MR1B, a natural spliced isoform of the MHC-related 1 protein, is expressed as homodimers at the cell surface and activates MAIT cells.

The MHC-related 1 (MR1) protein is a monomorphic, evolutionarily conserved MHC class I-like molecule, which is necessary for the development and functions of mucosal-associated invariant T (MAIT) cells, a new subset of innate-like lymphocytes. Multiple isoforms of the MR1 gene are naturally transcribed, but only the full-length MR1A has been analyzed so far. Using transfected cell lines expressing an alternative spliced transcript, MR1B, characterized by the absence of the α3 extracellular domain, we show that MR1B is transcribed and glycosylated but remains in an immature (endoglycosidase H-sensitive) state. MR1B mostly accumulates in the ER, without interacting with proteins of the peptide-loading complex such as tapasin. Interestingly, it is nevertheless found expressed at the cell surface, independently of ß2-microglobulin, in a homodimeric form. MR1B is functional as its overexpression induces MAIT cell activation in vitro in the presence of bacteria. Altogether, these data show that MR1B displays several remarkable features, and probably plays a physiological role complementary to MR1A with respect to MAIT cell development and/or function.

The tumor suppressor hTid1 inhibits STAT5b activity via functional interaction.

STAT5a and -5b (signal transducers and activators of transcription 5a and 5b) proteins play an essential role in hematopoietic cell proliferation and survival and are frequently constitutively active in hematologic neoplasms and solid tumors. Because STAT5a and STAT5b differ mainly in the carboxyl-terminal transactivation domain, we sought to identify new proteins that bind specifically to this domain by using a bacterial two-hybrid screening. We isolated hTid1, a human DnaJ protein that acts as a tumor suppressor in various solid tumors. hTid1 interacts specifically with STAT5b but not with STAT5a in hematopoietic cell lines. This interaction involves the cysteine-rich region of the hTid1 DnaJ domain. We also demonstrated that hTid1 negatively regulates the expression and transcriptional activity of STAT5b and suppresses the growth of hematopoietic cells transformed by an oncogenic form of STAT5b. Our findings define hTid1 as a novel partner and negative regulator of STAT5b.

Regulation of IGF-1-dependent cyclin D1 and E expression by hEag1 channels in MCF-7 cells: the critical role of hEag1 channels in G1 phase progression.

Insulin-like Growth Factor-1 (IGF-1) plays a key role in breast cancer development and cell cycle regulation. It has been demonstrated that IGF-1 stimulates cyclin expression, thus regulating the G1 to S phase transition of the cell cycle. Potassium (K(+)) channels are involved in the G1 phase progression of the cell cycle induced by growth factors. However, mechanisms that allow growth factors to cooperate with K(+) channels in order to modulate the G1 phase progression and cyclin expression remain unknown. Here, we focused on hEag1 K(+) channels which are over-expressed in breast cancer and are involved in the G1 phase progression of breast cancer cells (MCF-7). As expected, IGF-1 increased cyclin D1 and E expression of MCF-7 cells in a cyclic manner, whereas the increase of CDK4 and 2 levels was sustained. IGF-1 stimulated p21(WAF1/Cip1) expression with a kinetic similar to that of cyclin D1, however p27(Kip1) expression was insensitive to IGF-1. Interestingly, astemizole, a blocker of hEag1 channels, but not E4031, a blocker of HERG channels, inhibited the expression of both cyclins after 6-8h of co-stimulation with IGF-1. However, astemizole failed to modulate CDK4, CDK2, p21(WAF1/Cip1) and p27(Kip1) expression. The down-regulation of hEag1 by siRNA provoked a decrease in cyclin expression. This study is the first to demonstrate that K(+) channels such as hEag1 are directly involved in the IGF-1-induced up-regulation of cyclin D1 and E expression in MCF-7 cells. By identifying more specifically the temporal position of the arrest site induced by the inhibition of hEag1 channels, we confirmed that hEag1 activity is predominantly upstream of the arrest site induced by serum-deprivation, prior to the up-regulation of both cyclins D1 and E. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Iron overload in HFE C282Y heterozygotes at first genetic testing: a strategy for identifying rare HFE variants.

