Showing papers by "Guido Kroemer published in 2006"
TL;DR: At the early stages of carcinogenesis, cell-intrinsic barriers to tumour development seem to be associated with stimulation of an active antitumour immune response, whereas overt tumours development seems to correlate with changes in the immunogenic properties of tumour cells.
Abstract: Numerous innate and adaptive immune effector cells and molecules participate in the recognition and destruction of cancer cells, a process that is known as cancer immunosurveillance. But cancer cells avoid such immunosurveillance through the outgrowth of poorly immunogenic tumour-cell variants (immunoselection) and through subversion of the immune system (immunosubversion). At the early stages of carcinogenesis, cell-intrinsic barriers to tumour development seem to be associated with stimulation of an active antitumour immune response, whereas overt tumour development seems to correlate with changes in the immunogenic properties of tumour cells. The permanent success of treatments for cancer might depend on using immunogenic chemotherapy to re-establish antitumour immune responses.
1,213 citations
TL;DR: Cyt c has been associated also to vital cell functions (i.e. differentiation), suggesting that its release not always occurs in an all-or-nothing fashion and that mitochondrial outer membrane permeabilization may not invariably lead to cell death.
Abstract: In healthy cells, cytochrome c (Cyt c) is located in the mitochondrial intermembrane/intercristae spaces, where it functions as an electron shuttle in the respiratory chain and interacts with cardiolipin (CL). Several proapoptotic stimuli induce the permeabilization of the outer membrane, facilitate the communication between intermembrane and intercristae spaces and promote the mobilization of Cyt c from CL, allowing for Cyt c release. In the cytosol, Cyt c mediates the allosteric activation of apoptosis-protease activating factor 1, which is required for the proteolytic maturation of caspase-9 and caspase-3. Activated caspases ultimately lead to apoptotic cell dismantling. Nevertheless, cytosolic Cyt c has been associated also to vital cell functions (i.e. differentiation), suggesting that its release not always occurs in an all-or-nothing fashion and that mitochondrial outer membrane permeabilization may not invariably lead to cell death. This review deals with the events involved in Cyt c release from mitochondria, with special attention to its regulation and final consequences.
1,059 citations
TL;DR: The clinical development of this drug class is reviewed and future prospects for incorporating these agents into multitarget or multimodality strategies against cancer are looked at.
Abstract: Following the development of the first mTOR inhibitor that successfully improves therapeutic survival in cancer, Raymond and colleagues look at how novel biomarker identification and the use of multitargeted and multimodality therapies could advance the next generation of these drugs. Mammalian target of rapamycin (mTOR) is a kinase that functions as a master switch between catabolic and anabolic metabolism and as such is a target for the design of anticancer agents. The most established mTOR inhibitors — rapamycin and its derivatives — showed long-lasting objective tumour responses in clinical trials, with CCI-779 being a first-in-class mTOR inhibitor that improved the survival of patients with advanced renal cell carcinoma. This heralded the beginning of extensive clinical programmes to further evaluate mTOR inhibitors in several tumour types. Here we review the clinical development of this drug class and look at future prospects for incorporating these agents into multitarget or multimodality strategies against cancer.
941 citations
TL;DR: The depletion or inhibition of HSP27 and HS70 frequently reduces the size of the tumors and even can cause their complete involution (for HSP70).
Abstract: Heat shock proteins (HSP) HSP27 and HSP70 are expressed in response to a wide variety of physiological and environmental insults including anticancer chemotherapy, thus allowing the cell to survive to lethal conditions. Several mechanisms account for the cytoprotective effect of HSP27 and HSP70. (1) Both proteins are powerful chaperones. (2) They both inhibit key effectors of the apoptotic machinery at the pre and post-mitochondrial level. (3) They participate in the proteasome-mediated degradation of proteins under stress conditions, thereby contributing to the so called "protein triage". In cancer cells, the expression of HSP27 and/or HSP70 is abnormally high, and both HSP27 and HSP70 may participate in oncogenesis and in resistance to chemotherapy. In rodent models, HSP27 or HSP70 over-expression increases tumor growth and metastatic potential. The depletion or inhibition of HSP27 and HS70 frequently reduces the size of the tumors and even can cause their complete involution (for HSP70). Therefore, the inhibition of HSP70 and HSP27 has become a novel strategy of cancer therapy.
641 citations
TL;DR: Adoptive transfer of these IFN-producing killer dendritic cells into tumor-bearing Rag2/−Il2rg−/− mice prevented tumor outgrowth, whereas transfer of conventional NK cells did not and was identified as pivotal sensors and effectors of the innate antitumor immune response.
