Ikaros sets the threshold for negative B-cell selection by regulation of the signaling strength of the AKT pathway.

Inhibitory phosphatases, such as the inositol-5-phosphatase SHIP1 could potentially contribute to B-cell acute lymphoblastic leukemia (B-ALL) by raising the threshold for activation of the autoimmunity checkpoint, allowing malignant cells with strong oncogenic B-cell receptor signaling to escape negative selection. Here, we show that SHIP1 is differentially expressed across B-ALL subtypes and that high versus low SHIP1 expression is associated with specific B-ALL subgroups. In particular, we found high SHIP1 expression in both, Philadelphia chromosome (Ph)-positive and ETV6-RUNX1-rearranged B-ALL cells.

SHIP1 Is Present but Strongly Downregulated in T-ALL, and after Restoration Suppresses Leukemia Growth in a T-ALL Xenotransplantation Mouse Model.

Acute lymphoblastic leukemia (ALL) is the most common cause of cancer-related death in children. Despite significantly increased chances of cure, especially for high-risk ALL patients, it still represents a poor prognosis for a substantial fraction of patients. Misregulated proteins in central switching points of the cellular signaling pathways represent potentially important therapeutic targets.

Targeted hyperactivation of AKT through inhibition of ectopic expressed SHIP1 induces cell death in colon carcinoma cells and derived metastases.

Current therapeutic approaches for colorectal cancer (CRC) focus on the suppression of oncogenic kinase signaling. Here, we test the hypothesis that targeted hyperactivation of the PI3K/AKT-signaling may lead to trigger CRC cell death. Recently we found that hematopoietic SHIP1 is ectopically expressed in CRC cells.

Activated Src kinases downstream of BCR-ABL and Flt3 induces proteasomal degradation of SHIP1 by phosphorylation of tyrosine 1021.

Within the various subtypes of ALL, patients with a BCR-ABL-positive background as well as with a genetic change in the KMT2A gene have by far the worst survival probabilities. Interestingly, both subtypes are characterized by highly activated tyrosine kinases. SHIP1 serves as an important negative regulator of the PI3K/AKT signaling pathway, which is often constitutively activated in ALL.

Reduced expression and activity of patient-derived SHIP1 phosphatase domain mutants.

The characterization of dysregulated proteins in cell signaling pathways is important for the development of therapeutic approaches. The PI3K/AKT/mTOR pathway is frequently upregulated in cancer cells and the SH2-containing inositol 5-phosphatase SHIP1 can act as a negative regulator of the PI3K/AKT pathway. In this study, we investigated different patient-derived mutations within the conserved phosphatase domain of SHIP1.

JAK2-V617F is a negative regulation factor of SHIP1 protein and thus influences the AKT signaling pathway in patients with Myeloproliferative neoplasm (MPN).

Background: Myeloproliferative neoplasms (MPN) are a group of chronic haematological disorders. At the molecular level of MPN cells, the gain-of-function mutation V617F of the Janus kinase 2 (JAK2) leads to a constitutive activation of the downstream signaling cascade and is a conventional criteria for diagnosis. Here, the functional role of the tumor suppressor SHIP1 (SH2 domain containing inositol-5 phosphatase 1) in the pathogenesis of MPNs was investigated.

Investigation of the function of the PI3-Kinase / AKT signaling pathway for leukemogenesis and therapy of acute childhood lymphoblastic leukemia (ALL).

Acute lymphoblastic leukemia is the most common cause of cancer-related death in children and, especially for patients in a high-risk group, still represents a poor prognosis. The PI3K/AKT/mTOR signaling pathway has been identified as a frequently constitutively activated switching point in the disease of ALL. Despite the knowledge of the therapeutic importance of the signaling pathway, the results of clinically effective treatment strategies have so far been extremely sobering.

Combined Targeting of AKT and mTOR Synergistically Inhibits Formation of Primary Colorectal Carcinoma Tumouroids : A 3D Tumour Model for Pre-therapeutic Drug Screening.

Background: Pre-therapeutic analysis of three-dimensional spheroid cultures of primary tumour samples is a promising approach of assessing susceptibility to potential treatment. The phosphatidylinositol-3-kinase/AKT serine/threonine kinase/mammalian target of rapamycin (PI3K/AKT/mTOR) signalling pathway is frequently activated in colorectal cancer (CRC). In previous work, we showed combined inhibition of AKT and mTOR to be highly synergistic in cell lines from patients with hepatocellular carcinoma and cholangiocarcinoma in vitro as well as in vivo in murine xenograft tumour models.

