Retinoic acid inhibits IL-6-dependent but not constitutive STAT3 activation in Epstein-Barr virus-immortalized B lymphocytes

IL-6-mediated B-cell growth promotion is involved in the pathogenesis of EBV+ lymphoproliferative disorders of immunosuppressed patients. Since retinoic acid (RA) inhibits the proliferation of EBV-immortalized lymphoblastoid B-cell lines (LCLs), we have investigated the effects of RA on IL-6 signaling in these cells. RA down-regulated IL-6-receptor components with IL-6 agonist activity (membrane and soluble gp80) and increased the levels of soluble gp130, an IL-6 antagonist. These changes, however, were not related to the enhanced production of endogenous IL-6 induced by RA in LCLs. RA-induced modulation of IL-6 receptor components did not abolish IL-6-mediated phosphorylation of gp130, whereas JAK1 and STAT3 phosphorylation and activation induced by IL-6 were markedly inhibited. Overall, the effects of RA resulted in the induction of a complete resistance of LCLs to IL-6-mediated growth promotion. Conversely, RA did not inhibit the constitutive activation of JAK1, TYK2, STAT3 and ERK1/2, ruling out that the JAK/STAT and MAPK pathways may mediate the antiproliferative activity of RA. The finding that RA severely impairs IL-6-dependent signalings in LCLs and inhibits their growth despite the presence of constitutively active JAK/STAT and MAPK cascades provide additional support for a role of RA in the prevention and treatment of EBV-related lymphoproliferative disorders of immunosuppressed patients.     

STAT3 activation by IL-6 from mesenchymal stem cells promotes the proliferation and metastasis of osteosarcoma

We previously demonstrated that human mesenchymal stem cells (MSCs) promote the growth of osteosarcoma in the bone microenvironment. The aim of the present study was to further determine the effect of IL-6/STAT3 signaling on the progression of osteosarcoma. First, conditioned medium from MSCs was used to stimulate the growth of osteosarcoma cells (Saos-2) in vitro. We found that STAT3 was activated and that the activation could be blocked by an IL-6-neutralizing antibody. The inhibition of STAT3 in Saos-2 cells by siRNA or AG490 decreased cell proliferation, migration and invasion, down-regulated the mRNA expression of Cyclin D, Bcl-xL and Survivin and enhanced the apoptotic response. Furthermore, a nude mouse osteosarcoma model was established by injecting luciferase-labeled Saos-2 cells into the tibia, and the effect of STAT3 on tumor growth was determined by treating the mice with AG490. In vivo bioluminescence images showed that tumor growth was dramatically reduced in the AG490 group. In addition, STAT3 inhibition decreased the lung metastasis rate and prolonged the survival of these mice. After treatment with AG490, the protein levels of IL-6, p-STAT3 and PCNA were decreased, and the level of apoptosis in the tumor was increased. Altogether, these data indicate that MSCs in the bone microenvironment might promote the progression of osteosarcoma and protect tumor cells from drug-induced apoptosis through IL-6/STAT3 signaling.     

Mesenchymal stem cells enhance lung cancer initiation through activation of IL-6/JAK2/STAT3 pathway

Background

The role of mesenchymal stem cells (MSCs) and IL-6 in lung cancer has not been well-addressed. We aimed to determine if MSCs can enhance the ability of tumor initiation of lung cancer cells, and link MSCs with activation of the IL-6/JAK2/STAT3 signaling pathway.

Materials and methods

Lung cancer cell lines A549 and CL1-5 were directly or indirectly cocultured with MSCs. Spheres were defined as cell colonies with >50% area showing 3-dimensional structure and blurred cell margins. Cells without and with MSCs were injected into NOD/SCID mice. The percentage of tumor formation was determined. The influence of the IL-6/JAK2/STAT3 signaling pathway in cancer cell sphere formation and tumor growth were investigated.

Results

A very small number of lung cancer cells, when mixed with otherwise non-tumorigenic MSCs, obtained de novo tumorigenicity when injected subcutaneously and allowed to form a tumor xenograft. Secretion of IL-6 from MSCs increased activation of the JAK2/STAT3 pathway in cancer cells, and enhanced sphere formation and tumor initiation. A reduced capacity of tumor formation of A549 and CL1-5 lung cancer cells when IL-6 was inhibited in MSCs or STAT3 was silenced in A549 and CL1-5 admixed with MSCs.

Conclusions

Culture of A549 or CL1-5 lung cancer cells with MSCs increased sphere formation, drug resistance, and overexpression of pluripotency markers through activation of the IL-6/JAK2/STAT3 pathway. MSCs enhanced the capability of A549 and CL1-5 lung cancer cells to form tumors in immunodeficient mice. Blockade of the IL-6/JAK2/STAT3 pathway attenuated the capability of A549 and CL1-5 cells to form tumors.     

IL-6/STAT3信号传导通路及其在肿瘤靶向治疗中的作用

白细胞介素-6(IL-6)与肿瘤患者的分期、预后、转归以及对化疗药物的敏感性有关,且在患者的肿瘤组织及血清中常呈过表达.IL-6主要通过介导信号转换和转录激活因子3(STAT3)信号传导通路(IL-6/STAT3信号传导通路)来调节肿瘤细胞的增殖和分化.因此,IL-6/STAT3信号传导通路的阻断,对肿瘤具有潜在治疗意...     