BACKGROUND: Heterozygotes for the p.Cys282Tyr (C282Y) mutation of the HFE gene do not usually express a hemochromatosis phenotype. Apart from the compound heterozygous state for C282Y and the widespread p.His63Asp (H63D) variant allele, other rare HFE mutations can be found in trans on chromosome 6. DESIGN AND METHODS: We performed molecular investigation of the genes implicated in hereditary hemochromatosis in six patients who presented with iron overload but were simple heterozygotes for the HFE C282Y mutation at first genetic testing. Functional impairment of new variants was deduced from computational methods including molecular modeling studies. RESULTS: We identified four rare HFE mutant alleles, three of which have not been previously described. One mutation is a 13-nucleotide deletion in exon 6 (c.1022_1034del13, p.His341_Ala345 > LeufsX119), which is predicted to lead to an elongated and unstable protein. The second one is a substitution of the last nucleotide of exon 2 (c.340G > A, p.Glu114Lys) which modifies the relative solvent accessibility in a loop interface. The third mutation, p.Arg67Cys, also lies in exon 2 and introduces a destabilization of the secondary structure within a loop of the α1 domain. We also found the previously reported c.548T > C (p.Leu183Pro) missense mutation in exon 3. No other known iron genes were mutated. We present an algorithm at the clinical and genetic levels for identifying patients deserving further investigation. Conclusions Our results suggest that additional mutations in HFE may have a clinical impact in C282Y carriers. In conjunction with results from previously described cases we conclude that an elevated transferrin saturation level and elevated hepatic iron index should indicate the utility of searching for further HFE mutations in C282Y heterozygotes prior to other iron gene studies.

Oncogenic Kit controls neoplastic mast cell growth through a Stat5/PI3-kinase signaling cascade.

The D816V-mutated variant of Kit triggers multiple signaling pathways and is considered essential for malignant transformation in mast cell (MC) neoplasms. We here describe that constitutive activation of the Stat5-PI3K-Akt-cascade controls neoplastic MC development. Retrovirally transduced active Stat5 (cS5(F)) was found to trigger PI3K and Akt activation, and to transform murine bone marrow progenitors into tissue-infiltrating MCs. Primary neoplastic Kit D816V(+) MCs in patients with mastocytosis also displayed activated Stat5, which was found to localize to the cytoplasm and to form a signaling complex with PI3K, with consecutive Akt activation. Finally, the knock-down of either Stat5 or Akt activity resulted in growth inhibition of neoplastic Kit D816V(+) MCs. These data suggest that a downstream Stat5-PI3K-Akt signaling cascade is essential for Kit D816V-mediated growth and survival of neoplastic MCs.

Extracellular signal-regulated kinases 1 and 2 and TRPC1 channels are required for calcium-sensing receptor-stimulated MCF-7 breast cancer cell proliferation.

The calcium-sensing receptor (CaR), is a G protein-dependent receptor that responds to increments in extracellular Ca(2+) ([Ca(2+)](o)). We previously reported that an increase in [Ca(2+)](o) induced a release of intracellular calcium and Ca(2+) entry via store operated channels (SOCs). We also demonstrated that MCF-7 cells express Transient Receptor Potential canonical 1 (TRPC1) channels. Herein, we investigated CaR intracellular signaling pathways and examined the role of TRPC1 in CaR-induced cell proliferation, through the extracellular signal-regulated Kinases 1 & 2 (ERK1/2) pathways. Treatment by [Ca(2+)](o) increased both MCF-7 cell proliferation and TRPC1 expression. Both the [Ca(2+)](o) proliferative effect and TRPC1 protein levels were abolished by the ERK1/2 inhibitors. Moreover, [Ca(2+)](o) failed to increase cell proliferation either in the presence of CaR or TRPC1 siRNAs. Both [Ca(2+)](o) and the selective CaR activator spermine, elicited time and dose-dependent ERK1/2 phosphorylation. ERK1/2 phosphorylation was almost completely inhibited by treatment with the phospholipase C and the protein kinase C inhibitors. Treatment with 2-aminoethoxydiphenyl borate (2-APB), and SKF-96365 or by siTRPC1 diminished both [Ca(2+)](o)- and spermine-stimulated ERK1/2 phosphorylation. Moreover, down-regulation of TRPC1 by siRNA reduced the Ca(2+) entry induced by CaR activation. We conclude that the CaR activates ERK1/2 via a PLC/PKC-dependent pathway. Moreover, TRPC1 is required for the ERK1/2 phosphorylation, Ca(2+) entry and the CaR-proliferative effect.

