Project description:The regulation of necrotic death and its relevance in anti-cancer therapy are largely unknown. Here we have investigated the pro-apoptotic and pro-necrotic activities of two ubiquitin-proteasome system inhibitors (UPSIs): bortezomib and G5. The present study points out that the glioblastoma cell lines U87MG and T98G are useful models to study the susceptibility to apoptosis and necrosis in response to UPSIs. U87MG cells are resistant to apoptosis induced by bortezomib and G5 but susceptible to necrosis induced by G5. On the opposite T98G cells are susceptible to apoptosis induced by both inhibitors but show some resistance to G5-induced necrosis. By comparing the transcriptional profiles of the two cell lines, we have found that the resistance to G5-induced necrosis could arise from differences in glutathione synthesis/utilization and in the microenvironment. In particular collagen IV, which is highly expressed in T98G cells, and fibronectin, whose adhesive function is counteracted by tenascin-C in U87MG cells, can restrain the necrotic response to G5. Collectively, our results provide an initial characterization of the molecular signals governing cell death by necrosis in glioblastoma cell lines. Keywords: cell line comparison
Project description:The regulation of necrotic death and its relevance in anti-cancer therapy are largely unknown. Here we have investigated the pro-apoptotic and pro-necrotic activities of two ubiquitin-proteasome system inhibitors (UPSIs): bortezomib and G5. The present study points out that the glioblastoma cell lines U87MG and T98G are useful models to study the susceptibility to apoptosis and necrosis in response to UPSIs. U87MG cells are resistant to apoptosis induced by bortezomib and G5 but susceptible to necrosis induced by G5. On the opposite T98G cells are susceptible to apoptosis induced by both inhibitors but show some resistance to G5-induced necrosis. By comparing the transcriptional profiles of the two cell lines, we have found that the resistance to G5-induced necrosis could arise from differences in glutathione synthesis/utilization and in the microenvironment. In particular collagen IV, which is highly expressed in T98G cells, and fibronectin, whose adhesive function is counteracted by tenascin-C in U87MG cells, can restrain the necrotic response to G5. Collectively, our results provide an initial characterization of the molecular signals governing cell death by necrosis in glioblastoma cell lines. Experiment Overall Design: Gene expression profiling was evaluated from 3 replicates each of T98G and U87MG cells.
Project description:Cell death is a fundamental process for health and disease. Emerging research unveiled numerous distinct cell death modalities with similar and intertwined signaling pathways, but different outcomes, rising the need to understand the decision points during cell death signaling. Paracetamol (Acetaminophen, APAP)-induced hepatocyte death includes several apoptotic processes, but eventually ends as oncotic necrosis without any caspase activation. Here, we studied this paradoxical form of cell death and revealed that APAP not only fails to activate caspases, but also strongly impedes their activation upon classical apoptosis induction. We explored different hypotheses and deciphered that high oxidative stress consistently blocks caspase activity. Importantly, caspase inhibition and the associated switch from apoptotic to necrotic cell death is reversible through the administration of antioxidants. Thus, exemplified by APAP-induced cell death, our study stresses that the cellular redox status is a critical decision maker between different forms of cell death as it directly affects caspase activity.
Project description:Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a well-known inducer of apoptosis via formation of the primary death-inducing signaling complex (TRAIL-DISC) at the level of membrane death receptors (DR4 and DR5) which recruit successively FADD and caspase-8. TRAIL can also induce necroptosis when caspases are inhibited. Necroptosis is a regulated cell death dependent on the formation of a cytosolic necrosome complex which includes RIPK1, RIPK3 and MLKL proteins. Elucidating the molecular mechanisms involved in TRAIL-induced necroptosis might provide new insights into the TRAIL death signaling pathway. Here, we report the analysis by mass spectrometry of endogenous RIPK3-dependent necrosome complex constituents upon necroptosis induced by TRAIL/z-VAD/Birinapant (TzB) in HT29 cells. Besides characterization of RIPK1, RIPK3, MLKL, FADD, caspase-8, we find TRIM21 as a new constituent of the necrosome complex. Moreover RIPK1, RIPK3, MLKL, P-MLKL, FADD, caspase-8 and TRIM21 are also found associated to the native TRAIL-DISC upon TzB stimulation showing initiation of the necrotic pathway at the level of TRAIL death receptors in HT29 cells. Finally, TRIM21 may positively modulate necroptosis induction by downregulating NF-kB activation.