Abstract: The interferon (IFN)-γ–induced TRAIL effector mechanism is a vital component of cancer immunosurveillance by natural killer (NK) cells in mice1,2. Here we show that the main source of IFN-γ is not the conventional NK cell but a subset of B220+Ly6C− dendritic cells, which are atypical insofar as they express NK cell-surface molecules. Upon contact with a variety of tumor cells that are poorly recognized by NK cells, B220+NK1.1+ dendritic cells secrete high levels of IFN-γ and mediate TRAIL-dependent lysis of tumor cells. Adoptive transfer of these IFN-producing killer dendritic cells (IKDCs) into tumor-bearing Rag2−/−Il2rg−/− mice prevented tumor outgrowth, whereas transfer of conventional NK cells did not. In conclusion, we identified IKDCs as pivotal sensors and effectors of the innate antitumor immune response.
423 citations
TL;DR: A variety of experimental therapeutic agents can directly target mitochondria, causing apoptosis induction, and it is possible to design molecules that neutralize inhibitor of apoptosis proteins (IAPs) or heat shock protein 70 (HSP70).
Abstract: Mitochondria are vital for cellular bioenergetics and play a central role in determining the point-of-no-return of the apoptotic process. As a consequence, mitochondria exert a dual function in carcinogenesis. Cancer-associated changes in cellular metabolism (the Warburg effect) influence mitochondrial function, and the invalidation of apoptosis is linked to an inhibition of mitochondrial outer membrane permeabilization (MOMP). On theoretical grounds, it is tempting to develop specific therapeutic interventions that target the mitochondrial Achilles' heel, rendering cancer cells metabolically unviable or subverting endogenous MOMP inhibitors. A variety of experimental therapeutic agents can directly target mitochondria, causing apoptosis induction. This applies to a heterogeneous collection of chemically unrelated compounds including positively charged α-helical peptides, agents designed to mimic the Bcl-2 homology domain 3 of Bcl-2-like proteins, ampholytic cations, metals and steroid-like compounds. Such MOMP inducers or facilitators can induce apoptosis by themselves (monotherapy) or facilitate apoptosis induction in combination therapies, bypassing chemoresistance against DNA-damaging agents. In addition, it is possible to design molecules that neutralize inhibitor of apoptosis proteins (IAPs) or heat shock protein 70 (HSP70). Such IAP or HSP70 inhibitors can mimic the action of mitochondrion-derived mediators (Smac/DIABLO, that is, second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with a low isoelectric point, in the case of IAPs; AIF, that is apoptosis-inducing factor, in the case of HSP70) and exert potent chemosensitizing effects.
340 citations
TL;DR: Recent progress is discussed in the quest to understand the contribution of AIF to life and death.
319 citations
TL;DR: Cancer-specific mitochondrial alterations and bioenergetics may be taken advantage for the development of two novel classes of antineoplastic agents that aim at inducing apoptosis by targeting mitochondrial proteins and membranes.
Abstract: Prominent features of cancer cells include metabolic imbalances and enhanced resistance to mitochondrial apoptosis. The fact that tumors rely heavily on glycolysis to meet their metabolic demands has been recognized since the beginning of the twentieth century, yet a complete elucidation of the so-called Warburg effect has not been achieved. Several mechanisms have been proposed to explain this phenomenon, including the upregulation of rate-limiting steps of glycolysis, the accumulation of mutations in the mitochondrial genome, the hypoxia-induced switch from mitochondrial respiration to glycolysis or the metabolic reprogramming resulting from the loss-of-function of enzymes like fumarate and succinate dehydrogenases. How aerobic glycolysis and apoptosis resistance are linked remains to be elucidated. On the one hand, these alterations may be acquired independently by cancer cells during multistep oncogenesis. On the other hand, the suppression of the intrinsic apoptotic program may be achieved through mechanisms that directly lead to the Warburg phenotype. Cancer-specific mitochondrial alterations and bioenergetics may be taken advantage for the development of two novel classes of antineoplastic agents. A first approach would target glycolysis and/or revert the Warburg phenomenon, whereas a second approach would aim at inducing apoptosis by targeting mitochondrial proteins and membranes. In both instances, encouraging pre-clinical results have been obtained.
197 citations
TL;DR: Tetraploid cells exhibited an enhanced rate of spontaneous apoptosis that could be suppressed by inhibition of p53 or by knockdown of proapoptotic p53 target genes such as BBC3/Puma, GADD45A and ferredoxin reductase.
