Phosphorylation Level Of Signal Transducer And Activator Of Transcription 3 Research Articles

Activation of the Notch1/STAT3/Twist signaling axis promotes gastric cancer progression

Gastric carcinoma is one of the most common malignancies and a lethal cancer in the world. Notch signaling and transcription factors STAT3 (signal transducer and activator of transcription 3) and Twist regulate tumor development and are critical regulators of gastric cancer progression. Herein, the relationship among Notch, STAT3 and Twist pathways in the control of gastric cancer progression was studied. We found that Twist and phosphorylated STAT3 levels were promoted by the activated Notch1 receptor in human stomach adenocarcinoma SC-M1, embryonic kidney HEK293 and erythroleukemia K562 cells. Notch1 signaling dramatically induced Twist promoter activity through a C promoter binding factor-1-independent manner and STAT3 phosphorylation. Overexpression of Notch1 receptor intracellular domain (N1IC) enhanced the interaction between nuclear STAT3 and Twist promoter in cells. Gastric cancer progression of SC-M1 cells was promoted by N1IC through STAT3 phosphorylation and Twist expression including colony formation, migration and invasion. STAT3 regulated gastric cancer progression of SC-M1 cells via Twist. N1IC also elevated the progression of other gastric cancer cells such as AGS and KATO III cells through STAT3 and Twist. The N1IC-promoted tumor growth and lung metastasis of SC-M1 cells in mice were suppressed by the STAT3 inhibitor JSI-124 and Twist knockdown. Furthermore, Notch1 and Notch ligand Jagged1 expressions were significantly associated with phosphorylated STAT3 and Twist levels in gastric cancer tissues of patients. Taken together, these results suggest that Notch1/STAT3/Twist signaling axis is involved in progression of human gastric cancer and modulation of this cascade has potential for the targeted combination therapy.

RAGE signaling mediates post-injury arterial neointima formation by suppression of liver kinase B1 and AMPK activity

ObjectiveIntima formation involves smooth muscle cell (SMC) proliferation and migration that ultimately drives arterial stenosis, thrombosis, and ischemia in atherosclerosis, hypertension, and arterial revascularization. Receptor for advanced glycation endproducts (RAGE) is a transmembrane signaling receptor implicated in diabetic renal and vascular complications, and post-injury intima formation, partly via Signal transducer and activator of transcription 3 (STAT3) activation. The metabolic super-regulator Adenosine monophosphate kinase (AMPK) inhibits SMC proliferation and intima formation. AMPK activation is promoted by liver kinase B1 (LKB1), and LKB1 inhibits STAT3 activation. Here, we tested the hypothesis that RAGE promotes arterial intima formation by modulating both LKB1 and AMPK. Methods and resultsRAGE ligands (the calgranulin S100A11, and glycated albumin) suppressed AMPK activation in conjunction with increased proliferation and migration of cultured SMCs. These effects were inhibited both by RAGE deficiency and by prior AMPK activation. In SMCs, RAGE ligands decreased LKB1 activity. Moreover, knockdown of both LKB1 and AMPK were associated with increased STAT3 phosphorylation levels. In response to murine carotid artery ligation, expression of RAGE and S100A11 increased, whereas AMPK and LKB1 activity decreased in situ. Conversely, LKB1 and AMPK activity increased in situ, and neointima formation was attenuated in Rage−/− mice. ConclusionThe linkage of decreased LKB1 and AMPK activity with increased STAT3 in SMCs mediates the capacity of RAGE ligand-induced signaling to promote neointima formation in response to arterial injury.

