BMI1 (BMI1 polycomb ring finger oncogene)

Review on BMI1 (BMI1 polycomb ring finger oncogene), with data on DNA, on the protein encoded, and where the gene is implicated

HUWE1 cooperates with RAS activation to control leukemia cell proliferation and human hematopoietic stem cells differentiation fate

Acute myeloid leukemia (AML) is a poor prognosis hematopoietic malignance characterized by abnormal proliferation and differentiation of hematopoietic stem cells (HSCs). Although advances in treatment have greatly improved survival rates in young patients, in the elderly population, ~70% of patients present poor prognosis. A pan-cancer analysis on the TCGA cohort showed that AML has the second higher HUWE1 expression in tumor samples among all cancer types. In addition, pathway enrichment analysis pointed to RAS signaling cascade as one of the most important pathways associated to HUWE1 expression in this particular AML cohort. In silico analysis for biological processes enrichment also revealed that HUWE1 expression is correlated with 13 genes involved in myeloid differentiation. Therefore, to understand the role of HUWE1 in human hematopoietic stem and progenitor cells (HSPC) we constitutively expressed KRASG12V oncogene concomitantly to HUWE1 knockdown in stromal co-cultures. The results showed that, in the context of KRASG12V, HUWE1 significantly reduces cell cumulative growth and changes myeloid differentiation profile of HSPCs. Overall, these observations suggest that HUWE1 might contribute to leukemic cell proliferation and impact myeloid differentiation of human HSCs, thus providing new venues for RAS-driven leukemia targeted therapy approach

Δ40 Isoform of p53 Controls β-Cell Proliferation and Glucose Homeostasis in Mice

Objective: Investigating the dynamics of pancreatic $\beta$-cell mass is critical for developing strategies to treat both type 1 and type 2 diabetes. p53, a key regulator of the cell cycle and apoptosis, has mostly been a focus of investigation as a tumor suppressor. Although p53 alternative transcripts can modulate p53 activity, their functions are not fully understood. We hypothesized that $\beta$-cell proliferation and glucose homeostasis were controlled by $\Delta$40p53, a p53 isoform lacking the transactivation domain of the full-length protein that modulates total p53 activity and regulates organ size and life span in mice. Research Design and Methods: We phenotyped metabolic parameters in $\Delta$40p53 transgenic (p44tg) mice and used quantitative RT-PCR, Western blotting, and immunohistochemistry to examine $\beta$-cell proliferation. Results: Transgenic mice with an ectopic p53 gene encoding $\Delta$40p53 developed hypoinsulinemia and glucose intolerance by 3 months of age, which worsened in older mice and led to overt diabetes and premature death from $\sim$14 months of age. Consistent with a dramatic decrease in $\beta$-cell mass and reduced $\beta$-cell proliferation, lower expression of cyclin D2 and pancreatic duodenal homeobox-1, two key regulators of proliferation, was observed, whereas expression of the cell cycle inhibitor p21, a p53 target gene, was increased. Conclusions: These data indicate a significant and novel role for $\Delta$40p53 in $\beta$-cell proliferation with implications for the development of age-dependent diabetes

Identification of Cancer Cell-Line Origins Using Fluorescence Image-Based Phenomic Screening

Universal phenotyping techniques that can discriminate among various states of biological systems have great potential. We applied 557 fluorescent library compounds to NCI's 60 human cancer cell-lines (NCI-60) to generate a systematic fluorescence phenotypic profiling data. By the kinetic fluorescence intensity analysis, we successfully discriminated the organ origin of all the 60 cell-lines

The SDF-1α/CXCR4 Axis is Required for Proliferation and Maturation of Human Fetal Pancreatic Endocrine Progenitor Cells