Abstract: Tetraploidy can result in cancer-associated aneuploidy. As shown here, freshly generated tetraploid cells arising due to mitotic slippage or failed cytokinesis are prone to undergo Bax-dependent mitochondrial membrane permeabilization and subsequent apoptosis. Knockout of Bax or overexpression of Bcl-2 facilitated the survival of tetraploid cells at least as efficiently as the p53 or p21 knockout. When tetraploid cells were derived from diploid p53 and Bax-proficient precursors, such cells exhibited an enhanced transcription of p53 target genes. Tetraploid cells exhibited an enhanced rate of spontaneous apoptosis that could be suppressed by inhibition of p53 or by knockdown of proapoptotic p53 target genes such as BBC3/Puma, GADD45A and ferredoxin reductase. Unexpectedly, tetraploid cells were more resistant to DNA damaging agents (cisplatin, oxaliplatin and camptothecin) than their diploid counterparts, and this difference disappeared upon inhibition of p53 or knockdown of p53-inducible ribonucleotide reductase. Tetraploid cells were also more resistant against UVC and gamma-irradiation. These data indicate the existence of p53-dependent alterations in apoptosis regulation in tetraploid cells.
189 citations
TL;DR: Yeast apoptosis during aging, mating, or exposure to killer toxins is described, underscoring the evolutionary benefit of a cell suicide program in yeast and, thus, giving a unicellular organism causes to die for.
Abstract: The purpose of apoptosis in multicellular organisms is obvious: single cells die for the benefit of the whole organism (for example, during tissue development or embryogenesis). Although apoptosis has also been shown in various microorganisms, the reason for this cell death program has remained unexplained. Recently published studies have now described yeast apoptosis during aging, mating, or exposure to killer toxins (Fabrizio, P., L. Battistella, R. Vardavas, C. Gattazzo, L.L. Liou, A. Diaspro, J.W. Dossen, E.B. Gralla, and V.D. Longo. 2004. J. Cell Biol. 166:1055–1067; Herker, E., H. Jungwirth, K.A. Lehmann, C. Maldener, K.U. Frohlich, S. Wissing, S. Buttner, M. Fehr, S. Sigrist, and F. Madeo. 2004. J. Cell Biol. 164:501–507, underscoring the evolutionary benefit of a cell suicide program in yeast and, thus, giving a unicellular organism causes to die for.
180 citations
TL;DR: It is shown that expression of ADD70 in tumor cells decreases their tumorigenicity in syngeneic animals without affecting their growth in immunodeficient animals, indicating the potential interest of targeting the HSP70 interaction with AIF for cancer therapy.
Abstract: When overexpressed, the stress protein heat shock protein 70 (HSP70) increases the oncogenic potential of cancer cells in rodent models. HSP70 also prevents apoptosis, thereby increasing the survival of cells exposed to a wide range of otherwise lethal stimuli. These protective functions of HSP70 involve its interaction with and neutralization of the adaptor molecule apoptotic protease activation factor-1, implicated in caspase activation, and the flavoprotein apoptosis-inducing factor (AIF), involved in caspase-independent cell death. We have shown previously that a peptide containing the AIF sequence involved in its interaction with HSP70 (ADD70, amino acids 150-228) binds to and neutralizes HSP70 in the cytosol, thereby sensitizing cancer cells to apoptosis induced by a variety of death stimuli. Here, we show that expression of ADD70 in tumor cells decreases their tumorigenicity in syngeneic animals without affecting their growth in immunodeficient animals. ADD70 antitumorigenic effects are associated with an increase in tumor-infiltrating cytotoxic CD8+ T cells. In addition, ADD70 sensitizes rat colon cancer cells (PROb) and mouse melanoma cells (B16F10) to the chemotherapeutic agent cisplatin. ADD70 also shows an additive effect with HSP90 inhibition by 17-allylamino-17-demethoxygeldanamycin in vitro . Altogether, these data indicate the potential interest of targeting the HSP70 interaction with AIF for cancer therapy. (Cancer Res 2006; 66(8): 4191-7)
TL;DR: NF-κB inhibitory molecules may be clinically useful, either as single therapeutic agents or in combination with classical chemotherapeutic agents, for the treatment of hematological malignancies.