Pien Tze Huang inhibits tumor cell proliferation and promotes apoptosis via suppressing the STAT3 pathway in a colorectal cancer mouse model

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in cell survival and proliferation. Constitutive activation of STAT3 is strongly correlated with pathogenesis of various types of malignant tumors including colorectal cancer (CRC), and therefore is a major focus in the development of anti-cancer agents. Pien Tze Huang (PZH), a well-known traditional Chinese formula prescribed already in the Ming Dynasty, has been demonstrated to be clinically effective in the treatment of CRC. However, the precise mechanism of its anti-cancer activity remains largely unknown. In the present study we evaluated the efficacy of PZH against tumor growth in vivo in the CRC mouse xenograft model, and investigated the underlying molecular mechanisms. We found that administration of PZH reduced tumor volume and tumor weight but had no effect on body weight gain in CRC mice, demonstrating that PZH can inhibit colon cancer growth in vivo without apparent adverse effect. We also observed that PZH treatment inhibited the phosphorylation level of STAT3 in tumor tissues. Consequently, the inhibitory effect of PZH on STAT3 activation resulted in the up-regulation of Bax/Bcl-2 ratio as well as down-regulation of Cyclin D1 and CDK4 expression, leading to the induction of apoptosis as well as the inhibition of cell proliferation. These results suggest that promotion of cancer cell apoptosis and inhibition of proliferation via suppression of STAT3 pathway might be one of the mechanisms by which PZH treats colorectal cancer.

A highly selective, orally active inhibitor of Janus kinase 2, CEP-33779, ablates disease in two mouse models of rheumatoid arthritis

IntroductionJanus kinase 2 (JAK2) is involved in the downstream activation of signal transducer and activator of transcription 3 (STAT3) and STAT5 and is responsible for transducing signals for several proinflammatory cytokines involved in the pathogenesis of rheumatoid arthritis (RA), including interleukin (IL)-6, interferon γ (IFNγ) and IL-12. In this paper, we describe the efficacy profile of CEP-33779, a highly selective, orally active, small-molecule inhibitor of JAK2 evaluated in two mouse models of RA.MethodsCollagen antibody-induced arthritis (CAIA) and collagen type II (CII)-induced arthritis (CIA) were established before the oral administration of a small-molecule JAK2 inhibitor, CEP-33779, twice daily at 10 mg/kg, 30 mg/kg, 55 mg/kg or 100 mg/kg over a period of 4 to 8 weeks.ResultsPharmacodynamic inhibition of JAK2 reduced mean paw edema and clinical scores in both CIA and CAIA models of arthritis. Reduction in paw cytokines (IL-12, IFNγ and tumor necrosis factor α) and serum cytokines (IL-12 and IL-2) correlated with reduced spleen CII-specific T helper 1 cell frequencies as measured by ex vivo IFNγ enzyme-linked immunosorbent spot assay. Both models demonstrated histological evidence of disease amelioration upon treatment (for example, reduced matrix erosion, subchondral osteolysis, pannus formation and synovial inflammation) and reduced paw phosphorylated STAT3 levels. No changes in body weight or serum anti-CII autoantibody titers were observed in either RA model.ConclusionsThis study demonstrates the utility of using a potent and highly selective, orally bioavailable JAK2 inhibitor for the treatment of RA. Using a selective inhibitor of JAK2 rather than pan-JAK inhibitors avoids the potential complication of immunosuppression while targeting critical signaling pathways involved in autoimmune disease progression.

Antiphospholipid antibodies limit trophoblast migration by reducing IL-6 production and STAT3 activity

PROBLEM: Women with antiphospholipid antibodies (aPL) are at risk of recurrent miscarriage and pre-eclampsia. aPL target the placenta by binding to beta(2)-glycoprotein I (beta(2) GPI) expressed by the trophoblast. The objective of this study was to evaluate if and how aPL affect first trimester trophoblast migration. METHOD OF STUDY: First trimester trophoblast cells were treated with anti-beta(2) GPI monoclonal antibodies. Migration was determined using a two-chamber assay. Interleukin (IL)-6 production was evaluated by RT-PCR and enzyme-linked immunosorbent assay, and signal transducer and activator of transcription 3 (STAT3) activation was assessed by western blot. RESULTS: Trophoblast cells constitutively secreted IL-6 in a time-dependent manner and this directly correlated with STAT3 phosphorylation. In the presence of anti-beta(2) GPI Abs, trophoblast IL-6 mRNA levels and secretion was downregulated in a Toll-like receptor 4/MyD88-independent manner and this correlated with a reduction in phosphorylated STAT3 levels. In addition, the anti-beta(2) GPI Abs reduced the migratory potential of trophoblast. Heparin was able to reverse aPL-dependent inhibition of trophoblast IL-6 secretion and migration. CONCLUSION: This study demonstrates that aPL limit trophoblast cell migration by downregulating trophoblast IL-6 secretion and STAT3 activity. As heparin was unable to prevent these effects, our findings may explain why women with antiphospholipid syndrome, treated with heparin, remain at risk of developing obstetrical syndromes, associated with impaired deep placentation, such as pre-eclampsia.

