Suchergebnisse

The retinoblastoma protein (Rb1) is a prototypical tumor suppressor protein whose role was described more than 40 years ago. Together with p107 (also known as RBL1) and p130 (also known as RBL2), the Rb1 belongs to a family of structurally and functionally similar proteins that inhibits cell cycle progression. Given the central role of Rb1 in regulating proliferation, its expression or function is altered in most types of cancer. One of the mechanisms underlying Rb-mediated cell cycle inhibition is the binding and repression of E2F transcription factors, and these processes are dependent on Rb1 phosphorylation status. However, recent work shows that Rb1 is a convergent point of many pathways and thus the regulation of its function through post-translational modifications is more complex than initially expected. Moreover, depending on the context, downstream signaling can be both E2F-dependent and -independent. This review seeks to summarize the most recent research on Rb1 function and regulation and discuss potential avenues for the design of novel cancer therapies. ; This project received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie PROBIST grant agreement No. 754510 (postdoctoral fellowship to R.J.) and from BIST Living Allowance Fellowship to A.T.-S. This work was supported by grants from the Spanish Ministry of Economy and Competitiveness [BFU2017-85152-P and FEDER to E.d.N. and PGC2018-094136-B-I00 and FEDER to F.P.], the AECC Foundation [PROYE18010POSA to F.P.] and the Government of Catalonia [2017 SGR 799 to E.d.N. and F.P.]. E.d.N. and F.P. are recipients of ICREA Acadèmia awards (Government of Catalonia). We gratefully acknowledge institutional funding from the Ministry of Science, Innovation and Universities through the Centres of Excellence Severo Ochoa Award, and from the CERCA Programme of the Government of Catalonia and the Unidad de Excelencia María de Maeztu, funded by the AEI (CEX2018-000792-M).

9 páginas, 8 figuras. ; Previous studies have demonstrated a protective effect of the cyclin-dependent kinase (CDK) inhibitor p27Kip1 against atherosclerosis and restenosis, two disorders characterized by abundant proliferation and migration of vascular smooth muscle cells and adventitial fibroblasts. These therapeutic effects might result from p27Kip1-dependent suppression of both cell proliferation and migration. However, the interplay between cell growth and locomotion remains obscure. We show here that p27Kip1 inhibits cellular changes that normally occur during cell locomotion (eg, lamellipodia formation and reorganization of actin filaments and focal adhesions). Importantly, a p27Kip1 mutant lacking CDK inhibitory activity failed to inhibit vascular smooth muscle cell and fibroblast proliferation and migration. Moreover, a constitutively active mutant of the retinoblastoma protein (pRb) insensitive to CDK-dependent hyperphosphorylation inhibited both cell proliferation and migration. In contrast, inactivation of pRb by forced expression of the adenoviral oncogene E1A correlated with high proliferative and migratory activity. Collectively, these results suggest that cellular proliferation and migration are regulated in a coordinated manner by the p27Kip1/CDK/pRb pathway. These findings might have important implications for the development of novel therapeutic strategies targeting the fibroproliferative/migratory component of vascular occlusive disorders. ; Work in the laboratory of Dr Andrés is currently supported by the Spanish Ministerio de Ciencia y Tecnología and Fondo Europeo de Desarrollo Regional (grants SAF2001-2358 and SAF2002-1143) and by Generalitat Valenciana (grants GV01-488 and CTGCA/2002/04). Dr Díez-Juan received salary support from the Spanish Government and Fondo Europeo de Desarrollo Regional (grant 1FD97-1035-C02- 02) and from Fondo Social Europeo (CSIC-Programa I3P). ; Peer reviewed

Although BRCA1 function is essential for maintaining genomic integrity in all cell types, it is unclear why increased risk of cancer in individuals harbouring deleterious mutations in BRCA1 is restricted to only a select few tissues. Here we show that human mammary epithelial cells (HMECs) from BRCA1-mutation carriers (BRCA1(mut/+)) exhibit increased genomic instability and rapid telomere erosion in the absence of tumour-suppressor loss. Furthermore, we uncover a novel form of haploinsufficiency-induced senescence (HIS) specific to epithelial cells, which is triggered by pRb pathway activation rather than p53 induction. HIS and telomere erosion in HMECs correlate with misregulation of SIRT1 leading to increased levels of acetylated pRb as well as acetylated H4K16 both globally and at telomeric regions. These results identify a novel form of cellular senescence and provide a potential molecular basis for the rapid cell- and tissue- specific predisposition of breast cancer development associated with BRCA1 haploinsufficiency. ; This work was supported by grants from the Raymond and Beverly Sackler Foundation (M.S.), the Breast Cancer Research Foundation (B.K. and C.K.), the Silvian Foundation (C.K. and A.S.) and the NIH/NCI CA125554 (C.K.), CA092644 (C.K.). Research in the Blasco laboratory was funded by ERC Project Project TEL STEM CELL, FP7 Projects MARK-AGE and EuroBATS, Spanish Ministry of Economy and Competitiveness Projects SAF2008-05384 and CSD2007-00017, Regional of Government of Madrid Project S2010/BMD-2303, AXA Research Fund, Fundacion Botin (Spain) and Fundacion Lilly (Spain). We thank members of the Kuperwasser laboratory for valuable discussions as well as Benjamin Dake, Sarah Phillips and Agueda Tejera for their help with experiments. ; Sí

