Interleukin-6 activates phosphatidylinositol-3 kinase, which inhibits apoptosis in human prostate cancer cell lines

IL-6 is involved in thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is a heterotopic ossification of spinal ligaments. TOLF is the major cause of thoracic spinal canal stenosis and myelopathy, and its underlying mechanisms are not clear. Bone formation is a complex developmental process involving the differentiation of mesenchymal stem cells to osteoblasts, and regulated by BMP2, RUNX2, Osterix (OSX), etc. In this study, we continue to further characterize properties of TOLF. Our immunohistochemistry experiments showed that expressions of osteoblastic factors such as BMP2 and RUNX2 increased in TOLF. According to flow cytometry analysis the proportion of S phase of cell cycle in primary TOLF cells was 9% higher than the control. Alizarin red staining and ALP staining observations were consistent with immunohistochemistry results. It was also observed that inflammatory cytokine IL-6 level dramatically increased in the culture supernatant of primary TOLF cells. We propose the hypothesis that IL-6 is involved in TOLF. To testify the hypothesis, we examined the effect of IL-6. Our results showed that IL-6 was able to activate expressions of osteoblastic factors such as BMP2, RUNX2, OSX, OCN and ALP, and that expressions of cell proliferation factors cyclin D1 and cyclin C increased in the presence of IL-6. Moreover, IL-6-induced BMP2 expression was inhibited by p38 inhibitor SB203580, indicating that IL-6 regulated the osteogenic BMP2 activation through p38 MAPK pathway. These data suggest that IL-6 is involved in TOLF.

Interleukin-6 Function and Targeting in Prostate Cancer

Interleukin-6 (IL-6) is a proinflammatory cytokine, which is involved in pathogenesis of several cancers. Its expression and function in prostate cancer have been extensively studied in cellular models and clinical specimens. High levels of IL-6 were detected in conditioned media from cells which do not respond to androgens. Increased phosphorylation of signal transducer and activator of transcription (STAT)3 factor which is induced in response to IL-6 is one of the typical features of prostate cancer. However, reports in the literature show regulation of neuroendocrine phenotype by IL-6. Effects of IL-6 on stimulation of proliferation, migration, and invasion lead to the establishment of experimental and clinical approaches to target IL-6. In prostate cancer, anti-IL-6 antibodies were demonstrated to inhibit growth in vitro and in vivo. Clinically, application of anti-IL-6 therapies did not improve survival of patients with metastatic prostate cancer. However, clinical trial design in the future may include different treatment schedule and combinations with experimental and clinical therapies. Endogenous inhibitors of IL-6 such as suppressors of cytokine signaling and protein inhibitors of activated STAT have variable effects on prostate cells, depending on presence or absence of the androgen receptor.

Emerging chemical scaffolds with potential SHP2 phosphatase inhibitory capabilities - A comprehensive review

The drug discovery panorama is cluttered with promising therapeutic targets that have been deserted because of inadequate authentication and screening failures. Molecular targets formerly tagged as "undruggable" are nowadays being more cautiously cross-examined, and whilst they stay intriguing, numerous targets are emerging more accessible. Protein tyrosine phosphatases (PTPs) excellently exemplifies a class of molecular targets that have transpired as druggable, with several small molecules and antibodies recently turned available for further development. In this respect, SHP2, a PTP, has emerged as one of the potential targets in the current pharmacological research, particularly for cancer, due to its critical role in various signalling pathways. Recently, few molecules with excellent potency have entered clinical trials, but none could reach the clinic. Consequently, search for novel, non-toxic, and specific SHP2 inhibitors are on purview. In this review, general aspects of SHP2 including its structure and mechanistic role in carcinogenesis have been presented. It also sheds light on the development of novel molecular architectures belonging to diverse chemical classes that have been proposed as SHP2-specific inhibitors along with their structure-activity relationships (SARs), stemming from chemical, mechanism-based and computer-aided studies reported since January 2015 to July 2020 (excluding patents), focusing on their potency and selectivity. The encyclopedic facts and discussions presented herein will hopefully facilitate researchers to design new ligands with better efficacy and selectivity against SHP2.

Interleukin-6 derived from cancer-associated fibroblasts attenuates the p53 response to doxorubicin in prostate cancer cells

Cancer-associated fibroblasts (CAFs) promote tumor growth and progression, and increase drug resistance through several mechanisms. We have investigated the effect of CAFs on the p53 response to doxorubicin in prostate cancer cells. We show that CAFs produce interleukin-6 (IL-6), and that IL-6 attenuates p53 induction and upregulation of the pro-apoptotic p53 target Bax upon treatment with doxorubicin. This is associated with increased levels of MDM2 mRNA, Mdm2 protein bound to p53, and ubiquitinated p53. IL-6 also inhibited doxorubicin-induced cell death. Inhibition of JAK or STAT3 alleviated this effect, indicating that IL-6 attenuates p53 via the JAK/STAT signaling pathway. These results suggest that CAF-derived IL-6 plays an important role in protecting cancer cells from chemotherapy and that inhibition of IL-6 could have significant therapeutic value.

Deferoxamine-induced high expression of TfR1 and DMT1 enhanced iron uptake in triple-negative breast cancer cells by activating IL-6/PI3K/AKT pathway

Background: Deferoxamine (DFO) is a commonly used iron chelator, which can reduce the iron levels in cells. DFO is normally used to treat iron-overload disease, including some types of cancer. However, our previous studies revealed that DFO treatment significantly increased the iron concentrations in triple-negative breast cancer cells (TNBCs) resulting in enhanced cell migration. But the mechanism of DFO-induced increasing iron uptake in aggressive TNBCs still remained unclear. Materials and methods: Iron metabolism-related proteins in aggressive breast cancer MDA-MB-231, HS578T and BT549 cells and nonaggressive breast cancer MCF-7 and T47D cells were examined by immunofluorescence and Western blotting. The possible regulatory mechanism was explored by Western blotting, co-incubation with neutralizing antibodies or inhibitors, and transwell assay. Results: In this study, we found that DFO treatment significantly increased the levels of iron uptake proteins, DMT1 and TfR1, in aggressive TNBCs. Moreover, both TfR1 and DMT1 expressed on cell membrane were involved in high iron uptake in TNBCs under DFO-induced iron deficient condition. For the possible regulatory mechanism, we found that DFO treatment could promote a high expression level of IL-6 in aggressive MDA-MB-231 cells. The activated IL-6/PI3K/AKT pathway upregulated the expression of iron-uptake related proteins, TfR1 and DMT1, leading to increased iron uptakes. Conclusion: We demonstrated that DFO could upregulate expression of TfR1 and DMT1 , which enhanced iron uptake via activating IL-6/PI3K/AKT signaling pathway in aggressive TNBCs.