The chemokine receptor CXCR4 and ligand SDF-1α are expressed in fetal and adult mouse islets. Neutralization of CXCR4 has previously been shown to diminish ductal cell proliferation and increase apoptosis in the IFNγ transgenic mouse model in which the adult mouse pancreas displays islet regeneration. Here, we demonstrate that CXCR4 and SDF-1α are expressed in the human fetal pancreas and that during early gestation, CXCR4 colocalizes with neurogenin 3 (ngn3), a key transcription factor for endocrine specification in the pancreas. Treatment of islet like clusters (ICCs) derived from human fetal pancreas with SDF-1α resulted in increased proliferation of epithelial cells in ICCs without a concomitant increase in total insulin expression. Exposure of ICCs in vitro to AMD3100, a pharmacological inhibitor of CXCR4, did not alter expression of endocrine hormones insulin and glucagon, or the pancreatic endocrine transcription factors PDX1, Nkx6.1, Ngn3 and PAX4. However, a strong inhibition of β cell genesis was observed when in vitro AMD3100 treatment of ICCs was followed by two weeks of in vivo treatment with AMD3100 after ICC transplantation into mice. Analysis of the grafts for human C-peptide found that inhibition of CXCR4 activity profoundly inhibits islet development. Subsequently, a model pancreatic epithelial cell system (CFPAC-1) was employed to study the signals that regulate proliferation and apoptosis by the SDF-1α/CXCR4 axis. From a selected panel of inhibitors tested, both the PI 3-kinase and MAPK pathways were identified as critical regulators of CFPAC-1 proliferation. SDF-1α stimulated Akt phosphorylation, but failed to increase phosphorylation of Erk above the high basal levels observed. Taken together, these results indicate that SDF-1α/CXCR4 axis plays a critical regulatory role in the genesis of human islets

Malignant Transformation Involving CXXC4 Mutations Identified in a Leukemic Progression Model of Severe Congenital Neutropenia

Olofsen et al. show that acquisition of a mutation in Cxxc4 results in increased CXXC4 protein levels, reduced TET2 protein, increased inflammatory signaling, and leukemic progression of a CSF3R/RUNX1 mutant mouse model of severe congenital neutropenia (SCN).Severe congenital neutropenia (SCN) patients treated with CSF3/G-CSF to alleviate neutropenia frequently develop acute myeloid leukemia (AML). A common pattern of leukemic transformation involves the appearance of hematopoietic clones with CSF3 receptor (CSF3R) mutations in the neutropenic phase, followed by mutations in RUNX1 before AML becomes overt. To investigate how the combination of CSF3 therapy and CSF3R and RUNX1 mutations contributes to AML development, we make use of mouse models, SCN-derived induced pluripotent stem cells (iPSCs), and SCN and SCN-AML patient samples. CSF3 provokes a hyper-proliferative state in CSF3R/RUNX1 mutant hematopoietic progenitors but does not cause overt AML. Intriguingly, an additional acquired driver mutation in Cxxc4 causes elevated CXXC4 and reduced TET2 protein levels in murine AML samples. Expression of multiple pro-inflammatory pathways is elevated in mouse AML and human SCN-AML, suggesting that inflammation driven by downregulation of TET2 activity is a critical step in the malignant transformation of SCN

Defective insulin secretion and increased susceptibility to experimental diabetes are induced by reduced Akt activity in pancreatic islet β cells

The insulin and IGF signaling pathways are critical for development and maintenance of pancreatic β cell mass and function. The serine-threonine kinase Akt is one of several mediators regulated by these pathways. We have studied the role of Akt in pancreatic β cell physiology by generating transgenic mice expressing a kinase-dead mutant of this enzyme in β cells. Reduction of Akt activity in transgenic animals resulted in impaired glucose tolerance due to defective insulin secretion. The mechanisms involved in dysregulation of secretion in these mice lie at the level of insulin exocytosis and are not the result of abnormalities in glucose signaling or function of voltage-gated Ca(2+) channels. Therefore, transgenic mice showed increased susceptibility to developing glucose intolerance and diabetes following fat feeding. These observations suggest that Akt plays a novel and important role in the regulation of distal components of the secretory pathway and that this enzyme represents a therapeutic target for improvement of β cell function in diabetes