arrays), HMF3A cells shifted to 39°C for 2 days (4 arrays, 2 biological repeats), HMF3A cells shifted to 39°C for 7 days and then shifted back to 33°C for 3 days (8 arrays, 4 biological repeats) or 7 days (4 arrays, 2 biological repeats). As a comparison to the irreversible process of senescence, we sought to identify genes that changed upon reversible growth arrest, quiescence. Thus changes that occurred when the cells were grown to confluency and starved were also determined (2 biological replicate, 6 arrays). Keywords = Rb Keywords = fibroblast Keywords = immortalization Keywords = LT antigen Keywords = p53 Keywords = quiescence Keywords = senescence
Project description:Activated Ha-ras was introduced to HMF3A cells. HMF3A cells are conditionally immortalised human mammary fibroblasts. They undergo co-ordinated senescence upon inactivation of LT antigen, when cultured at 39C. The introduction of Ras did not prevent this but affected the molecular profile. Keywords = Senescence Keywords = fibroblast Keywords = Ras Keywords = immortalization Keywords = transformation
Project description:Activated Ha-ras was introduced to HMF3A cells. HMF3A cells are conditionally immortalised human mammary fibroblasts. They undergo co-ordinated senescence upon inactivation of LT antigen, when cultured at 39C. The introduction of Ras did not prevent this but affected the molecular profile. Keywords = Senescence Keywords = fibroblast Keywords = Ras Keywords = immortalization Keywords = transformation Keywords: ordered
Project description:HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. HMF3A cells cease proliferating by 4 days at 39°C. We directly compared the gene expression profiles of cells at 33.5°C and after shift up to 39.5°C for 7 days (10 arrays, 3 biological replicates). To eliminate genes that change in response to the temperature shift, we compared the profiles of HMF3Dwt cells at 33°C and those shifted up to 39°C for 7 days (4 arrays, 2 biological replicates). Since HMF3Dwt cells were immortalised with wild type U19 LT antigen, they proliferate at both temperatures. To break up the list of genes obtained with the 7 day shift, we performed several further comparisons on the arrays. HMF3A cells at 33°C were compared to the primary donor fibroblasts (HMF3 passage 8, 4 arrays), HMF3A cells shifted to 39°C for 2 days (4 arrays, 2 biological repeats), HMF3A cells shifted to 39°C for 7 days and then shifted back to 33°C for 3 days (8 arrays, 4 biological repeats) or 7 days (4 arrays, 2 biological repeats). As a comparison to the irreversible process of senescence, we sought to identify genes that changed upon reversible growth arrest, quiescence. Thus changes that occurred when the cells were grown to confluency and starved were also determined (2 biological replicate, 6 arrays). Keywords = Rb Keywords = fibroblast Keywords = immortalization Keywords = LT antigen Keywords = p53 Keywords = quiescence Keywords = senescence Keywords: ordered
Project description:HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. The pSUPER-retro vector system (Brummelkamp, 2002) was used to selectively target genes for mRNA degradation in an attempt to determine if they had a role, in the changes to the transcriptome upon LT inactivation. The genes chosen for targeting were BTG2, NR4A3, DUSP1, PHLDA1 and STACb. Keywords = LT antigen Keywords = senescence Keywords = fibroblast Keywords = BTG2 Keywords = DUSP1 Keywords = MKP-1 Keywords = NR4A3 Keywords = STAC Keywords = PHLDA1 Keywords = RNAi
Project description:HMF3A cells, created from adult human mammary fibroblasts by immortalisation with a thermolabile SV40 large T antigen and the catalytic sub-unit of human telomerase, undergo co-ordinated induction of cellular senescence upon inactivation of T antigen. The pSUPER-retro vector system (Brummelkamp, 2002) was used to selectively target genes for mRNA degradation in an attempt to determine if they had a role, in the changes to the transcriptome upon LT inactivation. The genes chosen for targeting were BTG2, NR4A3, DUSP1, PHLDA1 and STACb. Keywords = LT antigen Keywords = senescence Keywords = fibroblast Keywords = BTG2 Keywords = DUSP1 Keywords = MKP-1 Keywords = NR4A3 Keywords = STAC Keywords = PHLDA1 Keywords = RNAi Keywords: other
Project description:Cellular senescence is a program of irreversible cell cycle arrest that normal cells undergo in response to progressive shortening of telomeres, changes in telomeric structure, oncogene activation or oxidative stress. The underlying signalling pathways, potentially of major clinicopathological relevance, are unknown. A major stumbling block to studying senescence has been the absence of suitable model systems because of the asynchrony of this process in heterogeneous cell populations. To simplify this process many investigators study oncogene-induced senescence due to expression of activated oncogenes where senescence occurs prematurely without telomere attrition and can be induced acutely in a variety of cell types. We have taken a different approach by making use of the finding that reconstitution of telomerase activity by introduction of the catalytic subunit of