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Retinoblastoma: A malignant tumor arising from the nuclear layer of the retina that is the most common primary tumor of the eye in children. The tumor tends to occur in early childhood or infancy and may be present at birth. The majority are sporadic, but the condition may be transmitted as an autosomal dominant trait. Histologic features include dense cellularity, small round polygonal cells, and areas of calcification and necrosis. An abnormal pupil reflex (leukokoria); NYSTAGMUS, PATHOLOGIC; STRABISMUS; and visual loss represent common clinical characteristics of this condition. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, p2104)Retinoblastoma Protein: Product of the retinoblastoma tumor suppressor gene. It is a nuclear phosphoprotein hypothesized to normally act as an inhibitor of cell proliferation. Rb protein is absent in retinoblastoma cell lines. It also has been shown to form complexes with the adenovirus E1A protein, the SV40 T antigen, and the human papilloma virus E7 protein.Retinal Neoplasms: Tumors or cancer of the RETINA.Genes, Retinoblastoma: Tumor suppressor genes located on human chromosome 13 in the region 13q14 and coding for a family of phosphoproteins with molecular weights ranging from 104 kDa to 115 kDa. One copy of the wild-type Rb gene is necessary for normal retinal development. Loss or inactivation of both alleles at this locus results in retinoblastoma.Eye Neoplasms: Tumors or cancer of the EYE.Eye Enucleation: The surgical removal of the eyeball leaving the eye muscles and remaining orbital contents intact.E2F Transcription Factors: A family of basic helix-loop-helix transcription factors that control expression of a variety of GENES involved in CELL CYCLE regulation. E2F transcription factors typically form heterodimeric complexes with TRANSCRIPTION FACTOR DP1 or transcription factor DP2, and they have N-terminal DNA binding and dimerization domains. E2F transcription factors can act as mediators of transcriptional repression or transcriptional activation.Retinoblastoma-Like Protein p107: A negative regulator of the CELL CYCLE that undergoes PHOSPHORYLATION by CYCLIN-DEPENDENT KINASES. It contains a conserved pocket region that binds E2F4 TRANSCRIPTION FACTOR and interacts with viral ONCOPROTEINS such as POLYOMAVIRUS TUMOR ANTIGENS; ADENOVIRUS E1A PROTEINS; and PAPILLOMAVIRUS E7 PROTEINS.Retinoblastoma-Like Protein p130: A negative regulator of the CELL CYCLE that undergoes PHOSPHORYLATION by CYCLIN-DEPENDENT KINASES. RBL2 contains a conserved pocket region that binds E2F4 TRANSCRIPTION FACTOR and E2F5 TRANSCRIPTION FACTOR. RBL2 also interacts with viral ONCOPROTEINS such as POLYOMAVIRUS TUMOR ANTIGENS; ADENOVIRUS E1A PROTEINS; and PAPILLOMAVIRUS E7 PROTEINS.Transcription Factor DP1: A transcription factor that possesses DNA-binding and E2F-binding domains but lacks a transcriptional activation domain. It is a binding partner for E2F TRANSCRIPTION FACTORS and enhances the DNA binding and transactivation function of the DP-E2F complex.E2F1 Transcription Factor: An E2F transcription factor that interacts directly with RETINOBLASTOMA PROTEIN and CYCLIN A and activates GENETIC TRANSCRIPTION required for CELL CYCLE entry and DNA synthesis. E2F1 is involved in DNA REPAIR and APOPTOSIS.Retinoblastoma-Binding Protein 1: A ubiquitously expressed regulatory protein that contains a retinoblastoma protein binding domain and an AT-rich interactive domain. The protein may play a role in recruiting HISTONE DEACETYLASES to the site of RETINOBLASTOMA PROTEIN-containing transcriptional repressor complexes.Cyclin-Dependent Kinases: Protein kinases that control cell cycle progression in all eukaryotes and require physical association with CYCLINS to achieve full enzymatic activity. Cyclin-dependent kinases are regulated by phosphorylation and dephosphorylation events.