P53 Protein Isoform Profiles in AML: Correlation with Distinct Differentiation Stages and Response to Epigenetic Differentiation Therapy.
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ABSTRACT:
SUBMITTER: Haaland I
PROVIDER: S-EPMC8068061 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Perinatally-acquired HIV has persistent effects on long-term health outcomes, even after early treatment. We hypothesize that epigenetic indicators, such as DNA methylation, may elucidate cellular processes that explain these effects. Here, we compared DNA methylation profiles in whole blood from 120 HIV-infected children on antiretroviral therapy (ART) and 60 frequency age-matched HIV-uninfected children aged 4-9 years in Johannesburg, South Africa. Using an individual CpG site approach, we found 1,309 differentially-methylated (DM) CpG sites between groups, including 1,271 CpG sites that were hyper-methylated in the HIV-infected group and 38 CpG sites that were hypo-methylated in the HIV-infected group. Six hyper-methylated CpG sites were in EBF4, which codes for a transcription factor involved in B-cell maturation. The top hypomethylated site was in the promoter region of NLRC5, encoding a transcription factor that regulates major histocompatibility complex (MHC) class I molecule expression. Using a differentially-methylated region (DMR) approach, we found 315 DMRs between groups, including 28 regions encompassing 686 CpG sites on chromosome 6. A large number of the genes identified in both the CpG site and DMR approaches were located in the MHC region on chromosome 6, which plays an important role in the adaptive immune system. This study provides the first evidence that changes in the epigenome are detectable in children with perinatally-acquired HIV infection on suppressive ART started at an early age.
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Project description:Thymocyte differentiation is dependent on the availability and transport of metabolites in the thymus niche. As expression of metabolite transporters is a rate-limiting step in nutrient utilization, cell surface transporter levels generally reflect the cell's metabolic state. The GLUT1 glucose transporter is upregulated on actively dividing thymocytes, identifying thymocytes with an increased metabolism. However, it is not clear whether transporters of essential elements such as phosphate are modulated during thymocyte differentiation. While PiT1 and PiT2 are both phosphate transporters in the SLC20 family, we show here that they exhibit distinct expression profiles on both murine and human thymocytes. PiT2 expression distinguishes thymocytes with high metabolic activity, identifying immature murine double negative (CD4-CD8-) DN3b and DN4 thymocyte blasts as well as immature single positive (ISP) CD8 thymocytes. Notably, the absence of PiT2 expression on RAG2-deficient thymocytes, blocked at the DN3a stage, strongly suggests that high PiT2 expression is restricted to thymocytes having undergone a productive TCRβ rearrangement at the DN3a/DN3b transition. Similarly, in the human thymus, PiT2 was upregulated on early post-β selection CD4+ISP and TCRαβ-CD4hiDP thymocytes co-expressing the CD71 transferrin receptor, a marker of metabolic activity. In marked contrast, expression of the PiT1 phosphate importer was detected on mature CD3+ murine and human thymocytes. Notably, PiT1 expression on CD3+DN thymocytes was identified as a biomarker of an aging thymus, increasing from 8.4 ± 1.5% to 42.4 ± 9.4% by 1 year of age (p < 0.0001). We identified these cells as TCRγδ and, most significantly, NKT, representing 77 ± 9% of PiT1+DN thymocytes by 1 year of age (p < 0.001). Thus, metabolic activity and thymic aging are associated with distinct expression profiles of the PiT1 and PiT2 phosphate transporters.
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Project description:The success of all-trans retinoic acid (ATRA) therapy in acute promeylocytic leukemia (APL) has spawned numerous attempts to translate the paradigm of differentiation therapy to non-APL acute myelocytic leukemia (AML). However, the results of clinical trials have been overall disappointing. In this review we discuss the mechanism of retinoic acid signaling and the results of major clinical trials that have attempted to incorporate ATRA into AML regimens. We discuss recent evidence that indicate that the retinoic acid signaling pathway may be dysfunctional in AML. Preliminary studies suggest that targeting the pathways that modify retinoic acid receptor activity may reactivate the dormant retinoic acid-signaling pathway. Such strategies may revive the ability of ATRA to induce myeloid differentiation and apoptosis in non-APL AML.