Downregulation of IL-6-induced STAT3 tyrosine phosphorylation by TGF-beta1 is mediated by caspase-dependent and -independent processes.

To explore the possible cross-talk between the IL-6 and TGF-beta1 pathways in AML blast cells, the effect of TGF-beta1 pretreatment on IL-6-induced STAT3 tyrosine phosphorylation was studied. A reduction of STAT3 tyrosine phosphorylation after TGF-beta1 pretreatment was observed in four out of 40 AML cases (10%), although all of the AML cases responded to TGF-beta1 by means of SMAD3 translocation. The reduced IL-6-mediated STAT3 tyrosine phosphorylation after pre-treatment with TGF-beta1 was associated with apoptosis and coincided with the degradation of certain cellular proteins, including JAK1 and -2 and Tyk2, without affecting the ERK expression and phosphorylation. Furthermore, treatment of AML blasts with the cytostatic agent VP16, as an alternative way to induce apoptosis, resulted in a similar degree of degradation of JAK kinases and concomitant reduction of IL-6-mediated STAT3 tyrosine phosphorylation. Although degradation of JAK kinases could be rescued by incubating the cells with the pan-caspase inhibitor Z-VAD-fmk, the attenuating effect of TGF-beta1 treatment on the STAT3 tyrosine phosphorylation was still partly present. It was shown that in AML cells cultured in the presence of Z-VAD-fmk, TGF-beta1 pretreatment resulted in a reduction of JAK1 phosphorylation upon IL-6 stimulation. Expression of SOCS1 and -3 could be ruled out as a possible cause of reduced JAK1 phosphorylation levels in the investigated AML case.     

Epstein‐Barr virus infection induces miR‐21 in terminally differentiated malignant B cells

The association of Epstein‐Barr virus (EBV) with plasmacytoid malignancies is now well established but how the virus influences microRNA expression in such cells is not known. We have used multiple myeloma (MM) cell lines to address this issue and find that an oncomiR, miR‐21 is induced after in vitro EBV infection. The PU.1 binding site in miR‐21 promoter was essential for its activation by the virus. In accordance with its noted oncogenic functions, miR‐21 induction in EBV infected MM cells caused downregulation of p21 and an increase in cyclin D3 expression. EBV infected MM cells were highly tumorigenic in SCID mice. Given the importance of miR‐21 in plasmacytoid malignancies, our findings that EBV could further exacerbate the disease by inducing miR‐21 has interesting implications both in terms of diagnosis and future miR based therapeutical approaches for the virus associated plasmacytoid tumors.     

Reciprocal activation between IL-6/STAT3 and NOX4/Akt signalings promotes proliferation and survival of non-small cell lung cancer cells

Inflammatory cytokines and oxidative stress are two critical mediators in inflammation-associated cancer. Interleukin-6 (IL-6) is one of the most critical tumor-promoting cytokines in non-small cell lung cancer (NSCLC). In our recent study, we confirmed that NADPH oxidase 4 (NOX4), an important source of reactive oxygen species (ROS) production in NSCLC cells, promotes malignant progression of NSCLC. However, whether the crosstalk of NOX4 and IL-6 signalings exists in NSCLC remains undentified. In this study, we show that NOX4 expression is positively correlated with IL-6 expression in NSCLC tissues. Exogenous IL-6 treatment significantly enhances NOX4/ROS/Akt signaling in NSCLC cells. NOX4 also enhances IL-6 production and activates IL-6/STAT3 signaling in NSCLC cells. Specifically, NOX4 is confirmed to functionally interplay with IL-6 to promote NSCLC cell proliferation and survival. The in vivo results were similar to those obtained in vitro. These data indicate a novel NOX4-dependent link among IL-6 in the NSCLC microenvironment, oxidative stress in NSCLC cells and autocrined IL-6 in NSCLC cells. NOX4/Akt and IL-6/STAT3 signalings can reciprocally and positively regulate each other, leading to enhanced NSCLC cell proliferation and survival. Therefore, NOX4 may serve as a promising target against NSCLC alone with IL-6 signaling.     

STAT3介导G-CSF对原代APL细胞增殖的调控作用

目的 探讨全反式维甲酸（ATRA）诱导后。白细胞介素（IL）-1β和粒细胞集落刺激因子（G-CSF）对原代急性早幼粒细胞白血病（APL）细胞增殖调控的信号传导因子。方法采用酶联免疫吸附试验（ELISA）法测定原代APL细胞培养上清中IL-1β和G-CSF水平的变化,逆转录．聚合酶链反应（RT-PCR）方法测定IL-1β和G-CSF mRNA表达水平。Western blot测定信号转导和转录激活因子（STAT）1α和STAT3表达水平变化。结果ATRA治疗后APL患者外周血白细胞明显升高,平均12天达到高峰,并且以中晚幼粒细胞为主。ATRA治疗后7天和高峰期的APL细胞体外培养24h后。IL-1β（P〈0．05）和G-CSF（P〈0．05）分泌水平显著升高。RT-PCR结果表明分泌IL-1β和（或）G-CSF升高的原代APL细胞。IL-1β和（或）G-CSF mRNA表达升高。所有患者原代APL细胞的STAT1α蛋白表达均升高,与IL-1β或G-CSF的表达无关。但STAT3的升高却与G-CSF表达和分泌水平变化相一致。结论ATRA诱导高表达的G-CSF,通过STAT3发挥对原代APL细胞的调节作用。