Abstract: The transcription factor nuclear factor kappa B (NF-κB) can intervene in oncogenesis by virtue of its capacity to regulate the expression of a plethora of genes that modulate apoptosis, and cell survival as well as proliferation, inflammation, tumor metastasis and angiogenesis Different reports demonstrate the intrinsic activation of NF-κB in lymphoid and myeloid malignancies, including preneoplastic conditions such as myelodysplastic syndromes, underscoring its implication in malignant transformation Targeting intrinsic NF-κB activation, as well as its upstream and downstream regulators, may hence constitute an additional approach to the oncologist's armamentarium Several small inhibitors of the NF-κB-activatory kinase IκB kinase, of the proteaseome, or of the DNA binding of NF-κB subunits are under intensive investigation Currently used cytotoxic agents can induce NF-κB activation as an unwarranted side effect, which confers apoptosis suppression and hence resistance to these drugs Thus, NF-κB inhibitory molecules may be clinically useful, either as single therapeutic agents or in combination with classical chemotherapeutic agents, for the treatment of hematological malignancies
Journal Article•
TL;DR: It is shown that acute hTERT depletion has no adverse effects on the viability or proliferation of cervical and colon carcinoma cell lines, as evaluated within 72 h after transfection with h TERT-specific small interfering RNAs (siRNAs).
Abstract: Proc Amer Assoc Cancer Res, Volume 47, 2006
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Introduction: hTERT is the catalytic subunit of the telomerase and is hence required for telomerase maintenance and cancer cell immortalization. Importantly, several groups have found that cancer cells are somehow “addicted” to hTERT expression, meaning that down-modulation of hTERT by anti-sense oligonucleotides or small interfering RNAs (siRNAs) compromises cell survival and this effect involves alterations that are unrelated to the shortening of telomerases, suggesting that hTERT may have other functions than telomere maintenance. Materials and Methods: Wild type HeLa cells, or Hela transfected with the pcDNA3.1 vector encoding the neomycin resistance gene (Neo), Bcl-2 cells or the Cytomegaloviurs-encoded viral mitochondrial inhibitor of apoptosis (vMIA) and wild type, p53 knockout and Bax knockout HCT116 cells were transfected with two distinct hTERT-specific siRNA. We decided to investigate the role of hTERT in apoptosis control and the effect of acute hTERT depletion in short-term transfection assays on cell proliferation, cell cycle progression and cell death (cytofluorometric methods). Results: We show that acute hTERT depletion has no adverse effects on the viability or proliferation of cervical and colon carcinoma cell lines, as evaluated within 72 hours after transfection with hTERT-specific small interfering RNAs (siRNAs). Within the same time frame, hTERT depletion facilitated the induction of apoptotic cell death by cisplatin, etoposide, mitomycin C and reactive oxygen species, yet failed to sensitize cells to death induction via the CD95 death receptor. Experiments performed with p53 knock-out cells or chemical p53 inhibitors revealed that p53 was not involved in the chemosensitizing effect of hTERT knock-down. However, the pro-apoptotic Bcl-2 family protein Bax was involved in cell death induction by hTERT siRNAs. hTERT depletion facilitated the conformational activation of Bax induced by genotoxic agents. Moreover, Bax knock-out abolished the chemosensitizing effect of hTERT siRNAs. Inhibition of mitochondrial membrane permeabilization by overexpression of Bcl-2 or expression of the Cytomegalovirus-encoded protein vMIA, which acts as a specific Bax inhibitor, prevented the induction of cell death by the combination of hTERT depletion and chemotherapeutic agents. Conclusion: Using this approach, we found that acute hTERT inhibition facilitates apoptosis induction through the mitochondrial pathway. Our results unravel a novel role of hTERT as an endogenous inhibitor of mitochondrial apoptosis. Moreover, our data indicate that hTERT inhibition may constitute a promising strategy for facilitating the induction of the mitochondrial pathway of apoptosis. Key words: hTERT, apoptosis, Bax, Bcl-2, chemosensitization, p53
TL;DR: In this article, the authors show that hTERT depletion has no adverse effects on the viability or proliferation of cervical and colon carcinoma cell lines, as evaluated within 72 h after transfection with hTERTs-specific small interfering RNAs (siRNAs).
