The p53 Tumor Suppressor Is Stabilized by Inhibitor of Growth 1 (ING1) by Blocking Polyubiquitination

The INhibitor of Growth tumor suppressors (ING1-ING5) affect aging, apoptosis, DNA repair and tumorigenesis. Plant homeodomains (PHD) of ING proteins bind histones in a methylation-sensitive manner to regulate chromatin structure. ING1 and ING2 contain a polybasic region (PBR) adjacent to their PHDs that binds stress-inducible phosphatidylinositol monophosphate (PtIn-MP) signaling lipids to activate these INGs. ING1 induces apoptosis independently of p53 but other studies suggest proapoptotic interdependence of ING1 and p53 leaving their functional relationship unclear. Here we identify a novel ubiquitin-binding domain (UBD) that overlaps with the PBR of ING1 and shows similarity to previously described UBDs involved in DNA damage responses. The ING1 UBD binds ubiquitin with high affinity (Kd∼100 nM) and ubiquitin competes with PtIn-MPs for ING1 binding. ING1 expression stabilized wild-type, but not mutant p53 in an MDM2-independent manner and knockdown of endogenous ING1 depressed p53 levels in a transcription-independent manner. ING1 stabilized unmodified and six multimonoubiquitinated forms of wild-type p53 that were also seen upon DNA damage, but not p53 mutants lacking the six known sites of ubiquitination. We also find that ING1 physically interacts with herpesvirus-associated ubiquitin-specific protease (HAUSP), a p53 and MDM2 deubiquitinase (DUB), and knockdown of HAUSP blocks the ability of ING1 to stabilize p53. These data link lipid stress signaling to ubiquitin-mediated proteasomal degradation through the PBR/UBD of ING1 and further indicate that ING1 stabilizes p53 by inhibiting polyubiquitination of multimonoubiquitinated forms via interaction with and colocalization of the HAUSP-deubiquitinase with p53

The role of the tumour suppressor and epigenetic reulator "Inhibitor of Growth 1" (ING1) in glioma biology and as a molecular target for epigenetic treatment concepts in paediatric neurooncology

Die Prognose von Kindern und Jugendlichen mit Gliomen wurde in den letzten Jahren dank technischer Fortschritte in den diagnostischen Verfahren und in der Mikroneurochirurgie, sowie durch Polychemo- und Strahlentherapie im Rahmen standardisierter Behandlungsprotokolle deutlich verbessert. Zu den Herausforderungen in der pädiatrischen Neuroonkologie gehören jetzt zum einen die weitere Steigerung der Heilungsquantität, das heisst eine Anhebung der Langzeitüberlebensraten auch für die Patienten, die heute noch eine ungünstige Prognose haben, zum anderen eine Verbesserung der Heilungsqualität, das heisst das Erreichen einer bestmöglichen Lebensqualität. Insofern ist nun eine optimierte Kombination von konservativen und neuen Therapieelementen notwendig, damit die Behandlung so gestaltet werden kann, dass sowohl die akuten als auch die Langzeitnebenwirkungen so gering wie möglich bleiben. In diesem Zusammenhang zeigen epigenetische Therapieansätze zwar bereits vielversprechende Ergebnisse in der pädiatrischen Neuroonkologie, jedoch ist der Einsatz epigenetisch wirksamer Substanzen bei jungen Gliompatienten derzeit aufgrund von möglicher Toxizität, Mangel an Spezifität bei hoher genomischer und epigenomischer Variabilität der einzelnen Gliom-Subentitäten und von Resistenzentwicklung noch limitiert. Entsprechend müssen epigenetisch regulierte oder -regulierende Biomarker identifiziert werden, die dazu beitragen, ein individuelles Therapieansprechen vorauszusagen. Zu diesem Zweck wurde in dieser Arbeit die Rolle des Tumorsuppressors und epigenetischen Regulators "Inhibitor of Growth 1 (ING1)" bei der Biologie humaner Gliome an Tumorpräparaten und in vitro untersucht. Die Ergebnisse zeigen eine Beteiligung von ING1 an verschiedenen Basismechanismen der Gliombiologie und suggerieren, dass der Tumorsuppressor in diesen Tumoren einerseits epigenetisch reguliert wird und andererseits epigenetisch regulieren kann: ING1 ist in Gliomen nicht mutiert, wird jedoch korrelierend mit deren Malignitätsgrad reduziert exprimiert. ING1 hemmt Neoangiogenese von Gliomzellen und ist in deren Antwort auf DNS-Schädigungen involviert. ING1-Alterationen beeinflussen die Sensitivität von Gliomzellen gegenüber Mitosehemmern, DNS-schädigenden Agenzien und Histondeacetylase-Inhibitoren. Somit repräsentiert ING1 einen Kandidaten für einen molekularen Faktor, der zukünftig im Rahmen epigenetischer Behandlungskonzepte für Kinder und Jugendliche mit Gliomen, beispielsweise als Marker für das individuelle Ansprechen auf die Therapie oder auch als antineoplastisch wirksames Agenz, genutzt werden kann.Continuous progress in diagnostic and treatment concepts has remarkably improved the prognosis for children and adolescents with gliomas over the last decades. One major challenge in paediatric neurooncology is now to further improve the chances of cure, i. e. to increase the longterm survival rates also for those patients whose prognosis is still unfavourable. Another principle goal is to optimise the quality of cure by achieving best possible life quality for the survivors. Hence, in order to reduce the side- and the late effects of the treatment, individual combinations of conventional, but also new agents are required. In this context, epigenetic treatment concepts have shown promising results in paediatric neurooncology. Nevertheless, the use of epigenetically active drugs for the treatment of children and adolescents with gliomas is still limited due to possible toxicity, high genomic and epigenomic variability of glioma-subgroups, and resistance. Therefore, the identification of epigenetically regulated and -regulating biomarkers may help predicting individual treatment response. Based on this background, the underlying project served to analyse the role of the tumour suppressor and epigenetic regulator "Inhibitor of Growth 1 (ING1)" in glioma biology both in surgical samples of human gliomas and in vitro. The results reveal a regulatory contribution of ING1 to various basic biological mechanisms of gliomas: ING1 is both epigenetically regulated and -regulating in these neoplasms - ING1 was not found mutated in gliomas, however, low ING1-expression in these neoplasms correlated with high grades of malignancy. ING1 inhibits glioma-cell induced, pathological neoangiogenesis and is involved in the reponse of malignant glioma cells to various forms of stress. Altering ING1-levels in glioma cells results in changes of sensitivity to different conventional and experimental treatment elements, such as inhibitors of mitosis, DNA-damaging agents and epigenetically active drugs. In conclusion, this work identified ING1 as a molecular factor, which may contribute to improved future treatment concepts for children and adolescents with gliomas both as a biomarker for predicting individual treatment response and as a therapeutical agent itself