ORIGINAL ARTICLE: Antiphospholipid Antibodies Limit Trophoblast Migration by Reducing IL‐6 Production and STAT3 Activity

Citation Mulla MJ, Myrtolli K, Brosens JJ, Chamley LW, Kwak‐Kim JY, Paidas MJ, Abrahams VM. Antiphospholipid antibodies limit trophoblast migration by reducing IL‐6 production and STAT3 activity. Am J Reprod Immunol 2010ProblemWomen with antiphospholipid antibodies (aPL) are at risk of recurrent miscarriage and pre‐eclampsia. aPL target the placenta by binding to β2‐glycoprotein I (β2 GPI) expressed by the trophoblast. The objective of this study was to evaluate if and how aPL affect first trimester trophoblast migration.Method of studyFirst trimester trophoblast cells were treated with anti‐β2 GPI monoclonal antibodies. Migration was determined using a two‐chamber assay. Interleukin (IL)‐6 production was evaluated by RT‐PCR and enzyme‐linked immunosorbent assay, and signal transducer and activator of transcription 3 (STAT3) activation was assessed by western blot.ResultsTrophoblast cells constitutively secreted IL‐6 in a time‐dependent manner and this directly correlated with STAT3 phosphorylation. In the presence of anti‐β2 GPI Abs, trophoblast IL‐6 mRNA levels and secretion was downregulated in a Toll‐like receptor 4/MyD88‐independent manner and this correlated with a reduction in phosphorylated STAT3 levels. In addition, the anti‐β2 GPI Abs reduced the migratory potential of trophoblast. Heparin was able to reverse aPL‐dependent inhibition of trophoblast IL‐6 secretion and migration.ConclusionThis study demonstrates that aPL limit trophoblast cell migration by downregulating trophoblast IL‐6 secretion and STAT3 activity. As heparin was unable to prevent these effects, our findings may explain why women with antiphospholipid syndrome, treated with heparin, remain at risk of developing obstetrical syndromes, associated with impaired deep placentation, such as pre‐eclampsia.

Curcumin suppresses constitutive activation of STAT‐3 by up‐regulating protein inhibitor of activated STAT‐3 (PIAS‐3) in ovarian and endometrial cancer cells

Signal transducer and activator of transcription-3 (STAT-3) is constitutively activated in ovarian and endometrial cancers and is implicated in uncontrolled cell growth. Thus, its disruption could be an effective approach to control tumorigenesis. Curcumin is a dihydroxyphenolic compound, with proven anti-cancer efficacy in various cancer models. We examined the anti-tumor mechanism of curcumin on STAT-3 and on the negative regulators of STAT-3, including suppressors of cytokine signaling proteins (SOCS-1 and SOCS-3), protein inhibitors of activated STAT (PIAS-1 and PIAS-3), and SH2 domain-containing phosphatases (SHP-1 and SHP-2) in ovarian and endometrial cancer cell lines. Treatment of cancer cells with curcumin induced a dose- and time-dependent decrease of constitutive IL-6 expression and of constitutive and IL-6-induced STAT-3 phosphorylation, which is associated with decreased cell viability and increased cleavage of caspase-3. The inhibition of STAT-3 activation by curcumin was reversible, and phosphorylated STAT-3 levels returned to control levels 24 h after curcumin removal. Compared to normal cells baseline expression of SOCS-3 was high in cancer cells and a marked decrease in SOCS-3 expression was seen following curcumin treatment. Overexpression of SOCS-3 in curcumin-treated cells increased expression of phosphorylated STAT-3 and resulted in increased cell viability. Normal ovarian and endometrial cells exhibited high expression of PIAS-3 protein, whereas in cancer cells the expression was greatly reduced. Curcumin increased PIAS-3 expression in cancer cells. Of significance, siRNA-mediated knockdown of PIAS-3 overcomes the inhibitory effect of curcumin on STAT-3 phosphorylation and cell viability. In conclusion, curcumin suppresses JAK-STAT signaling via activation of PIAS-3, thus attenuating STAT-3 phosphorylation and tumor cell growth.