Abstract: hTERT is the catalytic subunit of the telomerase and is hence required for telomerase maintenance activity and cancer cell immortalization. Here, we show that acute hTERT depletion has no adverse effects on the viability or proliferation of cervical and colon carcinoma cell lines, as evaluated within 72 h after transfection with hTERT-specific small interfering RNAs (siRNAs). Within the same time frame, hTERT depletion facilitated the induction of apoptotic cell death by cisplatin, etoposide, mitomycin C and reactive oxygen species, yet failed to sensitize cells to death induction via the CD95 death receptor. Experiments performed with p53 knockout cells or chemical p53 inhibitors revealed that p53 was not involved in the chemosensitizing effect of hTERT knockdown. However, the proapoptotic Bcl-2 family protein Bax was involved in cell death induction by hTERT siRNAs. Depletion of hTERT facilitated the conformational activation of Bax induced by genotoxic agents. Moreover, Bax knockout abolished the chemosensitizing effect of hTERT siRNAs. Inhibition of mitochondrial membrane permeabilization by overexpression of Bcl-2 or expression of the cytomegalovirus-encoded protein vMIA (viral mitochondrial inhibitor of apoptosis), which acts as a specific Bax inhibitor, prevented the induction of cell death by the combination of hTERT depletion and chemotherapeutic agents. Altogether, our data indicate that hTERT inhibition may constitute a promising strategy for facilitating the induction of the mitochondrial pathway of apoptosis.
TL;DR: It is shown that caspase-9 plays a dual role in cell death signaling, as an activator of effector caspases and lysosomal membrane permeabilization, and consistent with the ability of TNF to activate the intrinsic apoptosis pathway.
Abstract: The apoptosome, a heptameric complex of Apaf-1, cytochrome c, and caspase-9, has been considered indispensable for the activation of caspase-9 during apoptosis. By using a large panel of genetically modified murine embryonic fibroblasts, we show here that, in response to tumor necrosis factor (TNF), caspase-8 cleaves and activates caspase-9 in an apoptosome-independent manner. Interestingly, caspase-8-cleaved caspase-9 induced lysosomal membrane permeabilization but failed to activate the effector caspases whereas apoptosome-dependent activation of caspase-9 could trigger both events. Consistent with the ability of TNF to activate the intrinsic apoptosis pathway and the caspase-9-dependent lysosomal cell death pathway in parallel, their individual inhibition conferred only a modest delay in TNF-induced cell death whereas simultaneous inhibition of both pathways was required to achieve protection comparable to that observed in caspase-9-deficient cells. Taken together, the findings indicate that caspase-9 plays a dual role in cell death signaling, as an activator of effector caspases and lysosomal membrane permeabilization.
TL;DR: It is shown that the ANT2 gene is up-regulated in several hormone-dependent cancers and suggested that its selective inhibition could constitute a promising strategy of chemosensitization.
Abstract: Mitochondrial membrane permeabilization (MMP) is a rate-limiting step of apoptosis, including in anticancer chemotherapy. Adenine nucleotide translocase (ANT) mediates the exchange of ADP and ATP on the inner mitochondrial membrane in healthy cells. In addition, ANT can cooperate with Bax to form a lethal pore during apoptosis. Humans possess four distinct ANT isoforms, encoded by four genes, whose transcription depends on the cell type, developmental stage, cell proliferation, and hormone status. Here, we show that the ANT2 gene is up-regulated in several hormone-dependent cancers. Knockdown of ANT2 by RNA interference induced no major changes in the aspect of the mitochondrial network or cell cycle but provoked minor increase in mitochondrial transmembrane potential and reactive oxygen species level and reduced intracellular ATP concentration without affecting glycolysis. At expression and functional levels, ANT2 depletion was not compensated by other ANT isoforms. Most importantly, ANT2, but not ANT1, silencing facilitated MMP induction by lonidamine, a mitochondrion-targeted antitumor compound already used in clinical studies for breast, ovarian, glioma, and lung cancer as well as prostate adenoma. The combination of ANT2 knockdown with lonidamine induced apoptosis irrespective of the Bcl-2 status. These data identify ANT2 as an endogenous inhibitor of MMP and suggest that its selective inhibition could constitute a promising strategy of chemosensitization.
TL;DR: It is shown that vMIA decreases cell size, reduces actin polymerization, and induces cell rounding, which suggests that the cytopathic effect of CMV can be explained by vMia effects on mitochondrial bioenergetics.