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Cyclin-Dependent Kinase 4: Cyclin-dependent kinase 4 is a key regulator of G1 PHASE of the CELL CYCLE. It partners with CYCLIN D to phosphorylate RETINOBLASTOMA PROTEIN. CDK4 activity is inhibited by CYCLIN-DEPENDENT KINASE INHIBITOR P16.G1 Phase: The period of the CELL CYCLE preceding DNA REPLICATION in S PHASE. Subphases of G1 include "competence" (to respond to growth factors), G1a (entry into G1), G1b (progression), and G1c (assembly). Progression through the G1 subphases is effected by limiting growth factors, nutrients, or inhibitors.Cyclins: A large family of regulatory proteins that function as accessory subunits to a variety of CYCLIN-DEPENDENT KINASES. They generally function as ENZYME ACTIVATORS that drive the CELL CYCLE through transitions between phases. A subset of cyclins may also function as transcriptional regulators.Cell Cycle Proteins: Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.Chromosomes, Human, Pair 13: A specific pair of GROUP D CHROMOSOMES of the human chromosome classification.Cyclin D1: Protein encoded by the bcl-1 gene which plays a critical role in regulating the cell cycle. Overexpression of cyclin D1 is the result of bcl-1 rearrangement, a t(11;14) translocation, and is implicated in various neoplasms.Tumor Cells, Cultured: Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.Adenovirus E1A Proteins: Proteins transcribed from the E1A genome region of ADENOVIRUSES which are involved in positive regulation of transcription of the early genes of host infection.Cyclin-Dependent Kinase Inhibitor p16: A product of the p16 tumor suppressor gene (GENES, P16). It is also called INK4 or INK4A because it is the prototype member of the INK4 CYCLIN-DEPENDENT KINASE INHIBITORS. This protein is produced from the alpha mRNA transcript of the p16 gene. The other gene product, produced from the alternatively spliced beta transcript, is TUMOR SUPPRESSOR PROTEIN P14ARF. Both p16 gene products have tumor suppressor functions.Cyclin-Dependent Kinase 2: A key regulator of CELL CYCLE progression. It partners with CYCLIN E to regulate entry into S PHASE and also interacts with CYCLIN A to phosphorylate RETINOBLASTOMA PROTEIN. Its activity is inhibited by CYCLIN-DEPENDENT KINASE INHIBITOR P27 and CYCLIN-DEPENDENT KINASE INHIBITOR P21.Cyclin-Dependent Kinase 6: Cyclin-dependent kinase 6 associates with CYCLIN D and phosphorylates RETINOBLASTOMA PROTEIN during G1 PHASE of the CELL CYCLE. It helps regulate the transition to S PHASE and its kinase activity is inhibited by CYCLIN-DEPENDENT KINASE INHIBITOR P18.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.E2F3 Transcription Factor: An E2F transcription factor that interacts directly with RETINOBLASTOMA PROTEIN and CYCLIN A. E2F3 regulates GENETIC TRANSCRIPTION required for CELL CYCLE entry and DNA synthesis.Papillomavirus E7 Proteins: ONCOGENE PROTEINS from papillomavirus that deregulate the CELL CYCLE of infected cells and lead to NEOPLASTIC CELL TRANSFORMATION. Papillomavirus E7 proteins have been shown to interact with various regulators of the cell cycle including RETINOBLASTOMA PROTEIN and certain cyclin-dependent kinase inhibitors.Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.S Phase: Phase of the CELL CYCLE following G1 and preceding G2 when the entire DNA content of the nucleus is replicated. It is achieved by bidirectional replication at multiple sites along each chromosome.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.CDC2-CDC28 Kinases: A family of cell cycle-dependent kinases that are related in structure to CDC28 PROTEIN KINASE; S CEREVISIAE; and the CDC2 PROTEIN KINASE found in mammalian species.Cyclin E: A 50-kDa protein that complexes with CYCLIN-DEPENDENT KINASE 2 in the late G1 phase of the cell cycle.Antigens, Polyomavirus Transforming: Polyomavirus antigens which cause infection and cellular transformation. The large T antigen is necessary for the initiation of viral DNA synthesis, repression of transcription of the early region and is responsible in conjunction with the middle T antigen for the transformation of primary cells. Small T antigen is necessary for the completion of the productive infection cycle.Tumor Suppressor Protein p53: Nuclear phosphoprotein encoded by the p53 gene (GENES, P53) whose normal function is to control CELL PROLIFERATION and APOPTOSIS. A mutant or absent p53 protein has been found in LEUKEMIA; OSTEOSARCOMA; LUNG CANCER; and COLORECTAL CANCER.E2F4 Transcription Factor: An E2F transcription factor that represses GENETIC TRANSCRIPTION required for CELL CYCLE entry and DNA synthesis. E2F4 recruits chromatin remodeling factors indirectly to target gene PROMOTER REGIONS through RETINOBLASTOMA LIKE PROTEIN P130 and RETINOBLASTOMA LIKE PROTEIN P107.Cyclin-Dependent Kinase Inhibitor p27: A cyclin-dependent kinase inhibitor that coordinates the activation of CYCLIN and CYCLIN-DEPENDENT KINASES during the CELL CYCLE. It interacts with active CYCLIN D complexed to CYCLIN-DEPENDENT KINASE 4 in proliferating cells, while in arrested cells it binds and inhibits CYCLIN E complexed to CYCLIN-DEPENDENT KINASE 2.