Ectopic Expression of Hematopoietic SHIP1 in Human Colorectal Cancer.

Colorectal cancer (CRC) is a heterogeneous disease that results from the accumulation of mutations in colonic mucosa cells. A subclass of CRC is characterized by microsatellite instability, which is thought to occur mainly through inactivation of the DNA mismatch repair genes and . The inositol 5-phosphatase SHIP1 is expressed predominantly in hematopoietic cells.

Analysis of the FLVR motif of SHIP1 and its importance for the protein stability of SH2 containing signaling proteins.

Binding of proteins with SH2 domains to tyrosine-phosphorylated signaling proteins is a key mechanism for transmission of biological signals within the cell. Characterization of dysregulated proteins in cell signaling pathways is important for the development of therapeutic approaches. The AKT pathway is a frequently upregulated pathway in most cancer cells and the SH2-containing inositol 5-phosphatase SHIP1 is a negative regulator of the AKT pathway.

Nuclear accumulation of SHIP1 mutants derived from AML patients leads to increased proliferation of leukemic cells.

The inositol 5-phosphatase SHIP1 acts as negative regulator of intracellular signaling in myeloid cells and is a tumor suppressor in myeloid leukemogenesis. After relocalization from the cytoplasm to the plasma membrane SHIP1 terminates PI3-kinase mediated signaling processes. Furthermore, SHIP1 is also found in distinct puncta in the cell nucleus and nuclear SHIP1 has a pro-proliferative function.

Expression of Hedgehog Pathway Mediator GLI Represents a Negative Prognostic Marker in Human Acute Myeloid Leukemia and Its Inhibition Exerts Antileukemic Effects.

Purpose: The Hedgehog pathway plays an important role in stem-cell biology and malignant transformation. Therefore, we investigated the expression and prognostic impact of Hedgehog pathway members in acute myeloid leukemia (AML).

Experimental Design: Pretreatment samples from 104 newly diagnosed AML patients (AMLSG 07-04 trial) were analyzed by qPCR, and expression of Hedgehog family members was correlated with clinical outcome.

The tumor suppressor SHIP1 colocalizes in nucleolar cavities with p53 and components of PML nuclear bodies.

The inositol 5-phosphatase SHIP1 is a negative regulator of signaling processes in haematopoietic cells. By converting PI(3,4,5)P3 to PtdIns(3,4)P2 at the plasma membrane, SHIP1 modifies PI3-kinase mediated signaling. We have recently demonstrated that SHIP1 is a nucleo-cytoplasmic shuttling protein and SHIP1 nuclear puncta partially colocalize with FLASH, a component of nuclear bodies.

Efficacious inhibition of Importin α/β-mediated nuclear import of human inositol phosphate multikinase.

Human inositol phosphate multikinase (IPMK) is a nucleocytoplasmic shuttling protein involved in multiple signal transduction pathways located both in the nucleus and in the cytoplasm. To efficaciously inhibit the conventional nuclear import of IPMK, we first examined the effect of different inhibitors and cellular stressors on nuclear import of enhanced green fluorescent protein monomer and octamer, both fused with a monopartite nuclear localization signal (NLS), in HeLa and H1299 cells. Most efficacious inhibition of conventional nuclear protein import was observed when using Importazole and hydrogen peroxide.

Nucleocytoplasmic shuttling of human inositol phosphate multikinase is influenced by CK2 phosphorylation.

Human inositol phosphate multikinase (IPMK) is a multifunctional protein in cellular signal transduction, namely, a multispecific inositol phosphate kinase, phosphatidylinositol 3-kinase, and a scaffold within the mTOR-raptor complex. To fulfill these nuclear and cytoplasmic functions, intracellular targeting of IPMK needs to be regulated. We show here that IPMK, which has been considered to be a preferentially nuclear protein, is a nucleocytoplasmic shuttling protein, whose nuclear export is mediated by classical nuclear export receptor CRM1.

A toolkit for graded expression of green fluorescent protein fusion proteins in mammalian cells.

Green fluorescent protein (GFP) and GFP-like proteins of different colors are important tools in cell biology. In many studies, the intracellular targeting of proteins has been determined by transiently expressing GFP fusion proteins and analyzing their intracellular localization by fluorescence microscopy. In most vectors, expression of GFP is driven by the enhancer/promoter cassette of the immediate early gene of human cytomegalovirus (hCMV).