Project description:Mouse haematopoietic stem cells (HSCs) undergo a post-natal transition in several properties, including a marked reduction in their self-renewal activity. We now show that the developmentally timed change in this key function of HSCs is associated with their decreased expression of Lin28b and an accompanying increase in their let-7 microRNA levels. Lentivirus(LV)-mediated overexpression of Lin28 in adult HSCs elevates their self-renewal activity in transplanted irradiated hosts, as does overexpression of Hmga2, a well-established let-7 target that is upregulated in fetal HSCs. Conversely, HSCs from fetal Hmga2-/- mice do not display the heightened self-renewal activity that is characteristic of wild-type fetal HSCs. Interestingly, overexpression of Hmga2 in adult HSCs does not mimic the ability of elevated Lin28 to activate a fetal lymphoid differentiation program. Thus Lin28b may act as a master regulator of developmentally timed changes in HSC programs with Hmga2 serving as its specific downstream modulator of HSC self-renewal potential. Lin-Sca1+cKit+ cells were isolated from E14.5 fetal livers (of wild-type of Hmga2-/- embryos) or the bone marrow of 8-12 week old mice by fluorescence activated cell sorting. The RNA was extracted and hybridized on Affymetrix mpuse gene 1.0 ST microarrays.
Project description:Mouse haematopoietic stem cells (HSCs) undergo a post-natal transition in several properties, including a marked reduction in their self-renewal activity. We now show that the developmentally timed change in this key function of HSCs is associated with their decreased expression of Lin28b and an accompanying increase in their let-7 microRNA levels. Lentivirus(LV)-mediated overexpression of Lin28 in adult HSCs elevates their self-renewal activity in transplanted irradiated hosts, as does overexpression of Hmga2, a well-established let-7 target that is upregulated in fetal HSCs. Conversely, HSCs from fetal Hmga2-/- mice do not display the heightened self-renewal activity that is characteristic of wild-type fetal HSCs. Interestingly, overexpression of Hmga2 in adult HSCs does not mimic the ability of elevated Lin28 to activate a fetal lymphoid differentiation program. Thus Lin28b may act as a master regulator of developmentally timed changes in HSC programs with Hmga2 serving as its specific downstream modulator of HSC self-renewal potential.
Project description:Juvenile myelomonocytic leukemia (JMML) is a very rare and aggressive stem cell disease that mainly occurs in young children. RAS activation constitutes the core component of oncogenic signaling. In addition, the leukemic blasts of a quarter of JMML patients present with monosomy 7 (-7), whereas more than half of the patients show enhanced age-adjusted fetal hemoglobin (HbF) levels. Hematopoietic stem cell transplantation is the current standard of care. This results in an event-free survival of 50 - 60%, indicating that novel molecular driven therapeutic options are urgently needed. Using gene expression profiling in an extensive series of 82 patient samples, we aimed at understanding the molecular biology behind JMML and identified a previously unrecognized molecular subgroup characterized by high LIN28B expression. Interestingly, LIN28B overexpression was significantly correlated with higher HbF levels whereas patients with -7 seldom showed enhanced LIN28B expression. In line with LIN28Bâ??s role as mediator of fetal hematopoiesis, this explains the biology behind the observation that patients with -7 are rarely diagnosed with high age-adjusted HbF levels. In addition, this new fetal-like JMML subgroup presented with reduced levels of most members of the let-7 microRNA family and showed characteristic overexpression of genes involved in fetal hematopoiesis and stem cell self-renewal. Finally, high LIN28B expression was associated with poor clinical outcome in our JMML patient series, but not independent from other prognostic factors such as age and age-adjusted HbF levels. In conclusion, we identified LIN28B as a crucial molecular player at the heart of a novel fetal-like subgroup in JMML. Gene expression was measured on Affymetrix in 38 JMML patients and 9 healthy donors in a validation cohort.