G protein-coupled receptor GPR160 is associated with apoptosis and cell cycle arrest of prostate cancer cells

G protein-coupled receptors (GPCRs) represent the largest membrane protein family implicated in the therapeutic intervention of a variety of diseases including cancer. Exploration of biological actions of orphan GPCRs may lead to the identification of new targets for drug discovery. This study investigates potential roles of GPR160, an orphan GPCR, in the pathogenesis of prostate cancer. The transcription levels of GPR160 in the prostate cancer tissue samples and cell lines, such as PC-3, LNCaP, DU145 and 22Rv1 cells, were significantly higher than that seen in normal prostate tissue and cells. Knockdown of GPR160 by lentivirus-mediated short hairpin RNA constructs targeting human GPR160 gene (ShGPR160) resulted in prostate cancer cell apoptosis and growth arrest both in vitro and in athymic mice. Differential gene expression patterns in PC-3 cells infected with ShGPR160 or scramble lentivirus showed that 815 genes were activated and 1193 repressed. Functional annotation of differentially expressed genes (DEGs) revealed that microtubule cytoskeleton, cytokine activity, cell cycle phase and mitosis are the most evident functions enriched by the repressed genes, while regulation of programmed cell death, apoptosis and chemotaxis are enriched significantly by the activated genes. Treatment of cells with GPR160-targeting shRNA lentiviruses or duplex siRNA oligos increased the transcription of IL6 and CASP1 gene significantly. Our data suggest that the expression level of endogenous GPR160 is associated with the pathogenesis of prostate cancer.

Ginsenoside Re Protects Trimethyltin-Induced Neurotoxicity via Activation of IL-6-Mediated Phosphoinositol 3-Kinase/Akt Signaling in Mice

Ginseng (Panax ginseng), an herbal medicine, has been used to prevent neurodegenerative disorders. Ginsenosides (e.g., Re, Rb1, or Rg1) were obtained from Korean mountain cultivated ginseng. The anticonvulsant activity of ginsenoside Re (20 mg/kg/day × 3) against trimethyltin (TMT) insult was the most pronounced out of ginsenosides (e.g., Re, Rb1, and Rg1). Re itself did not significantly alter tumor necrosis factor-α (TNF-α), interferon-ϒ (IFN-ϒ), and interleukin-1β (IL-1β) expression, however, it significantly increases the interleukin-6 (IL-6) expression. In addition, Re attenuated the TMT-induced decreases in IL-6 protein level. Therefore, IL-6 knockout (-/-) mice were employed to investigate whether Re requires IL-6-dependent neuroprotective activity against TMT toxicity. Re significantly attenuated TMT-induced lipid peroxidation, protein peroxidation, and reactive oxygen species in the hippocampus. Re-mediated antioxidant effects were more pronounced in IL-6 (-/-) mice than in WT mice. Consistently, TMT-induced increase in c-Fos-immunoreactivity (c-Fos-IR), TUNEL-positive cells, and nuclear chromatin clumping in the dentate gyrus of the hippocampus were significantly attenuated by Re. Furthermore, Re attenuated TMT-induced proapoptotic changes. Protective potentials by Re were comparable to those by recombinant IL-6 protein (rIL-6) against TMT-insult in IL-6 (-/-) mice. Moreover, treatment with a phosphoinositol 3-kinase (PI3K) inhibitor, LY294002 (1.6 µg, i.c.v) counteracted the protective potential mediated by Re or rIL-6 against TMT insult. The results suggest that ginsenoside Re requires IL-6-dependent PI3K/Akt signaling for its protective potential against TMT-induced neurotoxicity.

Immune mediators in the tumor microenvironment of prostate cancer

Prostate cancer tissue is composed of both cancer cells and host cells. The milieu of host components that compose the tumor is termed the tumor microenvironment (TME). Host cells can be those derived from the tissue in which the tumor originates (e.g., fibroblasts and endothelial cells) or those recruited, through chemotactic or other factors, to the tumor (e.g., circulating immune cells). Some immune cells are key players in the TME and represent a large proportion of non-tumor cells found within the tumor. Immune cells can have both anti-tumor and pro-tumor activity. In addition, crosstalk between prostate cancer cells and immune cells affects immune cell functions. In this review, we focus on immune cells and cytokines that contribute to tumor progression. We discuss T-regulatory and T helper 17 cells and macrophages as key modulators in prostate cancer progression. In addition, we discuss the roles of interleukin-6 and receptor activator of nuclear factor kappa-B ligand in modulating prostate cancer progression. This review highlights the concept that immune cells and cytokines offer a potentially promising target for prostate cancer therapy.

Shp2 Plays a Critical Role in IL-6-Induced EMT in Breast Cancer Cells

Accumulative evidence demonstrates that the protein tyrosine phosphatase Shp2 functions as a powerful tumor promoter in many types of cancers. Abnormal expression of Shp2 has been implicated in many human malignancies. Overexpression of Shp2 in cancer tissues is correlated with cancer metastasis, resistance to targeted therapy, and poor prognosis. The well-known function of Shp2 is its positive role in regulating cellular signaling initiated by growth factors and cytokines, including interleukin-6 (IL-6). Several recent studies have shown that Shp2 is required for epithelial-mesenchymal transition (EMT), triggered by growth factors. However, whether Shp2 is involved in IL-6-signaling-promoted breast cancer EMT and progression, remains undefined. In this study, we showed that exogenous and endogenous IL-6 can enhance breast cancer invasion and migration, through the promotion of EMT. IL-6 also induces the activation of Erk1/2 and the phosphorylation of Shp2. Knockdown of Shp2 attenuated the IL-6-induced downregulation of E-cadherin, as well as IL-6-promoted cell migration and invasion. Moreover, by using Shp2 phosphatase mutants, phosphor-tyrosine mimicking, and deficiency mutants, we provided evidence that the phosphatase activity of Shp2 and its tyrosine phosphorylation, are necessary for the IL-6-induced downregulation of E-cadherin and the phosphorylation of Erk1/2. Our findings uncover an important function that links Shp2 to IL-6-promoted breast cancer progression.

