Reduced activation of phosphatidylinositol-3 kinase and increased serine 636 phosphorylation of insulin receptor substrate-1 in primary culture of skeletal muscle cells from patients with type 2 diabetes

To understand better the defects in the proximal steps of insulin signaling during type 2 diabetes, we used differentiated human skeletal muscle cells in primary culture. When compared with cells from control subjects, myotubes established from patients with type 2 diabetes presented the same defects as those previously evidenced in vivo in muscle biopsies, including defective stimulation of phosphatidylinositol (PI) 3-kinase activity, decreased association of PI 3-kinase with insulin receptor substrate (IRS)-1 and reduced IRS-1 tyrosine phosphorylation during insulin stimulation. In contrast to IRS-1, the signaling through IRS-2 was not altered. Investigating the causes of the reduced tyrosine phosphorylation of IRS-1, we found a more than twofold increase in the basal phosphorylation of IRS-1 on serine 636 in myotubes from patients with diabetes. Concomitantly, there was a higher basal mitogen-activated protein kinase (MAPK) activity in these cells, and inhibition of the MAPKs with PD98059 strongly reduced the level of serine 636 phosphorylation. These results suggest that IRS-1 phosphorylation on serine 636 might be involved in the reduced phosphorylation of IRS-1 on tyrosine and in the subsequent alteration of insulin-induced PI 3-kinase activation. Moreover, increased MAPK activity seems to play a role in the phosphorylation of IRS-1 on serine residue in human muscle cells.     

Hyperhomocysteinemia and vitamin score: correlations with silent brain ischemic lesions and brain atrophy

Elevated fasting plasma total homocysteine concentration (tHcy) and lower vitamin status are associated with atherosclerotic states. Silent brain ischemic lesions and brain atrophy, prevailing in the elderly, are affected by tHcy and vitamin status. The study was performed on 56 outpatients who had undergone brain computed tomography (CT) before the onset of the study. According to brain CT evaluation, three groups were set: minor brain ischemia, brain atrophy and control. Brain CT, tHcy, plasma pyridoxal phosphate (PLP), vitamin B(12), folic acid and cognitive and functional capacities were measured or evaluated in all of the subjects. Plasma vitamin score for three vitamins was calculated. In subjects with minor brain ischemic lesions (n = 21), tHcy was higher by 5.6 microM, whereas vitamin score and cognitive function were lower than in controls (n = 24). In subjects with brain atrophy (n = 11), plasma PLP and cognitive function were lower. Particular attention should be paid to tHcy monitoring, vitamin status assessment and brain impairment evaluation.     

TP53 is frequently altered by methylation, mutation, and/or deletion in acute lymphoblastic leukaemia

Different mechanisms, such as chromosomal rearrangements, deletions, mutations, and methylation/demethylation of the promoter regions of genes, have been shown to be involved in acute lymphoblastic leukaemia (ALL). These genetic and epigenetic alterations lead to the activation of protooncogenes or to inactivation of tumour suppressor genes promoting cell proliferation. One of the most frequently inactivated tumour suppressor genes is TP53, which is altered in 50% of human tumours. In this study, we have analysed: (1) the complete coding region, all intron-exon junctions and noncoding regions of exons 1-11 of TP53 by lexon-DGGE; (2) the methylation status of the 5' region of TP53 and (3) the deletion of one or both alleles of the gene by fluorescence in situ hybridisation (FISH) in 57 ALL patients. Using these techniques, we have found promoter methylation in 32% of the cases, missense mutations in 8.8%, and deletion of one allele in 7.5% of the samples, with TP53 being altered in 40% of the ALL samples studied in this series.     