Project description:Combining direct anti-tumor effects with targeting of tumor microenvironment is an attractive strategy that may lead to more effective therapies for advanced melanoma. Here, we tested whether association of TRAIL with co-targeting of MEK and PI3K/mTOR, or with MEK blockade, could have synergistic anti-melanoma activity mediated not only by induction of tumor cell death, but also by effects on the tumor microenvironment. Drug interaction analysis by the Chou-Talalay approach in a panel of 21 melanoma cell lines indicated that strong synergism could be achieved by association of the MEK1/2 inhibitor AZD6244, the PI3K/mTOR inhibitor NPV-BEZ235 and TRAIL, as well as by the AZD6244/TRAIL combination. Synergism was observed on most tumors including TRAIL- or inhibitor-resistant melanomas, irrespective of the BRAF, NRAS, p53 and PTEN status, and was explained by enhanced induction of caspase-dependent melanoma apoptosis. The AZD/BEZ/TRAIL and AZD/TRAIL combinatorial treatments induced strong modulation of key apoptosis regulators along the extrinsic and intrinsic cell death pathways, including c-FLIP down-regulation, caspase-8 cleavage, BIMs and BAXa upregulation, clusterin and Mcl-1 inhibition, enhanced mitochondrial depolarization, suppression of inhibitors of apoptosis c-IAP1, c-IAP2, XIAP and Apollon, and caspase 3/7 activation. In an in vivo model, the AZD6244/TRAIL combinatorial treatment induced highly significant growth inhibition of a TRAIL-resistant tumor associated not only with melanoma cell death, but even with suppression of pro-angiogenic molecules HIF1a, VEGFa, IL-8 and TGFb1, and with inhibition of tumor angiogenesis. These results provide a proof of principle supporting the rationale for combinatorial treatments with synergistic anti-melanoma activity based on direct and indirect anti-tumor effects.
Project description:We identified a novel form of caspase-independent cell death (CICD) induced by BH3-mimetics. To characterize the transcriptional changes during CICD and compare these to apoptotic changes, we performed RNA Seq analysis on SUDHL6 lymphoma cells treated with the MCL1 inhibitor S63845 in the presence or abscence of the broad spectrum caspase inhibitor zVAD.fmk.
Project description:Caspases are cysteine-proteases with key roles in the execution phase of apoptosis. Additional cellular activities, unrelated to cell death seem to be influenced by these enzymes. Identification of genes co-regulated with caspases could help to ascertain new biological roles for these proteases.To identify genes and pathways under the influence of caspase-2 we silenced its expression in U87MG glioblastoma cell line. Transcriptional expression profiles of cells transfected with caspase-2 siRNA or control siRNA were compared. Gene expression profiling was evaluated from 2 replicates of U87MG cells transfected with CASP2-siRNA, or with Control-siRNA.
Project description:Many anticancer agents induce apoptosis, mitotic catastrophe or cellular senescence. Here, we report the functional characterization of an experimental inducer of tumor necrosis factor (TNF)-independent necrosis, necrocide-1 (NC1). NC1 (but not its stereoisomer) killed a panel of human cancer cells (but not normal cells) at nanomolar concentrations and with a non-apoptotic, necrotic morphotype, both in vitro and in vivo. NC1-induced killing was not inhibited by caspase blockers, anti-apoptotic BCL2 overexpression or TNFα neutralization, suggesting that NC1 elicits a bona fide necrotic pathway. However, pharmacological or genetic inhibition of necroptosis, pyroptosis and ferroptosis failed to block NC1-mediated cell death. Instead, NC1 elicited reactive oxygen species (ROS) production by mitochondria, and elimination of mitochondrial DNA, quenching of mitochondrial ROS, as well as blockade of mitochondrial permeability transition with cyclosporine A, interfered with NC1-induced cell death. NC1 induced hallmarks of immunogenic cell death incurring calreticulin (CALR) exposure, ATP secretion and high mobility group box 1 (HMGB1) release. Taken together, these data identify a previously uncharacterized signaling cascade leading to an immunogenic variant of mitochondrion-regulated necrosis, supporting the notion that eliciting regulated necrosis may constitute a valid approach for anticancer therapy.