Leptin receptor 170 kDa (OB‐R170) protein expression is reduced in obese human skeletal muscle: a potential mechanism of leptin resistance

To examine whether obesity-associated leptin resistance could be due to down-regulation of leptin receptors (OB-Rs) and/or up-regulation of suppressor of cytokine signalling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) in skeletal muscle, which blunt janus kinase 2-dependent leptin signalling and signal transducer and activator of transcription 3 (STAT3) phosphorylation and reduce AMP-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase (ACC) phosphorylation. Deltoid and vastus lateralis muscle biopsies were obtained from 20 men: 10 non-obese control subjects (mean +/- s.d. age, 31 +/- 5 years; height, 184 +/- 9 cm; weight, 91 +/- 13 kg; and percentage body fat, 24.8 +/- 5.8%) and 10 obese (age, 30 +/- 7 years; height, 184 +/- 8 cm; weight, 115 +/- 8 kg; and percentage body fat, 34.9 +/- 5.1%). Skeletal muscle OB-R170 (OB-R long isoform) protein expression was 28 and 25% lower (both P < 0.05) in arm and leg muscles, respectively, of obese men compared with control subjects. In normal-weight subjects, SOCS3 protein expression, and STAT3, AMPKalpha and ACCbeta phosphorylation, were similar in the deltoid and vastus lateralis muscles. In obese subjects, the deltoid muscle had a greater amount of leptin receptors than the vastus lateralis, whilst SOCS3 protein expression was increased and basal STAT3, AMPKalpha and ACCbeta phosphorylation levels were reduced in the vastus lateralis compared with the deltoid muscle (all P < 0.05). In summary, skeletal muscle leptin receptors and leptin signalling are reduced in obesity, particularly in the leg muscles.

12-O-Tetradecanoylphorbol-13-acetate Inhibits Melanoma Growth by Inactivation of STAT3 through Protein Kinase C-activated Tyrosine Phosphatase(s)

The growth of most melanoma cells in vitro is inhibited by the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In this study, the involvement of the signal transducer and activator of transcription 3 (STAT3) in the TPA-induced growth inhibition of melanoma cells was examined. The in vitro growth and DNA synthesis of five melanoma cell lines, whose STAT3 was activated (phosphorylated), was inhibited by TPA, whereas that of WM35 and WM39 cells, whose STAT3 activity was at negligible levels, was considerably slow and not affected by TPA. Blockade of STAT3 activity by small interfering RNAs suppressed the growth of WM1205Lu cells containing constitutively activated STAT3. Treatment of WM1205Lu cells with TPA decreased both the phosphorylated STAT3 and the DNA-binding activity of STAT3. Pretreatment of WM1205Lu cells with either a protein-tyrosine phosphatase inhibitor or a protein kinase C (PKC) inhibitor prevented the inhibitory effects of TPA on the level of phosphorylated STAT3. The five melanoma cell lines containing phosphorylated STAT3 commonly expressed PKCalpha, PKCdelta, and PKCepsilon. Introduction of the dominant negative mutant of one of these PKC isoforms into WM1205Lu cells inhibited the TPA-induced dephosphorylation of STAT3. A Src inhibitor attenuated the STAT3 phosphorylation in WM1205Lu cells. These results indicate that constitutively activated STAT3 is positively regulated by c-Src and negatively regulated by a PKC-activated tyrosine phosphatase(s) in melanoma cells. Because TPA did not affect c-Src activity, we conclude that the growth inhibitory effect of TPA on melanoma cells is mediated through inactivation of STAT3 by a PKC-activated tyrosine phosphatase(s).