Durable Resolution of Severe Psoriasis in a Patient Treated with Pentostatin for Hairy Cell Leukemia: A Case Report.

INTRODUCTION: Pentostatin (2'-deoxycoformycin) and cladribine (2-chlorodeoxyadenosine) are adenosine analogues widely used to treat lymphoid malignancies, mainly hairy cell leukemia (HCL). Oral or parenteral adenosine analogues have been also used as immunomodulatory agents in multiple sclerosis and in acute graft-versus-host disease. CASE REPORT: Here, we report the case of a 43-year-old patient with a history of extensive psoriasis who later developed HCL. RESULTS: The patient had achieved complete remission of both psoriasis and HCL after receiving intravenous infusions of pentostatin. It is worth noting that cladribine has already been reported to treat plaque psoriasis lesions in two patients with HCL and in a third patient with gastric marginal zone B cell lymphoma [1]. CONCLUSION: We believe that adenosine analogues constitute a promising therapeutic option for moderate to severe psoriasis, especially for severe and refractory psoriasis, as well as for patients with adjacent lymphoid malignancies.

Activated STAT5 proteins induce activation of the PI 3-kinase/Akt and Ras/MAPK pathways via the Gab2 scaffolding adapter.

The active forms of STAT5A (signal transducer and activator of transcription 5A) and STAT5B are able to relieve the cytokine dependence of haematopoietic cells and to induce leukaemia in mice. We have demonstrated previously that activation of the PI3K (phosphoinositide 3-kinase) signalling cascade plays a major role in cell growth and survival induced by these proteins. Interaction between STAT5 and p85, the regulatory subunit of the PI3K, has been suggested to be required for this activation. We show in the present study that the scaffolding protein Gab2 [Grb2 (growth-factor-receptor-bound protein 2)-associated binder-2] is an essential component of this interaction. Gab2 is persistently tyrosine-phosphorylated in Ba/F3 cells expressing caSTAT5 (constitutively activated STAT5), independent of JAK2 (Janus kinase 2) activation where it interacts with STAT5, p85 and Grb2, but not with Shp2 [SH2 (Src homology 2)-domain-containing tyrosine phosphatase] proteins. Interaction of STAT5 with Gab2 was also observed in Ba/F3 cells stimulated with interleukin-3 or expressing the oncogenic fusion protein Tel-JAK2. The MAPKs (mitogen-activated protein kinases) ERK1 (extracellular-signal-regulated kinase 1) and ERK2 were constitutively activated in the caSTAT5-expressing cells and were found to be required for caSTAT5-induced cell proliferation. Overexpression of Gab2-3YF, a mutant of Gab2 incapable of binding PI3K, inhibited the proliferation and survival of caSTAT5-expressing cells as well as ERK1/2 and Akt/protein kinase B phosphorylation. Taken together, our results indicate that Gab2 is required for caSTAT5-induced cell proliferation by regulating both the PI3K/Akt and the Ras/MAPK pathways.

[Diagnosis of primary immunodeficiency in adult patients]. / Diagnostic des déficits immunitaires primitifs à l'âge adulte.

The molecular bases of approximately one hundred primary immune deficiencies (PID) have been identified over the last 15 years. In adults, the diagnosis of PID cannot be evoked before ruling out acquired immunodeficiencies, which are far more frequent. The search for specific PIDs may be oriented by the type of agent responsible for severe and/or recurrent infection. More rarely, other clinical manifestations such as granulomatosis, autoimmune manifestations, hemophagocytic syndrome, lymphoproliferation, or solid tumors may also lead to the identification of PID.

Interleukin-7 induces apoptosis of 697 pre-B cells expressing dominant-negative forms of STAT5: evidence for caspase-dependent and -independent mechanisms.

