Consequences of mutant TET2 on clonality and subclonal hierarchy.
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ABSTRACT:
SUBMITTER: Hirsch CM
PROVIDER: S-EPMC8673139 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Acute myeloid leukemia (AML) is a heterogeneous clonal disease characterized by the proliferation and accumulation of myeloid blast cells in the bone marrow, which eventually lead to hematopoietic failure. Chemoresistance presents as a major burden for therapy of AML patients. p53 is the most important tumor suppressor protein that regulates cellular response to various stress. It is also important for hematopoietic stem cell development and hematopoiesis. Mutation or deletion of TP53 has been found to be linked to cancer progression, therapy-related resistance, and poor prognosis. TP53 mutation occurs in less than 10% of AML patients; however, it represents a subset of AML with therapy resistance and poor outcome. In addition, there is a subgroup of patients with low-frequency TP53 mutations. The percentage ranges from 1% to 3% of all AML patients. These patients have outcomes comparable to those of the high-frequency TP53 mutation patients. TP53-mutated clones isolated from the parental cells exhibit a survival advantage under drug treatment compared with cells with wild-type TP53, and have a higher population of leukemia stem cell (LSC) marker-positive cells, a characteristic of chemo-resistant cells. Therefore, low-frequency TP53 mutation, which is currently underappreciated, is an important prognosis factor for AML patients. Epigenetic drugs, such as hypomethylating agent and histone deacetylase inhibitors, have been found effective in targeting TP53-mutated AML. Histone deacetylase inhibitors can preferentially target the TP53-mutated subpopulation by reactivating p53-targeted genes and by eradicating LSC marker-positive cells. Therefore, combined treatment with epigenetic drugs may represent a new therapeutic strategy for treatments of TP53-mutated AML.
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Project description:Recent improvements in next-generation sequencing of tumor samples and the ability to identify somatic mutations at low allelic fractions have opened the way for new approaches to model the evolution of individual cancers. The power and utility of these models is increased when tumor samples from multiple sites are sequenced. Temporal ordering of the samples may provide insight into the etiology of both primary and metastatic lesions and rationalizations for tumor recurrence and therapeutic failures. Additional insights may be provided by temporal ordering of evolving subclones--cellular subpopulations with unique mutational profiles. Current methods for subclone hierarchy inference tightly couple the problem of temporal ordering with that of estimating the fraction of cancer cells harboring each mutation. We present a new framework that includes a rigorous statistical hypothesis test and a collection of tools that make it possible to decouple these problems, which we believe will enable substantial progress in the field of subclone hierarchy inference. The methods presented here can be flexibly combined with methods developed by others addressing either of these problems. We provide tools to interpret hypothesis test results, which inform phylogenetic tree construction, and we introduce the first genetic algorithm designed for this purpose. The utility of our framework is systematically demonstrated in simulations. For most tested combinations of tumor purity, sequencing coverage, and tree complexity, good power (≥ 0.8) can be achieved and Type 1 error is well controlled when at least three tumor samples are available from a patient. Using data from three published multi-region tumor sequencing studies of (murine) small cell lung cancer, acute myeloid leukemia, and chronic lymphocytic leukemia, in which the authors reconstructed subclonal phylogenetic trees by manual expert curation, we show how different configurations of our tools can identify either a single tree in agreement with the authors, or a small set of trees, which include the authors' preferred tree. Our results have implications for improved modeling of tumor evolution and the importance of multi-region tumor sequencing.