MUC1 is a downstream target of STAT3 and regulates lung cancer cell survival and invasion

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in human cancer including lung cancer and has been implicated in transformation, tumorigenicity, and metastasis. One putative downstream gene regulated by Stat3 is MUC1 which also has important roles in tumorigenesis. We determined if Stat3 regulates MUC1 in lung cancer cell lines and what function MUC1 plays in lung cancer cell biology. We examined MUC1 expression in non-small cell lung cancer (NSCLC) cell lines and found high levels of MUC1 protein expression associated with higher levels of tyrosine phosphorylated STAT3. STAT3 knockdown downregulated MUC1 expression whereas constitutive STAT3 expression increased MUC1 expression at mRNA and protein levels. MUC1 knockdown induced cellular apoptosis concomitant with reduced Bcl-XL and sensitized cells to cisplatin treatment. MUC1 knockdown inhibited tumor growth and metastasis in an orthotopic mouse model of lung cancer by activating apoptosis and inhibiting cell proliferation in vivo. These results demonstrate that constitutively activated STAT3 regulates expression of MUC1, which mediates lung cancer cell survival and metastasis in vitro and in vivo. MUC1 appears to be a cooperating oncoprotein with multiple oncogenic tyrosine kinase pathways and could be an effective target for the treatment of lung cancer.

Dual activation of STAT-3 and Akt is required during the trigger phase of ischaemic preconditioning

During preconditioning by tumour necrosis factor-alpha (TNFalpha), activation of the signal transducer and activator of transcription-3 (STAT-3) but not Akt, is essential, whereas ischaemic cardiac preconditioning (IPC) requires both STAT-3 and Akt at the time of reperfusion. However, it is not known whether the same signalling pattern occurs during the preconditioning stimulus (trigger phase) and whether links exist between STAT-3 and Akt. Hence, our hypothesis is that concomitant activation or co-interaction between these two key signals is required during the trigger phase for IPC. Conversely, we proposed that there would be no such interaction when preconditioning was induced by TNFalpha (TNF-PC). Cardiomyocytes, isolated from adult wild-type (WT) and cardiac-specific STAT-3 knockout (KO) mice, were exposed to simulated ischaemia (SI) reperfusion. Cells were preconditioned either by 30 min SI or by 30 min TNFalpha (0.5 ng/mL) in the presence or absence of AG490 (100 nM) or wortmannin (100 nM) to inhibit STAT-3 or Akt, respectively. Cell viability was evaluated by trypan blue, and phosphorylation levels of STAT-3 and Akt were measured by Western blot analysis. Similar experiments were conducted in isolated rat hearts subjected to an ischaemia-reperfusion insult. Both preconditioning stimuli failed to protect KO cardiomyocytes, and addition of AG490 abolished preconditioning in WT cardiomyocytes or isolated hearts. Wortmannin abolished the protection afforded by IPC, but did not affect TNF-PC in both models. Western blot analysis demonstrated that added wortmannin during IPC stimulus decreased STAT-3 phosphorylation while, conversely, AG490 reduced Akt phosphorylation. STAT-3 activation could be achieved independent of Akt during TNF-PC. In contrast, during an IPC stimulus, both prosurvival signalling molecule cascades acted in concert so that inhibiting activation of STAT-3 also inhibited that of Akt and vice versa.

Influence of maternal undernutrition and overfeeding on cardiac ciliary neurotrophic factor receptor and ventricular size in fetal sheep