Interleukin-6 influences stress-signalling by reducing the expression of the mTOR-inhibitor REDD1 in a STAT3-dependent manner

Interleukin 6 (IL-6) is a pleiotropic cytokine and a strong activator of Mammalian Target of Rapamycin (mTOR). In contrast, mTOR activity is negatively regulated by Regulated in Development and DNA Damage Responses 1 (REDD1). Expression of REDD1 is induced by cellular stressors such as glucocorticoids and DNA damaging agents. We show that the expression of basal as well as stress-induced REDD1 is reduced by IL-6. The reduction of REDD1 expression by IL-6 is independent of proteasomal or caspase-mediated degradation of REDD1 protein. Instead, induction of REDD1 mRNA is reduced by IL-6. The regulation of REDD1 expression by IL-6 is independent of Phosphatidylinositide-3-Kinase (PI3K) and Mitogen-Activated Protein Kinase (MAPK) signalling but depends on the expression and activation of Signal Transducer and Activator of Transcription 3 (STAT3). Furthermore, the reduction of basal REDD1 expression by IL-6 correlates with IL-6-induced activation of mTOR signalling. Inhibition of STAT3 activation blocks IL-6-induced mTOR activation. In summary, we present a novel STAT3-dependent mechanism of both IL-6-induced activation of mTOR and IL-6-dependent reversion of stress-induced inhibition of mTOR activity.

Identification of potential therapeutic targets for lung cancer by bioinformatics analysis

The aim of the present study was to identify potential therapeutic targets for lung cancer and explore underlying molecular mechanisms of its development and progression. The gene expression profile datasets no. GSE3268 and GSE19804, which included five and 60 pairs of tumor and normal lung tissue specimens, respectively, were downloaded from Gene Expression Omnibus. Differentially expressed genes (DEGs) between lung cancer and normal tissues were identified, and gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of the DEGs was performed. Furthermore, protein‑protein interaction (PPI) networks and a transcription factor (TF) regulatory network were constructed and key target genes were screened. A total of 466 DEGs were identified, and the PPI network indicated that IL‑6 and MMP9 had key roles in lung cancer. A PPI module containing 34 nodes and 547 edges was obtained, including PTTG1. The TF regulatory network indicated that TFs of FOSB and LMO2 had a key role. Furthermore, MMP9 was indicated to be the target of FOSB, while PTTG1 was the target of LMO2. In conclusion, the bioinformatics analysis of the present study indicated that IL‑6, MMP9 and PTTG1 may have key roles in the progression and development of lung cancer and may potentially be used as biomarkers or specific therapeutic targets for lung cancer.

IL-6 negatively regulates osteoblast differentiation through the SHP2/MEK2 and SHP2/Akt2 pathways in vitro

It has been suggested that interleukin-6 (IL-6)plays a key role in the pathogenesis of rheumatoid arthritis(RA), including osteoporosis not only in inflamed joints but also in the whole body. However, previous in vitro studies regarding the effects of IL-6 on osteoblast differentiation are inconsistent. The aim of this study was to examine the effects and signal transduction of IL-6 on osteoblast differentiation in MC3T3-E1 cells and primary murine calvarial osteoblasts. IL-6 and its soluble receptor significantly reduced alkaline phosphatase (ALP) activity, the expression of osteoblastic genes (Runx2, osterix, and osteocalcin), and mineralization in a dose-dependent manner, which indicates negative effects of IL-6 on osteoblast differentiation. Signal transduction studies demonstrated that IL-6 activated not only two major signaling pathways, SHP2/MEK/ERK and JAK/STAT3, but also the SHP2/PI3K/Akt2 signaling pathway. The negative effect of IL-6 on osteoblast differentiation was restored by inhibition of MEK as well as PI3K, while it was enhanced by inhibition of STAT3. Knockdown of MEK2 and Akt2 transfected with siRNA enhanced ALP activity and gene expression of Runx2. These results indicate that IL-6 negatively regulates osteoblast differentiation through SHP2/MEK2/ERK and SHP2/PI3K/Akt2 pathways, while affecting it positively through JAK/STAT3. Inhibition of MEK2 and Akt2 signaling in osteoblasts might be of potential use in the treatment of osteoporosis in RA.

IL-6 and related cytokines as the critical lynchpins between inflammation and cancer

Inflammatory responses play pivotal roles in cancer development, including tumor initiation, promotion, progression, and metastasis. Cytokines are now recognized as important mediators linking inflammation and cancer, and are therefore potential therapeutic and preventive targets as well as prognostic factors. The interleukin (IL)-6 family of cytokines, especially IL-6 and IL-11, is highly up-regulated in many cancers and considered as one of the most important cytokine families during tumorigenesis and metastasis. This review discusses molecular mechanisms linking the IL-6 cytokine family to solid malignancies and their treatment.

RAMP1 is a direct NKX3.1 target gene up-regulated in prostate cancer that promotes tumorigenesis

The homeodomain-containing transcription factor, NKX3.1, plays an important role in the suppression of prostate tumorigenesis. Herein, we identify the receptor activity-modifying protein 1 (RAMP1) as a direct NKX3.1 target gene through analysis of chromatin immunoprecipitation coupled to massively parallel sequencing and gene expression data. RAMP1 is a coreceptor for certain G-protein-coupled receptors, such as the calcitonin gene-related peptide receptor, to the plasma membrane. We found that RAMP1 expression is specifically elevated in human prostate cancer relative to other tumor types. Furthermore, RAMP1 mRNA and protein levels are significantly higher in human prostate cancer compared with benign glands. We identified multiple NKX3.1 binding sites in the RAMP1 locus in human prostate cancer cells and in the normal mouse prostate. Analyses of Nkx3.1 knockout mice and human prostate cancer cell lines indicate that NKX3.1 represses RAMP1 expression. Knockdown of RAMP1 by shRNA decreased prostate cancer cell proliferation and tumorigenicity in vitro and in vivo. By using gene expression profiling and pathway analyses, we identified several cancer-related pathways that are significantly altered in RAMP1 knockdown cells, including the mitogen-activated protein kinase signaling pathway. Further experiments confirmed a reduction in MAP2KI (MEK1) expression and phosphorylated-extracellular signal-regulated kinase 1/2 levels in RAMP1 knockdown cells. These data provide novel insights into the role of RAMP1 in promoting prostate tumorigenesis and support the potential of RAMP1 as a novel biomarker and possible therapeutic target in prostate cancer.

