Blast cells surviving acute myeloid leukemia induction therapy are in cycle with a signature of FOXM1 activity

From Springer Nature via Jisc Publications RouterHistory: received 2020-12-01, accepted 2021-10-05, registration 2021-10-06, pub-electronic 2021-10-28, online 2021-10-28, collection 2021-12Publication status: PublishedFunder: Cancer Research UK; doi: http://dx.doi.org/10.13039/501100000289; Grant(s): C5759/A20971Funder: Kay Kendall Leukaemia Fund; doi: http://dx.doi.org/10.13039/501100000402; Grant(s): KKL954Funder: Christie Charity; doi: http://dx.doi.org/10.13039/100013684; Grant(s): NAFunder: Imago Biosciences; Grant(s): NAFunder: cancer research uk; Grant(s): A27412Funder: blood cancer ukFunder: the oglesby charitable trustAbstract: Background: Disease relapse remains common following treatment of acute myeloid leukemia (AML) and is due to chemoresistance of leukemia cells with disease repopulating potential. To date, attempts to define the characteristics of in vivo resistant blasts have focused on comparisons between leukemic cells at presentation and relapse. However, further treatment responses are often seen following relapse, suggesting that most blasts remain chemosensitive. We sought to characterise in vivo chemoresistant blasts by studying the transcriptional and genetic features of blasts from before and shortly after induction chemotherapy using paired samples from six patients with primary refractory AML. Methods: Leukemic blasts were isolated by fluorescence-activated cell sorting. Fluorescence in situ hybridization (FISH), targeted genetic sequencing and detailed immunophenotypic analysis were used to confirm that sorted cells were leukemic. Sorted blasts were subjected to RNA sequencing. Lentiviral vectors expressing short hairpin RNAs were used to assess the effect of FOXM1 knockdown on colony forming capacity, proliferative capacity and apoptosis in cell lines, primary AML cells and CD34+ cells from healthy donors. Results: Molecular genetic analysis revealed early clonal selection occurring after induction chemotherapy. Immunophenotypic characterisation found leukemia-associated immunophenotypes in all cases that persisted following treatment. Despite the genetic heterogeneity of the leukemias studied, transcriptional analysis found concerted changes in gene expression in resistant blasts. Remarkably, the gene expression signature suggested that post-chemotherapy blasts were more proliferative than those at presentation. Resistant blasts also appeared less differentiated and expressed leukemia stem cell (LSC) maintenance genes. However, the proportion of immunophenotypically defined LSCs appeared to decrease following treatment, with implications for the targeting of these cells on the basis of cell surface antigen expression. The refractory gene signature was highly enriched with targets of the transcription factor FOXM1. shRNA knockdown experiments demonstrated that the viability of primary AML cells, but not normal CD34+ cells, depended on FOXM1 expression. Conclusions: We found that chemorefractory blasts from leukemias with varied genetic backgrounds expressed a common transcriptional program. In contrast to the notion that LSC quiescence confers resistance to chemotherapy we find that refractory blasts are both actively proliferating and enriched with LSC maintenance genes. Using primary patient material from a relevant clinical context we also provide further support for the role of FOXM1 in chemotherapy resistance, proliferation and stem cell function in AML

EVI1 oncoprotein expression and CtBP1-association oscillate through the cell cycle