Intrauterine nutrition status is reported to correlate with risk of cardiovascular diseases in adulthood. Either under- or overnutrition during early to mid gestation contributes to altered fetal growth and ventricular geometry. This study was designed to examine myocardial expression of ciliary neurotrophic factor receptor α (CNTFRα) and its downstream mediator signal transducer and activator of transcription 3 (STAT3) on maternal undernutrition- or overnutrition-induced changes in fetal heart weight. Multiparous ewes were fed with 50% [nutrient-restricted (NR)], 100% (control) or 150% [overfed (OF)] of National Research Council requirements from 28 to 78 days of gestation (dG; term, 148 dG). Ewes were euthanized on Day 78, and the gravid uteri and fetuses recovered. Ventricular protein expression of CNTFRα, STAT3, phosphorylated STAT3, insulin-like growth factor I receptor (IGF-1R), and IGF binding protein 3 (IGFBP3) were quantitated using Western blot. Plasma cortisol levels were higher in both NR and OF fetuses, whereas plasma IGF-1 levels were lower and higher in NR and OF fetuses. Fetal weights were reduced by 29.9% in NR ewes and were increased by 22.2% in fetuses from OF ewes compared to control group. Nutrient restriction did not affect fetal heart or ventricular weights, whereas overfeeding increased heart and ventricular weights. Protein expression of CNTFRα in fetal ventricular tissue was reduced in OF group, whereas STAT3 and phosphorylated STAT3 levels were reduced in both NR and OF groups. Expression of IGF-1R and IGFBP3 was unaffected in either NR or OF group. These data suggested that, compared with maternal undernutrition, intrauterine overfeeding during early to mid gestation is associated with increases in fetal blood concentrations of cortisol and IGF-1, in association with ventricular hypertrophy where reduced expression of CNTFRα and STAT3 may play a role.

A novel inhibitor of the STAT3 pathway induces apoptosis in malignant glioma cells both in vitro and in vivo

Signal transducer and activator of transcription-3 (STAT3) is constitutively activated in a variety of cancer types, including malignant gliomas. STAT3 is activated by phosphorylation of a tyrosine residue, after which it dimerizes and translocates into the nucleus. There it regulates the expression of several genes responsible for proliferation and survival at the transcriptional level. A selective inhibitor of STAT3 phosphorylation, AG490, has been shown to inhibit growth and induce apoptosis in some cancer cell types. However, although AG490 routinely shows in vitro anticancer activity, it has not consistently demonstrated an in vivo anticancer effect in animal models. Here, we have tested WP1066, a novel inhibitor structurally related to AG490 but significantly more potent and active, against human malignant glioma U87-MG and U373-MG cells in vitro and in vivo. IC(50) values for WP1066 were 5.6 muM in U87-MG cells and 3.7 muM in U373-MG cells, which represents 18-fold and eightfold increases in potency, respectively, over that of AG490. WP1066 activated Bax, suppressed the expression of c-myc, Bcl-X(L) and Mcl-1, and induced apoptosis. Systemic intraperitoneal administration of WP1066 in mice significantly (P<0.001) inhibited the growth of subcutaneous malignant glioma xenografts during the 30-day follow-up period. Immunohistochemical analysis of the excised tumors revealed that phosphorylated STAT3 levels in the WP1066 treatment group remained inhibited at 3 weeks after the final WP1066 injection, whereas tumors from the control group expressed high levels of phosphorylated STAT3. We conclude that WP1066 holds promise as a therapeutic agent against malignant gliomas.

1141638491 Hepatocyte growth factor (HGF) stimulates mammalian target of rapamycin (mTOR) in choriocarcinoma cell lines and human trophoblast cells

Introduction: Hepatocyte growth factor (HGF), interleukin‐6 (IL‐6) and insulin‐like growth factor‐II (IGF‐II) are involved in the regulation of trophoblast cell migration and invasion. Signal Transducer and Activator of Transcription 3 (STAT3) and Mammalian Target Of Rapamycin (mTOR) signalling regulate cell invasion, growth and proliferation. mTOR plays also a key role during embryogenesis. Knock‐out mice embryos die after implantation and blastocysts trophoblast outgrowth is reduced.Aim: Stimuli which might trigger such invasive behaviour through mTOR should be defined.Methods: The human choriocarcinoma cell lines JEG‐3, JAR, the human choriocarcinoma‐trophoblast hybrid AC1‐M59 and human term trophoblast cells were stimulated with HGF, IL‐6 or IGF‐II. At several time points, the phosphorylation level of mTOR and STAT3 were tested by Western blot. STAT3 DNA‐binding capacity was analyzed by Electrophorectic Mobility Shift Assay (EMSA). To examine the role of mTOR for invasion and proliferation, mTOR expression was silenced by RNA interference (RNAi).Results: HGF, IGF‐II and IL‐6 did neither induce tyrosine (705) phosphorylation of STAT3 nor STAT3 DNA binding capacity as assessed by EMSA. HGF led to an increase of mTOR serine (2448) phosphorylation for all cell types after 15 and 30 min while IL‐6 and IGF‐II did not induce mTOR phosphorylation. Simultaneously, HGF decreased STAT3 serine (727) phosphorylation. mTOR silencing in AC1‐M59 correlates with reduced proliferation and invasion. STAT3 expression was not affected by mTOR knock down.Conclusion: HGF triggers mTOR activity in trophoblast and trophoblast‐like cells. mTOR is a main regulator of crucial trophoblast functions.