Epigenetically decipherING the genome: A role for PHDs

International audienceWhile completion of the initial phase of the human genome project redefined genetics over two decades ago, the field of epigenetics is currently redefining how chromatin structure affects the gene expression to mold the proteome and the cell phenotype. Posttranslational modification (PTM) of nucleic acids and proteins is central to chromatin organization and helps govern transcription and translation to affect specific phenotypes. Zinc fingers are a common constituent of chromatin regulators and the plant homeodomain (PHD) forms of zinc finger function as readers of the histone code. Understanding the structural mechanisms driving the recognition of PTMs by PHDs is at the core of efforts to understand how chromatin architecture is maintained and modulated. Here, we describe the roles of PHD finger proteins in chromatin remodeling through their specific binding to PTMs on histone proteins with an emphasis on the Inhibitor of Growth (ING) family. Once bound to methylated chromatin, ING1-5 family members serve as scaffolds for the docking of complexes of effector proteins that are vital to gene-specific activation and/or inactivation events that occur within chromatin. All members of the ING family recognize different methylated forms of lysine 4 near the amino terminus of core histone 3 (H3K4me1/2/3), but different members target either histone acetyltransferase (HAT) or histone deacetylase (HDAC) complexes to regulate histone acetylation and subsequently chromatin structure and gene expression. ING-mediated changes in gene expression have now been shown to profoundly affect a broad range of biological processes including development, differentiation, cellular senescence, and oncogenesis. © 2024 Elsevier Inc. All rights reserved

Long-term outcome in children with relapsed acute lymphoblastic leukemia after time-point and site-of-relapse stratification and intensified short-course multidrug chemotherapy: results of trial ALL-REZ BFM 90

PURPOSE: The multicenter trial ALL-REZ BFM (ie, Acute Lymphoblastic Leukemia Relapse Berlin-Frankfurt-Münster) 90 was designed to improve prognosis for children with relapsed acute lymphoblastic leukemia (ALL) by time-to-relapse- and site-of-relapse-adapted stratification and by introduction of novel chemotherapy elements and to evaluate new prognostic parameters in a large, population-based cohort. PATIENTS AND METHODS: Five hundred twenty-five patients stratified into risk groups A (early bone marrow [BM] relapses), B (late BM relapses), and C (isolated extramedullary relapses) received alternating short-course intensive polychemotherapy (in blocks R1, R2, or R3) and cranial/craniospinal irradiation followed by maintenance therapy. Block R3 (high-dose cytarabine and etoposide) was introduced to improve the outcome compared with historical controls. Patients with early BM or T-ALL relapse (poor prognosis group [PPG]) were eligible for experimental regimens. One hundred seventeen patients received stem-cell transplantation (SCT). RESULTS: The probabilities (and standard deviations) of event-free survival (pEFS) and overall survival (pOS) at 10 years were 0.30 +/- .02 and 0.36 +/- .02, respectively. Significant differences existed between strategic groups (pEFS(A) = .17 +/- .03; pEFS(B) = .43 +/- .04; pEFS(C) = .54 +/- .06; pEFS(PPG) = .15 +/- .03; log-rank P < .001). Patients of high-risk groups A plus PPG did better with SCT than with chemotherapy (pEFS = .33 +/- .05 v 0.20 +/- .05; P = .005). The pEFS was similar to trials ALL-REZ BFM 85/87 (.36 +/- .03. v 0.37 +/- .03; P = .419; PPG excluded). Time point, site of relapse, immunophenotype, and SCT were significant predictors of pEFS in multivariate analyses. CONCLUSION: More than one third of patients in this large, population-based trial were cured. Neither R3 nor adaptation of chemotherapy intensity was capable of improving pEFS or of overcoming prognostic factors. In high-risk patients, remission induction regimens must be improved, and allogeneic SCT should be recommended in patients achieving second complete remission