Persistent activation of Stat5 is frequently found in hematologic neoplasms. Studies conducted with constitutively active Stat5 mutants (Stat51*6 and cS5 F ) have shown that deregulated Stat5 activity promotes leukemogenesis. To investigate the oncogenic properties of these mutants, we used cS5 F -expressing bone marrow cells which induce a multilineage leukemia when transplanted into recipient mice. Here, we show by immunocytochemistry that cS5 F is localized mainly in the cytoplasmic compartment of leukemic cells, suggesting that the transforming nature of cS5 F may be associated with a cytoplasmic function. In support of this hypothesis, we found that cS5 F 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 cS5 F 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. IntroductionStat5A and Stat5B transcription factors are important mediators of cytokine-induced cell survival and proliferation. 1 There is a large body of evidence indicating that they play crucial roles in hematopoiesis in humans and mice. Stat5a/b Ϫ/Ϫ mice have multiple hematopoietic defects which affect the proliferation and/or survival of both lymphoid and myeloid lineages. [2][3][4][5][6][7] In addition, Stat5 proteins regulate the growth of hematopoietic progenitor cells, and a recent report has suggested that Stat5 might be involved in self-renewal of human CD34 ϩ progenitor cells. 8,9 Deregulation of the Jak-Stat signaling pathway, particularly Stat3 and Stat5, was reported in many different types of cancer, including hematopoietic neoplasms. 10,11 Persistent activation of these transcription factors is frequently found in many tumor cells, most probably as a consequence of deregulated tyrosine kinase activity. Importantly, Stat5 is a common target for different oncoproteins with tyrosine kinase activity such as Tel-Jak2, Bcr-Abl, the mutated forms of Flt3 and c-Kit, and the Jak2V617F mutant which has been recently characterized in various myeloproliferative disorders. [12][13][14][15][16] Furthermore, it was shown that Stat5 plays a critical role in Bcr-Abl-and Tel-Jak2-induced leukemia. [17][18][19] The most direct evidence that constitutive activation of Stat5 is an important causative event in cell transformation came from the analysis of the Stat5 mutants, Stat5A1*6, Stat5B1*6, and cS5 F . These proteins with mutations at residues H 299 3R and S 711/716 3F (Stat5A1*6) or with the single mutation S 711 3F (cS5 ...

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 IntroductionMast cells (MCs) are critical effector cells in innate and acquired immunity. 1,2 Under various circumstances and pathologic conditions, MCs increase in number and accumulate in various tissues and organs. In many cases, reactive MC hyperplasia is found. 1 However, MCs (MC progenitors) may also undergo neoplastic transformation. 3,4 Disorders that lead to enhanced proliferation and/or accumulation of neoplastic MCs are well defined by WHO criteria. [3][4][5][6] MCs are derived from pluripotent hematopoietic cells in the bone marrow and undergo terminal maturation in their ultimate tissue destinations under the influence of stem cell factor, also known as Kit ligand. [7][8][9] Studies in MC-deficient mouse strains displaying mutations in the stem cell factor (SCF) gene or the gene encoding the SCF receptor, c-Kit, as well as activating c-Kit mutations that are considered to represent major transforming hits in mastocytosis, underline the importance of SCF and Kit for MC development. [10][11][12][13][14][15][16] Binding of SCF to Kit induces activation of various signaling molecules including phospholipase C, the Src family tyrosine kinase, the scaffolding molecule Gab2, the MAP Kinases Erk1/2, the JAK tyrosine kinase, the Phosphatidyl-inositol 3-kinase (PI3K), and the Stat transcription factors. [17][18][19] Lessons from gene deletion studies in mice have indicated that PI3K, Gab2, and Stat5 play a critical role in MC development and function, suggesting that these molecules may represent important downstream effectors of c-Kit signaling. [20][21][22] Moreover, recent data have shown that Stat5 and Gab2 are also required for signaling via the high affinity IgE receptor Fc⑀RI that plays a critical role in MC function and allergic response. 23,24 Besides their physiologic role in MCs, accumulating evidence suggests that persistent Stat5 and PI3K activation is frequently found in hematopoietic neoplasms and solid tumors. 25,26 It has also been described that disease-related oncogenic tyrosine kinases like Tel-Jak2, Bcr-Abl, Tel-PDGFR␤, mutated Kit or Flt3 receptors, and the Jak2 (V617F) mutant, detectable in most myeloproliferative disorders (MPDs), induce constitutive activation of Stat5, PI3K and its downstream effector, the serine threonine kinase Akt. [27][28][29][30][31][32][33][34][35] Moreover, Stat5 proteins were found to be required for Tel-Jak2-and Bcr-Abl-induc...

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.

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.

GeneXpert MTB/RIF assay is efficient and reliable technique for the rapid diagnostic of TB. It's simplicity, high sensitivity and specificity for RIF resistance detection make this technique a very attractive tool for diagnostic of MTB and RIF resistance in MDR cases.

Endometriosis is often associated with a chronic pelvic immuno-inflammatory process, which is closely related to disease pathogenesis and major symptoms. Our studies led to the detection of a marked imbalance between IL-1 and its natural inhibitor IL-1 receptor type 2 (IL1R2) in women with endometriosis. This points to a deficiency in the local control of IL-1 that, in view of the cytokine's elevated levels and potent proinflammatory, angiogenic, and growth-promoting effects, may contribute to endometriosis development. Using an in vivo model in which human endometrial tissue was inoculated into nude mice and left to establish before any further treatment, our data showed that sIL1R2 interferes with the capability of endometrial tissue to invade, grow, disseminate, and stimulate angiogenesis into the host tissue. sIL1R2 significantly down-regulated the expression of major cell adhesion receptors (αv and β3 integrins), matrix metalloproteinases (MMP-2 and -9), and vascular endothelial cell growth factor. Interestingly, treatment with sILR2 (5 μg/kg) led to a concomitant upregulation of matrix metalloproteinases natural inhibitors (TIMP1 and TIMP2) and down-regulation of BclII, a potent anti-apoptotic protein. This creates an imbalance between pro- and anti-proteolytic and apoptotic factors and may further contribute to IL1R2 growth-inhibitory effects. This study provides evidence that sIL1R2 alters ectopic endometrial tissue growth, remodeling, and survival in vivo and may represent an interesting potential therapeutic tool.

According to our results, cholecystectomy could possibly be a risk factor for pancreatic cancer in Algerian population.

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