RESUMEN
The efficiency and outcome of CRISPR/Cas9 editing depends on the chromatin state at the cut site. It has been shown that changing the chromatin state can influence both the efficiency and repair outcome, and epigenetic drugs have been used to improve Cas9 editing. However, because the target proteins of these drugs are not homogeneously distributed across the genome, the efficacy of these drugs may be expected to vary from locus to locus. Here, we systematically analyzed this chromatin context-dependency for 160 epigenetic drugs. We used a human cell line with 19 stably integrated reporters to induce a double-stranded break in different chromatin environments. We then measured Cas9 editing efficiency and repair pathway usage by sequencing the mutational signatures. We identified 58 drugs that modulate Cas9 editing efficiency and/or repair outcome dependent on the local chromatin environment. For example, we find a subset of histone deacetylase inhibitors that improve Cas9 editing efficiency throughout all types of heterochromatin (e.g. PCI-24781), while others were only effective in euchromatin and H3K27me3-marked regions (e.g. apicidin). In summary, this study reveals that most epigenetic drugs alter CRISPR editing in a chromatin-dependent manner, and provides a resource to improve Cas9 editing more selectively at the desired location.
Asunto(s)
Sistemas CRISPR-Cas , Cromatina , Epigénesis Genética , Edición Génica , Inhibidores de Histona Desacetilasas , Humanos , Edición Génica/métodos , Epigénesis Genética/efectos de los fármacos , Cromatina/metabolismo , Cromatina/genética , Inhibidores de Histona Desacetilasas/farmacología , Reparación del ADN , Proteína 9 Asociada a CRISPR/metabolismo , Proteína 9 Asociada a CRISPR/genética , Heterocromatina/metabolismo , Heterocromatina/genética , Línea Celular , Histonas/metabolismo , Eucromatina/genética , Roturas del ADN de Doble Cadena/efectos de los fármacosRESUMEN
DNA double-strand breaks are repaired by multiple pathways, including non-homologous end-joining (NHEJ) and microhomology-mediated end-joining (MMEJ). The balance of these pathways is dependent on the local chromatin context, but the underlying mechanisms are poorly understood. By combining knockout screening with a dual MMEJ:NHEJ reporter inserted in 19 different chromatin environments, we identified dozens of DNA repair proteins that modulate pathway balance dependent on the local chromatin state. Proteins that favor NHEJ mostly synergize with euchromatin, while proteins that favor MMEJ generally synergize with distinct types of heterochromatin. Examples of the former are BRCA2 and POLL, and of the latter the FANC complex and ATM. Moreover, in a diversity of human cancer types, loss of several of these proteins alters the distribution of pathway-specific mutations between heterochromatin and euchromatin. Together, these results uncover a complex network of proteins that regulate MMEJ:NHEJ balance in a chromatin context-dependent manner.
Asunto(s)
Cromatina , Roturas del ADN de Doble Cadena , Reparación del ADN por Unión de Extremidades , Eucromatina , Heterocromatina , Humanos , Cromatina/metabolismo , Cromatina/genética , Heterocromatina/metabolismo , Heterocromatina/genética , Eucromatina/metabolismo , Eucromatina/genética , Proteína BRCA2/genética , Proteína BRCA2/metabolismo , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Proteínas de la Ataxia Telangiectasia Mutada/genética , Reparación del ADNRESUMEN
Cancer homeostasis depends on a balance between activated oncogenic pathways driving tumorigenesis and engagement of stress response programs that counteract the inherent toxicity of such aberrant signaling. Although inhibition of oncogenic signaling pathways has been explored extensively, there is increasing evidence that overactivation of the same pathways can also disrupt cancer homeostasis and cause lethality. We show here that inhibition of protein phosphatase 2A (PP2A) hyperactivates multiple oncogenic pathways and engages stress responses in colon cancer cells. Genetic and compound screens identify combined inhibition of PP2A and WEE1 as synergistic in multiple cancer models by collapsing DNA replication and triggering premature mitosis followed by cell death. This combination also suppressed the growth of patient-derived tumors in vivo. Remarkably, acquired resistance to this drug combination suppressed the ability of colon cancer cells to form tumors in vivo. Our data suggest that paradoxical activation of oncogenic signaling can result in tumor-suppressive resistance. Significance: A therapy consisting of deliberate hyperactivation of oncogenic signaling combined with perturbation of the stress responses that result from this is very effective in animal models of colon cancer. Resistance to this therapy is associated with loss of oncogenic signaling and reduced oncogenic capacity, indicative of tumor-suppressive drug resistance.