Role of SOCS3 evaluated by immunohistochemical analysis in a cohort of patients affected by prostate cancer: preliminary results

BACKGROUND

Chronic inflammation may play a role in prostate carcinogenesis. Molecular alterations of the Suppressor of Cytokine Signaling (SOCS)-3 can contribute to explain the pleiotropic role of interleukin (IL)-6 in this type of cancer. Recently, the methylation of SOCS3 gene has been demonstrated to cause the non-expression of the protein, being involved in the pathogenesis of prostate cancer (PC) and identifying a subset of aggressive tumors. We evaluated the expression of SOCS3 protein in patients (pt) with bioptically-diagnosed PC by immunohistochemical analysis, which is easier to perform, cheaper and more reproducible compared to DNA analysis.

METHODS

We analyzed the protein expression of SOCS3 by immunohistochemistry in 44 patients (pt) with PC diagnosed after biopsy. Slides were incubated with monoclonal antibody SOCS3 (1E4, 1.5 μg/mL; Abnova, Taiwan). The SOCS3 staining intensity was evaluated by two pathologists (FP and LML) in three different ways: positive (+), negative (-) and weak (+/-). Colonic mucosa was used as positive control. 36/44 patients underwent radical prostatectomy (RP).

RESULTS

Biopsy Gleason score (Gs) was: <7 in 8 pt, 7 in 33 pt (3 + 4 pattern in 21 pt, 4 + 3 pattern in 12 pt), >7 in 3 pt. 8/8 (100%) pt with Gs <7 and 7/33 (21%) with Gs 7 were SOCS+. 15/33 (45%) pt with Gs 7 and 3/3 (100%) pt with Gs >7 were negative. In 11/33 pt (33%) Gs 7 a weak intensity was found so they were classified as SOCS3 +/-.25/36 (69%) patients who underwent RP were SOCS3- (15 pt with Gs 7(3 + 4), 7 pt with Gs 7(4 + 3), 3 pt with Gs 8) and 11/36 (30%) SOCS3+ (8 pt with Gs 6 and 3 pt with Gs 7(3 + 4)) (Tab 2). 12/25 (48%) SOCS3- pt had an organ-confined disease (≤pT2), whereas 13/25 (52%) had an extra prostatic neoplasm (5 pT3a (one was N+), 6 pT3b, 1 pT4). All SOCS3+ patients (8/8 (100%)) had an organ-confined disease. 3/3 (100%) SOCS3+/- pt had an extra prostatic neoplasm (>pT2).

CONCLUSIONS

SOCS3- pt turned out to have a more aggressive disease compared with SOCS3+. In particular, also SOCS3+/- patients seemed to have an aggressive behavior. The non-expression of SOCS3 protein may identify PC with more aggressive behavior and can be evaluated with immunohystochemical analysis, which is a relatively easy and cheap procedure in clinical practice. These results, if confirmed by a wider population and a longer follow-up, may encourage the research on the use of this molecular family as a prognostic marker and a target for therapy with demethylating agents.

Interleukin-6: a multifunctional targetable cytokine in human prostate cancer

Several cytokines are involved in regulation of cellular events in prostate cancer. Interleukin-6 (IL-6) was frequently investigated in prostate cancer models because of its increased expression in cancer tissue at early stages of the disease. In patients with metastatic prostate cancer, it is well-known that IL-6 levels increase in serum. High levels of IL-6 were measured in the supernatants of cells which do not respond to androgenic stimulation. IL-6 expression in prostate cancer increases due to enhanced expression of transforming growth factor-beta, and members of the activating protein-1 complex, and loss of the retinoblastoma tumour suppressor. IL-6 activation of androgen receptor (AR) may contribute to progression of a subgroup of prostate cancers. Results obtained with two prostate cancer cell lines, LNCaP and MDA PCa 2b, indicate that IL-6 activation of AR may cause either stimulatory or inhibitory responses on proliferation. Interestingly, prolonged treatment with IL-6 led to establishment of an IL-6 autocrine loop, suppressed signal transducer and activator of transcription (STAT)3 activation, and increased mitogen-activated protein kinase phosphorylation. In several cell lines IL-6 acts as a survival molecule through activation of the signalling pathway of phosphotidylinositol 3-kinase. Expression of suppressors of cytokine signalling (SOCS) has been studied in prostate cancer. SOCS-3 prevents phosphorylation of STAT3 and is an important anti-apoptotic factor in AR-negative prostate cancer cells. Experimental therapy against IL-6 in prostate cancer is based on the use of the monoclonal antibody siltuximab which may be used for personalised therapy coming in the future.

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.

Expression of Id proteins is regulated by the Bcl-3 proto-oncogene in prostate cancer

B-cell leukemia 3 (Bcl-3) is a member of the inhibitor of κB family, which regulates a wide range of biological processes by functioning as a transcriptional activator or as a repressor of target genes. As high levels of Bcl-3 expression and activation have been detected in different types of human cancer, Bcl-3 has been labeled a proto-oncogene. Our study uncovered a markedly upregulated Bcl-3 expression in human prostate cancer (PCa), where inflammatory cell infiltration was observed. Elevated Bcl-3 expression in PCa was dependent on the proinflammatory cytokine interleukin-6-mediated STAT3 activation. Microarray analyses, using Bcl-3 knockdown in PCa cells, identified the inhibitor of DNA-binding (Id) family of helix-loop-helix proteins as potential Bcl-3-regulated genes. Bcl-3 knockdown reduced the abundance of Id-1 and Id-2 proteins and boosted PCa cells to be more receptive to undergoing apoptosis following treatment with anticancer drug. Our data imply that inactivation of Bcl-3 may lead to sensitization of cancer cells to chemotherapeutic drug-induced apoptosis, thus suggesting a potential therapeutic strategy in PCa treatment.

