Project description:Molecular mechanisms of cell cycle exit are poorly understood. A group of genes required for cell cycle exit and maintenance of cell quiescence in human fibroblasts following serum deprivation has been recently identified. Studies on lymphocytes following growth factor deprivation-induced cell cycle exit have predominantly focused on the initiation of apoptosis. A set of genes involved in lymphocyte quiescence have also been identified among genes highly expressed in resting lymphocytes and down-regulated after cell activation. In our study, proliferating IL-2-dependent human T cells were forced to exit cell cycle by growth factor withdrawal, and their gene expression profiles were examined. The differential gene expression analysis was performed in primary and immortalized IL-2-dependent T lymphocytes. Cell samples were collected directly from the IL-2-containing cultures and 8-hrs following IL-2 withdrawal, before apoptosis could be evidenced by the Annexin-V staining. The three primary T lymphoblast cell populations were obtained from the peripheral blood mononuclear cells (PBMC) stimulated for 24h by wheat germ agglutinin and cultured in the presence of IL-2 up to 4-8 population doublings. As shown by the cell surface analysis, these populations were composed of T cells exclusively. Samples of these cell populations were subsequently analyzed as biological replicates. Two spontaneously immortalized IL-2-dependent T cell lines were derived from normal spleen and from PBMC derived from Nijmegen Breakage Syndrome patient. Gene expression was assessed by the Affymetrix microarray HG-U133 2.0 Plus that detects 38,500 genes. The expression of a selected number of genes was verified by the qRT-PCR method. We have identified a set of 53 genes that we called a â??T lymphocyte cell cycle exit signatureâ??, comprised of 13 up-regulated and 40 down-regulated genes. Genes linked to transcription, cell cycle, cell growth, proliferation and differentiation, cell adhesion and immune functions were found to be overrepresented among the differentially expressed, before and after IL-2 deprivation. Among those, PIM1, BCL2, IL-8, HBEGF, DUSP6, OSM, CISH, SOCS2, SOCS3, LIF and IL13 were down-regulated and RPS24, SQSTM1, TMEM1, LRRC8D, ECOP, YY1AP1, C1orf63, ASAH1, SLC25A46 and MIA3 were up-regulated. Identification of genes involved in cell cycle exit and quiescence, may provide new insights into the mechanisms of tissue repair and regeneration as well as of cancer development. Experiment Overall Design: Cell sources and cell sample preparation. Experiment Overall Design: Samples of three primary, IL-2-dependent T lymphoblast cell lines, derived from three healthy donors (j, 43, 6) were collected from IL-2-containing culture and 8-hrs following IL-2 withdrawal (three pairs, each sample was analyzed once = 6 samples). Experiment Overall Design: The two spontaneously immortalized IL-2-dependent T cell lines were derived from normal spleen (line5) and from PBMC derived from a Nijmegen Breakage Syndrome patient (S9). Samples of the two immortalized cell lines were collected in three biological replicates each, from the cultures with and without IL-2 (2 x 2 x 3 = 12 samples).
Project description:Molecular mechanisms of cell cycle exit are poorly understood. A group of genes required for cell cycle exit and maintenance of cell quiescence in human fibroblasts following serum deprivation has been recently identified. Studies on lymphocytes following growth factor deprivation-induced cell cycle exit have predominantly focused on the initiation of apoptosis. A set of genes involved in lymphocyte quiescence have also been identified among genes highly expressed in resting lymphocytes and down-regulated after cell activation. In our study, proliferating IL-2-dependent human T cells were forced to exit cell cycle by growth factor withdrawal, and their gene expression profiles were examined. The differential gene expression analysis was performed in primary and immortalized IL-2-dependent T lymphocytes. Cell samples were collected directly from the IL-2-containing cultures and 8-hrs following IL-2 withdrawal, before apoptosis could be evidenced by the Annexin-V staining. The three primary T lymphoblast cell populations were obtained from the peripheral blood mononuclear cells (PBMC) stimulated for 24h by wheat germ agglutinin and cultured in the presence of IL-2 up to 4-8 population doublings. As shown by the cell surface analysis, these populations were composed of T cells exclusively. Samples of these cell populations were subsequently analyzed as biological replicates. Two spontaneously immortalized IL-2-dependent T cell lines were derived from normal spleen and from PBMC derived from Nijmegen Breakage Syndrome patient. Gene expression was assessed by the Affymetrix microarray HG-U133 2.0 Plus that detects 38,500 genes. The expression of a selected number of genes was verified by the qRT-PCR method. We have identified a set of 53 genes that we called a “T lymphocyte cell cycle exit signature”, comprised of 13 up-regulated and 40 down-regulated genes. Genes linked to transcription, cell cycle, cell growth, proliferation and differentiation, cell adhesion and immune functions were found to be overrepresented among the differentially expressed, before and after IL-2 deprivation. Among those, PIM1, BCL2, IL-8, HBEGF, DUSP6, OSM, CISH, SOCS2, SOCS3, LIF and IL13 were down-regulated and RPS24, SQSTM1, TMEM1, LRRC8D, ECOP, YY1AP1, C1orf63, ASAH1, SLC25A46 and MIA3 were up-regulated. Identification of genes involved in cell cycle exit and quiescence, may provide new insights into the mechanisms of tissue repair and regeneration as well as of cancer development.