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Project description:TET2 is a close relative of TET1, an enzyme that converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. The gene encoding TET2 resides at chromosome 4q24, in a region showing recurrent microdeletions and copy-neutral loss of heterozygosity (CN-LOH) in patients with diverse myeloid malignancies. Somatic TET2 mutations are frequently observed in myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), MDS/MPN overlap syndromes including chronic myelomonocytic leukaemia (CMML), acute myeloid leukaemias (AML) and secondary AML (sAML). We show here that TET2 mutations associated with myeloid malignancies compromise catalytic activity. Bone marrow samples from patients with TET2 mutations displayed uniformly low levels of 5hmC in genomic DNA compared to bone marrow samples from healthy controls. Moreover, small hairpin RNA (shRNA)-mediated depletion of Tet2 in mouse haematopoietic precursors skewed their differentiation towards monocyte/macrophage lineages in culture. There was no significant difference in DNA methylation between bone marrow samples from patients with high 5hmC versus healthy controls, but samples from patients with low 5hmC showed hypomethylation relative to controls at the majority of differentially methylated CpG sites. Our results demonstrate that Tet2 is important for normal myelopoiesis, and suggest that disruption of TET2 enzymatic activity favours myeloid tumorigenesis. Measurement of 5hmC levels in myeloid malignancies may prove valuable as a diagnostic and prognostic tool, to tailor therapies and assess responses to anticancer drugs.
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Project description:Clonality is a pervasive feature of sessile organisms, but this form of asexual reproduction is thought to interfere with sexual fitness via the movement of gametes among the modules that comprise the clone. This within-clone movement of gametes is expected to reduce sexual fitness via mate limitation of male reproductive success and, in some cases, via the production of highly inbred (i.e., self-fertilized) offspring. However, clonality also results in the spatial expansion of the genetic individual (i.e., genet), and this should decrease distances gametes and sexually produced offspring must travel to avoid competing with other gametes and offspring from the same clone. The extent to which any negative effects of clonality on mating success might be offset by the positive effects of spatial expansion is poorly understood. Here, we develop spatially explicit models in which fitness was determined by the success of genets through their male and female sex functions. Our results indicate that clonality serves to increase sexual fitness when it is associated with the outward expansion of the genet. Our models further reveal that the main fitness benefit of clonal expansion might occur through the dispersal of offspring over a wider area compared with nonclonal phenotypes. We conclude that, instead of interfering with sexual reproduction, clonal expansion should often serve to enhance sexual fitness.
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Project description:Loss-of-function TET2 mutations (TET2MT) are common in myeloid neoplasia. TET2, a DNA dioxygenase, requires 2-oxoglutarate and Fe(II) to oxidize 5-methylcytosine. TET2MT thus result in hypermethylation and transcriptional repression. Ascorbic acid (AA) increases dioxygenase activity by facilitating Fe(III)/Fe(II) redox reaction and may alleviate some biological consequences of TET2MT by restoring dioxygenase activity. Here, we report the utility of AA in the prevention of TET2MT myeloid neoplasia (MN), clarify the mechanistic underpinning of the TET2-AA interactions, and demonstrate that the ability of AA to restore TET2 activity in cells depends on N- and C-terminal lysine acetylation and nature of TET2MT. Consequently, pharmacologic modulation of acetyltransferases and histone deacetylases may regulate TET dioxygenase-dependent AA effects. Thus, our study highlights the contribution of factors that may enhance or attenuate AA effects on TET2 and provides a rationale for novel therapeutic approaches including combinations of AA with class I/II HDAC inhibitor or sirtuin activators in TET2MT leukemia.
