High-level IGF1R expression is required for leukemia-initiating cell activity in T-ALL and is supported by Notch signaling

Notch-driven expression of IGF1R promotes the growth, viability, and transplantability of T-ALL cells

Identification et étude de voies moléculaires oncogéniques dans les lymphomes et leucémies lymphoïdes

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

The Brain Pre-Metastatic Niche: Biological and Technical Advancements

Metastasis, particularly brain metastasis, continues to puzzle researchers to this day, and exploring its molecular basis promises to break ground in developing new strategies for combatting this deadly cancer. In recent years, the research focus has shifted toward the earliest steps in the formation of metastasis. In this regard, significant progress has been achieved in understanding how the primary tumor affects distant organ sites before the arrival of tumor cells. The term pre-metastatic niche was introduced for this concept and encompasses all influences on sites of future metastases, ranging from immunological modulation and ECM remodeling to the softening of the blood–brain barrier. The mechanisms governing the spread of metastasis to the brain remain elusive. However, we begin to understand these processes by looking at the earliest steps in the formation of metastasis. This review aims to present recent findings on the brain pre-metastatic niche and to discuss existing and emerging methods to further explore the field. We begin by giving an overview of the pre-metastatic and metastatic niches in general before focusing on their manifestations in the brain. To conclude, we reflect on the methods usually employed in this field of research and discuss novel approaches in imaging and sequencing

MiR144/451 expression is repressed by RUNX1 during megakaryopoiesis and disturbed by RUNX1/ETO

Abstract: A network of lineage-specific transcription factors and microRNAs tightly regulates differentiation of hematopoietic stem cells along the distinct lineages. Deregulation of this regulatory network contributes to impaired lineage fidelity and leukemogenesis. We found that the hematopoietic master regulator RUNX1 controls the expression of certain microRNAs, of importance during erythroid/megakaryocytic differentiation. In particular, we show that the erythorid miR144/451 cluster is epigenetically repressed by RUNX1 during megakaryopoiesis. Furthermore, the leukemogenic RUNX1/ETO fusion protein transcriptionally represses the miR144/451 pre-microRNA. Thus RUNX1/ETO contributes to increased expression of miR451 target genes and interferes with normal gene expression during differentiation. Furthermore, we observed that inhibition of RUNX1/ETO in Kasumi1 cells and in RUNX1/ETO positive primary acute myeloid leukemia patient samples leads to up-regulation of miR144/451. RUNX1 thus emerges as a key regulator of a microRNA network, driving differentiation at the megakaryocytic/erythroid branching point. The network is disturbed by the leukemogenic RUNX1/ETO fusion product. Author Summary: The regulatory network between transcription factors, epigenetic cofactors and microRNAs is decisive for normal hematopoiesis. The transcription factor RUNX1 is important for the establishment of a megakaryocytic gene expression program and the concomitant repression of erythroid genes during megakaryocytic differentiation. Gene regulation by RUNX1 is frequently disturbed by mutations and chromosomal translocations, such as the t(8;21) translocation, which gives rise to the leukemogenic RUNX1/ETO fusion protein. We found that RUNX1 regulates microRNAs, which are of importance at the megakaryocytic/erythroid branching point. Specifically, RUNX1 down-regulates expression of the microRNA cluster miR144/451 during megakaryocytic differentiation by changing the epigenetic histone modification pattern at the locus. We could show that miR451, one of the micorRNAs of the miR144/451 cluster, supports erythroid differentiation. We found that expression of miR451 is repressed by the RUNX1/ETO fusion protein, resulting in up regulation of miR451 target genes. Our data support the notion that RUNX1 suppresses the erythroid gene expression program including the erythroid microRNA miR451 and that the RUNX1/ETO fusion protein interferes with normal gene regulation by RUNX1

AKT-dependent NOTCH3 activation drives tumor progression in a model of mesenchymal colorectal cancer

Recently, a transcriptome-based consensus molecular subtype (CMS) classification of colorectal cancer (CRC) has been established, which may ultimately help to individualize CRC therapy. However, the lack of animal models that faithfully recapitulate the different molecular subtypes impedes adequate preclinical testing of stratified therapeutic concepts. Here, we demonstrate that constitutive AKT activation in intestinal epithelial cells markedly enhances tumor invasion and metastasis in Trp53ΔIEC mice (Trp53ΔIECAktE17K) upon challenge with the carcinogen azoxymethane. Gene-expression profiling indicates that Trp53ΔIECAktE17K tumors resemble the human mesenchymal colorectal cancer subtype (CMS4), which is characterized by the poorest survival rate among the four CMSs. Trp53ΔIECAktE17K tumor cells are characterized by Notch3 up-regulation, and treatment of Trp53ΔIECAktE17K mice with a NOTCH3-inhibiting antibody reduces invasion and metastasis. In CRC patients, NOTCH3 expression correlates positively with tumor grading and the presence of lymph node as well as distant metastases and is specifically up-regulated in CMS4 tumors. Therefore, we suggest NOTCH3 as a putative target for advanced CMS4 CRC patients.status: publishe

Inhibition of RUNX1/ETO increases miR144/451 expression.