Project description:Differentiation of multipotent stem cells into mature cells is fundamental for development and homeostasis of mammalian tissues, and requires the coordinated induction of lineage-specific transcriptional programs and cell cycle withdrawal. To understand the underlying regulatory mechanisms of this fundamental process, we investigated how the tissue-specific transcription factors, CEBPA and CEBPE, coordinate cell cycle exit and lineage-specification in vivo during granulocytic differentiation. We demonstrate that CEBPA promotes lineage-specification by launching an enhancer-primed differentiation program and direct activation of CEBPE expression. Subsequently, CEBPE confers promoter-driven cell cycle exit by sequential repression of MYC target gene expression at the G1/S transition and E2F-meditated G2/M gene expression, as well as by the up-regulation of Cdk1/2/4 inhibitors. Following cell cycle exit, CEBPE unleashes the CEBPA-primed differentiation program to generate mature granulocytes. These findings highlight how tissue-specific transcription factors coordinate cell cycle exit with differentiation through the use of distinct gene regulatory elements.
Project description:Treatment of hematological malignancies by adoptive transfer of activated natural killer (NK) cells is limited by poor post-infusion persistence. We compared the ability of interleukin-2 (IL-2) and IL-15 to sustain human NK cell functions following cytokine withdrawal to model post-infusion performance. In contrasts to IL-2, IL-15 mediated stronger signaling through the IL-2/15 receptor complex and provided functional advantages. Genome-wide analysis of cytosolic and polysome-associated mRNA revealed cytokine dependent differential mRNA levels and translation during cytokine activation but also that most gene expression differences were primed by IL-15 and only manifested after cytokine withdrawal. IL-15 augmented mTOR signaling, which correlated with increased expression of genes related to cell metabolism and respiration. Consistently, mTOR inhibition abrogated IL-15-induced functional advantages. Moreover, mTOR-independent STAT-5 signaling contributed to improved NK cell function during cytokine activation but not following cytokine withdrawal. The superior performance of IL-15 stimulated NK cells was also observed using a clinically applicable protocol for NK cell expansion. Finally, expression of IL-15 correlated with cytolytic immune functions in patients with B cell lymphoma and favorable clinical outcome. These findings highlight the importance of mTOR regulated metabolic processes for immune cell functions and argue for implementation of IL-15 in adoptive NK cell cancer therapy. Freshly isolated NK cells from 6 donors were activated with IL-2 or IL-15 for 48 hours, followed by cytokine withdrawal for 24 hours, resulting in four RNA samples per donor. From each sample, both the cytosolic as well as the polysomal fraction were collected. Donor 3 contains activation and post withdrawal data from two different donors due to poor RNA-quality obtained for some samples which did not allow for processing of the complete set of 6 donors (resulting in a total of 40 samples).
Project description:Comprehensive proteome analysis of rare cell phenotypes remains a significant challenge. We report a method for low cell number mass spectrometry (MS)-based proteomics using protease digestion of mildly formaldehyde-fixed cells in cellulo, which we call the ‘in-cell digest’. We combined this with AMPL (Averaged MS1 Precursor Library Matching) to make a major advance in the proteome coverage obtained from low cell numbers compared with previous methods. ~4,500 proteins were quantitated from 2,000 human lymphoblasts. ~2,500 proteins or >55% coverage was obtained using 200 lymphoblasts, i.e. an order of magnitude fewer cells. We applied the workflow to measure the proteomes of 16 cell cycle states (8 interphase, 8 mitotic) isolated from an asynchronous human lymphoblast culture (TK6), avoiding synchronisation. We identified 119 high confidence cell cycle-regulated proteins in 8 replicates. These proteins, including well-characterized and novel cell cycle-regulated factors, segregated into five clusters that differed in mitotic abundance patterns and regulatory short linear sequence motifs. We identified predictive protein signatures that accurately classified cell cycle states. These signatures enabled classification of an unexpected cell subset having 4N DNA content and low cyclin B levels as similar to early G0/G1 and telophase cells. These cells also exhibited low levels of APC/C substrates and evidence of a DNA damage response, consistent with a DNA damage-induced senescent state. This study demonstrates an advance in sensitivity in MS-based proteomics using the streamlined in-cell digest workflow. This is a powerful approach to obtain molecular definitions of important, rare cell phenotypes.