From Springer Nature via Jisc Publications RouterHistory: received 2020-06-18, registration 2020-09-07, accepted 2020-09-07, pub-electronic 2020-09-26, online 2020-09-26, pub-print 2020-10Publication status: PublishedFunder: Bloodwise; doi: http://dx.doi.org/10.13039/501100007903; Grant(s): 150380, 10037, 19007Funder: Kay Kendall Leukaemia Fund; doi: http://dx.doi.org/10.13039/501100000402; Grant(s): 792Funder: Cancer Research UK; doi: http://dx.doi.org/10.13039/501100000289; Grant(s): C18601/A5901, C5759/A20971Funder: Children's Cancer and Leukaemia Group; doi: http://dx.doi.org/10.13039/100011692; Grant(s): Toti Worboys Leukaemia ProjectFunder: University of ManchesterAbstract: Aberrantly high expression of EVI1 in acute myeloid leukaemia (AML) is associated with poor prognosis. For targeted treatment of EVI1 overexpressing AML a more detailed understanding of aspects of spatiotemporal interaction dynamics of the EVI1 protein is important. EVI1 overexpressing SB1690CB AML cells were used for quantification and protein interaction studies of EVI1 and ΔEVI1. Cells were cell cycle-synchronised by mimosine and nocodazole treatment and expression of EVI1 and related proteins assessed by western blot, immunoprecipitation and immunofluorescence. EVI1 protein levels oscillate through the cell cycle, and EVI1 is degraded partly by the proteasome complex. Both EVI1 and ΔEVI1 interact with the co-repressor CtBP1 but dissociate from CtBP1 complexes during mitosis. Furthermore, a large fraction of EVI1, but not ΔEVI1 or CtBP1, resides in the nuclear matrix. In conclusion, EVI1- protein levels and EVI1-CtBP1 interaction dynamics vary though the cell cycle and differ between EVI1 and ΔEVI1. These data ad to the functional characterisation of the EVI1 protein in AML and will be important for the development of targeted therapeutic approaches for EVI1-driven AML

HMG20B stabilizes association of LSD1 with GFI1 on chromatin to confer transcription repression and leukemia cell differentiation block

Pharmacologic inhibition of LSD1 induces molecular and morphologic differentiation of blast cells in acute myeloid leukemia (AML) patients harboring MLL gene translocations. In addition to its demethylase activity, LSD1 has a critical scaffolding function at genomic sites occupied by the SNAG domain transcription repressor GFI1. Importantly, inhibitors block both enzymatic and scaffolding activities, in the latter case by disrupting the protein:protein interaction of GFI1 with LSD1. To explore the wider consequences of LSD1 inhibition on the LSD1 protein complex we applied mass spectrometry technologies. We discovered that the interaction of the HMG-box protein HMG20B with LSD1 was also disrupted by LSD1 inhibition. Downstream investigations revealed that HMG20B is co-located on chromatin with GFI1 and LSD1 genome-wide; the strongest HMG20B binding co-locates with the strongest GFI1 and LSD1 binding. Functional assays demonstrated that HMG20B depletion induces leukemia cell differentiation and further revealed that HMG20B is required for the transcription repressor activity of GFI1 through stabilizing LSD1 on chromatin at GFI1 binding sites. Interaction of HMG20B with LSD1 is through its coiled-coil domain. Thus, HMG20B is a critical component of the GFI1:LSD1 transcription repressor complex which contributes to leukemia cell differentiation block

Divergent clonal evolution of blastic plasmacytoid dendritic cell neoplasm and chronic myelomonocytic leukemia from a shared TET2-mutated origin

From Springer Nature via Jisc Publications RouterHistory: received 2020-11-25, rev-recd 2021-02-15, accepted 2021-03-11, registration 2021-03-12, pub-electronic 2021-04-08, online 2021-04-08, pub-print 2021-11Publication status: PublishedFunder: Oglesby Charitable TrustFunder: Pickering family donationFunder: Blood Cancer UK Clinician Scientist Fellowship (15030) Oglesby Charitable Trus

Phosphorylation of the Leukemic Oncoprotein EVI1 on Serine 196 Modulates DNA Binding, Transcriptional Repression and Transforming Ability

The EVI1 (ecotropic viral integration site 1) gene at 3q26 codes for a transcriptional regulator with an essential role in haematopoiesis. Overexpression of EVI1 in acute myeloid leukaemia (AML) is frequently associated with 3q26 rearrangements and confers extremely poor prognosis. EVI1 mediates transcriptional regulation, signalling, and epigenetic modifications by interacting with DNA, proteins and protein complexes. To explore to what extent protein phosphorylation impacts on EVI1 functions, we analysed endogenous EVI1 protein from a high EVI1 expressing Fanconi anaemia (FA) derived AML cell line. Mass spectrometric analysis of immunoprecipitated EVI1 revealed phosphorylation at serine 196 (S196) in the sixth zinc finger of the N-terminal zinc finger domain. Mutated EVI1 with an aspartate substitution at serine 196 (S196D), which mimics serine phosphorylation of this site, exhibited reduced DNA-binding and transcriptional repression from a gene promotor selectively targeted by the N-terminal zinc finger domain. Forced expression of the S196D mutant significantly reduced EVI1 mediated transformation of Rat1 fibroblasts. While EVI1-mediated serial replating of murine haematopoietic progenitors was maintained by EVI1-S196D, this was associated with significantly higher Evi1-trancript levels compared with WT-EVI1 or EVI1-S196A, mimicking S196 non-phosphorylated EVI1. These data suggest that EVI1 function is modulated by phosphorylation of the first zinc finger domain