Asunto(s)
Neoplasias del Colon , Proteína Fosfatasa 2 , Transducción de Señal , Humanos , Animales , Proteína Fosfatasa 2/metabolismo , Ratones , Línea Celular Tumoral , Neoplasias del Colon/tratamiento farmacológico , Neoplasias del Colon/metabolismo , Neoplasias del Colon/patología , Neoplasias del Colon/genética , Ensayos Antitumor por Modelo de Xenoinjerto , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/antagonistas & inhibidores , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/metabolismo , Resistencia a Antineoplásicos , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Replicación del ADNRESUMEN
The diverse range of organizations contributing to the global research ecosystem is believed to enhance the overall quality and resilience of its output. Mid-sized autonomous research institutes, distinct from universities, play a crucial role in this landscape. They often lead the way in new research fields and experimental methods, including those in social and organizational domains, which are vital for driving innovation. The EU-LIFE alliance was established with the goal of fostering excellence by developing and disseminating best practices among European biomedical research institutes. As directors of the 15 EU-LIFE institutes, we have spent a decade comparing and refining our processes. Now, we are eager to share the insights we've gained. To this end, we have crafted this Charter, outlining 10 principles we deem essential for research institutes to flourish and achieve ground-breaking discoveries. These principles, detailed in the Charter, encompass excellence, independence, training, internationality and inclusivity, mission focus, technological advancement, administrative innovation, cooperation, societal impact, and public engagement. Our aim is to inspire the establishment of new institutes that adhere to these principles and to raise awareness about their significance. We are convinced that they should be viewed a crucial component of any national and international innovation strategies.
Asunto(s)
Disciplinas de las Ciencias Biológicas , Investigación Biomédica , Academias e InstitutosRESUMEN
To enable a collective effort that generates a new level of UNderstanding CANcer (UNCAN.eu) [Cancer Discov (2022) 12 (11): OF1], the European Union supports the creation of a sustainable platform that connects cancer research across Member States. A workshop hosted in Heidelberg gathered European cancer experts to identify ongoing initiatives that may contribute to building this platform and discuss the governance and long-term evolution of a European Federated Cancer Data Hub.
Asunto(s)
Neoplasias , Humanos , Investigación , Unión EuropeaRESUMEN
Acquired drug resistance is a major problem in the treatment of cancer. hTERT-immortalized, untransformed RPE-1 cells can acquire resistance to Taxol by derepressing the ABCB1 gene, encoding for the multidrug transporter P-gP. Here, we investigate how the ABCB1 gene is derepressed. ABCB1 activation is associated with reduced H3K9 trimethylation, increased H3K27 acetylation, and ABCB1 displacement from the nuclear lamina. While altering DNA methylation and H3K27 methylation had no major impact on ABCB1 expression, nor did it promote resistance, disrupting the nuclear lamina component Lamin B Receptor did promote the acquisition of a Taxol-resistant phenotype in a subset of cells. CRISPRa-mediated gene activation supported the notion that lamina dissociation influences ABCB1 derepression. We propose a model in which nuclear lamina dissociation of a repressed gene allows for its activation, implying that deregulation of the 3D genome topology could play an important role in tumor evolution and the acquisition of drug resistance.