IL-6/IL-6 receptor system and its role in physiological and pathological conditions

IL (interleukin)-6, which was originally identified as a B-cell differentiation factor, is a multifunctional cytokine that regulates the immune response, haemopoiesis, the acute phase response and inflammation. IL-6 is produced by various types of cell and influences various cell types, and has multiple biological activities through its unique receptor system. IL-6 exerts its biological activities through two molecules: IL-6R (IL-6 receptor) and gp130. When IL-6 binds to mIL-6R (membrane-bound form of IL-6R), homodimerization of gp130 is induced and a high-affinity functional receptor complex of IL-6, IL-6R and gp130 is formed. Interestingly, sIL-6R (soluble form of IL-6R) also binds with IL-6, and the IL-6-sIL-6R complex can then form a complex with gp130. The homodimerization of receptor complex activates JAKs (Janus kinases) that then phosphorylate tyrosine residues in the cytoplasmic domain of gp130. The gp130-mediated JAK activation by IL-6 triggers two main signalling pathways: the gp130 Tyr759-derived SHP-2 (Src homology 2 domain-containing protein tyrosine phosphatase-2)/ERK (extracellular-signal-regulated kinase) MAPK (mitogen-activated protein kinase) pathway and the gp130 YXXQ-mediated JAK/STAT (signal transducer and activator of transcription) pathway. Increased IL-6 levels are observed in several human inflammatory diseases, such as rheumatoid arthritis, Castleman's disease and systemic juvenile idiopathic arthritis. IL-6 is also critically involved in experimentally induced autoimmune diseases. All clinical findings and animal models suggest that IL-6 plays a number of critical roles in the pathogenesis of autoimmune diseases. In the present review, we first summarize the IL-6/IL-6R system and IL-6 signal transduction, and then go on to discuss the physiological and pathological roles of IL-6.

The anti-interleukin-6 antibody siltuximab down-regulates genes implicated in tumorigenesis in prostate cancer patients from a phase I study

BACKGROUND

Interleukin-6 (IL-6) is associated with prostate cancer morbidity. In several experimental models, IL-6 has been reported to have anti-apoptotic and pro-angiogenic effects. Siltuximab (CNTO 328) is a monoclonal anti-IL-6 antibody which has been successfully applied in several models representing prostate cancer. This study was designed to assess preliminary safety of siltuximab in patients with early prostate cancer.

PATIENTS AND METHODS

Twenty patients scheduled to undergo radical prostatectomy received either no drug or siltuximab (6 mg/kg, five patients per group with administration once, two times, and three times prior to surgery). Blood samples were collected for pharmacokinetic and pharmacodynamic analyses. Expression of elements of IL-6 signaling pathways was analyzed in tumor tissue by immunohistochemistry. Gene analysis in tumor specimens was performed with the DASL array.

RESULTS

No adverse events related to siltuximab were observed. Patients treated with siltuximab presented with higher levels of proliferation and apoptosis markers. Following a single dose, serum concentrations of siltuximab declined in a biexponential manner. This study revealed a decrease in phosphorylation of Stat3 and p44/p42 mitogen-activated protein kinases. In addition, gene expression analyses indicate down-regulation of genes immediately downstream of the IL-6 signaling pathway and key enzymes of the androgen signaling pathway.

CONCLUSIONS

Preliminary safety of siltuximab is favorable. Future studies in which siltuximab could be combined with androgen-deprivation therapy and experimental therapies in advanced prostate cancer are justified.

The PCa Tumor Microenvironment

The tumor microenvironment (TME) is a very complex niche that consists of multiple cell types, supportive matrix and soluble factors. Cells in the TME consist of both host cells that are present at tumor site at the onset of tumor growth and cells that are recruited in either response to tumor- or host-derived factors. PCa (PCa) thrives on crosstalk between tumor cells and the TME. Crosstalk results in an orchestrated evolution of both the tumor and microenvironment as the tumor progresses. The TME reacts to PCa-produced soluble factors as well as direct interaction with PCa cells. In return, the TME produces soluble factors, structural support and direct contact interactions that influence the establishment and progression of PCa. In this review, we focus on the host side of the equation to provide a foundation for understanding how different aspects of the TME contribute to PCa progression. We discuss immune effector cells, specialized niches, such as the vascular and bone marrow, and several key protein factors that mediate host effects on PCa. This discussion highlights the concept that the TME offers a potentially very fertile target for PCa therapy.

Clinical significance of interleukin (IL)-6 in cancer metastasis to bone: potential of anti-IL-6 therapies

Metastatic events to the bone occur frequently in numerous cancer types such as breast, prostate, lung, and renal carcinomas, melanoma, neuroblastoma, and multiple myeloma. Accumulating evidence suggests that the inflammatory cytokine interleukin (IL)-6 is frequently upregulated and is implicated in the ability of cancer cells to metastasize to bone. IL-6 is able to activate various cell signaling cascades that include the STAT (signal transducer and activator of transcription) pathway, the PI3K (phosphatidylinositol-3 kinase) pathway, and the MAPK (mitogen-activated protein kinase) pathway. Activation of these pathways may explain the ability of IL-6 to mediate various aspects of normal and pathogenic bone remodeling, inflammation, cell survival, proliferation, and pro-tumorigenic effects. This review article will discuss the role of IL-6: 1) in bone metabolism, 2) in cancer metastasis to bone, 3) in cancer prognosis, and 4) as potential therapies for metastatic bone cancer.