The transcription factors STAT5A and STAT5B (STAT: signal transducer and activator of transcription) play a major role in the signaling events elicited by a number of growth factor and cytokine receptors. In this work, we aimed to investigate the role of STAT5 in human precursor B cell survival by introducing dominant-negative (DN) forms of STAT5A or STAT5B in the 697 pre-B cell line. All clones expressing DN forms of either transcription factor exhibited a higher spontaneous apoptotic rate that was massively enhanced upon interleukin-7 (IL-7) stimulation. This was associated with caspase 8 cleavage, mitochondrial transmembrane potential disruption and caspase 3 activation. However, the DN forms of STAT5 did not alter the expression of Bcl-2, Bax, Bcl-x, Bim, A1 and Mcl1 proteins in IL-7-stimulated cells. The pancaspase inhibitor Z-Val-Ala-Asp-fluoromylmethyl ketone partially suppressed IL-7-mediated mitochondrial transmembrane potential disruption and cell death, suggesting that IL-7 induced the death of DN STAT5 expressing 697 cells through caspase-dependent and -independent mechanisms that both require mitochondrial activation.

ZAP-70 tyrosine kinase is constitutively expressed and phosphorylated in B-lineage acute lymphoblastic leukemia cells.

BACKGROUND AND OBJECTIVES: Zeta-associated protein 70 (ZAP-70), a member of the Syk family of protein tyrosine kinases, is normally expressed in T and NK cells. While little is known about ZAP-70 expression in normal human B cells, it has been reported that ZAP-70 is expressed in a subset of patients with chronic lymphocytic leukemia (CLL) with a poor prognosis. In this study, we examined the expression and phosphorylation status of ZAP-70 in B-lineage acute lymphoblastic leukemia (Blin-ALL). DESIGN AND METHODS: First, ZAP-70 protein expression was assessed by Western blotting and flow cytometry and ZAP-70 mRNA transcripts were analyzed by reverse transcription polymerase chain reaction (RT-PCR) on human precursor B cell lines. Experiments were then carried out on cells obtained from 18 patients with Blin-ALL and from normal human bone marrow. RESULTS: ZAP-70 was constitutively expressed and phosphorylated on tyr319 in human precursor Blin-ALL cell lines as well as in primary B leukemic cells from all examined Blin-ALL patients with pro-B, pre-B and B phenotypes, but not in malignant myeloid cells. Importantly, analysis of normal human bone marrow revealed expression of ZAP-70 transcripts only in the CD34+ cell fraction (either CD19-CD10- or CD19+CD10+) but not in the CD34- cell fraction (CD19+sIgM- pre-B cells or CD19+sIgM+ immature B cells). INTERPRETATION AND CONCLUSIONS: ZAP-70 was found to be expressed in the CD34+ normal bone marrow compartment including earlier B-cell progenitors, but not in CD34- pre-B and immature B cells. By contrast, ZAP-70 was consistently expressed and phosphorylated in Blin-ALL cells. Further studies are required to determine whether ZAP-70 may play a pathophysiological role in Blin-ALL.

The inhibition of cell spreading on a cellulose substrate (cuprophan) induces an apoptotic process via a mitochondria-dependent pathway.

Cell shape was found to be a strong indicator of whether individual cells grow or die, and may play an important role in controlling apoptosis as well as cell growth. We compared here the behaviour of rounded Swiss 3T3 cells aggregated on a cellulose cuprophan membrane to those cultured on dish polystyrene. We demonstrated that cells aggregated on cellulose substrates for up to 48 h underwent programmed cell death that was associated with phosphatidylserine flipping and caspase 9 and caspase 3 activation, suggesting a mitochondria-dependent apoptotic process. In addition, we found that this phenomenon cannot be entirely explained by disengagement of alpha 5 beta 1 integrin ligation.

Severe ADAMTS13 deficiency in adult idiopathic thrombotic microangiopathies defines a subset of patients characterized by various autoimmune manifestations, lower platelet count, and mild renal involvement.

