The t(12;21)(p13;q22) translocation is the most frequently occurring single genetic abnormality in pediatric leukemia. This translocation results in the fusion of the ETV6 and RUNX1 genes. Since its discovery in the 1990s, the function of the ETV6-RUNX1 fusion gene has attracted intense interest. In this chapter, we will summarize current knowledge on the clinical significance of ETV6-RUNX1, the experimental models used to unravel its function in leukemogenesis, the identification of co-operating mutations and the mechanisms responsible for their acquisition, the function of the encoded transcription factor and finally, the future therapeutic approaches available to mitigate the associated disease.
Background and Aims Previous studies modelling human neural crest differentiation from stem cells have resulted in a low yield of sympathetic neurons. Our aim was to optimise a method for the differentiation of human embryonic stem cells (hESCs) to sympathetic neuron-like cells (SN) to model normal human SNS development. Results Using stromal-derived inducing activity (SDIA) of PA6 cells plus BMP4 and B27 supplements, the H9 hESC line was differentiated to neural crest stem-like cells and SN-like cells. After 7 days of PA6 cell coculture, mRNA expression of SNAIL and SOX-9 neural crest specifier genes and the neural marker peripherin (PRPH) increased. Expression of the pluripotency marker OCT 4 decreased, whereas TP53 and LIN28B expression remained high at levels similar to SHSY5Y and IMR32 neuroblastoma cell lines. A 5-fold increase in the expression of the catecholaminergic marker tyrosine hydroxylase (TH) and the noradrenergic marker dopamine betahydroxylase (DBH) was observed by day 7 of differentiation. Fluorescence-activated cell sorting for the neural crest marker p75, enriched for cells expressing p75, DBH, TH, and PRPH, was more specific than p75 neural crest stem cell (NCSC) microbeads. On day 28 post p75 sorting, dual immunofluorescence identified sympathetic neurons by PRPH and TH copositivity cells in 20% of the cell population. Noradrenergic sympathetic neurons, identified by copositivity for both PHOX2B and DBH, were present in 9.4% ± 5.5% of cells. Conclusions We have optimised a method for noradrenergic SNS development using the H9 hESC line to improve our understanding of normal human SNS development and, in a future work, the pathogenesis of neuroblastoma.
The single most frequent chromosomal translocation associated with childhood Acute Lymphoblastic Leukaemia is the t(12;21) rearrangement, that creates a fusion gene between TEL (ETV6) and AML1 (RUNX1). Although TEL-AML1 + patients have a very good prognosis, relapses occur in up to 20% of cases and many patients face long-term side effects of chemotherapy. Our laboratory has previously shown that TEL-AML1 regulates Signal Transducer and Activator of Transcription 3 (STAT3) activation, which is critical for survival of the leukaemic cells. In this study, inhibition of STAT3 in TEL-AML1 + cells results in decreased SMAD7 gene expression. SMAD7 is an antagonist of TGF-β signalling, functioning through a negative feedback mechanism, but is also known to function in other biological pathways. In order to investigate the role of SMAD7 in TEL-AML1 + leukaemia, lentiviral mediated SMAD7 knockdown was performed in human TEL-AML1 + cell lines. SMAD7 silencing inhibited proliferation of TEL-AML1 + cell lines, eventually leading to growth arrest and apoptosis. Furthermore, our data showed that this effect is not mediated through TGF-β signalling, indicating that SMAD7 was functioning through an alternative pathway. We also observed growth arrest following SMAD7 knockdown in other ALL and AML subtypes. Furthermore, silencing of SMAD7 in TEL-AML1 + ALL cells transplanted into immunodeficient mice impaired disease progression in vivo, resulting in prolonged disease latency. To investigate the essential pathways regulated by SMAD7 in these leukaemic cells, we performed RNA-sequencing analysis on TEL-AML1 + cells following SMAD7 knockdown. Global gene expression analysis revealed SMAD7 to be a regulator of cholesterol biosynthesis, a pathway critical for leukaemia cell survival. Our
The single most frequent chromosomal translocation associated with childhood ALL is the t(12;21) rearrangement that creates a fusion gene between TEL (ETV6) and AML1 (RUNX1). Although TEL-AML1+ patients have very good prognoses, relapses occur in up to 20% of patients and many patients face long-term side effects of chemotherapy. Recent data has shown that TEL-AML1 has a direct role in inducing signal transducer and activator of transcription 3 (STAT3) activation in human t(12;21) leukemia. This activation has been shown to transcriptionally induce MYC and is critical for survival of TEL-AML+ leukemia cells. Here, we demonstrate that STAT3 also regulates SMAD7 gene expression. SMAD7 is an antagonist of TGF-β signaling, functioning through a negative feedback mechanism, but is also known to function in other biological pathways. Interestingly, SMAD7 has also been shown to play a role in promoting self-renewal of hematopoietic stem cells. We show that both pharmacological and mechanistic inhibition of STAT3 results in down regulation of SMAD7 gene expression in TEL-AML1+ cell lines. This result was specific to TEL-AML1+ cells and not found in cells of other ALL subtypes. To understand the role played by SMAD7 in TEL-AML1+ cells, we used lentiviral vectors expressing shRNA targeting SMAD7. Interestingly, SMAD7 silencing was found to inhibit proliferation of TEL-AML1+ cell lines, eventually leading to growth arrest and apoptosis. Furthermore, we have established that this effect is not mediated through TGF-β signalling. This poster highlights the results of RNA-seq performed on TEL-AML1+ cells with SMAD7 knockdown and in vivo xenograft model of SMAD7 shRNA in TEL-AML+ ALL. Disclosures No relevant conflicts of interest to declare.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.