The protein-tyrosine phosphatase DEP-1 modulates growth factor-stimulated cell migration and cell-matrix adhesion

Density-enhanced protein-tyrosine phosphatase-1 (DEP-1 also CD148) is a transmembrane molecule with a single intracellular PTP domain. It has recently been proposed to function as a tumor suppressor. We have previously shown that DEP-1 dephosphorylates the activated platelet-derived growth factor (PDGF) beta-receptor in a site-selective manner (Kovalenko et al. (2000). J. Biol. Chem. 275, 16219-16226). We analysed cell lines with inducible DEP-1 expression for cellular functions of DEP-1. Several aspects of PDGFbeta-receptor signaling were negatively affected by DEP-1 expression. These include PDGF-stimulated activation of inositol trisphosphate formation, Erk1/2, p21Ras, and Src. Activation of receptor-associated phosphoinositide-3 kinase activity and of Akt/PKB were weakly attenuated at early time points of stimulation. Inhibition of PDGF-stimulated signaling depended on DEP-1 catalytic activity. Importantly, DEP-1 inhibited PDGF-stimulated cell migration. The catalytically inactive DEP-1 C1239S variant enhanced cell migration and PDGF-stimulated Erk1/2 activation, suggesting a dominant negative interference with endogenous DEP-1. In contrast to cell migration, cell-substrate adhesion was promoted by active DEP-1 and delayed or suppressed by DEP-1 C1239S, correlating with positive effects of DEP-1 on adhesion-stimulated Src kinase. We propose that negative regulation of growth-factor stimulated cell migration and promotion of cell-matrix adhesion may be related to the function of DEP-1 as tumor suppressor.     

Differential diagnosis of Waldenstrom's macroglobulinemia from other low-grade B-cell lymphoproliferative disorders

Waldenstrom's macroglobulinemia (WM) is a rare lymphoproliferative disorder (LPD) characterized by lymphoplasmacytic infiltration of the bone marrow (BM) and/or occasionally other tissues and by the presence of a serum monoclonal IgM. The disease belongs to the lymphoplasmacytic lymphoma (LPL) subtype. Whether WM is indeed a separate entity or is merely an IgM-secreting subtype of low-grade B-cell lymphoma is still controversial. In our series of 67 patients, WM has a long median overall survival of 110 months, and the male/female ratio is 1.2/1. Clinical features include a wide spectrum of manifestations, many of which may be common to other LPDs. Differential diagnosis is based on: (1) clinical and laboratory features (anemia, organomegaly, lymphadenopathy, IgM paraproteinemia), (2) cell morphology (lymphocytes, lymphoplasmacytes, few plasma cells), (3) histopathology of bone marrow or lymph node, (4) immunophenotype (CD5 expression and the intensity of CD5, CD20, and CD79b antigens may help in discrimination from other LPDs and atypical CLL), and (5) characteristic genetic features (present in other LPDs). Based on the former, diagnosis is usually easy. It may be harder in LPL cases not secreting IgM. We consider that WM should be, for the time being, handled as a separate entity. Further studies are necessary.     

High-dose sequential chemotherapy and peripheral blood progenitor cell autografting in patients with refractory and/or recurrent Hodgkin lymphoma: a multicenter study of the intergruppo Italiano Linfomi showing prolonged disease free survival in patients treated at first recurrence