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Carrier Proteins: Transport proteins that carry specific substances in the blood or across cell membranes.Cyclin-Dependent Kinase Inhibitor p21: A cyclin-dependent kinase inhibitor that mediates TUMOR SUPPRESSOR PROTEIN P53-dependent CELL CYCLE arrest. p21 interacts with a range of CYCLIN-DEPENDENT KINASES and associates with PROLIFERATING CELL NUCLEAR ANTIGEN and CASPASE 3.Retinoblastoma-Binding Protein 2: A retinoblastoma binding protein that is also a member of the Jumonji-domain histone demethylases. It has demethylation activity towards specific LYSINE residues found on HISTONE H3.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Oncogene Proteins, Viral: Products of viral oncogenes, most commonly retroviral oncogenes. They usually have transforming and often protein kinase activities.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Cyclin A: A cyclin subtype that has specificity for CDC2 PROTEIN KINASE and CYCLIN-DEPENDENT KINASE 2. It plays a role in progression of the CELL CYCLE through G1/S and G2/M phase transitions.E2F2 Transcription Factor: An E2F transcription factor that interacts directly with RETINOBLASTOMA PROTEIN and CYCLIN A. E2F2 activates GENETIC TRANSCRIPTION required for CELL CYCLE entry and DNA synthesis.Chromosomes, Human, 13-15: The medium-sized, acrocentric human chromosomes, called group D in the human chromosome classification. This group consists of chromosome pairs 13, 14, and 15.Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.Cyclin D: A cyclin subtype that is specific for CYCLIN-DEPENDENT KINASE 4 and CYCLIN-DEPENDENT KINASE 6. Unlike most cyclins, cyclin D expression is not cyclical, but rather it is expressed in response to proliferative signals. Cyclin D may therefore play a role in cellular responses to mitogenic signals.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Osteosarcoma: A sarcoma originating in bone-forming cells, affecting the ends of long bones. It is the most common and most malignant of sarcomas of the bones, and occurs chiefly among 10- to 25-year-old youths. (From Stedman, 25th ed)Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Cyclin D3: A broadly expressed type D cyclin. Experiments using KNOCKOUT MICE suggest a role for cyclin D3 in LYMPHOCYTE development.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Gene Expression Regulation, Neoplastic: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in neoplastic tissue.Tumor Suppressor Proteins: Proteins that are normally involved in holding cellular growth in check. Deficiencies or abnormalities in these proteins may lead to unregulated cell growth and tumor development.Retina: The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.Neoplasms, Multiple Primary: Two or more abnormal growths of tissue occurring simultaneously and presumed to be of separate origin. The neoplasms may be histologically the same or different, and may be found in the same or different sites.Oncogene Proteins: Proteins coded by oncogenes. They include proteins resulting from the fusion of an oncogene and another gene (ONCOGENE PROTEINS, FUSION).Cell Line, Tumor: A cell line derived from cultured tumor cells.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Optic Nerve Neoplasms: Benign and malignant neoplasms that arise from the optic nerve or its sheath. OPTIC NERVE GLIOMA is the most common histologic type. Optic nerve neoplasms tend to cause unilateral visual loss and an afferent pupillary defect and may spread via neural pathways to the brain.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Proto-Oncogene Proteins: Products of proto-oncogenes. Normally they do not have oncogenic or transforming properties, but are involved in the regulation or differentiation of cell growth. They often have protein kinase activity.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Cyclin G: A cyclin subtype that is found associated with CYCLIN-DEPENDENT KINASE 5; cyclin G associated kinase, and PROTEIN PHOSPHATASE 2.