EVI1 phosphorylation at S436 regulates interactions with CtBP1 and DNMT3A and promotes self-renewal

From Springer Nature via Jisc Publications RouterHistory: received 2020-04-03, rev-recd 2020-08-02, accepted 2020-08-03, collection 2020-10, registration 2020-10-08, pub-electronic 2020-10-20, online 2020-10-20Publication status: PublishedFunder: Bloodwise; doi: https://doi.org/10.13039/501100007903; Grant(s): 10037, 150380, 19007Funder: Cancer Research UK (CRUK); doi: https://doi.org/10.13039/501100000289; Grant(s): C5759/A20971, C18601/A5901Funder: Kay Kendall Leukaemia Fund (KKLF); doi: https://doi.org/10.13039/501100000402; Grant(s): KKL 792Funder: CHILDREN with CANCER UK; doi: https://doi.org/10.13039/501100001273; Grant(s): 201609Funder: Kuweit Ministry of EducationFunder: Deutsche Forschungsgemeinschaft (German Research Foundation); doi: https://doi.org/10.13039/501100001659; Grant(s): EXC 62/1Abstract: The transcriptional regulator EVI1 has an essential role in early development and haematopoiesis. However, acute myeloid leukaemia (AML) driven by aberrantly high EVI1 expression has very poor prognosis. To investigate the effects of post-translational modifications on EVI1 function, we carried out a mass spectrometry (MS) analysis of EVI1 in AML and detected dynamic phosphorylation at serine 436 (S436). Wild-type EVI1 (EVI1-WT) with S436 available for phosphorylation, but not non-phosphorylatable EVI1-S436A, conferred haematopoietic progenitor cell self-renewal and was associated with significantly higher organised transcriptional patterns. In silico modelling of EVI1-S436 phosphorylation showed reduced affinity to CtBP1, and CtBP1 showed reduced interaction with EVI1-WT compared with EVI1-S436A. The motif harbouring S436 is a target of CDK2 and CDK3 kinases, which interacted with EVI1-WT. The methyltransferase DNMT3A bound preferentially to EVI1-WT compared with EVI1-S436A, and a hypomethylated cell population associated by EVI1-WT expression in murine haematopoietic progenitors is not maintained with EVI1-S436A. These data point to EVI1-S436 phosphorylation directing functional protein interactions for haematopoietic self-renewal. Targeting EVI1-S436 phosphorylation may be of therapeutic benefit when treating EVI1-driven leukaemia

Results of a national UK physician reported survey of COVID-19 infection in patients with a myeloproliferative neoplasm

Funder: Cancer Research UK (CRUK); doi: https://doi.org/10.13039/501100000289Funder: DH | National Institute for Health Research (NIHR); doi: https://doi.org/10.13039/50110000027

Tissue-inappropriate derepression of FOXC1 is frequent and functional in human acute myeloid leukemia

Tissue-inappropriate derepression of the mesenchymal transcription factor gene Forkhead Box C1 (FOXC1) occurs in approximately 20% of patients with acute myeloid leukemia. Through experimental and bioinformatics analyses, we have demonstrated this to be both functional (enhancing the myeloid lineage differentiation block characteristic of the disease) and adversely prognostic

The Diverse Consequences of FOXC1 Deregulation in Cancer

Forkhead box C1 (FOXC1) is a transcription factor with essential roles in mesenchymal lineage specification and organ development during normal embryogenesis. In keeping with these developmental properties, mutations that impair the activity of FOXC1 result in the heritable Axenfeld-Rieger Syndrome and other congenital disorders. Crucially, gain of FOXC1 function is emerging as a recurrent feature of malignancy; FOXC1 overexpression is now documented in more than 16 cancer types, often in association with an unfavorable prognosis. This review explores current evidence for FOXC1 deregulation in cancer and the putative mechanisms by which FOXC1 confers its oncogenic effects