IL-6 causes multiple effects in androgen-sensitive and -insensitive prostate cancer cell lines

The androgen receptor (AR) is expressed in most human prostate cancers. It can be activated in a hypersensitive manner by androgens, nonandrogenic steroids, nonsteroidal anti-androgens and in a ligand-independent manner. IL-6 is a proinflammatory cytokine that activates several signaling pathways. It can either stimulate or inhibit growth of prostate cancer cells. IL-6 is an important positive regulator of AR activity and can stimulate the expression of prostate-specific antigen in a ligand-independent manner. IL-6/AR interaction may either result in growth stimulation (MDA PCa 2b cells) or inhibition (LAPC-4 cells). IL-8 and IL-4 have also been observed to activate AR. Cells generated by prolonged treatment with IL-6 acquire a growth advantage. There are several therapeutic options to target IL-6 in prostate cancer and most laboratory studies have been performed with the monoclonal antibody siltuximab. Endogenous suppressors of cytokine signaling (SOCS)-3 and -1 are expressed in prostate cancer tissue. SOCS-3 inhibits apoptosis in AR-negative cells. However, in androgen-sensitive prostate cancer cell lines, SOCS-3 is induced by androgen and blocks its effects on proliferation and secretion. It is currently understood that there are numerous interactions between androgen and IL-6 signaling in human prostate cancer.

Epigenetic silencing of SOCS3 identifies a subset of prostate cancer with an aggressive behavior

BACKGROUND

Chronic inflammation and subsequent tissutal alterations may play a key role in prostate carcinogenesis. In this way, molecular alterations of the suppressor of cytokine signaling 3 (SOCS3), one of the most important inhibitory molecule of inflammatory signal transduction circuitries, could contribute to explain the pleiotropic role of interleukin-6 (IL-6) in this type of cancer.

METHODS

We analyzed the methylation status and mRNA expression of SOCS3 in 20 benign prostate hyperplasias (BPH) and in 51 prostate cancer specimens. We analyzed the SOCS3 methylation status using methylation-specific PCR. Hypermethylation was confirmed by sequencing after subcloning. Epigenetic silencing of this gene was also demonstrated by real-time PCR and by immunohistochemistry. Results and correlation with clinical data were statistically analyzed.

RESULTS

We found that the promoter of SOCS3 was methylated in 39.2% of prostate cancer. On the contrary, all BPH and normal controls had an unmethylated pattern. Real-time analysis showed that in methylated cases SOCS3 mRNA expression was reduced by three and four folds as compared to BPH and unmethylated cases, respectively. Interestingly, SOCS3 mRNA level was higher in unmethylated prostate cancer than in BPH. The immunohistochemical staining analysis for SOCS 3 confirmed mRNA results. Moreover, methylation of SOCS3 promoter significantly associated with intermediate-high grade Gleason score (P = 0.0007) and with an unfavorable clinical outcome (P = 0.0019).

CONCLUSIONS

Our data suggest that SOCS3 hypermethylation may be involved in the pathogenesis of prostate cancer and could identify a tumor subset with an aggressive behavior.

Inhibition of tumor growth and sensitization to chemotherapy by RNA interference targeting interleukin-6 in the androgen-independent human prostate cancer PC3 model

The objective of the present study was to investigate the inhibitory effects of interleukin-6 (IL-6) secretion by androgen-independent human prostate cancer PC3 cells on their growth and chemosensitivity. In this study, we established PC3 in which the expression vector containing short hairpin RNA (shRNA) targeting IL-6 was introduced (PC3/sh-IL6). Changes in the growth and sensitivity to docetaxel in PC3/sh-IL6 were compared with those in PC3 transfected with control vector alone (PC3/Co). Concentration of IL-6 in the culture supernatant from PC3/sh-IL6 was approximately 20% of that from PC3/Co. Both in vitro and in vivo, the growth of PC3/sh-IL-6 was significantly inferior to that of PC3/Co, accompanying downregulation of Bcl-2, Bcl-xL, phosphorylated Akt, p44/42 mitogen-activated protein kinase, and signal transducers and activation of transcription 3 in PC3/sh-IL-6 compared with that in PC3/Co. Despite the higher sensitivity of PC3/sh-IL6 to docetaxel than that of PC3/Co, the secretion of IL-6 by both cell lines was increased after treatment with docetaxel due to the formation of positive autocrine loops between these cell lines and NFκB signaling pathways. Furthermore, combined treatment with the proteasome inhibitor bortezomib, which completely inhibited the docetaxel-induced IL-6 secretion via the inactivation of NFκB signaling, resulted in the marked sensitization of these cell lines to docetaxel both in vitro and in vivo. These findings suggest that suppressed IL-6 secretion using shRNA, either alone or in combination with docetaxel and bortezomib, could be a useful therapeutic strategy against androgen-independent prostate cancer.

Cytokine disbalance in common human cancers

Interleukin (IL)-6, -4, and -8 levels have been elevated in most patients suffering from prostate, breast, or colon cancer. There is a large body of evidence suggesting that chronic inflammation is one of the etiologic factors in these tumors. IL-6 is a multifunctional cytokine which is known to influence proliferation, apoptosis, and angiogenesis in cancer. Its transcription factor STAT3 is known as an oncogene that is constitutively phosphorylated in these malignancies. However, IL-6-induced STAT3 phosphorylation may result in growth arrest. IL-6 activation of androgen receptor in prostate cancer may yield either tumor cell proliferation or differentiation. Prolonged treatment with IL-6 results in generation of sublines which express a more malignant phenotype. Therapy options against IL-6 have been established and the antibody siltuximab has been applied in preclinical and clinical studies. Recently, investigations of the role of suppressors of cytokine signaling have been carried out. IL-4 and -8 are implicated in regulation of apoptosis, migration, and angiogenesis in cancers associated with chronic inflammation. All cytokines mentioned above regulate cellular events in stem cells. These cells could not be targeted by most conventional cancer therapies.

Enhanced sensitivity to androgen withdrawal due to overexpression of interleukin-6 in androgen-dependent human prostate cancer LNCaP cells

Background:

The objective of this study was to investigate the effects of interleukin-6 (IL-6) overexpression in androgen-dependent prostate cancer LNCaP cells on their phenotype under an androgen-deprived condition.

Methods:

We established IL-6-overexpressing LNCaP (LNCaP/IL-6) by introducing the expression vector containing IL-6 cDNA. Changes in the phenotype in LNCaP/IL-6 were compared with that in LNCaP transfected with control vector alone (LNCaP/Co).

