Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rapp-Hodgkin syndrome (RHS) is an autosomal dominant disorder characterized by ectodermal dysplasia and cleft lip/cleft palate. Very recently, mutations in p63 have been identified as a cause of RHS; to date five such mutations have been identified. We describe a Thai girl with RHS. She had short stature, ectodermal dysplasia, epiphora, cleft lip, cleft palate, and normal development. Mutation analysis for the entire coding region of p63 identified a novel and de novo mutation, 1622C--> A (S541Y), in the SAM domain, predicting an abnormal alpha tail of the p63alpha protein isotypes. This observation supports that majority of patients with RHS are caused by mutations affecting the tail of p63alpha, a region that also contains most of the pathogenic mutations in ankyloblepharon-ectodermal dysplasia-clefting (AEC) syndrome.
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PMID:De novo missense mutation, S541Y, in the p63 gene underlying Rapp-Hodgkin ectodermal dysplasia syndrome. 1580 90

The ankyloblepharon-ectodermal defects-cleft lip and palate (Hay-Wells or AEC) and the Rapp-Hodgkin syndrome (RHS) are rare autosomal dominant ectodermal dysplasias due to mutations in the transcription factor gene P63. Both are caused by mutations affecting SAM or TID domains of TP63 protein. The two disorders share common features and may represent different phenotypic expressions of the same clinical entity. To date more than 20 P63 mutations have been described associated with AEC and RHS, the majority of which are missense or nonsense mutations. Molecular heterogeneity cannot account for the clinical heterogeneity, because the same mutations were observed both in patient with RHS and with AEC syndrome. Here we report on a novel P63 mutation (the first repeat variation described in the gene) in a patient showing overlapping phenotype of AEC and RH syndromes.
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PMID:An intermediate phenotype between Hay-Wells and Rapp-Hodgkin syndromes in a patient with a novel P63 mutation: confirmation of a variable phenotypic spectrum with a common aetiology. 1923 83

Heterozygous mutations in the p63 gene underlie a group of at least seven allelic syndromes, including ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC) and Rapp Hodgkin syndrome (RHS), which involves varying degrees of ectodermal dysplasia, orofacial clefting and limb malformations. Mutations in the AEC and Rapp Hodgkin syndromes cluster in the 3' end of the p63 gene. Previously reported mutations are mainly missense and frameshift mutations in exons 13 and 14, affecting the p63alpha-specific SAM (sterile alpha motif) and TI (transactivation inhibitory) domains. A patient cohort affected by AEC syndrome was evaluated during International Research Symposium supported by the National Foundation for Ectodermal Dysplasias. Nineteen patients underwent full clinical evaluations and 18 had findings consistent with a diagnosis of AEC syndrome. These 19 patients, along with 5 additional relatives had genomic DNA analysis. Twenty-one of the 24 participants from 12 families were found to have mutations in the p63 gene. Eleven different mutations were identified; 10 were novel mutations. Eight were missense mutations within the coding region of the SAM domain. Three other mutations were located in exon 14 sequences, which encode the TI domain. The effects of the mutations in the SAM and TI domains are poorly understood and functional studies are required to understand the pathological mechanisms. However, AEC and RHS mutations in the 5' and 3' ends of the p63 gene point towards a critical role of the DeltaNp63alpha isoform for the AEC/RHS phenotype.
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PMID:Spectrum of p63 mutations in a selected patient cohort affected with ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC). 1967 60

EZH2/PRC2 catalyzes transcriptionally repressive methylation at lysine 27 of histone H3 and has been associated with numerous cancer types. Point mutations in EZH2 at Tyr641 and Ala677 identified in non-Hodgkin lymphomas alter substrate specificity and result in increased trimethylation at histone H3K27. Interestingly, EZH2/PRC2 is activated by binding H3K27me3 marks on histones, and this activation is proposed as a mechanism for self-propagation of gene silencing. Recent work has identified GSK126 as a potent, selective, SAM-competitive inhibitor of EZH2 capable of globally decreasing H3K27 trimethylation in cells. Here we show that activation of PRC2 by an H3 peptide trimethylated at K27 is primarily an effect on the rate-limiting step (kcat) with no effect on substrate binding (Km). Additionally, GSK126 is shown to have a significantly longer residence time of inhibition on the activated form of EZH2/PRC2 as compared to unactivated EZH2/PRC2. Overall inhibition constant (Ki*) values for GSK126 were determined to be as low as 93 pM and appear to be driven by slow dissociation of inhibitor from the activated enzyme. The data suggest that activation of EZH2 allows the enzyme to adopt a conformation that possesses greater affinity for GSK126. The long residence time of GSK126 may be beneficial in vivo and may result in durable target inhibition after drug systemic clearance.
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PMID:Long residence time inhibition of EZH2 in activated polycomb repressive complex 2. 2430 66

Mutations within the catalytic domain of the histone methyltransferase EZH2 have been identified in subsets of patients with non-Hodgkin lymphoma (NHL). These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We have previously reported the discovery of EPZ005678 and EPZ-6438, potent and selective S-adenosyl-methionine-competitive small molecule inhibitors of EZH2. Although both compounds are similar with respect to their mechanism of action and selectivity, EPZ-6438 possesses superior potency and drug-like properties, including good oral bioavailability in animals. Here, we characterize the activity of EPZ-6438 in preclinical models of NHL. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration- and time-dependent manner in both EZH2 wild-type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) leads to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of EZH2-mutant NHL xenograft-bearing mice with EPZ-6438 causes dose-dependent tumor growth inhibition, including complete and sustained tumor regressions with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 days after stopping compound treatment in two EZH2-mutant xenograft models. These data confirm the dependency of EZH2-mutant NHL on EZH2 activity and portend the utility of EPZ-6438 as a potential treatment for these genetically defined cancers.
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PMID:Selective inhibition of EZH2 by EPZ-6438 leads to potent antitumor activity in EZH2-mutant non-Hodgkin lymphoma. 2456 39