The significance of ADAMTS13 deficiency in adult thrombotic microangiopathy (TMA) remains controversial. In an attempt to define the characteristics of adult TMA with severe ADAMTS13 deficiency, we determined 2 groups of patients on the basis of ADAMTS13 activity (undetectable or detectable). Clinical presentation, laboratory values, autoimmune manifestations, and outcome were compared between the groups. Patients were included retrospectively from 12 centers. All fulfilled the diagnosis criteria of TMA. Patients with a history of transplantation, cancer and chemotherapy, and Centers for Disease Control and Prevention (CDC) stage C human immunodeficiency virus (HIV) infection were not included. Forty-six patients were included. Thirty-one patients had an undetectable ADAMTS13 activity (<5%), and the remaining 15 patients had ADAMTS13 activity of >25%. Severe ADAMTS13 deficiency was associated with a plasmatic inhibitor in 17 cases (55%), suggesting an immune-mediated mechanism. Patients with undetectable ADAMTS13 were more frequently of Afro-Caribbean origin than patients with detectable ADAMTS13 activity (48.4% vs 13.3%, respectively; p = 0.03). As opposed to patients with detectable ADAMTS13 activity, patients with severe ADAMTS13 deficiency displayed various autoimmune manifestations that consisted of nondestructive polyarthritis (4 cases) associated in 1 case with malar rash and extramembranous glomerulonephritis, discoid lupus (3 cases), and autoimmune endocrinopathies, Raynaud phenomenon, and sarcoidosis-like disease (1 case each). In patients with severe ADAMTS13 deficiency, antinuclear antibodies, anti-double-stranded DNA antibodies, and anticardiolipin antibodies were positive in 22 (71%) cases, 3 (9.7%) cases, and 1 (3.2%) case, respectively. One patient fulfilled the criteria for the diagnosis of systemic lupus erythematosus. During follow-up, 1 patient with severe ADAMTS13 deficiency developed antinuclear antibodies, and 3 others developed anti-double-stranded DNA antibodies, in association with neurologic manifestations and anticardiolipin antibodies in 1 case. Patients with severe ADAMTS13 deficiency also had a lower platelet count (12 x 10(9)/L; range, 2-69 x 10(9)/L) and less severe renal failure (estimated glomerular filtration rate: 78 mL/min; range, 9-157 mL/min) than patients with detectable ADAMTS13 activity (49.5 x 10(9)/L; range, 6-103 x 10(9)/L; p = 0.0004, and 15.8 mL/min; range, 5.6-80 mL/min; p < 0.0001, respectively). End-stage renal failure occurred in 1 patient with severe ADAMTS13 deficiency and in 3 patients with detectable ADAMTS13 activity (3.2% vs 21.4%, respectively; p = 0.08). Flare-up and relapse episodes and survival were comparable between the groups. Taken together, these data indicate that adult idiopathic thrombotic thrombocytopenic purpura, as defined by severe ADAMTS13 deficiency, may occur preferentially in a particular ethnic group, and is characterized by severe thrombocytopenia, mild renal involvement, and a wide spectrum of autoimmune manifestations that may be completed during follow-up. Indeed, apparently idiopathic thrombotic thrombocytopenic purpura may be considered a specific autoimmune disease.

Control of a relapse and induction of long-term remission of Wegener's granulomatosis by cyclosporine.

We report a case of severe Wegener's granulomatosis that caused end-stage renal failure and recurrent flares of sinusitis and pulmonary manifestations. To avoid the cumulative toxicity of iterative treatments with cyclophosphamide pulses and glucocorticoids, treatment with cyclosporine as a single agent was instituted in the early phase of the third relapse, before any pulmonary involvement. Cyclosporine enabled rapid control of the disease and induced a complete remission of more than 30 months.

[Polyclonal CD8+/CD57+ T cell expansions: clinical significance]. / Signification clinique des expansions polyclonales lymphocytaires T CD8+/CD57+.