429.e7–429.e20 páginas, 8 figuras, 1 tabla ; Frontotemporal lobar degeneration with neuronal inclusions containing TAR DNA binding protein 43 (TDP-43) is associated in most cases with null-mutations in the progranulin gene (PGRN). While the mechanisms by which PGRN haploinsufficiency leads to neurodegeneration remained speculative, increasing evidence support the hypothesis that cell cycle reentry of postmitotic neurons precedes many instances of neuronal death. Based in the mitogenic and neurotrophic activities of PGRN, we hypothesized that PGRN deficit may induce cell cycle disturbances and alterations in neuronal vulnerability. Because cell cycle dysfunction is not restricted to neurons, we studied the influence of PGRN haploinsufficiency, on cell cycle control in peripheral cells from patients suffering from frontotemporal dementia, bearing the PGRN mutation c.709-1G>A. Here we show that progranulin deficit increased cell cycle activity in immortalized lymphocytes. This effect was associated with increased levels of cyclin-dependent kinase 6 (CDK6) and phosphorylation of retinoblastoma protein (pRb), resulting in a G1/S regulatory failure. A loss of function of TDP-43 repressing CDK6 expression may result from altered subcellular TDP-43 distribution. The distinct functional features of lymphoblastoid cells from c.709-1 G>A carriers offer an invaluable, noninvasive tool to investigate the etiopathogenesis of frontotemporal lobar degeneration ; This work has been supported by grants from Ministry of Education and science (SAF2007-62405, SAF2010-15700), Fundación Eugenio Rodríguez Pascual, Diputación Foral de Gipuzkoa (76/08) and Basque Government (Saiotek program). N.E. holds a fellowship of the JAE predoctoral program of the CSIC. J.J. Merino holds a contract of the Ramon y Cajal Program of the Spanish Ministry of Science and Innovation ; Peer reviewed

As orchestrators of essential cellular processes like proliferation, ERK1/2 mitogen-activated protein kinase signals impact on cell cycle regulation. A-type lamins are major constituents of the nuclear matrix that also control the cell cycle machinery by largely unknown mechanisms. In this paper, we disclose a functional liaison between ERK1/2 and lamin A whereby cell cycle progression is regulated. We demonstrate that lamin A serves as a mutually exclusive dock for ERK1/2 and the retinoblastoma (Rb) protein. Our results reveal that, immediately after their postactivation entrance in the nucleus, ERK1/2 dislodge Rb from its interaction with lamin A, thereby facilitating its rapid phosphorylation and consequently promoting E2F activation and cell cycle entry. Interestingly, these effects are independent of ERK1/2 kinase activity. We also show that cellular transformation and tumor cell proliferation are dependent on the balance between lamin A and nuclear ERK1/2 levels, which determines Rb accessibility for phosphorylation/inactivation. ; P. Crespo's laboratory is supported by grants from the Spanish Ministry of Science and Innovation (BFU2008-01728), the GROWTHSTOP project from the European Union VI Framework Program (LSHC-CT-2006-037731), and the Red Temática de Investigación Cooperativa en Cáncer (RD06/0020/0105), Spanish Ministry of Health. V. Andrés's laboratory is supported by the Spanish Ministry of Science and Innovation (SAF2007-62110), the European Regional Development Fund, and the Red Temática de Investigación Cooperativa en Enfermedades Cardiovasculares (RD06/0014/0021). The Centro Nacional de Investigaciones Cardiovasculares is supported by the Spanish Ministry of Science and Innovation and the Fundación Pro–Centro Nacional de Investigaciones Cardiovasculares. ; Peer reviewed

