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.
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
Project description:The growth arrest and DNA-damage induced 45 gamma (GADD45g) is rapidly induced by various physiological and environmental stresses associated with growth arrest. GADD45g has been observed implicated in cell survival, apoptosis, senescence, cell cycle regulation and DNA repair in a variety of human solid tumor types, acting as either tumor promoter or tumor suppressor. To date, the role of GADD45g in hematopoietic malignancies remains completely unknown. Here, we transduced Molm-13 cells with lentiviral vectors expressing doxycycline-inducible GADD45g. Molm-13 cells with dox administration or not were collected for RNA-seq.
Project description:G-quadruplex ligands (G4L) exert their anti-proliferative effect through telomere-dependent and -independent mechanisms, but the inter-relationship between autophagy, cell growth arrest and cell death induced by these ligands remains largely unexplored. 20A is a 2,4,6-triarylpyridine derivative that binds to G4-DNA with fair to excellent selectivity. Here, we demonstrate that this compound impairs cancer cell viability through induction of senescence and apoptotic cell death in a p53-independent manner. In vivo results corroborate those obtained in in vitro, showing that 20A elicits an important tumor growth inhibition in HeLa-xenografted tumor model. The transcriptomic and proteomic analyses reveal the functional enrichment in the growth arrest, DDR and lysosomal pathways upon 20A treatment. More particularly, we find that ATM and autophagy are activated upon 20A treatment. Genetic inhibition of ATM following 20A treatment inhibits both autophagy and senescence and directs cells to apoptosis. Moreover, loss of autophagy by deletion of two essential autophagy genes ATG5 and ATG7 leads to failure of CHK1 activation and increased cell death triggered by 20A. Our results therefore identify ATM as a critical determinant in the balance between senescence and apoptosis and uncover autophagy as one of the key mediators of such regulation. Thus, targeting the ATM/autophagy pathway might be a promising strategy to achieve the maximal therapeutic effect of the 20A G4-ligand.
Project description:Immune checkpoint bloackade (ICB)-based or natural cancer immune responses largely eliminate tumours. Yet, they require additional mechanisms to arrest those cancer cells that are not rejected. Cytokine-induced senescence (CIS) can stably arrest cancer cells, suggesting that interferon-dependent induction of senescence-inducing cell cycle regulators is needed to control those cancer cells that escape from killing. Here we report in two different cancers sensitive to T cell-mediated rejection, we show that deletion of the senescence-inducing cell cycle regulators p16Ink4a/p19Arf (Cdkn2a) or p21Cip1 (Cdkn1a) in the tumour cells abrogated both, the natural and the ICB-induced cancer immune control. Also in humans, melanoma metastases that progressed rapidly during ICB have losses of senescence-inducing genes and amplifications of senescence inhibitors. Metastatic cells also resist CIS. Such genetic and functional alterations are infrequent in metastatic melanomas regressing during ICB. Thus, activation of tumour-intrinsic, senescence-inducing cell cycle regulators is required to stably arrest those cancer cells that escape from eradication.
Project description:Cell size and the cell cycle are intrinsically coupled and abnormal increases in cell size are associated with senescence and permanent cell cycle arrest. The mechanism by which overgrowth primes cells to withdraw from the cell cycle remains unknown. We investigate this here using CDK4/6 inhibitors that arrest cell cycle progression during G0/G1 and are used in the clinic to treat ER+/HER2- metastatic breast cancer. We demonstrate that CDK4/6 inhibition promotes cellular overgrowth during G0/G1, causing p38MAPK-p53-p21-dependent cell cycle withdrawal. We find that cell cycle withdrawal is triggered by two waves of p21 induction. First, overgrowth during a long-term G0/G1 arrest induces an osmotic stress response. This stress response produces the first wave of p21 induction. Second, when CDK4/6 inhibitors are removed, a fraction of cells escape long term G0/G1 arrest and enter S-phase where overgrowth-driven replication stress results in a second wave of p21 induction that causes cell cycle withdrawal from G2, or the subsequent G1. We propose a model whereby both waves of p21 induction contribute to promote permanent cell cycle arrest. This model could explain why cellular hypertrophy is associated with senescence and why CDK4/6 inhibitors have long-lasting effects in patients.
Project description:Cellular senescence is a stress or damage response that causes a permanent proliferative arrest and secretion of numerous factors with potent biological activities. This senescence-associated secretory phenotype (SASP) has been characterized largely for secreted proteins that participate in embryogenesis, wound healing, inflammation and many age-related pathologies. By contrast, lipid components of the SASP are understudied. We show that senescent cells activate the biosynthesis of several oxylipins that promote segments of the SASP and reinforce the proliferative arrest. Notably, senescent cells synthesize and accumulate an unstudied intracellular prostaglandin, 1a,1b-dihomo-15-deoxy-delta-12,14-prostaglandin J2. Released 15-deoxy-delta-12,14-prostaglandin J2 is a biomarker of senolysis in culture and in vivo. This and other prostaglandin D2-related lipids promote the senescence arrest and SASP by activating RAS signaling. These data identify an important aspect of cellular senescence and a method to detect senolysis
Project description:G-quadruplex ligands (G4L) exert their anti-proliferative effect through telomere-dependent and -independent mechanisms, but the inter-relationship between autophagy, cell growth arrest and cell death induced by these ligands remains largely unexplored. 20A is a 2,4,6-triarylpyridine derivative that binds to G4-DNA with fair to excellent selectivity. Here, we demonstrate that this compound impairs cancer cell viability through induction of senescence and apoptotic cell death in a p53-independent manner. In vivo results corroborate those obtained in in vitro, showing that 20A elicits an important tumor growth inhibition in HeLa-xenografted tumor model. The transcriptomic and proteomic analyses reveal the functional enrichment in the growth arrest, DDR and lysosomal pathways upon 20A treatment. More particularly, we find that ATM and autophagy are activated upon 20A treatment. Genetic inhibition of ATM following 20A treatment inhibits both autophagy and senescence and directs cells to apoptosis. Moreover, loss of autophagy by deletion of two essential autophagy genes ATG5 and ATG7 leads to failure of CHK1 activation and increased cell death triggered by 20A. Our results therefore identify ATM as a critical determinant in the balance between senescence and apoptosis and uncover autophagy as one of the key mediators of such regulation. Thus, targeting the ATM/autophagy pathway might be a promising strategy to achieve the maximal therapeutic effect of the 20A G4-ligand.
Project description:Cellular senescence is defined as permanent growth arrest induced by various stresses. Although the transcriptional activity of p53 is essential for senescence induction, the downstream genes that are crucial for senescence remain unsolved. We developed an experimental system in which either senescence or apoptosis is specifically induced in the same cell line (hepatocarcinoma HepG2 cells having the intact p53 gene) by altering concentrations of a DNA-damaging drug and compared gene expression profiles by using microarray analysis to distinguish genes specific for senescence from those universally respond to DNA damage. When we compared the expression profiles at low versus high doses of etoposide, 20 genes were found to be differentially upregulated by more than 2-fold at a low dose of etoposide, which are expected to function in senescence induction. Microarray results were further confirmed by qPCR.