Asunto(s)
Resistencia a Antineoplásicos , Neoplasias , Humanos , Resistencia a Antineoplásicos/genética , Paclitaxel/farmacología , Resistencia a Múltiples Medicamentos/genética , Neoplasias/genética , Metilación de ADN/genética , Línea Celular TumoralRESUMEN
Although treatment with taxanes does not always lead to clinical benefit, all patients are at risk of their detrimental side effects such as peripheral neuropathy. Understanding the in vivo mode of action of taxanes can help design improved treatment regimens. Here, we demonstrate that in vivo, taxanes directly trigger T cells to selectively kill cancer cells in a non-canonical, T cell receptor-independent manner. Mechanistically, taxanes induce T cells to release cytotoxic extracellular vesicles, which lead to apoptosis specifically in tumor cells while leaving healthy epithelial cells intact. We exploit these findings to develop an effective therapeutic approach, based on transfer of T cells pre-treated with taxanes ex vivo, thereby avoiding toxicity of systemic treatment. Our study reveals a different in vivo mode of action of one of the most commonly used chemotherapies, and opens avenues to harness T cell-dependent anti-tumor effects of taxanes while avoiding systemic toxicity.
Asunto(s)
Vesículas Extracelulares , Neoplasias , Humanos , Linfocitos T , Taxoides/farmacología , Apoptosis , Células Epiteliales , Neoplasias/tratamiento farmacológicoRESUMEN
Faithful and timely repair of DNA double-strand breaks (DSBs) is fundamental for the maintenance of genomic integrity. Here, we demonstrate that the meiotic recombination co-factor MND1 facilitates the repair of DSBs in somatic cells. We show that MND1 localizes to DSBs, where it stimulates DNA repair through homologous recombination (HR). Importantly, MND1 is not involved in the response to replication-associated DSBs, implying that it is dispensable for HR-mediated repair of one-ended DSBs. Instead, we find that MND1 specifically plays a role in the response to two-ended DSBs that are induced by irradiation (IR) or various chemotherapeutic drugs. Surprisingly, we find that MND1 is specifically active in G2 phase, whereas it only marginally affects repair during S phase. MND1 localization to DSBs is dependent on resection of the DNA ends and seemingly occurs through direct binding of MND1 to RAD51-coated ssDNA. Importantly, the lack of MND1-driven HR repair directly potentiates the toxicity of IR-induced damage, which could open new possibilities for therapeutic intervention, specifically in HR-proficient tumors.
Asunto(s)
Reparación del ADN , Recombinación Homóloga , Humanos , Reparación del ADN/genética , Recombinación Homóloga/genética , Roturas del ADN de Doble Cadena , Reparación del ADN por Recombinación , Fase S , Proteínas de Ciclo Celular/metabolismoRESUMEN
Cells respond to double-strand breaks (DSBs) by activating DNA damage response pathways, including cell cycle arrest. We have previously shown that a single double-strand break generated via CRISPR/Cas9 is sufficient to delay cell cycle progression and compromise cell viability. However, we also found that the cellular response to DSBs can vary, independent of the number of lesions. This implies that not all DSBs are equally toxic, and raises the question if the location of a single double-strand break could influence its toxicity. To systematically investigate if DSB-location is a determinant of toxicity we performed a CRISPR/Cas9 screen targeting 6237 single sites in the human genome. Next, we developed a data-driven framework to design CRISPR/Cas9 sgRNA (crRNA) pools targeting specific chromatin features. The chromatin context was defined using ChromHMM states, Lamin-B1 DAM-iD, DNAseI hypersensitivity, and RNA-sequencing data. We computationally designed 6 distinct crRNA pools, each containing 10 crRNAs targeting the same chromatin state. We show that the toxicity of a DSB is highly similar across the different ChromHMM states. Rather, we find that the major determinants of toxicity of a sgRNA are cutting efficiency and off-target effects. Thus, chromatin features have little to no effect on the toxicity of a single CRISPR/Cas9-induced DSB.
Asunto(s)
Roturas del ADN de Doble Cadena , Sistemas CRISPR-Cas , Cromatina/genética , Reparación del ADN , Humanos , Laminas , ARNRESUMEN
"UNCAN.eu" refers to a collective European effort seeking to enable a leap forward in our understanding of cancer. This initiative, which includes the creation of a European cancer research data hub, will pave the way to new advances in cancer care. Starting on September 1, 2022, a 15-month coordination and support action will generate a blueprint for UNCAN.eu. Here, we summarize the cancer research issues that the blueprint will propose to tackle at the European level.
Asunto(s)
Neoplasias , Humanos , Europa (Continente)RESUMEN
Inducing senescence in cancer cells is emerging as a new therapeutic strategy. In order to find ways to enhance senescence induction by palbociclib, a CDK4/6 inhibitor approved for treatment of metastatic breast cancer, we performed functional genetic screens in palbociclib-resistant cells. Using this approach, we found that loss of CDK2 results in strong senescence induction in palbociclib-treated cells. Treatment with the CDK2 inhibitor indisulam, which phenocopies genetic CDK2 inactivation, led to sustained senescence induction when combined with palbociclib in various cell lines and lung cancer xenografts. Treating cells with indisulam led to downregulation of cyclin H, which prevented CDK2 activation. Combined treatment with palbociclib and indisulam induced a senescence program and sensitized cells to senolytic therapy. Our data indicate that inhibition of CDK2 through indisulam treatment can enhance senescence induction by CDK4/6 inhibition.
Asunto(s)
Quinasa 6 Dependiente de la Ciclina , Inhibidores de Proteínas Quinasas , Línea Celular Tumoral , Quinasa 2 Dependiente de la Ciclina , Quinasa 4 Dependiente de la Ciclina/metabolismo , Quinasa 6 Dependiente de la Ciclina/metabolismo , Humanos , Piperazinas , Inhibidores de Proteínas Quinasas/farmacología , Piridinas , SulfonamidasRESUMEN
Technologies to study DNA double-strand break (DSB) repair have traditionally mostly relied on fluorescence read-outs, either by microscopy or flow cytometry. The advent of high throughput sequencing (HTS) has created fundamentally new opportunities to study the mechanisms underlying DSB repair. Here, we review the suite of HTS-based assays that are used to study three different aspects of DNA repair: detection of broken ends, protein recruitment and pathway usage. We highlight new opportunities that HTS technology offers towards a better understanding of the DSB repair process.
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Roturas del ADN de Doble Cadena , Reparación del ADN , ADN/metabolismo , Secuenciación de Nucleótidos de Alto Rendimiento , TecnologíaRESUMEN
Aneuploidy and chromosomal instability are both commonly found in cancer. Chromosomal instability leads to karyotype heterogeneity in tumors and is associated with therapy resistance, metastasis and poor prognosis. It has been hypothesized that aneuploidy per se is sufficient to drive CIN, however due to limited models and heterogenous results, it has remained controversial which aspects of aneuploidy can drive CIN. In this study we systematically tested the impact of different types of aneuploidies on the induction of CIN. We generated a plethora of isogenic aneuploid clones harboring whole chromosome or segmental aneuploidies in human p53-deficient RPE-1 cells. We observed increased segregation errors in cells harboring trisomies that strongly correlated to the number of gained genes. Strikingly, we found that clones harboring only monosomies do not induce a CIN phenotype. Finally, we found that an initial chromosome breakage event and subsequent fusion can instigate breakage-fusion-bridge cycles. By investigating the impact of monosomies, trisomies and segmental aneuploidies on chromosomal instability we further deciphered the complex relationship between aneuploidy and CIN.
Asunto(s)
Aneuploidia , Trisomía , Inestabilidad Cromosómica , Pruebas Genéticas , Humanos , Monosomía , Trisomía/genéticaRESUMEN
In prostate cancer, androgen receptor (AR)-targeting agents are very effective in various disease stages. However, therapy resistance inevitably occurs, and little is known about how tumor cells adapt to bypass AR suppression. Here, we performed integrative multiomics analyses on tissues isolated before and after 3 months of AR-targeting enzalutamide monotherapy from patients with high-risk prostate cancer enrolled in a neoadjuvant clinical trial. Transcriptomic analyses demonstrated that AR inhibition drove tumors toward a neuroendocrine-like disease state. Additionally, epigenomic profiling revealed massive enzalutamide-induced reprogramming of pioneer factor FOXA1 from inactive chromatin sites toward active cis-regulatory elements that dictate prosurvival signals. Notably, treatment-induced FOXA1 sites were enriched for the circadian clock component ARNTL. Posttreatment ARNTL levels were associated with patients' clinical outcomes, and ARNTL knockout strongly decreased prostate cancer cell growth. Our data highlight a remarkable cistromic plasticity of FOXA1 following AR-targeted therapy and revealed an acquired dependency on the circadian regulator ARNTL, a novel candidate therapeutic target. SIGNIFICANCE: Understanding how prostate cancers adapt to AR-targeted interventions is critical for identifying novel drug targets to improve the clinical management of treatment-resistant disease. Our study revealed an enzalutamide-induced epigenomic plasticity toward prosurvival signaling and uncovered the circadian regulator ARNTL as an acquired vulnerability after AR inhibition, presenting a novel lead for therapeutic development. See related commentary by Zhang et al., p. 2017. This article is highlighted in the In This Issue feature, p. 2007.
Asunto(s)
Andrógenos , Neoplasias de la Próstata Resistentes a la Castración , Factores de Transcripción ARNTL/genética , Andrógenos/farmacología , Andrógenos/uso terapéutico , Línea Celular Tumoral , Ritmo Circadiano , Resistencia a Antineoplásicos/genética , Epigenómica , Humanos , Masculino , Nitrilos/uso terapéutico , Neoplasias de la Próstata Resistentes a la Castración/tratamiento farmacológico , Neoplasias de la Próstata Resistentes a la Castración/genética , Neoplasias de la Próstata Resistentes a la Castración/patología , Receptores Androgénicos/genéticaRESUMEN
Advances in genome sequencing have revealed a type of extrachromosomal DNA, historically named double minutes (also referred to as ecDNA), to be common in a wide range of cancer types, but not in healthy tissues. These cancer-associated circular DNA molecules contain one or a few genes that are amplified when double minutes accumulate. Double minutes harbor oncogenes or drug resistance genes that contribute to tumor aggressiveness through copy number amplification in combination with favorable epigenetic properties. Unequal distribution of double minutes over daughter cells contributes to intratumoral heterogeneity, thereby increasing tumor adaptability. In this review, we discuss various models delineating the mechanism of generation of double minutes. Furthermore, we highlight how double minutes are maintained, how they evolve, and discuss possible mechanisms driving their elimination.
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Amplificación de Genes , Neoplasias , Aberraciones Cromosómicas , ADN , Humanos , Neoplasias/genética , OncogenesRESUMEN
The discovery of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and its development as a genome editing tool has revolutionized the field of molecular biology. In the DNA damage field, CRISPR has brought an alternative to induce endogenous double-strand breaks (DSBs) at desired genomic locations and study the DNA damage response and its consequences. Many systems for sgRNA delivery have been reported in order to efficiently generate this DSB, including lentiviral vectors. However, some of the consequences of these systems are not yet well understood. Here, we report that lentiviral-based sgRNA vectors can integrate into the endogenous genomic target location, leading to undesired activation of the target gene. By generating a DSB in the regulatory region of the ABCB1 gene using a lentiviral sgRNA vector, we can induce the formation of Taxol-resistant colonies. We show that these colonies upregulate ABCB1 via integration of the EEF1A1 and the U6 promoters from the sgRNA vector. We believe that this is an unreported CRISPR/Cas9 on-target effect that researchers need to be aware of when using lentiviral vectors for genome editing.
Asunto(s)
Sistemas CRISPR-Cas , Edición Génica , Activación TranscripcionalRESUMEN
The glucocorticoid receptor (GR) regulates gene expression, governing aspects of homeostasis, but is also involved in cancer. Pharmacological GR activation is frequently used to alleviate therapy-related side-effects. While prior studies have shown GR activation might also have anti-proliferative action on tumours, the underpinnings of glucocorticoid action and its direct effectors in non-lymphoid solid cancers remain elusive. Here, we study the mechanisms of glucocorticoid response, focusing on lung cancer. We show that GR activation induces reversible cancer cell dormancy characterised by anticancer drug tolerance, and activation of growth factor survival signalling accompanied by vulnerability to inhibitors. GR-induced dormancy is dependent on a single GR-target gene, CDKN1C, regulated through chromatin looping of a GR-occupied upstream distal enhancer in a SWI/SNF-dependent fashion. These insights illustrate the importance of GR signalling in non-lymphoid solid cancer biology, particularly in lung cancer, and warrant caution for use of glucocorticoids in treatment of anticancer therapy related side-effects.
Asunto(s)
Antineoplásicos/farmacología , Proliferación Celular/efectos de los fármacos , Cromatina/metabolismo , Inhibidor p57 de las Quinasas Dependientes de la Ciclina/metabolismo , Glucocorticoides/farmacología , Neoplasias Pulmonares/metabolismo , Receptores de Glucocorticoides/metabolismo , Animales , Ciclo Celular/genética , Línea Celular Tumoral , Proliferación Celular/genética , Supervivencia Celular/efectos de los fármacos , Cromatina/genética , Secuenciación de Inmunoprecipitación de Cromatina , Proteínas Cromosómicas no Histona/genética , Proteínas Cromosómicas no Histona/metabolismo , Inhibidor p57 de las Quinasas Dependientes de la Ciclina/genética , Elementos de Facilitación Genéticos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica/genética , Humanos , Imidazoles/farmacología , Inmunohistoquímica , Neoplasias Pulmonares/genética , Ratones , Proteómica , Pirazinas/farmacología , ARN Interferente Pequeño , RNA-Seq , Receptor IGF Tipo 1/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Basal-like breast cancers (BLBC) are characterized by defects in homologous recombination (HR), deficient mitotic checkpoint, and high-proliferation activity. Here, we discover CIP2A as a candidate driver of BLBC. CIP2A was essential for DNA damage-induced initiation of mouse BLBC-like mammary tumors and for survival of HR-defective BLBC cells. CIP2A was dispensable for normal mammary gland development and for unperturbed mitosis, but selectively essential for mitotic progression of DNA damaged cells. A direct interaction between CIP2A and a DNA repair scaffold protein TopBP1 was identified, and CIP2A inhibition resulted in enhanced DNA damage-induced TopBP1 and RAD51 recruitment to chromatin in mammary epithelial cells. In addition to its role in tumor initiation, and survival of BRCA-deficient cells, CIP2A also drove proliferative MYC and E2F1 signaling in basal-like triple-negative breast cancer (BL-TNBC) cells. Clinically, high CIP2A expression was associated with poor patient prognosis in BL-TNBCs but not in other breast cancer subtypes. Small-molecule reactivators of PP2A (SMAP) inhibited CIP2A transcription, phenocopied the CIP2A-deficient DNA damage response (DDR), and inhibited growth of patient-derived BLBC xenograft. In summary, these results demonstrate that CIP2A directly interacts with TopBP1 and coordinates DNA damage-induced mitotic checkpoint and proliferation, thereby driving BLBC initiation and progression. SMAPs could serve as a surrogate therapeutic strategy to inhibit the oncogenic activity of CIP2A in BLBCs. SIGNIFICANCE: These results identify CIP2A as a nongenetic driver and therapeutic target in basal-like breast cancer that regulates DNA damage-induced G2-M checkpoint and proliferative signaling.
Asunto(s)
Autoantígenos/metabolismo , Neoplasias de la Mama/metabolismo , Carcinogénesis , Proteínas Portadoras/metabolismo , Proteínas de Unión al ADN/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas Nucleares/metabolismo , 9,10-Dimetil-1,2-benzantraceno , Animales , Ciclo Celular , Línea Celular Tumoral , Proliferación Celular , Daño del ADN , Femenino , Humanos , Inmunohistoquímica , Ratones , Ratones Noqueados , Ratones Transgénicos , Mitosis , Mutación , Proteoma , Recombinación Genética , Transducción de SeñalRESUMEN
Upon exposure to genotoxic stress, cells activate DNA damage response (DDR) that coordinates DNA repair with a temporal arrest in the cell cycle progression. DDR is triggered by activation of ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related protein kinases that phosphorylate multiple targets including tumor suppressor protein tumor suppressor p53 (p53). In addition, DNA damage can activate parallel stress response pathways [such as mitogen-activated protein kinase p38 alpha (p38)/MAPK-activated protein kinase 2 (MK2) kinases] contributing to establishing the cell cycle arrest. Wild-type p53-induced phosphatase 1 (WIP1) controls timely inactivation of DDR and is needed for recovery from the G2 checkpoint by counteracting the function of p53. Here, we developed a simple in vitro assay for testing WIP1 substrates in nuclear extracts. Whereas we did not detect any activity of WIP1 toward p38/MK2, we confirmed p53 as a substrate of WIP1. Inhibition or inactivation of WIP1 in U2OS cells increased phosphorylation of p53 at S15 and potentiated its acetylation at K382. Further, we identified Deleted in breast cancer gene 1 (DBC1) as a new substrate of WIP1 but surprisingly, depletion of DBC1 did not interfere with the ability of WIP1 to regulate p53 acetylation. Instead, we have found that WIP1 activity suppresses p53-K382 acetylation by inhibiting the interaction between p53 and the acetyltransferase p300. Newly established phosphatase assay allows an easy comparison of WIP1 ability to dephosphorylate various proteins and thus contributes to identification of its physiological substrates.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Bioensayo/métodos , Neoplasias Óseas/patología , Núcleo Celular/metabolismo , Osteosarcoma/patología , Proteína Fosfatasa 2C/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Acetilación , Proteínas Adaptadoras Transductoras de Señales/genética , Neoplasias Óseas/genética , Neoplasias Óseas/metabolismo , Núcleo Celular/genética , Daño del ADN , Reparación del ADN , Humanos , Osteosarcoma/genética , Osteosarcoma/metabolismo , Fosforilación , Dominios y Motivos de Interacción de Proteínas , Proteína Fosfatasa 2C/genética , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Double strand breaks (DSBs) are highly toxic to a cell, a property that is exploited in radiation therapy. A critical component for the damage induction is cellular oxygen, making hypoxic tumor areas refractory to the efficacy of radiation treatment. During a fractionated radiation regimen, these hypoxic areas can be re-oxygenated. Nonetheless, hypoxia still constitutes a negative prognostic factor for the patient's outcome. We hypothesized that this might be attributed to specific hypoxia-induced cellular traits that are maintained upon reoxygenation. Here, we show that reoxygenation of hypoxic non-transformed RPE-1 cells fully restored induction of DSBs but the cells remain radioresistant as a consequence of hypoxia-induced quiescence. With the use of the cell cycle indicators (FUCCI), cell cycle-specific radiation sensitivity, the cell cycle phase duration with live cell imaging, and single cell tracing were assessed. We observed that RPE-1 cells experience a longer G1 phase under hypoxia and retain a large fraction of cells that are non-cycling. Expression of HPV oncoprotein E7 prevents hypoxia-induced quiescence and abolishes the radioprotective effect. In line with this, HPV-negative cancer cell lines retain radioresistance, while HPV-positive cancer cell lines are radiosensitized upon reoxygenation. Quiescence induction in hypoxia and its HPV-driven prevention was observed in 3D multicellular spheroids. Collectively, we identify a new hypoxia-dependent radioprotective phenotype due to hypoxia-induced quiescence that accounts for a global decrease in radiosensitivity that can be retained upon reoxygenation and is absent in cells expressing oncoprotein E7.