human telomerase alone is incapable of immortalising all human somatic cells, but inactivation of the p16-pRB and p53-p21 pathways are required in addition. The ability of SV40 large T antigen to inactivate the p16-pRB and p53-p21 pathways has enabled us to use a thermolabile mutant of LT antigen, in conjunction with hTERT, to develop conditionally immortalised human (HMF3A) fibroblasts that are immortal but undergo an irreversible growth arrest when the thermolabile LT antigen is inactivated leading to activation of pRB and p53. When these cells cease dividing, senescence-associated- b-galactosidase activity is induced and the growth-arrested cells have morphological features and express genes in common with senescent cells. Since these cells growth arrest in a synchronous manner they are an excellent starting point for dissecting the pathways that underlie cellular senescence and act downstream of p16-pRB and p53-p21 pathways. We have combined genome-wide expression profiling with genetic complementation to undertake identification of genes that are differentially expressed when these conditionally immortalised human fibroblasts undergo senescence upon activation of the p16-pRB and p53-p21 tumour suppressor pathways. Genes differentially expressed upon senescence will be identified by comparing arrays from growing versus senescent cells. Changes in gene expression due to the temperature shift will be eliminated by comparing with array data from the non-conditional HMF3S cells grown at 34°C ±0.5°C and 38°C ±0.5°C. To determine if the changes in gene expression upon senescence are specific and reversible, the set of differential genes will then be overlaid with array data from cells in which senescence has been bypassed by inactivation of the p16-pRB and p53-p21 tumour suppressor pathways
Project description:Cellular senescence is a program of irreversible cell cycle arrest that normal cells undergo in response to progressive shortening of telomeres, changes in telomeric structure, oncogene activation or oxidative stress. The underlying signalling pathways, potentially of major clinicopathological relevance, are unknown. A major stumbling block to studying senescence has been the absence of suitable model systems because of the asynchrony of this process in heterogeneous cell populations. To simplify this process many investigators study oncogene-induced senescence due to expression of activated oncogenes where senescence occurs prematurely without telomere attrition and can be induced acutely in a variety of cell types. We have taken a different approach by making use of the finding that reconstitution of telomerase activity by introduction of the catalytic subunit of human telomerase alone is incapable of immortalising all human somatic cells, but inactivation of the p16-pRB and p53-p21 pathways are required in addition. The ability of SV40 large T antigen to inactivate the p16-pRB and p53-p21 pathways has enabled us to use a thermolabile mutant of LT antigen, in conjunction with hTERT, to develop conditionally immortalised human (HMF3A) fibroblasts that are immortal but undergo an irreversible growth arrest when the thermolabile LT antigen is inactivated leading to activation of pRB and p53. When these cells cease dividing, senescence-associated- b-galactosidase activity is induced and the growth-arrested cells have morphological features and express genes in common with senescent cells. Since these cells growth arrest in a synchronous manner they are an excellent starting point for dissecting the pathways that underlie cellular senescence and act downstream of p16-pRB and p53-p21 pathways. We have combined genome-wide expression profiling with genetic complementation to undertake identification of genes that are differentially expressed when these conditionally immortalised human fibroblasts undergo senescence upon activation of the p16-pRB and p53-p21 tumour suppressor pathways.
Project description:<p>Cellular senescence affects many physiological and pathological processes and is characterized by durable cell cycle arrest, an inflammatory secretory phenotype and metabolic reprogramming. Here, by using dynamic transcriptome and metabolome profiling in human fibroblasts with different subtypes of senescence, we show that a homeostatic switch which results in glycerol-3-phosphate (G3P) and phosphoethanolamine (PEtn) accumulation links lipid metabolism to the senescence gene expression program. Mechanistically, p53-dependent glycerol kinase (GK) activation and post-translational inactivation of Phosphate Cytidylyltransferase 2-Ethanolamine (PCYT2) regulate this metabolic switch, which promotes triglyceride accumulation in lipid droplets and induces the senescence gene expression program. Conversely, G3P phosphatase (G3PP) and Ethanolamine-Phosphate Phospho-Lyase (ETNPPL)-based scavenging of G3P and PEtn acts in a senomorphic way by reducing G3P and PEtn accumulation. Collectively, our study ties G3P and PEtn accumulation to controlling lipid droplet biogenesis and phospholipid flux in senescent cells, providing a potential therapeutic avenue for targeting senescence and related pathophysiology.</p>