| S-EPMC4494875 | biostudies-literature
Project description:Therapy-related acute myeloid leukaemia (t-AML) is a late side effect of previous chemotherapy (ct-AML) and/or radiotherapy (rt-AML) or immunosuppressive treatment. t-AMLs, which account for ∼10-20 % of all AML cases, are extremely aggressive and have a poor prognosis compared to de novo AML. Our hypothesis is that exposure to radiation causes genome-wide epigenetic changes in rt-AML. An epigenome-wide association study was undertaken, measuring over 850K methylation sites across the genome from fifteen donors (five healthy, five de novo, and five t-AMLs). The study predominantly focussed on 94K sites that lie in CpG-rich gene promoter regions. Genome-wide hypomethylation was discovered in AML, primarily in intergenic regions. Additionally, genes specific to AML were identified with promoter hypermethylation. A two-step validation was conducted, both internally, using pyrosequencing to measure methylation levels in specific regions across fifteen primary samples, and externally, with an additional eight AML samples. We demonstrated that the MEST and GATA5 gene promoters, which were previously identified as tumour suppressors, were noticeably hypermethylated in rt-AML, as opposed to other subtypes of AML and control samples. These may indicate the epigenetic involvement in the development of rt-AML at the molecular level and could serve as potential targets for drug therapy in rt-AML.
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Project description:The tumor suppressor protein p53 is a transcription factor that is mutated in many cancers. Regulation of gene expression by binding of wild-type p53 to its target sites is accompanied by changes in epigenetic marks like histone acetylation. We studied DNA binding and epigenetic changes induced by wild-type and mutant p53 in non-malignant hTERT-immortalized human mammary epithelial cells overexpressing either wild-type p53 or one of four p53 mutants (R175H, R249S, R273H and R280K) on a wild-type p53 background.Using chromatin immunoprecipitation coupled to a 13,000 human promoter microarray, we found that wild-type p53 bound 197 promoters on the microarray including known and novel p53 targets. Of these p53 targets only 20% showed a concomitant increase in histone acetylation, which was linked to increased gene expression, while 80% of targets showed no changes in histone acetylation. We did not observe any decreases in histone acetylation in genes directly bound by wild-type p53. DNA binding in samples expressing mutant p53 was reduced over 95% relative to wild-type p53 and very few changes in histone acetylation and no changes in DNA methylation were observed in mutant p53 expressing samples.We conclude that wild-type p53 induces transcription of target genes by binding to DNA and differential induction of histone acetylation at target promoters. Several new wild-type p53 target genes, including DGKZ, FBXO22 and GDF9, were found. DNA binding of wild-type p53 is highly compromised if mutant p53 is present due to interaction of both p53 forms resulting in no direct effect on epigenetic marks.
| S-EPMC2585595 | biostudies-literature
Project description:BACKGROUND:Eukaryotic genome duplication starts at discrete sequences (replication origins) that coordinate cell cycle progression, ensure genomic stability and modulate gene expression. Origins share some sequence features, but their activity also responds to changes in transcription and cellular differentiation status. RESULTS:To identify chromatin states and histone modifications that locally mark replication origins, we profiled origin distributions in eight human cell lines representing embryonic and differentiated cell types. Consistent with a role of chromatin structure in determining origin activity, we found that cancer and non-cancer cells of similar lineages exhibited highly similar replication origin distributions. Surprisingly, our study revealed that DNase hypersensitivity, which often correlates with early replication at large-scale chromatin domains, did not emerge as a strong local determinant of origin activity. Instead, we found that two distinct sets of chromatin modifications exhibited strong local associations with two discrete groups of replication origins. The first origin group consisted of about 40,000 regions that actively initiated replication in all cell types and preferentially colocalized with unmethylated CpGs and with the euchromatin markers, H3K4me3 and H3K9Ac. The second group included origins that were consistently active in cells of a single type or lineage and preferentially colocalized with the heterochromatin marker, H3K9me3. Shared origins replicated throughout the S-phase of the cell cycle, whereas cell-type-specific origins preferentially replicated during late S-phase. CONCLUSIONS:These observations are in line with the hypothesis that differentiation-associated changes in chromatin and gene expression affect the activation of specific replication origins.