Results:

In vitro, the growth of LNCaP/IL-6 was significantly inferior to that of LNCaP/Co under an androgen-deprived condition. Similarly, LNCaP/IL-6 tumour in nude mice rapidly regressed after castration; however, LNCaP/Co tumour growth was transiently inhibited after castration and then continuously accelerated. After androgen withdrawal, expression levels of phosphorylated p44/42 mitogen-activated protein kinase (MAPK) and Akt in LNCaP/IL-6 were markedly upregulated compared with those in LNCaP/Co; however, additional treatment with specific inhibitor of the MAPK or Akt signalling pathway significantly inhibited the growth of LNCaP/IL-6 compared with that of LNCaP/Co. Furthermore, gene microarray analyses showed that androgen deprivation resulted in differential expression of genes involved in growth, apoptotsis and tumorigenesis between LNCaP/Co and LNCaP/IL-6.

Conclusion:

Excessive secretion of IL-6 by LNCaP cells in an autocrine manner may have a suppressive function in their growth and acquisition of androgen-independent phenotype under an androgen-deprived condition.

Ethanolic Hwaeumjeon induces mitochondrial dependent apoptosis partly via PI3K/AKT/HSP27/ERK pathways and inhibits PSA and AR in LNCaP cells

Hwaeumjeon is a classical prescription that has been traditionally used for treatment of urogenital diseases with no scientific evidences until now. Thus, the present study was performed to evaluate antitumor mechanism of ethanolic Hwaeumjeon (EHEJ). 2-Dimensional electrophoresis (2-DE) proteomic analysis, cell culture study, and Western blotting on apoptosis and prostate-specific antigen (PSA) related proteins were carried out in LNCaP prostate cancer cells. Eight spots with significant increased or decreased expression revealed by 2-DE based comparative proteomic analysis were identified as an increased protein ENC-1AS, four decreased proteins such as RAB34, SFRS1, heat shock 27, and proteasome activator, and three novel proteins such as Rho GDP dissociation inhibitor alpha, cytoplasmic antiproteinase, and EIF3EIP protein in EHEJ-treated LNCaP cells. In addition, EHEJ selectively inhibited the growth of LNCaP prostate cancer cells compared to normal human umbilical vein endothelial cells. Furthermore, EHEJ inhibited PSA and androgen receptor (AR) expression in androgen sensitive LNCaP prostate cancer cells at nontoxic concentrations. Also, EHEJ increased sub-G1 apoptotic portion, activated caspase-9 and -3, cleaved poly (ADP-ribose) polymerase (PARP) and increased the ratio of Bax to Bcl-2. Interestingly, EHEJ also attenuated phosphatidylinositol-3 kinase (PI3K) expression and suppressed the phosphorylation of survival gene AKT, ERK, and HSP27 in LNCaP cells. Consistently, PI3K and ERK inhibitors potentiated EHEJ-induced cytotoxicity and overexpression of Bcl-2 attenuated EHEJ-mediated apoptosis in LNCaP cells. These findings suggest that EHEJ induces mitochondrial dependent apoptosis partly via PI3K/AKT/HSP27/ERK pathways and inhibits PSA and AR in LNCaP cells as a prostate cancer chemopreventive candidate.

Over-expression of IkappaB-kinase-epsilon (IKKepsilon/IKKi) induces secretion of inflammatory cytokines in prostate cancer cell lines

BACKGROUND

Elevated inflammatory cytokine levels in serum have been associated with advanced stage metastasis-related morbidity in prostate cancer. Several studies have shown that IL-6 and IL-8 can accelerate the growth of human prostate cancer cell lines. Previous studies, in murine embryonic fibroblasts, have shown that Ikappa-B kinase-epsilon (IKKepsilon/IKKi)-deficiency results in the reduction of lipopolysaccharide-mediated expression of IL-6.

RESULTS

In this study, we report that over-expression of IKKepsilon in hormone-sensitive 22Rv1 and LNCaP prostate cancer cells induces the secretion of several inflammatory cytokines including IL-6 and IL-8. Both of these cytokines are secreted by hormone-refractory PC-3 prostate cancer cells and IKKepsilon knock-down in these cells correlates with a strong decrease in IL-6 secretion. Furthermore, we demonstrate that IKKepsilon over-expression does not induce the activation of the IKKepsilon classical targets NF-kappaB and IRF-3, two transcription factors involved in the regulation of several cytokines. Finally, we observe that high IKKepsilon expression results in its nuclear translocation, a phenomena that is TBK1-independent.

CONCLUSIONS

This study identifies IKKepsilon as a potential prostate cancer gene that may favor chronic inflammation and create a tumor-supporting microenvironment that promotes prostate cancer progression, particularly by the induction of IL-6 secretion that may act as a positive growth factor in prostate cancer.

The Fer tyrosine kinase cooperates with interleukin-6 to activate signal transducer and activator of transcription 3 and promote human prostate cancer cell growth

Androgen withdrawal is the most effective form of systemic therapy for men with advanced prostate cancer. Unfortunately, androgen-independent progression is inevitable, and the development of hormone-refractory disease and death occurs within 2 to 3 years in most men. The understanding of molecular mechanisms promoting the growth of androgen-independent prostate cancer cells is essential for the rational design of agents to treat advanced disease. We previously reported that Fer tyrosine kinase level correlates with the development of prostate cancer and aggressiveness of prostate cancer cell lines. Moreover, knocking down Fer expression interferes with prostate cancer cell growth in vitro. However, the mechanism by which Fer mediates prostate cancer progression remains elusive. We present here that Fer and phospho-Y705 signal transducer and activator of transcription 3 (STAT3) are barely detectable in human benign prostate tissues but constitutively expressed in the cytoplasm and nucleus of the same subsets of tumor cells in human prostate cancer. The interaction between STAT3 and Fer was observed in all prostate cancer cell lines tested, and this interaction is mediated via the Fer Src homology 2 domain and modulated by interleukin-6 (IL-6). Moreover, IL-6 triggered a rapid formation of Fer/gp130 and Fer/STAT3 complexes in a time-dependent manner and consistent with changes in Fer and STAT3 phosphorylation and cytoplasmic/nuclear distribution. The modulation of Fer expression/activation resulted in inhibitory or stimulatory effects on STAT3 phosphorylation, nuclear translocation, and transcriptional activation. These effects translated in IL-6-mediated PC-3 cell growth. Taken together, these results support an important function of Fer in prostate cancer.