Project description:Juvenile myelomonocytic leukemia (JMML) is a very rare and aggressive stem cell disease that mainly occurs in young children. RAS activation constitutes the core component of oncogenic signaling. In addition, the leukemic blasts of a quarter of JMML patients present with monosomy 7 (-7), whereas more than half of the patients show enhanced age-adjusted fetal hemoglobin (HbF) levels. Hematopoietic stem cell transplantation is the current standard of care. This results in an event-free survival of 50 - 60%, indicating that novel molecular driven therapeutic options are urgently needed. Using gene expression profiling in an extensive series of 82 patient samples, we aimed at understanding the molecular biology behind JMML and identified a previously unrecognized molecular subgroup characterized by high LIN28B expression. Interestingly, LIN28B overexpression was significantly correlated with higher HbF levels whereas patients with -7 seldom showed enhanced LIN28B expression. In line with LIN28Bâ??s role as mediator of fetal hematopoiesis, this explains the biology behind the observation that patients with -7 are rarely diagnosed with high age-adjusted HbF levels. In addition, this new fetal-like JMML subgroup presented with reduced levels of most members of the let-7 microRNA family and showed characteristic overexpression of genes involved in fetal hematopoiesis and stem cell self-renewal. Finally, high LIN28B expression was associated with poor clinical outcome in our JMML patient series, but not independent from other prognostic factors such as age and age-adjusted HbF levels. In conclusion, we identified LIN28B as a crucial molecular player at the heart of a novel fetal-like subgroup in JMML. Gene expression was measured on Agilent in 44 JMML patients and 7 healthy donors in the discovery cohort. A validation cohort of 38 patients and 9 healthy donors was measured on Affymetrix. All patient data can be found in Supplementary Table S1.
Project description:Juvenile myelomonocytic leukemia (JMML) is a very rare and aggressive stem cell disease that mainly occurs in young children. RAS activation constitutes the core component of oncogenic signaling. In addition, the leukemic blasts of a quarter of JMML patients present with monosomy 7 (-7), whereas more than half of the patients show enhanced age-adjusted fetal hemoglobin (HbF) levels. Hematopoietic stem cell transplantation is the current standard of care. This results in an event-free survival of 50 - 60%, indicating that novel molecular driven therapeutic options are urgently needed. Using gene expression profiling in an extensive series of 82 patient samples, we aimed at understanding the molecular biology behind JMML and identified a previously unrecognized molecular subgroup characterized by high LIN28B expression. Interestingly, LIN28B overexpression was significantly correlated with higher HbF levels whereas patients with -7 seldom showed enhanced LIN28B expression. In line with LIN28B’s role as mediator of fetal hematopoiesis, this explains the biology behind the observation that patients with -7 are rarely diagnosed with high age-adjusted HbF levels. In addition, this new fetal-like JMML subgroup presented with reduced levels of most members of the let-7 microRNA family and showed characteristic overexpression of genes involved in fetal hematopoiesis and stem cell self-renewal. Finally, high LIN28B expression was associated with poor clinical outcome in our JMML patient series, but not independent from other prognostic factors such as age and age-adjusted HbF levels. In conclusion, we identified LIN28B as a crucial molecular player at the heart of a novel fetal-like subgroup in JMML.
Project description:Juvenile myelomonocytic leukemia (JMML) is a very rare and aggressive stem cell disease that mainly occurs in young children. RAS activation constitutes the core component of oncogenic signaling. In addition, the leukemic blasts of a quarter of JMML patients present with monosomy 7 (-7), whereas more than half of the patients show enhanced age-adjusted fetal hemoglobin (HbF) levels. Hematopoietic stem cell transplantation is the current standard of care. This results in an event-free survival of 50 - 60%, indicating that novel molecular driven therapeutic options are urgently needed. Using gene expression profiling in an extensive series of 82 patient samples, we aimed at understanding the molecular biology behind JMML and identified a previously unrecognized molecular subgroup characterized by high LIN28B expression. Interestingly, LIN28B overexpression was significantly correlated with higher HbF levels whereas patients with -7 seldom showed enhanced LIN28B expression. In line with LIN28B’s role as mediator of fetal hematopoiesis, this explains the biology behind the observation that patients with -7 are rarely diagnosed with high age-adjusted HbF levels. In addition, this new fetal-like JMML subgroup presented with reduced levels of most members of the let-7 microRNA family and showed characteristic overexpression of genes involved in fetal hematopoiesis and stem cell self-renewal. Finally, high LIN28B expression was associated with poor clinical outcome in our JMML patient series, but not independent from other prognostic factors such as age and age-adjusted HbF levels. In conclusion, we identified LIN28B as a crucial molecular player at the heart of a novel fetal-like subgroup in JMML.