The cell cycle is a tightly regulated process that is controlled by the conserved cyclin-dependent kinase (CDK)-cyclin protein complex1. However, control of the G0-to-G1 transition is not completely understood. Here we demonstrate that p38 MAPK gamma (p38γ) acts as a CDK-like kinase and thus cooperates with CDKs, regulating entry into the cell cycle. p38γ shares high sequence homology, inhibition sensitivity and substrate specificity with CDK family members. In mouse hepatocytes, p38γ induces proliferation after partial hepatectomy by promoting the phosphorylation of retinoblastoma tumour suppressor protein at known CDK target residues. Lack of p38γ or treatment with the p38γ inhibitor pirfenidone protects against the chemically induced formation of liver tumours. Furthermore, biopsies of human hepatocellular carcinoma show high expression of p38γ, suggesting that p38γ could be a therapeutic target in the treatment of this disease. ; G.S. (RYC-2009-04972), F.J.C. (RYC-2014-15242), and Y.A.N. (RYC-2015-17438) are investigators of the Ramón y Cajal Program. E.M. and M.T. were awarded La Caixa fellowships and R.R.-B. was a fellow of the Fundación Ramón Areces-UAM and FPU. B.G.-T. is a fellow of the FPI Severo Ochoa CNIC program (SVP-2013-067639). F.J.C. is a Gilead Liver Research Scholar. This work was funded by grants supported in part by funds from the European Regional Development Fund: the European Union's Seventh Framework Programme (FP7/2007-2013) ERC 260464, EFSD/Lilly European Diabetes Research Programme Dr Sabio, 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation (InvestigadoresBBVA-2017) IN[17]_BBM_BAS_0066, MINECO-FEDER SAF2016-79126-R, and Comunidad de Madrid IMMUNOTHERCAN-CM S2010/BMD-2326 and B2017/ BMD-3733 to G.S.; Juan de la Cierva and MINECO SAF2014-61233-JIN to A.T.-L.; the European Community for MSCA-IF-2014-EF-661160-MetAccembly grant to F.F.; Spanish MINECO CTQ2014-59212-P, European Community for CIG project (PCIG14-GA-2013-630978), and European Research Council (ERC) under the European Union's Horizon 2020 (ERC-2015-StG-679001- NetMoDEzyme) to S.O.; the German Research Foundation (SFB/TRR57/P04 and DFG NE 2128/2-1) and MINECO SAF2017-87919R to Y.A.N.; EXOHEP-CM S2017/BMD-3727 and the COST Action CA17112, MINECO SAF2016-78711, and the AMMF Cholangiocarcinoma Charity 2018/117 to F.J.C.; MINECO (SAF2015-69920-R co-funded by ERDF-EU), the Consolider-Ingenio 2010 Programme (SAF2014-57791-REDC), Excellence Network CellSYS (BFU2014- 52125-REDT), and the iLUNG Programme (B2017/BMD-3884) from the Comunidad de Madrid to M. Malumbres; MINECO SAF2015-67077-R and SAF2017-89901-R to J.B.; MINECO (BIO2015-67580-P), Carlos III Institute of Health-Fondo de Investigación Sanitaria (ProteoRed PRB3, IPT17/0019 - ISCIII-SGEFI/ERDF), Fundación La Marató and 'La Caixa' Banking Foundation (HR17-00247) to J.V.; ISCIII and FEDER PI16/01548 and Junta de Castilla y León GRS 1362/A/16 and INT/M/17/17 to M. Marcos; Junta de Castilla y León GRS 1356/A/16 and GRS 1587/A/17 to J.L.-T.; and MCNU (SAF2017- 84494-C2-1-R) to J.R.-C. The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades (MCNU) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). ; Sí

The chromatin high mobility group protein 1 (HMGB1) is a very abundant and conserved protein that is structured into two HMG box domains plus a highly acidic C-terminal domain. From the ability to bind DNA nonspecifically and to interact with various proteins, several functions in DNA-related processes have been assigned to HMGB1. Nevertheless, its functional role remains the subject of controversy. Using a phage display approach we have shown that HMGB1 can recognize several peptide motifs. A computer search of the protein data bases found peptide homologies with proteins already known to interact with HMGB1, like p53, and have allowed us to identify new potential candidates. Among them, transcriptional activators like the heterogeneous nuclear ribonucleoprotein K (hnRNP K), repressors like methyl-CpG binding protein 2 (MeCP2), and co-repressors like the retinoblastoma susceptibility protein (pRb) and Groucho-related gene proteins 1 (Grg1) and 5 (Grg5) can be found. A detailed analysis of the interaction of Grgl with HMGB1 confirmed that the binding region contained the sequence homologous to one of the peptides identified. Our results have led us to propose that HMGB1 may play a central role in the stabilization and/or assembly of several multifunctional complexes through protein-protein interactions. ; This work was supported by a European Union Grant FMRX-CT97-0109 and Comissió Interdepartamental de Recerca i Innovació Tecnològica (CIRIT) of the Generalitat de Catalunya Grant SGR97-55. This work was carried out in the context of the Centre de Referència en Biotecnologia of the CIRIT of the Generalitat de Catalunya ; Peer Reviewed