Project description:Glioblastoma (GBM) carries a dismal prognosis largely due to acquired resistance to the standard treatment, which incorporates the chemotherapy temozolomide (TMZ). Inhibiting the proteasomal pathway is an emerging strategy, where combination treatments are under clinical investigation. We hypothesized that pre-treatment of GBM with bortezomib (BTZ) might sensitize glioblastoma to TMZ by abolishing autophagy survival signals to augment DNA damage and apoptosis. P3 patient-derived GBM cells as well as the tumor cell lines U87, HF66, A172 and T98G were investigated for clonogenic survival after single or combined treatment with TMZ and BTZ in vitro. Change in autophagic flux was examined after experimental treatments in conjunction with inhibitors of autophagy or downregulation of autophagy-related genes -5 and -7 (ATG5 and ATG7, respectively). Autophagic flux was increased in TMZ-resistant P3 and T98G cells as indicated by diminished levels of the autophagy markers LC3A/B-II and increased STX17, higher protein degradation and no formation of p62 bodies nor induction of apoptosis. In contrast, BTZ treatment attenuated ULK1 mRNA, total and phosphorylated protein, and accumulated LC3A/B-II, p62 and autophagosomes analogously to Baf1 and chloroquine autophagy inhibitors. These autophagosomes did not fuse with lysosomes, indicated by attenuated STX17 expression and reduced degradation of long-lived proteins, which culminated in enhanced caspase-3/8 dependent apoptosis. BTZ synergistically enhanced TMZ efficacy, attenuated tumor cell proliferation, triggered ATM/Chk2 DNA damage signalling to further augment caspase-3/8 mediated apoptosis in the TMZ resistant P3 and T98G GBM cells. Genetic or chemical inhibition of autophagy (with CRISPR-CAs9 ATG5, ATG7 shRNA, MRT68921 or VPS34-IN1) abrogated BTZ efficacy and rescued BTZ+ TMZ treated GBM cells from death. We conclude that Bortezomib ameliorates temozolomide resistance through ATG5/7-dependent abrogated autophagic flux and may be amenable in combination treatment regimens for TMZ refractory GBM patients.
Project description:For years, the term apoptosis was used synonymously for programmed cell death. However, it was recently discovered that programmed necrosis M-bM-^@M-^S dependent on the kinases Receptor-Interacting-Protein-Kinase (RIP)1 and RIP3 (also called necroptosis) M-bM-^@M-^S represents a major programmed cell-death pathway in development and immunity. At present, the functions of necroptosis in hepatitis, liver cancer development and biliary disease are unclear. Here we show that in mice with chronic hepatitis due to conditional ablation of TGF-beta-activated kinase1 (TAK1) in liver parenchymal cells (LPC), both apoptotic and necroptotic signaling pathways are activated. Strikingly, only Caspase-8-dependent apoptosis promotes spontaneous liver cancer development, while in contrast LPC necroptosis inhibits hepatic tumourigenesis. The tumour-promoting effect of apoptosis results from an induction of strong compensatory proliferation of LPC, linked with the paracrine action of growth factors like Insulin-like growth factor-2 (IGF-2) not induced by necroptosis. In addition to prevention of HCC development, induction of necroptosis leads to massive cholestasis and hyperbilirubinemia, resulting from an insufficient ductular reaction and biliary regeneration from the hepatic stem cell niche as a response to chronic hepatitis. These results indicate previously undefined distinctive functions of apoptosis and programmed necrosis in controlling cancer development and cholestasis in the liver with important implications for future therapeutic strategies in chronic liver disease. 8 samples were analysed. We compared groups of 4 Tak1/Caspase8 LPC double knockout mice and 4 Tak1 LPC-KO/Rip3-/- mice to detect genes differentially regulated by apoptotic and necrotic signalling pathways.