Polyclonal CD8(+)/CD57(+)T cell lymphocytosis can be observed in various conditions such as chronic viral infections, autoimmune cytopenias, connective tissue diseases, chronic graft-versus-host disease and primary or secondary immune deficiencies. This population results from the chronic stimulation of CD8(+)/CD28(+)/CD57(-)lymphocytes by exogenous (mostly infection-related), autologous or allogeneic antigens. Paralleling chronic antigen stimulation, these CD8(+) T cells acquire a poor capacity to proliferate in standard conditions in relation with the loss of CD28, whereas CD57 antigen becomes expressed at their surface. CD8(+)/CD57(+)T cells represent activated cytotoxic T lymphocytes at a terminal stage of their differentiation with evidence of immunological senescence, which have usually lost their cytotoxic properties to become "regulatory" T cells. Patients with a CD8(+)/CD57(+)T cell lymphocytes expansion can display features of organ infiltration, as well as chronic idiopathic neutropenia. The search of this population has therefore a diagnostic value in clinical practice. A CD8(+)/CD57(+)T cell lymphocytes expansion must be suggested in patients with an organomegaly or organ(s) infiltration, particularly in patients infected by the human immunodeficiency virus or in the setting of allogeneic hematopoietic stem cell transplantation, as well as in patients with a neutropenia of unexplained origin. The identification of a CD8(+)/CD57(+)T cell lymphocytes expansion also has therapeutical consequences since patients with an organ infiltration or a neutropenia may respond remarkably to immunomodulatory therapies. The search of a CD8(+)/CD57(+) T cell expansion thus represents a useful and still poorly known diagnostic tool which clinical interest deserves further evaluation.

Clinical significance of autoantibodies to the pericentromeric heterochromatin protein 1a protein.

OBJECTIVE: The objective of the study is to determine the frequency and the clinical significance of autoantibodies to the pericentromeric heterochromatin protein 1 (HP1). So far this antinuclear antibody specificity has been mainly reported in patients with the CREST syndrome. METHODS: We screened the sera of 199 individuals, including patients suffering from various autoimmune disorders (Group I, n=145) and non autoimmune diseases (Group II, n=44 patients) as well as healthy individuals (Group III, n=30). The sera were systematically tested by Western blot and ELISA using a GST-HP1α fusion protein as an antigen. RESULTS: Anti-HP1 antibodies were detected in 32% of patients in Group I, 11.3% in Group II and 3.3% of individuals in Group III. They could be detected in sera containing or not antinuclear antibodies detectable by indirect immunofluorescence. Anti-HP1 antibodies were mostly associated with the CREST and Sjogren's syndromes (70% and 44.4%, respectively). They could also be detected in 22.2% of patients suffering from various other autoimmune diseases. However, their negative predictive value was 94% in the CREST syndrome. CONCLUSION: Anti-HP1 autoantibodies are associated with a large spectrum of disorders. However, they have a diagnostic value in the CREST syndrome.

Human pre-B cell receptor signal transduction: evidence for distinct roles of PI3kinase and MAP-kinase signalling pathways.

Pre-BCR acts as a critical checkpoint in B cell development. However, its signalling cascade still remains indistinctly characterised in human. We investigated pre-BCR signalling pathway to examine its regulation in normal primary pre-B lymphocytes and pre-B cell lines. In cell lines, early signalling events occurring after pre-BCR stimulation include phosphorylation of Lyn, Blk and Syk together with ZAP70, Btk, Vav, PLC-γ2 and various adaptor proteins, such as BLNK, LAB, LAT and SLP-76. Further downstream, these molecules induced activation of the PI3K/AKT and MAP-kinase resulting in an augmentation of canonical NF-κB pathways and cFos/AP1 activation. PI3K and MAPK exerted opposing effects on the pre-BCR-induced activation of the canonical NF-κB and c-Fos/AP1 pathways. Immediate nuclear export of FoxO3A and delayed import of IRF4 were additional events observed after pre-BCR crosslinking in primary cells. Pre-BCR-induced down-regulation of Rag1, Rag2, E2A and Pax5 transcripts occurred in a PI3K-dependent manner. Finally we bring evidence that pre-BCR stimulation or co stimulation with CD19 enhances cell cycle signal.

IGF-1 activates hEAG K(+) channels through an Akt-dependent signaling pathway in breast cancer cells: role in cell proliferation.