Abstract: Replication of human cytomegalovirus (CMV) requires the expression of the viral mitochondria-localized inhibitor of apoptosis (vMIA). vMIA inhibits apoptosis by recruiting Bax to mitochondria, resulting in its neutralization. We show that vMIA decreases cell size, reduces actin polymerization, and induces cell rounding. As compared with vMIA-expressing CMV, vMIA-deficient CMV, which replicates in fibroblasts expressing the adenoviral apoptosis suppressor E1B19K, induces less cytopathic effects. These vMIA effects can be separated from its cell death-inhibitory function because vMIA modulates cellular morphology in Bax-deficient cells. Expression of vMIA coincided with a reduction in the cellular adenosine triphosphate (ATP) level. vMIA selectively inhibited one component of the ATP synthasome, namely, the mitochondrial phosphate carrier. Exposure of cells to inhibitors of oxidative phosphorylation produced similar effects, such as an ATP level reduced by 30%, smaller cell size, and deficient actin polymerization. Similarly, knockdown of the phosphate carrier reduced cell size. Our data suggest that the cytopathic effect of CMV can be explained by vMIA effects on mitochondrial bioenergetics.
TL;DR: The data suggest the possibility that viruses employ multiple strategies to regulate host cell apoptosis by targeting mitochondria, and the structural motifs of the Vpr protein involved in MMP are conserved among most pathogenic HIV‐1 isolates.
Abstract: In most examples of physiological or pathological cell death, mitochondrial membrane permeabilization (MMP) constitutes an early critical event of the lethal process. Signs of MMP that precede nuclear apoptosis include the translocation of cytochrome c and apoptosis-inducing factor (AIF) from mitochondria to an extra-mitochondrial localization, as well as the dissipation of the mitochondrial transmembrane potential. MMP also occurs in HIV-1-induced apoptosis. Different HIV-1 encoded proteins (Env, Vpr, Tat, PR) can directly or indirectly trigger MMP, thereby causing cell death. The gp120/gp41 Env complex constitutes an example for an indirect MMP inducer. Env expressed on the plasma membrane of HIV-1 infected (or Env-transfected) cells mediates cell fusion with CD4/CXCR4-expressing uninfected cells. After a cell type-dependent latency period, syncytia then undergo MMP and apoptosis. Vpr exemplifies a direct MMP inducer. Vpr binds to the adenine nucleotide translocator (ANT), a mitochondrial inner membrane protein which also interacts with apoptosis-regulatory proteins from the Bcl-2/Bax family. Binding of Vpr to ANT favors formation of a non-specific pore leading to MMP. The structural motifs of the Vpr protein involved in MMP are conserved among most pathogenic HIV-1 isolates and determine the cytotoxic effect of Vpr. These data suggest the possibility that viruses employ multiple strategies to regulate host cell apoptosis by targeting mitochondria.
TL;DR: Inhibition of p53 abolished the difference in the susceptibility of diploid and tetraploid cancer cells to DNA damage‐induced apoptosis, pointing to an intrinsic resistance of tetraPloid cells against radiotherapy and DNA‐targeted chemotherapy that may be linked to the status of the p53 system.
Abstract: Aneuploidy and chromosomal instability, which are frequent in cancer, can result from the asymmetric division of tetraploid precursors. Genomic instability may favor the generation of more aggressive tumor cells with a reduced propensity for undergoing apoptosis. To assess the impact of tetraploidization on apoptosis regulation, we generated a series of stable tetraploid HCT116 and RKO colon carcinoma cell lines. When comparing diploid parental cells with tetraploid clones, we found that such cells were equally sensitive to a series of cytotoxic agents (staurosporine [STS], hydroxyurea, etoposide), as well as to the lysis by natural killer cells. In strict contrast, tetraploid cells were found to be relatively resistant against a series of DNA-damaging agents, namely cisplatin, oxaliplatin, camptothecin, and gamma- and UVC-irradiation. This increased resistance correlated with a reduced manifestation of apoptotic parameters (such as the dissipation of the mitochondrial transmembrane potential and the degradation of nuclear DNA) in tetraploid as compared to diploid cells subjected to DNA damage. Moreover, tetraploid cells manifested an enhanced baseline level of p53 activation. Inhibition of p53 abolished the difference in the susceptibility of diploid and tetraploid cancer cells to DNA damage-induced apoptosis. These data point to an intrinsic resistance of tetraploid cells against radiotherapy and DNA-targeted chemotherapy that may be linked to the status of the p53 system.
TL;DR: The AIF interactome, as determined by mass spectroscopy, contains a large panel of ribonucleoproteins, which apparently bind to AIF through the RNA moiety, and these data support a model in which a direct interaction of AIF contributes to the compaction of nucleic acids within apoptotic cells.
Abstract: Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein, which upon apoptosis induction translocates to the nucleus where it interacts with DNA by virtue of positive charges clustered on the AIF surface. Here we show that the AIF interactome, as determined by mass spectroscopy, contains a large panel of ribonucleoproteins, which apparently bind to AIF through the RNA moiety. However, AIF is devoid of any detectable RNAse activity both in vitro and in vivo. Recombinant AIF can directly bind to DNA as well as to RNA. This binding can be visualized by electron microscopy, revealing that AIF can condense DNA, showing a preferential binding to single-stranded over double-stranded DNA. AIF also binds and aggregates single-stranded and structured RNA in vitro. Single-stranded poly A, poly G and poly C, as well double-stranded A/T and G/C RNA competed with DNA for AIF binding with a similar efficiency, thus corroborating a computer-calculated molecular model in which the binding site within AIF is the same for distinct nucleic acid species, without a clear sequence specificity. Among the preferred electron donors and acceptors of AIF, nicotine adenine dinucleotide phosphate (NADP) was particularly efficient in enhancing the generation of higher-order AIF/DNA and AIF/RNA complexes. Altogether, these data support a model in which a direct interaction of AIF contributes to the compaction of nucleic acids within apoptotic cells.
TL;DR: In vitro, it is demonstrated that in vitro, the (27–51) and (71–82) Vpr peptides bind to a region encompassing the first ANT intermembrane space loop and part of its second and third trans Membrane helices.
Abstract: The HIV-1 protein Vpr circulates in the serum of seropositive individuals and in the cerebrospinal fluid of AIDS patients with neurological disorders. Vpr triggers apoptosis of numerous cell types after extracellular addition, vpr gene transfer or in the context of viral infection. Moreover, in vivo, transgenic mice over-expressing Vpr have enhanced T lymphocytes apoptosis. In previous studies, we suggested that the Vpr apoptotic activities were because of its binding to the adenine nucleotide translocator (ANT), a mitochondrial ATP/ADP antiporter. To specify this interaction, fragments of both proteins were synthesized and used in biochemical and biophysical experiments. We demonstrate here that in vitro, the (27-51) and (71-82) Vpr peptides bind to a region encompassing the first ANT intermembrane space loop and part of its second and third transmembrane helices. Computational analysis using a docking program associated to dynamic simulations enabled us to construct a three-dimensional model of the Vpr-ANT complex. In this model, the N-terminus of Vpr plunges in the ANT cavity whereas the Vpr C-terminal extremity is located at the surface of the ANT allowing possible interactions with a third partner. These results could be used to design molecules acting as pro-apoptotic Vpr analogs or as apoptosis inhibitors preventing the Vpr-ANT interaction.
TL;DR: It is suggested that genomic instability induced by γ-irradiation can trigger apoptosis, although apoptosis is dispensable for radio-induced clonogenic death.
Abstract: Colon carcinoma cells subjected to gamma-irradiation (4 Gy) manifest signs of apoptosis (caspase activation, chromatin condensation, phosphatidylserine (PS) exposure on the cell surface, sub-diploid DNA content), correlating with their radiosensitivity, which is increased in cells lacking the 14-3-3sigma protein as compared to wild-type controls. Inhibition of caspases by addition of Z-Val-Ala-DL-Asp (OMe)-fluoromethylketone, by stable transfection with the Baculovirus gene coding for p35, or by Bax knockout reduced all signs of apoptosis, yet failed to suppress radio-induced micro- and multinucleation. Moreover, pharmacological caspase inhibition, p35 expression or Bax knockout had no effect on the clonogenic survival that was reduced by gamma-irradiation and caspase inhibition failed to abolish the increased radiosensitivity of 14-3-3sigma-deficient cells. Micro- and multinucleation was detectable among non-apoptotic cells lacking PS exposure, as well as among cells undergoing apoptosis. Moreover, a fraction of micro- or multinucleated cells manifested caspase activation, and videomicroscopic analyses revealed that such cells could succumb to caspase-dependent apoptosis. Altogether, these results suggest that genomic instability induced by gamma-irradiation can trigger apoptosis, although apoptosis is dispensable for radio-induced clonogenic death.
TL;DR: A novel procedure for studying the intersection between cell cycle regulation and cell death mechanisms is delineated, based on the stable transfection of cells with a chimeric protein made up by histone H2B and green fluorescent protein (GFP).
TL;DR: HIV-1 protease inhibitors and cytomegalovirus vMIA induce mitochondrial fragmentation without triggering apoptosis and this effect is consistent with previous studies of this type of apoptosis.
Abstract: HIV-1 protease inhibitors and cytomegalovirus vMIA induce mitochondrial fragmentation without triggering apoptosis
TL;DR: Cell cycle-dependent cytotoxic and cytostatic effects of bortezomib on colon carcinoma cells are studied.
