Insulin Substrate Receptor (IRS) proteins in normal and malignant hematopoiesis

The insulin receptor substrate (IRS) proteins are a family of cytoplasmic proteins that integrate and coordinate the transmission of signals from the extracellular to the intracellular environment via transmembrane receptors, thus regulating cell growth, metabolism, survival and proliferation. The PI3K/AKT/mTOR and MAPK signaling pathways are the best-characterized downstream signaling pathways activated by IRS signaling (canonical pathways). However, novel signaling axes involving IRS proteins (noncanonical pathways) have recently been identified in solid tumor and hematologic neoplasm models. Insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 (IRS2) are the best-characterized IRS proteins in hematologic-related processes. IRS2 binds to important cellular receptors involved in normal hematopoiesis (EPOR, MPL and IGF1R). Moreover, the identification of IRS1/ABL1 and IRS2/JAK2V617F interactions and their functional consequences has opened a new frontier for investigating the roles of the IRS protein family in malignant hematopoiesis. Insulin receptor substrate-4 (IRS4) is absent in normal hematopoietic tissues but may be expressed under abnormal conditions. Moreover, insulin receptor substrate-5 (DOK4) and insulin receptor substrate-6 (DOK5) are linked to lymphocyte regulation. An improved understanding of the signaling pathways mediated by IRS proteins in hematopoiesis-related processes, along with the increased development of agonists and antagonists of these signaling axes, may generate new therapeutic approaches for hematological diseases. The scope of this review is to recapitulate and review the evidence for the functions of IRS proteins in normal and malignant hematopoiesis.

Incidência de síndrome de lise tumoral aguda em pacientes portadores de hemopatias malignas / Incidence of acute tumor lysis syndrome in patients with malignant blood diseases

O emprego de quimioterapia em tumores de alta replicaçäo celular é responsável pela liberaçäo de constituintes celulares, que podem levar a sérias alteraçöes metabólicas. Estas alteraçöes compreendem distúrbios no metabolismo do: potássio, cálcio, fosfato, uréia e ácido úrico; que caracterizam a SINDROME de LISE TUMORAL AGUDA (SLTA). No período de 29/03/93 a 23/08/93, foram estudados 20 pacientes com hemopatias malignas, com indicaçäo de tratamento poliquimioterápico. Estes pacientes receberam hiper-hidrataçäo com 2000ml/m2 de soluçäo fisiológico 0,9 por cento e alopurinol 200mg/m2 iniciando-se no dia anterior até o último dia de quimioterapia. O diagnóstico de SLTA foi considerado nos pacientes que nos 4 dias do tratamento, apresentaram duas ou mais das seguintes alteraçöes metabólicas: aumento de 25 por cento nos níveis de potássio, ácido úrico, uréia e fosfato; ou diminuiçäo de 25 por cento no nível de cálcio sérico. A SINDROME DE LISE TUMORAL AGUDA CLINICA (SLTAC), foi definida como SLTAC, associada a condiçöes clínicas que implicassem em risco de vida nenhum dos nossos pacientes apresentou SLTAC e apenas 30 por cento desenvolveram SLTAL, demonstrando que este esquema de tratamento foi efetivo.

Integrin receptors and TGF-Beta expression in chronic myeloid leukemia cells

To understand relationiship between transforming growth factor beta-1 (TGF-ß1) and the integrin profile presented by chronic myeloid leukemia cells, we have studied, using Northen analysis, the expression of TGF-ß1 messenger RNA (TGF-ß mRNA) in myeloid cell lines and in patient with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). In addition we determined the positivity for alfa4 and alfa5 integrin moleculas in those cell using specific monoclonal antibodies and flow cytometry. CML patients (N=3) presented mean values of alfa4 higher (alfa4: 60 ñ 20 per cent); alfa5: 70 ñ 41 per cent) than AML (N=10) blast cells (alfa4: 25 ñ 23 per cent); alfa5: 18 ñ 16 per cent). Northern analysis revealed an almost four-fold higher expression of TGF-ß mRNA in K562 (derived from a patient with chronic myeloid leukemia) compared to the myeloblastic cell line HL60. The highest TGF-ß mRNA levels were seen in the U937 lineage. CML leukemic cells (N=3) showed high TGF-ß mRNA levels comparable to the levels expressed by K562 which was paralleled by high ß1 integrin mRNA. AML blast cells presented a variable degree of expression of TGF-ß mRNA when compared to HL60. One patient with acute megakaryoblastic leukemia (FAB subtype M7), usually associated with myelofibrosis, presented the highest TGF-ß mRNA levels. We conclude that studing TGF-ß1 and its mechanisms of action will help in understanding fibrosis in leukemic patients, and perhaps to design treatments for such conditions

Simplified method for the analysis of cellular karyotype and phenotype in leukemias

The objective of this study was to develop a simplified method for the simultaneous analysis of cellular karyotype and phenotype which would permit the identification of cell origin. We studied 6 patients with AML, 3 with CML (one of which was in blastic transformation) and one ALL. We used a method in which the suspension of bone marrow cells was incubated in TC 199 medium with colchicine and with hypotonic solution formed from glycerol, NaCl, KCl, CaCl2, MgCl2 and sucrose. The slides were prepared from this cell suspension by cytospin and stained for peroxidase, PAS, esterases and iron. The karyotype was studied by direct method and culture. It was possible to relate the cytogenetic marker with cytochemistry characteristics in the same cell in 3 cases, showing the feasibility of cytochemistry techniques in cytogenetical preparations. The best preparations were found through peroxidase. The presence of iron granules allowed identification of erythroblastic lineage in the combined staining. Mitosis with a marker chromosome of leukemic clone in an AML cell with negative peroxidase probably showed a proliferation of more primitive precursor not sufficiently differentiated to show markers