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Project description:Somatic TET2 mutations (TET2 MT) are frequent in myeloid neoplasia (MN), particularly chronic myelomonocytic leukemia (CMML). TET2 MT includes mostly loss-of-function/hypomorphic hits. Impaired TET2 activity skews differentiation of hematopoietic stem cells toward proliferating myeloid precursors. This study was prompted by the observation of frequent biallelic TET2 gene inactivations (biTET2 i ) in CMML. We speculated that biTET2 i might be associated with distinct clinicohematological features. We analyzed TET2 MT in 1045 patients with MN. Of 82 biTET2 i cases, 66 were biTET2 MT, 13 were hemizygous TET2 MT, and 3 were homozygous TET2 MT (uniparental disomy); the remaining patients (denoted biTET2 - hereafter) were either monoallelic TET2 MT (n = 96) or wild-type TET2 (n = 823). Truncation mutations were found in 83% of biTET2 i vs 65% of biTET2 - cases (P = .02). TET2 hits were founder lesions in 72% of biTET2 i vs 38% of biTET2 - cases (P < .0001). In biTET2 i , significantly concurrent hits included SRSF2 MT (33%; P < .0001) and KRAS/NRAS MT (16%; P = .03) as compared with biTET2 - When the first TET2 hit was ancestral in biTET2 i , the most common subsequent hits affected a second TET2 MT, followed by SRSF2 MT, ASXL1 MT, RAS MT, and DNMT3A MT BiTET2 i patients without any monocytosis showed an absence of SRSF2 MT BiTET2 i patients were older and had monocytosis, CMML, normal karyotypes, and lower-risk disease compared with biTET2 - patients. Hence, while a second TET2 hit occurred frequently, biTET2 i did not portend faster progression but rather determined monocytic differentiation, consistent with its prevalence in CMML. Additionally, biTET2 i showed lower odds of cytopenias and marrow blasts (≥5%) and higher odds of myeloid dysplasia and marrow hypercellularity. Thus, biTET2 i might represent an auxiliary assessment tool in MN.
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2011-04-15 | E-MEXP-3042 | biostudies-arrayexpress
Project description:Isocitrate dehydrogenase (IDH) genes 1 and 2 are frequently mutated in acute myeloid leukaemia (AML), low-grade glioma, cholangiocarcinoma (CC) and chondrosarcoma (CS). For AML, low-grade glioma and CC, mutant IDH status is associated with a DNA hypermethylation phenotype, implicating altered epigenome dynamics in the aetiology of these cancers. Here we show that the IDH variants in CS are also associated with a hypermethylation phenotype and display increased production of the oncometabolite 2-hydroxyglutarate, supporting the role of mutant IDH-produced 2-hydroxyglutarate as an inhibitor of TET-mediated DNA demethylation. Meta-analysis of the acute myeloid leukaemia, low-grade glioma, cholangiocarcinoma and CS methylation data identifies cancer-specific effectors within the retinoic acid receptor activation pathway among the hypermethylated targets. By analysing sequence motifs surrounding hypermethylated sites across the four cancer types, and using chromatin immunoprecipitation and western blotting, we identify the transcription factor EBF1 (early B-cell factor 1) as an interaction partner for TET2, suggesting a sequence-specific mechanism for regulating DNA methylation.
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Project description:Mutations in splicing factors are recurrent somatic alterations identified in myelodysplastic syndromes (MDS) and they frequently coincide with mutations in epigenetic factors. About 25% of patients present concurrent mutations in such pathways, suggesting a cooperative role in the pathogenesis of MDS. We focused on the splicing factor U2AF1 involved in the recognition of the 3' splice site during pre-mRNA splicing. Using a CRISPR/Cas9 system, we created heterozygous mice with a carboxy-terminal truncated U2af1 allele (U2af1mut/+), studied the U2af1mut/+ hematopoietic system, and did not observe any gross differences in both young (12-13 weeks) and old (23 months) U2af1mut/+ mice, except for a reduction in size of approximately 20%. However, hematopoietic stem/progenitor cells lacked reconstitution capacity in transplantation assays and displayed an aberrant RNA splicing by RNA sequencing. We also evaluated U2af1mut/+ in conjunction with Tet2-deficiency. Novel double mutant U2af1mut/+Tet2-/- mice showed increased monogranulocytic precursors. Hematopoietic stem/progenitor cells were also enhanced and presented functional and transcriptomic alterations. Nonetheless, U2af1mut/+Tet2-/- mice did not succumb to MDS disease over a 6-month observation period. Collectively, our data suggest that cooperation between mutant U2af1 and Tet2 loss is not sufficient for MDS initiation in mice.
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