| S-EPMC4862150 | biostudies-literature
Project description:The use of low dose hypomethylating agents for patients with myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) has had made a significant impact. In the past, therapies for these diseases were limited and patients who elected to receive treatment were subject to highly toxic, inpatient chemotherapeutics, which were often ineffective. In the era of hypomethylating agents (azacitidine and decitabine), a patient with high grade MDS or AML with multilineage dysplasia can be offered the alternative of outpatient, relatively low-toxicity therapy. Despite the fact that CR (CR) rates to such agents remain relatively low at 15-20%, a much larger percentage of patients will have clinically significant improvements in hemoglobin, platelet, and neutrophil counts while maintaining good outpatient quality of life. As our clinical experience with azanucleotides expands, questions regarding patient selection, optimal dosing strategy, latency to best response and optimal duration of therapy following disease progression remain, but there is no question that for some patients these agents offer, for a time, an almost miraculous clinical benefit. Ongoing clinical trials in combination and in sequence with conventional therapeutics, with other epigenetically active agents, or in conjunction with bone marrow transplantation continue to provide promise for optimization of these agents for patients with myeloid disease. Although the mechanism(s) responsible for the proven efficacy of these agents remain a matter of some controversy, activity is thought to stem from induction of DNA hypomethylation, direct DNA damage, or possibly even immune modulation; there is no question that they have become a permanent part of the armamentarium against myeloid neoplasms.
| S-EPMC4086806 | biostudies-other
Project description:BackgroundTherapy-related, secondary acute myeloid leukemia (t-AML) is an increasingly frequent complication of intensive chemotherapy. This malignancy is often characterized by abnormalities of chromosome 7, including large deletions or chromosomal loss. A variety of studies suggest that decreased expression of the EZH2 gene located at 7q36.1 is critical in disease pathogenesis. This histone methyltransferase has been implicated in transcriptional repression through modifying histone H3 on lysine 27 (H3k27). However, the critical target genes of EZH2 and their regulatory roles remain unclear.MethodTo characterize the subset of EZH2 target genes that might contribute to t-AML pathogenesis, we developed a novel computational analysis to integrate tissue-specific histone modifications and genome-wide transcriptional regulation. Initial integrative analysis utilized a novel "seq2gene" strategy to explore largely the target genes of chromatin immuneprecipitation sequencing (ChIP-seq) enriched regions. By combining seq2gene with our Phenotype-Genotype-Network (PGNet) algorithm, we enriched genes with similar expression profiles and genomic or functional characteristics into "biomodules".ResultsInitial studies identified SEMA3A (semaphoring 3A) as a novel oncogenic candidate that is regulated by EZH2-silencing, using data derived from both normal and leukemic cell lines as well as murine cells deficient in EZH2. A microsatellite marker at the SEMA3A promoter has been associated with chemosensitivity and radiosensitivity. Notably, our subsequent studies in primary t-AML demonstrate an expected up-regulation of SEMA3A that is EZH2-modulated. Furthermore, we have identified three biomodules that are co-expressed with SEMA3A and up-regulated in t-AML, one of which consists of previously characterized EZH2-repressed gene targets. The other two biomodules include MAPK8 and TATA box targets. Together, our studies suggest an important role for EZH2 targets in t-AML pathogenesis that warrants further study.ConclusionThese developed computational algorithms and systems biology strategies will enhance the knowledge discovery and hypothesis-driven analysis of multiple next generation sequencing data, for t-AML and other complex diseases.
| S-EPMC4460748 | biostudies-literature
Project description:NB4 cells were treated with the 250 nM RPOTAC molecule CPS2 for 6 h before cell lysis. CDK2 stood out as the most down-regulated target.Quantitative analysis of the cells after treatment.
2020-09-21 | PXD021592 |
Project description:Acute myeloid leukemia (AML) is a typically lethal molecularly heterogeneous disease, with few broad-spectrum therapeutic targets. Unusually, most AML retain wild-type TP53, encoding the pro-apoptotic tumor suppressor p53. MDM2 inhibitors (MDM2i), which activate wild-type p53, and BET inhibitors (BETi), targeting the BET-family co-activator BRD4, both show encouraging pre-clinical activity, but limited clinical activity as single agents. Here, we report enhanced toxicity of combined MDM2i and BETi towards AML cell lines, primary human blasts and mouse models, resulting from BETi's ability to evict an unexpected repressive form of BRD4 from p53 target genes, and hence potentiate MDM2i-induced p53 activation. These results indicate that wild-type TP53 and a transcriptional repressor function of BRD4 together represent a potential broad-spectrum synthetic therapeutic vulnerability for AML.
| S-EPMC7801601 | biostudies-literature