Berberine inhibits TPA-induced MMP-9 and IL-6 expression in normal human keratinocytes

Berberine is a plant ingredient that has anti-inflammatory and anti-oxidative effects. Matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6) are known to be highly induced by ultraviolet (UV) light and may play important roles in UV-induced skin inflammation and the skin aging process. In this study, we investigated the effects of berberine on MMP-9 and IL-6 expression in normal human keratinocytes (NHK). Our results demonstrated that berberine dose-dependently inhibited basal and TPA-induced expression and activity of MMP-9, and also suppressed TPA-induced IL-6 expression. Berberine prevented TPA-induced ERK activation and AP-1 DNA binding activity. Therefore, berberine may be used as an effective ingredient for anti-skin aging products, which can prevent skin inflammation and the degradation of extracellular matrix proteins, including collagen, by MMPs.

Interleukin-6 activates PI3K/Akt pathway and regulates cyclin A1 to promote prostate cancer cell survival

Interleukin-6 (IL6) is a growth and survival factor in human prostate cancer (PCa) cells with aggressive phenotypes and has been implicated in the progression of hormone refractory PCas. In the present study, we characterized the IL6-triggered PI3K/Akt and MAPK/Erk signaling. We identified the A-type cyclin, cyclin A1 as an important downstream target of PI3K/Akt. Treatment of cells with PI3K inhibitor or cotransfection with a vector expressing wild-type PTEN decreased cyclin A1 promoter activity. Cyclin A1 promoter activity and its expression were upregulated by constitutively active myristoylated Akt and were downregulated by dominant negative Akt in response to IL6 stimulation. LNCaP cells overexpressing cyclin A1 are resistant to camptothecin-induced apoptosis. Conversely, targeted knockdown of cyclin A1 via shRNA in LNCaP IL6+ cells resulted in decreased survival after treatment with camptothecin. This suggests that cyclin A1 is an important downstream target of PI3K/Akt that transduces survival signals in response to IL6 stimulation. Xenograft tumors generated from LNCaP-IL6+ cells expressing IL6 had higher levels of cyclin A1 and had rapid tumor growth compared to LNCaP xenograft tumors. Taken together, IL6 might utilize PI3K/Akt and cyclin A1 to promote tumor cell survival in PCa.

The NF-kappaB/IL-6 pathway in metastatic androgen-independent prostate cancer: new therapeutic approaches?

The nuclear factor of kappa beta (NF-kappaB) transcription factor regulates the transcription of numerous genes including that of interleukin 6 (IL-6). The IL-6 acts as an autocrine and paracrine growth factor of androgen-independent prostate cancer. An aberrant expression of the IL-6 gene and an increase in IL-6 expression are detected in bone metastatic and hormone-refractory prostate cancer. IL-6 has been suggested to have a crucial role in the resistance to chemotherapy or hormonal therapy involving apoptotic cell death. The NF-kappaB/IL-6 dependent pathways promote tumour-cell survival and in most situations protect cells against apoptotic stimuli. These data provide a rational framework for targeting NF-kappaB and IL-6 activity in novel biologically based therapies for aggressive and androgen independent prostate cancers.

Suppressor of cytokine signaling-3 antagonizes cAMP effects on proliferation and apoptosis and is expressed in human prostate cancer

Interleukin-6, levels of which are elevated in prostate cancer, activates different signal transduction pathways including that of Janus kinases/signal transducer and activator of transcription (STAT)3. However, phosphorylation of STAT3 has been reported to be associated with either stimulatory or inhibitory effects on cellular proliferation. To better understand the mechanisms of STAT3 regulation in benign and malignant prostate, we have investigated the role of suppressor of cytokine signaling (SOCS)-3. Cell lines that did not express phosphorylated STAT3 were found to be SOCS-3-positive. SOCS-3 was re-expressed in LNCaP cells after treatment with a demethylating agent. SOCS-3 immunohistochemistry revealed a negative or weak reaction in benign areas, whereas its expression was detected in tumor tissue. To investigate the involvement of SOCS-3 in regulation of cellular events, we incubated cancer cells with a cAMP derivative. This treatment yielded higher SOCS-3 levels, reduced [3H]thymidine incorporation, and increased percentage of apoptotic cells. However, down-regulation of SOCS-3 by a short interfering RNA approach resulted in inhibition of proliferation and an increased apoptotic rate. Collectively, our results show that SOCS-3 antagonizes regulation of cellular events by cAMP and is expressed in human prostate cancer.

Regulation of growth of prostate cancer cells selected in the presence of interleukin-6 by the anti-interleukin-6 antibody CNTO 328

BACKGROUND

Interleukin-6 (IL-6) is a multifunctional regulator of cellular events in prostate cancer. LNCaP-IL-6+ cells selected in the presence of IL-6 were taken for assessment of effects of the chimeric monoclonal anti-IL-6 antibody CNTO 328.

METHODS

Cell viability was assessed after treatment with CNTO 328 by the ATP assay. Expression of Bcl-2 and Bax and activation of signaling pathways were evaluated by Western analysis. Nude mice were inoculated with LNCaP-IL-6+ cells and treated with CNTO 328. The tumors were analyzed by immunohistochemistry for expression of Ki-67, tissue transglutaminase, and vascular endothelial growth factor.

RESULTS

CNTO 328 caused a statistically significant inhibition of cell viability. The protein levels of Bcl-2 and the phosphorylation of ERK1/2 mitogen-activated protein kinases were decreased by the anti-IL-6 antibody. Treatment with CNTO 328 yielded an increase in the phosphorylation of signal transducers and activators of transcription factor 3. The mean tumor volume in animals inoculated with LNCaP-IL-6+ cells and treated with CNTO 328 was insignificantly lower than that in animals treated with the control antibody. There was a statistically significant decrease in the percentage of Ki-67-positive cells in CNTO 328-treated tumors.

CONCLUSION

CNTO 328 has a potential in prostate cancer therapy and could be further tested in various combination experimental treatments.

The antiapoptotic effect of IL-6 autocrine loop in a cellular model of advanced prostate cancer is mediated by Mcl-1

Levels of the proinflammatory cytokine interleukin-6 (IL-6) are increased in therapy-resistant prostate cancer. IL-6 has been considered a positive growth factor in late-stage prostate cancer cells and a potential target for therapeutic interference. