RESUMO
BACKGROUND & AIMS: WNT signaling is central to spatial tissue arrangement and regulating stem cell activity, and it represents the hallmark of gastrointestinal cancers. Although its role in driving intestinal tumors is well characterized, WNT's role in gastric tumorigenesis remains elusive. METHODS: We have developed mouse models to control the specific expression of an oncogenic form of ß-catenin (CTNNB1) in combination with MYC activation in Lgr5+ cells of the gastric antrum. We used multiomics approaches applied in vivo and in organoid models to characterize their cooperation in driving gastric tumorigenesis. RESULTS: We report that constitutive ß-catenin stabilization in the stomach has negligible oncogenic effects and requires MYC activation to induce gastric tumor formation. Although physiologically low MYC levels in gastric glands limit ß-catenin transcriptional activity, increased MYC expression unleashes the WNT oncogenic transcriptional program, promoting ß-catenin enhancer invasion without a direct transcriptional cooperation. MYC activation induces a metabolic rewiring that suppresses lysosomal biogenesis through mTOR and ERK activation and MiT/TFE inhibition. This prevents EPCAM degradation by macropinocytosis, promoting ß-catenin chromatin accumulation and activation of WNT oncogenic transcription. CONCLUSION: Our results uncovered a new signaling framework with important implications for the control of gastric epithelial architecture and WNT-dependent oncogenic transformation.
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Oncogenic mutations accumulating in many chromatin-associated proteins have been identified in different tumor types. With a mutation rate from 10 to 57%, ARID1A has been widely considered a tumor suppressor gene. However, whether this role is mainly due to its transcriptional-related activities or its ability to preserve genome integrity is still a matter of intense debate. Here, we show that ARID1A is largely dispensable for preserving enhancer-dependent transcriptional regulation, being ARID1B sufficient and required to compensate for ARID1A loss. We provide in vivo evidence that ARID1A is mainly required to preserve genomic integrity in adult tissues. ARID1A loss primarily results in DNA damage accumulation, interferon type I response activation, and chronic inflammation leading to tumor formation. Our data suggest that in healthy tissues, the increased genomic instability that follows ARID1A mutations and the selective pressure imposed by the microenvironment might result in the emergence of aggressive, possibly immune-resistant, tumors.
Assuntos
Neoplasias , Proteínas Nucleares , Humanos , Instabilidade Genômica , Mutação , Taxa de Mutação , Neoplasias/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Microambiente Tumoral , Animais , CamundongosRESUMO
Retinoic acid (RA) signaling is a master regulator of vertebrate development with crucial roles in directing body axis orientation and tissue differentiation, including in the reproductive system. However, a mechanistic understanding of how RA signaling promotes cell lineage identity in different tissues is often missing. Here, leveraging prostate organoid technology, we demonstrated that RA signaling orchestrates the commitment of adult mouse prostate progenitors to glandular identity, epithelial barrier integrity, and ultimately, proper specification of the prostatic lumen. Mechanistically, RA-dependent RARγ activation promotes the expression of the pioneer factor Foxa1, which synergizes with the androgen pathway for proper luminal expansion, cytoarchitecture and function. FOXA1 nucleotide variants are common in human prostate and breast cancers and considered driver mutations, though their pathogenic mechanism is incompletely understood. Combining functional genetics experiments with structural modeling of FOXA1 folding and chromatin binding analyses, we discovered that FOXA1 F254E255 is a loss-of-function mutation leading to compromised transcriptional function and lack of luminal fate commitment of prostate progenitors. Overall, we define RA as a crucial instructive signal for glandular identity in adult prostate progenitors. We propose deregulation of vitamin A metabolism as a risk factor for benign and malignant prostate disease, and identified cancer associated FOXA1 indels affecting residue F254 as loss-of-function mutations promoting dedifferentiation of adult prostate progenitors. Summary: Retinoic acid signaling orchestrates luminal differentiation of adult prostate progenitors.
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The long non-coding RNA EPR is expressed in epithelial tissues, binds to chromatin and controls distinct biological activities in mouse mammary gland cells. Because of its high expression in the intestine, in this study we have generated a colon-specific conditional targeted deletion (EPR cKO) to evaluate EPR in vivo functions in mice. EPR cKO mice display epithelium hyperproliferation, impaired mucus production and secretion, as well as inflammatory infiltration in the proximal portion of the large intestine. RNA sequencing analysis reveals a rearrangement of the colon crypt transcriptome with strong reduction of goblet cell-specific factors including those involved in the synthesis, assembly, transport and control of mucus proteins. Further, colon mucosa integrity and permeability are impaired in EPR cKO mice, and this results in higher susceptibility to dextran sodium sulfate (DSS)-induced colitis and tumor formation. Human EPR is down-regulated in human cancer cell lines as well as in human cancers, and overexpression of EPR in a colon cancer cell line results in enhanced expression of pro-apoptotic genes. Mechanistically, we show that EPR directly interacts with select genes involved in mucus metabolism whose expression is reduced in EPR cKO mice and that EPR deletion causes tridimensional chromatin organization changes.
Assuntos
Transformação Celular Neoplásica , Inflamação , Muco , RNA Longo não Codificante , Animais , Humanos , Camundongos , Transformação Celular Neoplásica/imunologia , Colo/metabolismo , Modelos Animais de Doenças , Inflamação/imunologia , Mucosa Intestinal/metabolismo , Camundongos Endogâmicos C57BL , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismoRESUMO
BACKGROUND AND AIMS: Activation of MYC and catenin beta-1 (CTNNB1, encoding ß-catenin) can co-occur in liver cancer, but how these oncogenes cooperate in tumorigenesis remains unclear. APPROACH AND RESULTS: We generated a mouse model allowing conditional activation of MYC and WNT/ß-catenin signaling (through either ß-catenin activation or loss of APC - adenomatous polyposis coli) upon expression of CRE recombinase in the liver and monitored their effects on hepatocyte proliferation, apoptosis, gene expression profiles, and tumorigenesis. Activation of WNT/ß-catenin signaling strongly accelerated MYC-driven carcinogenesis in the liver. Both pathways also cooperated in promoting cellular transformation in vitro, demonstrating their cell-autonomous action. Short-term induction of MYC and ß-catenin in hepatocytes, followed by RNA-sequencing profiling, allowed the identification of a "Myc/ß-catenin signature," composed of a discrete set of Myc-activated genes whose expression increased in the presence of active ß-catenin. Notably, this signature enriched for targets of Yes-associated protein (Yap) and transcriptional coactivator with PDZ-binding motif (Taz), two transcriptional coactivators known to be activated by WNT/ß-catenin signaling and to cooperate with MYC in mitogenic activation and liver transformation. Consistent with these regulatory connections, Yap/Taz accumulated upon Myc/ß-catenin activation and were required not only for the ensuing proliferative response, but also for tumor cell growth and survival. Finally, the Myc/ß-catenin signature was enriched in a subset of human hepatocellular carcinomas characterized by comparatively poor prognosis. CONCLUSIONS: Myc and ß-catenin show a strong cooperative action in liver carcinogenesis, with Yap and Taz serving as mediators of this effect. These findings warrant efforts toward therapeutic targeting of Yap/Taz in aggressive liver tumors marked by elevated Myc/ß-catenin activity.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Proteínas de Ciclo Celular/fisiologia , Neoplasias Hepáticas Experimentais/etiologia , Proteínas Proto-Oncogênicas c-myc/fisiologia , Transativadores/fisiologia , beta Catenina/fisiologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Via de Sinalização Wnt/fisiologia , Proteínas de Sinalização YAPRESUMO
Leukemia is a complex heterogeneous disease often driven by the expression of oncogenic fusion proteins with different molecular and biochemical properties. Whereas several fusion proteins induce leukemogenesis by activating Hox gene expression (Hox-activating fusions), others impinge on different pathways that do not involve the activation of Hox genes (non-Hox-activating fusions). It has been postulated that one of the main oncogenic properties of the HOXA9 transcription factor is its ability to control the expression of the p16/p19 tumor suppressor locus (Cdkn2a), thereby compensating Polycomb-mediated repression, which is dispensable for leukemias induced by Hox-activating fusions. We show, by genetically depleting the H2A ubiquitin ligase subunits of the Polycomb repressive complex 1 (PRC1), Ring1a and Ring1b, that Hoxa9 activation cannot repress Cdkn2a expression in the absence of PRC1 and its dependent deposition of H2AK119 monoubiquitination (H2AK119Ub). This demonstrates the essential role of PRC1 activity in supporting the oncogenic potential of Hox-activating fusion proteins. By combining genetic tools with genome-wide location and transcription analyses, we further show that PRC1 activity is required for the leukemogenic potential of both Hox-activating and non-Hox-activating fusions, thus preventing the differentiation of leukemic cells independently of the expression of the Cdkn2a locus. Overall, our results genetically demonstrate that PRC1 activity and the deposition of H2AK119Ub are critical factors that maintain the undifferentiated identity of cancer cells, positively sustaining the progression of different types of leukemia.
Assuntos
Regulação Leucêmica da Expressão Gênica , Leucemia , Proteínas de Neoplasias , Complexo Repressor Polycomb 1 , Animais , Linhagem Celular Tumoral , Leucemia/genética , Leucemia/metabolismo , Leucemia/patologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Complexo Repressor Polycomb 1/genética , Complexo Repressor Polycomb 1/metabolismoRESUMO
Polycomb repressive complexes (PRCs) are among the most important gatekeepers of establishing and maintaining cell identity in metazoans. PRC1, which plays a dominant role in this context, executes its functions via multiple subcomplexes, which all contribute to H2AK119 mono-ubiquitination (H2Aubq). Despite our comprehensive knowledge of PRC1-dependent H2Aubq in embryonic stem cells and during early development, its role in adult stem cells still remains poorly characterized. Here we show that PRC1 activity is required for the integrity of the intestinal epithelium, regulating stem cell self-renewal via a cell-autonomous mechanism that is independent from Cdkn2a expression. By dissecting the PRC1-dependent transcription program in intestinal stem cells, we demonstrate that PRC1 represses a large number of non-lineage-specific transcription factors that directly affect ß-catenin/Tcf transcriptional activity. Our data reveal that PRC1 preserves Wnt/ß-catenin activity in adult stem cells to maintain intestinal homeostasis and supports tumor formation induced by the constitutive activation of this pathway.
Assuntos
Células-Tronco Adultas/citologia , Intestinos/citologia , Proteínas do Grupo Polycomb/metabolismo , Transcrição Gênica , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Alelos , Animais , Proliferação de Células , Células Cultivadas , Imunoprecipitação da Cromatina , Citometria de Fluxo , Proteínas de Fluorescência Verde/metabolismo , Homeostase , Camundongos , Camundongos Knockout , Fenótipo , Distribuição Tecidual , Via de Sinalização WntRESUMO
We recently identified the long non-coding RNA (ncRNA) TRPM2-AS as a key regulator of survival in prostate cancer [1]. This essential role, coupled to the TRPM2-AS low-expression levels in healthy tissues, makes this ncRNA a suitable therapeutic target for further clinical studies. To get insights into the survival mechanism controlled by this molecule, we ablated its expression in prostate cancer cells and performed a genome-wide analysis of the transcripts differentially regulated in dying cells. Here, we describe in detail the experimental system, methods and quality control for the generation of the microarray data associated with our recent publication [1]. The data are related to [1]. Data have been deposited to the Gene Expression Omnibus (GEO) database repository with the dataset identifier GSE40687.
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Metabolic pathways play fundamental roles in several processes that regulate cell physiology and adaptation to environmental changes. Altered metabolic pathways predispose to several different pathologies ranging from diabetes to cancer. Specific transcriptional programs tightly regulate the enzymes involved in cell metabolism and dictate cell fate regulating the differentiation into specialized cell types that contribute to metabolic adaptation in higher organisms. For these reasons, it is of extreme importance to identify signaling pathways and transcription factors that positively and negatively regulate metabolism. Genomic organization allows a plethora of different strategies to regulate transcription. Importantly, large evidence suggests that the quality of diet and the caloric regimen can influence the epigenetic state of our genome and that certain metabolic pathways are also epigenetically controlled reveling a tight crosstalk between metabolism and epigenomes. Here we focus our attention on methylation-based epigenetic reactions, on how different metabolic pathways control these activities, and how these can influence metabolism. Altogether, the recent discoveries linking these apparent distant areas reveal that an exciting field of research is emerging.
Assuntos
Epigênese Genética , Redes e Vias Metabólicas , Animais , Cromatina/genética , Cromatina/metabolismo , DNA/genética , DNA/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Metilação , Metiltransferases/genética , Metiltransferases/metabolismo , Proteínas do Grupo Polycomb/genética , Proteínas do Grupo Polycomb/metabolismoRESUMO
O-linked N-acetylglucosamine (O-GlcNAc) transferase (Ogt) activity is essential for embryonic stem cell (ESC) viability and mouse development. Ogt is present both in the cytoplasm and the nucleus of different cell types and catalyzes serine and threonine glycosylation. We have characterized the biochemical features of nuclear Ogt and identified the ten-eleven translocation (TET) proteins Tet1 and Tet2 as stable partners of Ogt in the nucleus of ESCs. We show at a genome-wide level that Ogt preferentially associates with Tet1 to genes promoters in close proximity of CpG-rich transcription start sites. These regions are characterized by low levels of DNA modification, suggesting a link between Tet1 and Ogt activities in regulating CpG island methylation. Finally, we show that Tet1 is required for binding of Ogt to chromatin affecting Tet1 activity. Taken together, our data characterize how O-GlcNAcylation is recruited to chromatin and interacts with the activity of 5-methylcytosine hydroxylases.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Células-Tronco Embrionárias/enzimologia , N-Acetilglucosaminiltransferases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Animais , Sítios de Ligação , Núcleo Celular/metabolismo , Células Cultivadas , Cromatina , Ilhas de CpG , Proteínas de Ligação a DNA/isolamento & purificação , Dioxigenases , Células-Tronco Embrionárias/metabolismo , Regulação da Expressão Gênica , Imunoprecipitação , Redes e Vias Metabólicas/genética , Camundongos , N-Acetilglucosaminiltransferases/isolamento & purificação , Regiões Promotoras Genéticas , Ligação Proteica , Transporte Proteico , Proteínas Proto-Oncogênicas/isolamento & purificação , Transdução de Sinais/genética , Sítio de Iniciação de TranscriçãoRESUMO
Reduction of nutrient intake without malnutrition positively influences lifespan and healthspan from yeast to mice and exerts some beneficial effects also in humans. The AMPK-FoxO axis is one of the evolutionarily conserved nutrient-sensing pathways, and the FOXO3A locus is associated with human longevity. Interestingly, FoxO3A has been reported to be also a mitochondrial protein in mammalian cells and tissues. Here we report that glucose restriction triggers FoxO3A accumulation into mitochondria of fibroblasts and skeletal myotubes in an AMPK-dependent manner. A low-glucose regimen induces the formation of a protein complex containing FoxO3A, SIRT3, and mitochondrial RNA polymerase (mtRNAPol) at mitochondrial DNA-regulatory regions causing activation of the mitochondrial genome and a subsequent increase in mitochondrial respiration. Consistently, mitochondrial transcription increases in skeletal muscle of fasted mice, with a mitochondrial DNA-bound FoxO3A/SIRT3/mtRNAPol complex detectable also in vivo. Our results unveil a mitochondrial arm of the AMPK-FoxO3A axis acting as a recovery mechanism to sustain energy metabolism upon nutrient restriction.
Assuntos
Adenilato Quinase/fisiologia , Fatores de Transcrição Forkhead/fisiologia , Glucose/metabolismo , Mitocôndrias/metabolismo , Sirtuína 3/fisiologia , Adenilato Quinase/genética , Adenilato Quinase/metabolismo , Animais , Células Cultivadas , DNA Mitocondrial/metabolismo , Transporte de Elétrons , Metabolismo Energético , Privação de Alimentos , Proteína Forkhead Box O3 , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Regulação da Expressão Gênica , Genoma Mitocondrial , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Células NIH 3T3 , Sirtuína 3/genética , Sirtuína 3/metabolismoRESUMO
We recently demonstrated that p38α is required to maintain colorectal cancer (CRC) metabolism, as its inhibition leads to FoxO3A activation, autophagy, cell death, and tumor growth reduction both in vitro and in vivo. Here we show that inhibition of p38α is followed by TRAIL-mediated activation of caspase-8 and FoxO3A-dependent HER3 upregulation with consequent overactivation of the MEK-ERK1/2 survival pathway. p38α and MEK combined inhibition specifically induces apoptosis by enabling TRAIL signaling propagation through t-Bid and caspase-3, and fosters cell death in CRC cells and preclinical mouse models. Current MEK1-directed pharmacological strategies could thus be exploited, in combination with p38α inhibition, to develop new approaches for CRC treatment.
Assuntos
Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Idoso , Idoso de 80 Anos ou mais , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Benzamidas/farmacologia , Caspase 8/metabolismo , Morte Celular/efeitos dos fármacos , Morte Celular/genética , Linhagem Celular Tumoral , Neoplasias Colorretais/tratamento farmacológico , Difenilamina/análogos & derivados , Difenilamina/farmacologia , Inibidores Enzimáticos/farmacologia , Feminino , Células HT29 , Humanos , Imidazóis/farmacologia , MAP Quinase Quinase 1/antagonistas & inibidores , MAP Quinase Quinase 1/genética , MAP Quinase Quinase 1/metabolismo , Masculino , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Proteína Quinase 14 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Fosforilação , Piridinas/farmacologia , Ensaios Antitumorais Modelo de Xenoenxerto , Proteínas Quinases p38 Ativadas por Mitógeno/antagonistas & inibidoresRESUMO
FoxO proteins are an evolutionarily conserved subfamily of transcription factors involved in tumor suppression, regulation of energy metabolism and development in several tissues, and are mainly regulated by phosphorylation-dependent nuclear/cytoplasmic shuttling. The transcriptional activity of FoxO3A, one of the four members of the family, is further modulated by AMPK, one of the key regulators of cellular metabolism, which basically shifts cell machinery from energy-consuming to energy-producing pathways. We recently demonstrated that the AMPK/FoxO3A energy sensor pathway is still inducible in human cancer cells in response to metabolic stress, as it becomes activated in colorectal and ovarian cancer cells in response to the inhibition of p38α. Activation of the FoxO3A transcriptional program initially induces autophagy as an attempt to retain energy to survive, whereas under persistent stress conditions it triggers autophagic cell death. In this review, we focus on the connections between AMPK and FoxO3A, describing their central role as modulators of fundamental processes such as stress resistance, cell metabolism, autophagy and cell death, and highlighting the therapeutic potential of pharmacological modulation of the AMPK-FoxO3A axis.
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Proteínas Quinases Ativadas por AMP/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Terapia de Alvo Molecular , Neoplasias/enzimologia , Neoplasias/terapia , Transdução de Sinais , Envelhecimento/patologia , HumanosRESUMO
INTRODUCTION: Ovarian cancer is highly sensitive to chemotherapy but also shows a high rate of recurrence and drug resistance. These negative outcomes mostly depend on altered apoptotic pathways, making the design of new therapeutic strategies based on the induction of other types of cell death highly desirable. Several lines of research are now addressing cancer-specific features to specifically target tumor cells, thus reducing adverse effects. In this light, a great deal of attention has been devoted to the metabolic reprogramming occurring in cancer cells, which display increased levels of glycolysis compared with their normal counterparts. We recently showed that inhibition of p38alpha impairs key metabolic functions of colorectal cancer cells, inducing growth arrest, autophagy, and cell death both in vivo and in vitro. These effects are mediated by a switch from hypoxia-inducible factor 1alpha (HIF1alpha) to forkhead transcription factor O (FoxO)-dependent transcription. METHODS: We first characterized p38 expression in OVCAR-3, A2780, and SKOV-3 ovarian cancer cell lines. Then, we treated these cells with the p38alpha/p38beta-specific inhibitor SB202190 and performed a morphological, proliferation, and survival analyses. Finally, we studied HIF1alpha and FoxO3A expressions and signaling pathways to evaluate their role in SB202190-induced effects. RESULTS: p38alpha blockade induces the formation of intracellular autophagic vacuoles and reduces growth and viability of ovarian cancer cells. As in colorectal cancer, the underlying molecular mechanism seems to rely on a shift from HIF1alpha- to FoxO3A-dependent transcription, which is promoted by the activation of the adenosine monophosphate-activated protein kinase pathway. CONCLUSIONS: These data corroborate the hypothesis that pharmacological modulation of genes involved in cancer-specific homeostasis, such as p38alpha, might be exploited to design new therapeutic approaches to cancer treatment.
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Carcinoma/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Neoplasias Ovarianas/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Feminino , Proteína Forkhead Box O3 , Regulação Neoplásica da Expressão Gênica , Homeostase , Humanos , Transdução de SinaisRESUMO
C16orf35 is a highly conserved gene positioned upstream of the alpha-globins in humans and other vertebrates. The deduced protein is also highly conserved, it has no defined structural features or domains, and its function is currently unknown. Here we show that the C16orf35 protein has nuclear and cytosolic distribution, and can localize to PML nuclear bodies. The C16orf35 protein was detected in several human transformed cells lines, and studies of transient and stable overexpression indicate that increased levels of C16orf35 inhibit cell proliferation. We also find that C16orf35 interacts with human p73, and represses transcription by TAp73gamma but not by TAp73alpha. This selectivity is not due to differential interaction, since C16orf35 binds both p73 variants. Our data suggest that C16orf35 can modulate differentially the specific activities of selected p73 isoforms.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Linhagem Celular , Núcleo Celular/metabolismo , Proliferação de Células , Sequência Conservada , Citoplasma/metabolismo , Proteínas de Ligação a DNA/genética , Evolução Molecular , Proteínas Ativadoras de GTPase , Humanos , Proteínas Nucleares/genética , Ativação Transcricional , Proteína Tumoral p73 , Proteínas Supressoras de Tumor/genéticaRESUMO
Autophagy is an essential process for the maintenance of cellular and metabolic homeostasis. Indeed, it is required for the recovery of ATP-generating substrates in cells subjected to different types of stress insults. Thus, the activity of the autophagic machinery strongly depends on the metabolic status of the cell.(1) It has been proposed that this principle applies not only to normal, but also to cancer cells,(2) despite the profound differences in their metabolism. Cancer cells predominantly produce ATP through the constitutive activation of aerobic glycolysis, a process that generally relies on the stabilization and activation of the transcription factor HIF1alpha, which regulates the expression of glycolytic genes.(3) We recently showed that p38alpha is required to sustain the expression of HIF1alpha target genes, and that its inhibition causes a rapid drop in ATP levels in colorectal cancer cells (CRCs). This acute energy need triggers AMPK-dependent nuclear accumulation of FoxO3A and subsequent activation of its transcriptional program, leading to sequential induction of autophagy, cell cycle arrest and cell death. In vivo, pharmacological blockade of p38alpha has both a cytostatic and cytotoxic effect on colorectal neoplasms, associated with nuclear enrichment of FoxO3A and expression of its target genes p21 and PTEN.(4) Our data suggest that CRCs impaired in their glycolytic metabolism trigger autophagy as a reversible recovery mechanism and undergo cell cycle arrest; however, the persistence of the stress insults inevitably leads to cell death.
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Adenilato Quinase/metabolismo , Autofagia/fisiologia , Fatores de Transcrição Forkhead/metabolismo , Proteína Quinase 14 Ativada por Mitógeno/antagonistas & inibidores , Neoplasias/metabolismo , Linhagem Celular Tumoral , Proteína Forkhead Box O3 , Regulação da Expressão Gênica , Humanos , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Transdução de Sinais/fisiologiaRESUMO
Several tumors arise from deregulated signaling pathways leading to increased proliferation and impairment of differentiation. To bypass endogenous control mechanisms and to survive the environmental stress associated with increased growth, tumor cells acquire a plethora of modifications that ultimately tend to down-regulate the ability to undergo apoptosis and exacerbate prosurvival mechanisms. Autophagy is an evolutionarily conserved mechanism through which cells recycle essential molecular constituents or eliminate damaged organelles under stress conditions imposed by nutrients or growth factors deprivation. As such, autophagy acts as a prosurvival mechanism for cancer cells. However, when overactivated, autophagy could also represent a cell death mechanism acting through self-cannibalization. Therefore, understanding the various signaling pathways that regulate autophagy could be of extreme importance. Indeed, the identification of specific molecular targets amenable to pharmacological manipulation to induce cancer cell self-cannibalization could represent a promising approach to treat apoptosis-resistant tumors.
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Autofagia/fisiologia , Transdução de Sinais/fisiologia , Animais , Imunoprecipitação da Cromatina , Expressão Gênica/genética , Humanos , Immunoblotting , Imunoprecipitação , Transdução de Sinais/genética , Células Tumorais CultivadasRESUMO
Conjugation to SUMO is a reversible post-translational modification that regulates several transcription factors involved in cell proliferation, differentiation, and disease. The p53 tumor suppressor can be modified by SUMO-1 in mammalian cells, but the functional consequences of this modification are unclear. Here, we demonstrate that the Drosophila homolog of human p53 can be efficiently sumoylated in insect cells. We identify two lysine residues involved in SUMO attachment, one at the C terminus, between the DNA binding and oligomerization domains, and one at the N terminus of the protein. We find that sumoylation helps recruit Drosophila p53 to nuclear dot-like structures that can be marked by human PML and the Drosophila homologue of Daxx. We demonstrate that mutation of both sumoylation sites dramatically reduces the transcriptional activity of p53 and its ability to induce apoptosis in transgenic flies, providing in vivo evidence that sumoylation is critical for Drosophila p53 function.
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Drosophila/metabolismo , RNA Mensageiro/metabolismo , Ativação Transcricional , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Animais Geneticamente Modificados , Apoptose , Diferenciação Celular , Proliferação de Células , Modelos Biológicos , Mutação , Proteínas Nucleares/metabolismo , Estrutura Terciária de Proteína , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/metabolismo , Proteína Supressora de Tumor p53/metabolismoRESUMO
In the last year, several evidences indicated that pharmacological manipulation of relevant signaling pathways could selectively affect gene expression to influence cell fate. These findings render of extreme importance the elucidation of how external stimuli are transduced to mediate chromatin modifications, resulting in a permissive or repressive environment for gene expression. These signaling cascades activate or repress the function of chromatin binding proteins that represent attractive pharmacological targets for human diseases. Actually, the closer the target is to chromatin, the more the transcriptional effect will be selective. Recent studies suggest that pharmacological manipulation of signaling pathways to modulate cell fate is indeed possible and that chromatin-associated kinases could represent an optimal target. The p38 MAPK is the prototype of this class of enzymes and its central role in the transcription process is evolutionary conserved. In this review we will focus on the possibility to inhibit p38alpha in colorectal cancer to arrest tumor progression and induce autophagic cell death.