Abstract: Cell cycle-dependent cytotoxic and cytostatic effects of bortezomib on colon carcinoma cells
01 Jan 2006
TL;DR: NF-jB inhibitory molecules may be clinically useful, either as single therapeutic agents or in combination with classical chemotherapeutic agents, for the treatment of hematological malignancies.
Abstract: The transcription factor nuclear factor kappa B (NF-jB) can intervene in oncogenesis by virtue of its capacity to regulate the expression of a plethora of genes that modulate apoptosis, and cell survival as well as proliferation, inflammation, tumor metastasis and angiogenesis. Different reports demonstrate the intrinsic activation of NF-j Bi n lymphoid and myeloid malignancies, including preneoplastic conditions such as myelodysplastic syndromes, underscoring its implication in malignant transformation. Targeting intrinsic NF-jB activation, as well as its upstream and downstream regulators, may hence constitute an additional approach to the oncologist’s armamentarium. Several small inhibitors of the NF-jB-activatory kinase IjB kinase, of the proteaseome, or of the DNA binding of NF-jB subunits are under intensive investigation. Currently used cytotoxic agents can induce NF-jB activation as an unwarranted side effect, which confers apoptosis suppression and hence resistance to these drugs. Thus, NF-jB inhibitory molecules may be clinically useful, either as single therapeutic agents or in combination with classical chemotherapeutic agents, for the treatment of hematological malignancies. Cell Death and Differentiation (2006) 13, 748‐758. doi:10.1038/sj.cdd.4401874; published online 24 February 2006
Journal Article•
TL;DR: A large body of novel research studies illuminates the close relation between immunosurveillance and oncogenesis, suggesting new strategies for reestablishing the immune response against established tumors.
Abstract: The immune system usually detects and destroys pre-malignant cells, which are cells that have initiated oncogenic transformation. To fulfill this role, the immune system must distinguish between normal and transformed cells rather than between self and non-self. A large body of novel research studies illuminates the close relation between immunosurveillance and oncogenesis, suggesting new strategies for reestablishing the immune response against established tumors.
TL;DR: This poster presents a probabilistic procedure for estimating the intensity of the response of the immune system to EMTs using a simple, straightforward, and scalable apparatus.
Abstract: 1 Unité de Signalisation Moléculaire et Activation Cellulaire, Institut Pasteur, 25 rue du Dr Roux 75724 Paris Cedex 15, France 2 CNRS-UMR8125, Institut Gustave Roussy, 39 rue Camille-Desmoulins, F-94805 Villejuif, France * Corresponding author: G Kroemer, CNRS-UMR 8125, Institut Gustave Roussy, Pavillon de Recherche 1, 39 rue Camille-Desmoulins, F-94805 Villejuif, France. Tel: þ 33 1 42 11 60 46; Fax: þ 33 1 42 11 60 47; E-mail: kroemer@igr.fr
01 Jan 2006
TL;DR: It is shown that the ANT2 gene is up-regulated in several hormonedependent cancers and suggested that its selective inhibition could constitute a promising strategy of chemosensitization.
Abstract: Mitochondrial membrane permeabilization (MMP) is a ratelimiting step of apoptosis, including in anticancer chemotherapy. Adenine nucleotide translocase (ANT) mediates the exchange of ADP and ATP on the inner mitochondrial membrane in healthy cells. In addition, ANT can cooperate with Bax to form a lethal pore during apoptosis. Humans possess four distinct ANT isoforms, encoded by four genes, whose transcription depends on the cell type, developmental stage, cell proliferation, and hormone status. Here, we show that the ANT2 gene is up-regulated in several hormonedependent cancers. Knockdown of ANT2 by RNA interference induced no major changes in the aspect of the mitochondrial network or cell cycle but provoked minor increase in mitochondrial transmembrane potential and reactive oxygen species level and reduced intracellular ATP concentration without affecting glycolysis. At expression and functional levels, ANT2 depletion was not compensated by other ANT isoforms. Most importantly, ANT2, but not ANT1, silencing facilitated MMP induction by lonidamine, a mitochondriontargeted antitumor compound already used in clinical studies for breast, ovarian, glioma, and lung cancer as well as prostate adenoma. The combination of ANT2 knockdown with lonidamine induced apoptosis irrespective of the Bcl-2 status. These data identify ANT2 as an endogenous inhibitor of MMP and suggest that its selective inhibition could constitute a promising strategy of chemosensitization. (Cancer Res 2006; 66(18): 9143-52)