BACKGROUND: The objective of the current study was to evaluate in a multicenter setting the feasibility and efficacy of a high-dose sequential (HDS) chemotherapy regimen that combined intensive debulking and high-dose therapy (HDT) with peripheral blood progenitor cell (PBPC) autografting in patients with refractory or recurrent Hodgkin lymphoma (HL). METHODS: Data were collected from 102 patients with HL who were treated with the HDS regimen at 14 centers associated with the Intergruppo Italiano Linfomi. Twenty-four patients had primary refractory HL, 59 patients had their first recurrence of HL (within 1 year in 32 patients and > 1 year in 27 patients), and 19 patients had multiple disease recurrences. The HDS regimen included the sequential delivery of high-dose (hd) cyclophosphamide with PBPC harvesting, methotrexate, etoposide, then HDT (usually hd mitoxantrone plus L-phenylalanine mustard) with PBPC autografting. In addition, radiotherapy was delivered to 36 patients at sites of bulky or persistent disease. RESULTS: Ninety-two patients (90%) completed the HDS program. There were five toxic deaths (treatment-related mortality rate, 4.9%) and six secondary malignan cies (five patients developed myelodysplastic syndrome/acute myelogenous leukemia, and one patient developed colorectal carcinoma). At a median follow-up of 5 years, the 5-year overall survival (OS) and event-free survival (EFS) projections were 64% (95% confidence interval [95% CI], 54-74%) and 53% (95% CI, 43-63%), respectively. Patients with their first recurrence had the most favorable outcome, with 5-year OS and EFS projections of 77% (95% CI, 66-88%) and 63% (95% CI, 50-76%), respectively. There were no significant differences between patients with early first recurrence and late first recurrence. The poorest outcome was observed in patients with refractory HL, with 5-year OS and EFS projections of 36% (95% CI, 16-55%) and 33% (95% CI, 14-52%), respectively. Patients who received HDS chemotherapy after multiple recurrences had an intermediate outcome. Multivariate analysis showed that refractory disease and systemic symptoms at the time of initial presentation were associated significantly associated with poor OS and EFS. CONCLUSIONS: The use of HDS chemotherapy for patients with refractory and/or recurrent HL is feasible at the multicenter level. The combination of intensive debulking and HDT with PBPC autografting offers a good chance of prolonged disease free survival for patients with their first recurrence of HL.     

EBV-encoded EBNA-5 associates with P14ARF in extranucleolar inclusions and prolongs the survival of P14ARF-expressing cells

Epstein-Barr virus (EBV) carrying lymphoblastoid cells of normal origin express the full program of all 9 virus-encoded, growth transformation associated proteins. They have an intact p53 pathway as a rule. This raises the question of whether any of the viral proteins impair the pathway functionally. Using a yeast 2-hybrid system, we have shown that EBNA-5 but not the other EBNAs interacts with the p14ARF protein, a regulator of the p53 pathway. The interaction was confirmed in vitro using a GST pull-down assay. Moreover, expression of EBNA-5 increased the survival of p14ARF-transfected cells. EBV infection of resting B cells induced the expression of p14ARF mRNA without increased level of the protein. A fraction of the p14ARF localized to the nucleoli but the bulk of the protein accumulated in nuclear but extranucleolar inclusions. Formation of the extranucleolar inclusions led to complete relocalization of EBNA-5 from nucleoplasm to these structures. The inclusions also contained p53 and HDM2, and were surrounded by PML bodies and proteasomes, which suggests that these inclusions could be targets for proteasome dependent protein degradation.     

Rat liver ischemia-reperfusion-induced apoptosis and necrosis are decreased by FK506 pretreatment

The aim of this study was to demonstrate that tacrolimus (FK506) has a hepatoprotective effect by reducing ischemia-reperfusion-induced apoptosis and necrosis, both of which lead to post-surgical liver dysfunction. An ischemia-reperfusion model and primary cultured rat hepatocytes subjected to hypoxic and reoxygenation phases, mimicking the surgical process, were used. c-Jun N-terminal kinase 1/stress-activated protein kinase 1 (JNK1/SAPK1) activation leads to caspase 3 activation, a trigger of apoptosis. The activation status of JNK1/SAPK1 was evaluated by immunoprecipitation or Western-blotting experiments. Apoptosis was assessed by measuring caspase activation and by TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate-biotin nick-end labeling) reaction. Necrosis was assessed histologically. Tacrolimus improved the survival rate of rats subjected to ischemia-reperfusion. After FK506 pretreatment, the liver necrosis rate was reduced, and ischemia-reperfusion-induced JNK1/SAPK1 activation and apoptosis were significantly decreased. In hypoxia-reoxygenation-subjected hepatocytes, tacrolimus reduced JNK1/SAPK1 and caspase 3 activation. In the liver, tacrolimus prevented ischemia-reperfusion-induced apoptosis and necrosis.