Project description:Obesity is considered an important factor for many chronic diseases, including diabetes, cardiovascular disease and cancer. The expansion of adipose tissue in obesity is due to an increase in both adipocyte progenitor differentiation and mature adipocyte cell size. Adipocytes, however, are thought to be unable to divide or enter cell cycle. We demonstrate that mature human adipocytes unexpectedly display a gene and protein signature of cell cycle re-entry. Adipocyte cell cycle progression associates with obesity and hyperinsulinemia, with a concomitant increase in cell size, nuclear size and nuclear DNA content. However, chronic hyperinsulinemia in vitro or in patients, is associated with subsequent cell cycle exit, leading to a premature senescent transcriptomic and secretory profile in adipocytes. Premature senescence is rapidly becoming recognized as an important mediator of stress-induced tissue dysfunction. By demonstrating that adipocytes can re-enter cell cycle we define a mechanism for how mature, human adipocytes senesce and demonstrate that by targeting the adipocyte cell cycle program it is possible to impact adipocyte senescence and obesity-associated adipose tissue inflammation.
Project description:Treatment of hematological malignancies by adoptive transfer of activated natural killer (NK) cells is limited by poor post-infusion persistence. We compared the ability of interleukin-2 (IL-2) and IL-15 to sustain human NK cell functions following cytokine withdrawal to model post-infusion performance. In contrasts to IL-2, IL-15 mediated stronger signaling through the IL-2/15 receptor complex and provided functional advantages. Genome-wide analysis of cytosolic and polysome-associated mRNA revealed cytokine dependent differential mRNA levels and translation during cytokine activation but also that most gene expression differences were primed by IL-15 and only manifested after cytokine withdrawal. IL-15 augmented mTOR signaling, which correlated with increased expression of genes related to cell metabolism and respiration. Consistently, mTOR inhibition abrogated IL-15-induced functional advantages. Moreover, mTOR-independent STAT-5 signaling contributed to improved NK cell function during cytokine activation but not following cytokine withdrawal. The superior performance of IL-15 stimulated NK cells was also observed using a clinically applicable protocol for NK cell expansion. Finally, expression of IL-15 correlated with cytolytic immune functions in patients with B cell lymphoma and favorable clinical outcome. These findings highlight the importance of mTOR regulated metabolic processes for immune cell functions and argue for implementation of IL-15 in adoptive NK cell cancer therapy.
Project description:A long-term goal in cancer research has been to inhibit the cell cycle in tumour cells without causing toxicity in proliferative healthy tissues. The best evidence that this is achievable is provided by CDK4/6 inhibitors, which arrest the cell cycle in G1, are well-tolerated in patients, and are effective in treating ER+/HER2- breast cancer. CDK4/6 inhibitors are effective because they arrest tumour cells more efficiently than some healthy cell types and, in addition, they affect the tumour microenvironment to enhance anti-tumour immunity. We demonstrate here another reason to explain their efficacy. Tumour cells are specifically vulnerable to CDK4/6 inhibition because during the G1 arrest, oncogenic signals drive toxic cell overgrowth. This overgrowth causes permanent cell cycle withdrawal by either preventing progression from G1 or by inducing replication stress and genotoxic damage during the subsequent S-phase and mitosis. Inhibiting or reverting oncogenic signals that converge onto mTOR can rescue this excessive growth, DNA damage and cell cycle exit in cancer cells. Conversely, inducing oncogenic signals in non-transformed cells can drive these toxic phenotypes and sensitize cells to CDK4/6 inhibition. Together, this demonstrates how oncogenic signals that have evolved to stimulate constitutive tumour growth and proliferation driven subverted to cause toxic cell growth and irreversible cell cycle exit when proliferation is halted in G1.
Project description:Analysis of gene expression changes following replicative senescnce Here we induced normal (primary) human diploid fibroblasts into senescence using serial passaging to determine which genes changed expression as a function of exit from the cell cycle.
Project description:Cell differentiation involves profound changes in global gene expression that often have to occur in coordination with cell cycle exit. Because cyclin-dependent kinase inhibitor p27 reportedly regulates proliferation of neural progenitor cells in the subependymal neurogenic niche of the adult mouse brain, but can also have effects on gene expression, we decided to molecularly analyze its role in adult neurogenesis and oligodendrogenesis. At the cell level, we show that p27 restricts residual cyclin-dependent kinase activity after mitogen withdrawal to antagonize cycling, but is not essential for cell cycle exit. Contrasting gene expression with chromatin accessibility, we find that p27 is coincidentally necessary to globally repress many genes involved in the transit from multipotentiality to differentiation, including those coding for neural progenitor transcription factors SOX2, OLIG2, and ASCL1. Our data reveal both direct association of p27 with regulatory sequences in the three genes and an additional hierarchical relationship where p27 repression of the Sox2 gene leads to reduced levels of SOX2-downstream targets Olig2 and Ascl1. In vivo, p27 is also required for the regulation of the proper level of SOX2 necessary for neuroblasts and oligodendroglial progenitor cells to timely exit cell cycle in a lineage-dependent manner.