Functional significance of novel neurotrophin-1/B cell-stimulating factor-3 (cardiotrophin-like cytokine) for human myeloma cell growth and survival.

Cytokines of the gp130 family, particularly interleukin 6 (IL-6), play a central role in the growth and survival of malignant plasma cells. Recently, novel neurotrophin-1 (NNT-1)/B cell-stimulating factor-3 (BSF-3), also reported as cardiotrophin-like cytokine (CLC), was identified as a cytokine belonging to the gp130 family. BSF-3, similar to IL-6, exerts regulatory effects on normal B cell functions, but its functional significance in haematological malignancies has not been defined. The purpose of this study was to evaluate the biological effects and signalling pathways that are induced by BSF-3 in malignant plasma cells. Recombinant human BSF-3 was found to have growth stimulatory activity on plasmacytoma cell lines and primary tumour cells. In addition, BSF-3 was able to protect from Dexamethasone (Dex)-induced apoptosis. BSF-3 stimulated cell growth could not be inhibited by neutralizing anti-IL-6 or anti-IL-6 receptor antibodies, but was abrogated by anti-gp130 antibodies. In INA-6.Tu11 cells, a subline of the IL-6-dependent human plasma cell line INA-6 expressing gp130 and the receptor for leukaemia inhibitory factor (LIF), stimulation with BSF-3 induced tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3). AG490, an inhibitor of Janus kinases, decreased BSF-3 induced cell growth in a dose-dependent manner. This correlated with a reduction of STAT3 phosphorylation levels, while p44/42 mitogen-activated protein kinase (MAPK) phosphorylation was not affected. In conclusion, BSF-3 is a novel myeloma growth and survival factor with a potential role in the pathophysiology of the disease.

Induction of uncoupling protein 1 by central interleukin-6 gene delivery is dependent on sympathetic innervation of brown adipose tissue and underlies one mechanism of body weight reduction in rats

Interleukin-6 (IL-6) is a multifunctional cytokine that may have a role in energy regulation. Using a recombinant adeno-associated viral vector expressing murine interleukin-6 (rAAV-IL-6), we examined the chronic effects of centrally expressed IL-6 on food intake, body weight and adiposity in male Sprague–Dawley rats, and investigated the underlying mechanisms. Direct delivery of rAAV-IL-6 into rat hypothalamus suppressed weight gain and visceral adiposity without affecting food intake over a 5-week period. rAAV-IL-6 enhanced uncoupling protein 1 (UCP1) protein levels in interscapular brown adipose tissue (BAT). To investigate if the induction of UCP1 and the reduction in body weight are dependent on sympathetic innervation of BAT, we administered rAAV-IL-6 or a control vector into the hypothalamus of rats in which the interscapular BAT was unilaterally denervated. Over 21 days, there was no difference in food consumption or body weight between rAAV-IL-6- and control vector-treated rats. rAAV-IL-6 delivery increased UCP1 mRNA and protein levels in innervated BAT pads but not denervated BAT pads. Hypothalamic IL-6 signal transduction, indicated by phosphorylated signal transducer and activator of transcription 3 (P-STAT3) levels, was elevated by 2.6-fold at day 21, but returned to control levels by day 35. However, the suppressor of cytokine signaling-3 mRNA level was significantly elevated both at day 21 and day 35. These data demonstrate that chronic elevation of IL-6 in the CNS reduces body weight gain and visceral adiposity without affecting food intake. The mechanism involves sympathetic induction of UCP1 in BAT and, presumably, enhanced thermogenesis in BAT. Furthermore, chronic central IL-6 stimulation desensitizes IL-6 signal transduction characterized by reversal of elevated P-STAT3 levels.