The etiology and the molecular basis of lung adenocarcinomas (LuADs) in nonsmokers are currently unknown. Furthermore, the scarcity of available primary cultures continues to hamper our biological understanding of non-smoking-related lung adenocarcinomas (NSK-LuADs). We established patient-derived cancer cell (PDC) cultures from metastatic NSK-LuADs, including two pairs of matched EGFR-mutant PDCs before and after resistance to tyrosine kinase inhibitors (TKIs), and then performed whole-exome and RNA sequencing to delineate their genomic architecture. For validation, we analyzed independent cohorts of primary LuADs. In addition to known non-smoker-associated alterations (e.g. RET, ALK, EGFR, and ERBB2), we discovered novel fusions and recurrently mutated genes, including ATF7IP, a regulator of gene expression, that was inactivated in 5% of primary LuAD cases. We also found germline mutations at dominant familiar-cancer genes, highlighting the importance of genetic predisposition in the origin of a subset of NSK-LuADs. Furthermore, there was an over-representation of inactivating alterations at RB1, mostly through complex intragenic rearrangements, in treatment-naive EGFR-mutant LuADs. Three EGFR-mutant and one EGFR-wild-type tumors acquired resistance to EGFR-TKIs and chemotherapy, respectively, and histology on re-biopsies revealed the development of small-cell lung cancer/squamous cell carcinoma (SCLC/LuSCC) transformation. These features were consistent with RB1 inactivation and acquired EGFR-T790M mutation or FGFR3-TACC3 fusion in EGFR-mutant tumors. We found recurrent alterations in LuADs that deserve further exploration. Our work also demonstrates that a subset of NSK-LuADs arises within cancer-predisposition syndromes. The preferential occurrence of RB1 inactivation, via complex rearrangements, found in EGFR-mutant tumors appears to favor SCLC/LuSCC transformation under growth-inhibition pressures. Thus RB1 inactivation may predict the risk of LuAD transformation to a more aggressive type of lung cancer, and may need to be considered as a part of the clinical management of NSK-LuADs patients. ; This work was supported by the Fundacion Cientifica Asociacion Española Contra el Cancer-AECC (grant number GCB14142170MONT) to LMM, MS-C, and EF; the Spanish Ministry of Economy and Competitivity-MINECO (grant number SAF-2017-82186R to MS-C; Rio Hortega-CM17/00180 to MS; PROYBAR17005NADA to EN); the Health Institute Carlos III-ISCIII, Fondo Europeo de Desarrollo Regional-FEDER (grant Number PT13/0001/0044, PT17/0009/0019, PI16 01821); the Government of Navarra (grant number DIANA project); and the Ramon Areces Foundation (no grant number is applicable) to LMM and RP. ; Sí

This work provides a comprehensive CpG methylation landscape of the different layers of the human eye that unveils the gene networks associated with their biological functions and how these are disrupted in common visual disorders. Herein, we firstly determined the role of CpG methylation in the regulation of ocular tissue-specification and described hypermethylation of retinal transcription factors (i.e., PAX6, RAX, SIX6) in a tissue-dependent manner. Second, we have characterized the DNA methylome of visual disorders linked to internal and external environmental factors. Main conclusions allow certifying that crucial pathways related to Wnt-MAPK signaling pathways or neuroinflammation are epigenetically controlled in the fibrotic disorders involved in retinal detachment, but results also reinforced the contribution of neurovascularization (ETS1, HES5, PRDM16) in diabetic retinopathy. Finally, we had studied the methylome in the most frequent intraocular tumors in adults and children (uveal melanoma and retinoblastoma, respectively). We observed that hypermethylation of tumor suppressor genes is a frequent event in ocular tumors, but also unmethylation is associated with tumorogenesis. Interestingly, unmethylation of the proto-oncogen RAB31 was a predictor of metastasis risk in uveal melanoma. Loss of methylation of the oncogenic mir-17-92 cluster was detected in primary tissues but also in blood from patients. ; The research leading to these results was supported by European Research Council Advanced Grant EPINORC, RecerCaixa Foundation, Federación Española de Enfermedades Raras (FEDER), Federación Española de Enfermedades Neuromusculares (ASEM), Fundación Isabel Gemio, COST CM1406, Instituto de Salud Carlos III (PI/00816) and Health and Sciences Departments of the Catalan Government (Generalitat de Catalunya). M.E. is an Institució Catalana de Recerca i Estudis Avançats (ICREA) Research Professor. We thank the staff of the Biobank Facility at the Bellvitge Biomedical Research Institute (IDIBELL), Spanish National Cancer Research Center (CNIO), Institute of Rare Diseases Research (BioNER-ISCIII), Vall d'Hebron Research Institute (VHIR) and Banc de Sang i Teixits (BST) of the Catalan Ministry of Health. We also thank Dr. Mercedes Hurtado (Department of Ophthalmology, University and Polytechnic Hospital La Fe) and Dr. Dolores Pinazo (Department of Ophthalmology, Dr. Peset University Hospital) for obtaining samples from glaucomatous patients. We thank the patients and their families. ; Sí

A discordant twin gestation, in which one fetus is significantly growth restricted, compared to the other normal twin, is a unique model that can be used to elucidate the mechanism(s) by which the intrauterine environment affects fetal growth. In many model systems, placental transcription factor genes regulate fetal growth. Transcription factors regulate growth through their activation or repression of downstream target genes that mediate important cell functions. The objective of this study was to determine the expression of the placental HLX homeobox gene transcription factor and its downstream target genes in dizygotic twins with growth discordance. In this cross-sectional study, HLX and its downstream target genes' retinoblastoma 1 (RB1) and cyclin kinase D (CDKN1C) expression levels were determined in placentae obtained from dichorionic diamniotic twin pregnancies (n = 23) where one of the twins was growth restricted. Fetal growth restriction (FGR) was defined as small for gestational age with abnormal umbilical artery Doppler indices when compared with the normal control co-twin. Homeobox gene HLX expression was significantly decreased at both the mRNA and protein levels in FGR twin placentae compared with the normal control co-twin placentae (p < .05). Downstream target genes CDKN1C and RB1 were also significantly decreased and increased, respectively, at both the mRNA and protein levels in FGR twin placentae compared with normal control co-twin placentae (p < .05). Together, these observations suggest an important association between HLX transcription factor expression and abnormal human placental development in discordant twin pregnancies.

The retinoblastoma tumor suppressor protein pRb restricts cell growth through inhibition of cell cycle progression. Increasing evidence suggests that pRb also promotes differentiation, but the mechanisms are poorly understood, and the key question remains as to how differentiation in tumor cells can be enhanced in order to diminish their aggressive potential. Previously, we identified the histone demethylase KDM5A (lysine [K]-specific demethylase 5A), which demethylates histone H3 on Lys4 (H3K4), as a pRB-interacting protein counteracting pRB's role in promoting differentiation. Here we show that loss of Kdm5a restores differentiation through increasing mitochondrial respiration. This metabolic effect is both necessary and sufficient to induce the expression of a network of cell type-specific signaling and structural genes. Importantly, the regulatory functions of pRB in the cell cycle and differentiation are distinct because although restoring differentiation requires intact mitochondrial function, it does not necessitate cell cycle exit. Cells lacking Rb1 exhibit defective mitochondria and decreased oxygen consumption. Kdm5a is a direct repressor of metabolic regulatory genes, thus explaining the compensatory role of Kdm5a deletion in restoring mitochondrial function and differentiation. Significantly, activation of mitochondrial function by the mitochondrial biogenesis regulator Pgc-1α (peroxisome proliferator-activated receptor γ-coactivator 1α; also called PPARGC1A) a coactivator of the Kdm5a target genes, is sufficient to override the differentiation block. Overexpression of Pgc-1α, like KDM5A deletion, inhibits cell growth in RB-negative human cancer cell lines. The rescue of differentiation by loss of KDM5A or by activation of mitochondrial biogenesis reveals the switch to oxidative phosphorylation as an essential step in restoring differentiation and a less aggressive cancer phenotype. ; This work was supported by R01CA138631 (to E.V.B.) and R01GM094220 (to J.R.) from the National Institutes of Health, educational grant SAF2009-06954 (to N.L.-B.) from the Spanish Ministry of Science, and a fellowship from the Agencia de Gestió d'Ajuts Universitaris i de Recerca of the Catalonian Government, Spain (to A.B.M.M.K.I.)