<p><b>(A)</b> Expression of endogenous RUNX1/ETO in Kasumi1, SKNO1 and two RUNX/ETO positive patient samples. Expression of RUNX1/ETO in Kasumi1 cells was set as 1 and the expression levels of the SKNO1 cells and two patient samples are shown as fold compared to Kasumi1 cells. HEK293 and hCD34+ serve as RUNX1/ETO negative controls. Values were gathered by q-RT-PCR and normalised to GAPDH. <b>(B)</b> Expression of miR144/451 in Kasumi1, SKNO1 and two different patient samples. HEK293 and hCD34+ served as miR144/451 negative and positive controls, respectively. Q-RT-PCR values were normalised to GAPDH expression and are shown as fold relative to values gathered with Kasumi1 cells. <b>(C)</b> Knock-down of RUNX1/ETO in Kasumi1 cells. Knock-down of RUNX1/ETO by an shRNA targeting the R/E fusion site leads to increased miR144/451 expression. <b>(D)</b> Treatment of Kasumi1 cells with trichostatin-A (TSA) leads to degradation of RUNX1/ETO. Kasumi1 cells were treated with the indicated concentrations of TSA for 24 hours. Protein expression was determined by Western blot using an anti-ETO antibody. R/E runs at about 100 kD. As loading control (l.c.) a protein band running at 55 kD visible upon Ponceau S staining of the membrane is shown. <b>(E)</b> MiR144/451 expression is up-regulated in Kasumi1 cells upon TSA treatment. MiR144/451 expression upon treatment with TSA was measured by q-RT-PCR. Values were normalised to GAPDH expression. <b>(F)</b> MiR144/451 expression is up-regulated in patient samples upon TSA treatment. Cells were treated with 1 uM TSA for 24 hours. Q-RT-PCR values were normalised to GAPDH expression. Q-RT-PCR against RUNX/ETO was performed with specific primers detecting the fusion protein. Error bars give the standard deviation from at least four independent determinations. The P-values were calculated using Student’s t test. **P <0.01, ***P <0.001.</p

Identification of RUNX1 regulated microRNAs.

<p><b>(A)</b> Schematic representation of the experimental setup. K562 cells were transduced with RUNX1 expression vector or empty vector control. The transductions were performed in independent triplicates and differentially expressed microRNAs were determined by small-RNA sequencing. <b>(B)</b> 588 small RNAs were differentially expressed upon RUNX1 expression in K562 cells. 31 were snRNAs (small nuclear RNA), 45 rRNAs (ribosomal RNA), 142 snoRNAs (small nucleolar RNA) and 370 microRNAs. RNAs were included if they displayed an at least -0.5 or +0.5 log2-fold change and a P-value <0.05. <b>(C)</b> Of the 370 identified microRNAs, 237 were up-regulated and 133 down-regulated upon RUNX1 expression. <b>(D)</b> Schematic representation of hematopoiesis from the stem cell throughout the myeloid lineage. Those microRNAs are shown, which were altered upon RUNX1 over-expression. The green arrow indicates a positive role and the red blunted arrow indicates a negative role in differentiation according to published work. HSC: hematopoietic stem cell, MPP: multipotent progenitor, CMP: common myeloid progenitor, GMP: granulocyte monocyte progenitor, MEP: megakaryocyte erythrocyte progenitor, MkP: megakaryocyte progenitor, EP: erythrocyte progenitor. <b>(E)</b> Independent evaluation of microRNA expression. A subset of mature microRNAs influenced by RUNX1 and with a role in myeloid differentiation identified by RNA-sequencing, was tested by q-RT-PCR. Q-RT-PCR values are given as relative expression of RUNX1 transduced K562 cells, compared to K562 cells transduced with empty vector. Values were normalised to RNU6-2 expression. The error bars give the standard deviation from four independent determinations. All values were significantly different from the control according to Student’s t test P <0.05. <b>(F)</b> RUNX1 over-expression leads to a decrease of miR144/451 (pri-microRNA) transcript. Q-RT-PCR values are shown as fold expression compared to empty vector transduced K562 cells. Error bars represent the standard deviation from four independent determinations. The P-value was calculated using Student’s t test. **P <0.01.</p