Previous work from our laboratory has shown that human ether à go-go (hEAG) K(+) channels are crucial for breast cancer cell proliferation and cell cycle progression. In this study, we investigated the regulation of hEAG channels by an insulin-like growth factor-1 (IGF-1), which is known to stimulate cell proliferation. Acute applications of IGF-1 increased K(+) current-density and hyperpolarized MCF-7 cells. The effects of IGF-1 were inhibited by hEAG inhibitors. Moreover, IGF-1 increased mRNA expression of hEAG in a time-dependent manner in parallel with an enhancement of cell proliferation. The MCF-7 cell proliferation induced by IGF-1 is inhibited pharmacologically by Astemizole or Quinidine or more specifically using siRNA against hEAG channel. Either mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K) are known to mediate IGF-1 cell proliferative signals through the activation of extracellular signal-regulated kinase 1/2 (Erk 1/2) and Akt, respectively. In MCF-7 cells, IGF-1 rapidly stimulated Akt phosphorylation, whereas IGF-1 had little stimulating effect on Erk 1/2 which seems to be constitutively activated. The application of wortmannin was found to block the effects of IGF-1 on K(+) current. Moreover, the inhibition of Akt phosphorylation by the application of wortmannin or by a specific reduction of Akt kinase activity reduced the hEAG mRNA levels. Taken together, our results show, for the first time, that IGF-1 increases both the activity and the expression of hEAG channels through an Akt-dependent pathway. Since a hEAG channel is necessary for cell proliferation, its regulation by IGF-1 may thus play an important role in IGF-1 signaling to promote a mitogenic effect in breast cancer cells.

Constitutive activation of Stat5 promotes its cytoplasmic localization and association with PI3-kinase in myeloid leukemias.

Persistent activation of Stat5 is frequently found in hematologic neoplasms. Studies conducted with constitutively active Stat5 mutants (Stat51*6 and cS5F) have shown that deregulated Stat5 activity promotes leukemogenesis. To investigate the oncogenic properties of these mutants, we used cS5F-expressing bone marrow cells which induce a multilineage leukemia when transplanted into recipient mice. Here, we show by immunocytochemistry that cS5F is localized mainly in the cytoplasmic compartment of leukemic cells, suggesting that the transforming nature of cS5F may be associated with a cytoplasmic function. In support of this hypothesis, we found that cS5F forms a complex with the p85 subunit of the phosphatidylinositol 3-kinase (PI3-K) and the scaffolding adapter Gab2 in leukemic bone marrow cells, resulting in the activation of Akt/PKB, a crucial downstream target of PI3-K. By using transducible TAT-Gab2 or TAT-Akt recombinant proteins, we were able to demonstrate that activation of the PI3-kinase/Akt pathway by cS5F molecules through Gab2 is essential for induction of cell growth. We also found that persistently phosphorylated Stat5 in primary cells from patients with myeloid leukemias has a cytoplasmic localization. These data suggest that oncogenic Stat5 proteins exert dual transforming capabilities not only as transcriptional activators but also as cytoplasmic signaling effectors.

Polyclonal IgG4 hypergammaglobulinemia associated with plasmacytic lymphadenopathy, anemia and nephropathy.

Marked polyclonal immunoglobulin (Ig)G4 hypergammaglobulinemia has exceptionally been reported. Here we report on two Algerian patients who presented a syndrome characterized by anemia, plasmacytic lymphadenopathy, renal manifestations, and a marked polyclonal IgG4 hypergammaglobulinemia leading to a hyperviscosity syndrome in one case. The IgG4-expressing cell percentage was significantly increased in the peripheral blood lymphocytes collected from the two patients upon diagnosis. Moreover, in contrast with normal sera, both patients' sera significantly increased the percentage of IgG4-expressing cells when incubated with CD40-stimulated normal B lymphocytes. Similar effects were obtained with the culture supernatants of the patients' activated T cells. Anti-interleukin (IL) 4 and/or anti-IL-13 antibodies were unable to antagonize the IgG4 production. IL-4 and IL-13 serum concentrations were found to be normal in the two patients. The increased IgG4 production was found to be mediated by soluble factor(s), most probably secreted by activated T cells, which did not require the signal transducer and activator of transcription 6 signaling pathway.