Project description:Juvenile myelomonocytic leukemia (JMML) is a very rare and aggressive stem cell disease that mainly occurs in young children. RAS activation constitutes the core component of oncogenic signaling. In addition, the leukemic blasts of a quarter of JMML patients present with monosomy 7 (-7), whereas more than half of the patients show enhanced age-adjusted fetal hemoglobin (HbF) levels. Hematopoietic stem cell transplantation is the current standard of care. This results in an event-free survival of 50 - 60%, indicating that novel molecular driven therapeutic options are urgently needed. Using gene expression profiling in an extensive series of 82 patient samples, we aimed at understanding the molecular biology behind JMML and identified a previously unrecognized molecular subgroup characterized by high LIN28B expression. Interestingly, LIN28B overexpression was significantly correlated with higher HbF levels whereas patients with -7 seldom showed enhanced LIN28B expression. In line with LIN28B’s role as mediator of fetal hematopoiesis, this explains the biology behind the observation that patients with -7 are rarely diagnosed with high age-adjusted HbF levels. In addition, this new fetal-like JMML subgroup presented with reduced levels of most members of the let-7 microRNA family and showed characteristic overexpression of genes involved in fetal hematopoiesis and stem cell self-renewal. Finally, high LIN28B expression was associated with poor clinical outcome in our JMML patient series, but not independent from other prognostic factors such as age and age-adjusted HbF levels. In conclusion, we identified LIN28B as a crucial molecular player at the heart of a novel fetal-like subgroup in JMML.
Project description:Chromatin remodeling proteins are frequently dysregulated in human cancer, yet little is known about how they control tumorigenesis. Here, we uncover an epigenetic program mediated by the NAD+-dependent histone deacetylase Sirtuin 6 (SIRT6) that is critical for suppression of pancreatic ductal adenocarcinoma (PDAC), one of the most lethal malignancies. SIRT6 inactivation accelerates PDAC progression and metastasis via upregulation of Lin28b, a negative regulator of the let-7 microRNA. SIRT6 loss results in histone hyperacetylation at the Lin28b promoter, Myc recruitment, and pronounced induction of Lin28b and downstream let-7 target genes, HMGA2, IGF2BP1 and IGF2BP3. This epigenetic program defines a distinct subset representing 30-40% of human PDAC, characterized by poor prognosis and an exquisite dependence on Lin28b for tumor growth. Thus, we identify SIRT6 as an important PDAC tumor suppressor, and uncover the Lin28b pathway as a potential therapeutic target in a molecularlydefined PDAC subset. Small RNA-Seq experiments for PLKO and shLIN28B (three replicates each) in human Panc3.27 PDAC cells to identify miRNAs modulateed by LIN28B knockdown.
Project description:Chromatin remodeling proteins are frequently dysregulated in human cancer, yet little is known about how they control tumorigenesis. Here, we uncover an epigenetic program mediated by the NAD+-dependent histone deacetylase Sirtuin 6 (SIRT6) that is critical for suppression of pancreatic ductal adenocarcinoma (PDAC), one of the most lethal malignancies. SIRT6 inactivation accelerates PDAC progression and metastasis via upregulation of Lin28b, a negative regulator of the let-7 microRNA. SIRT6 loss results in histone hyperacetylation at the Lin28b promoter, Myc recruitment, and pronounced induction of Lin28b and downstream let-7 target genes, HMGA2, IGF2BP1 and IGF2BP3. This epigenetic program defines a distinct subset representing 30-40% of human PDAC, characterized by poor prognosis and an exquisite dependence on Lin28b for tumor growth. Thus, we identify SIRT6 as an important PDAC tumor suppressor, and uncover the Lin28b pathway as a potential therapeutic target in a molecularlydefined PDAC subset. ChIP-Seq experiments to examine H3K56ac histone modifications in murine PDAC cells that are Sirt6 wild type (WT), Sirt6 knock-out (KO), and Sirt6 KO cells engineered to express Sirt6 WT (Sirt6 KO + Sirt6 WT Restored).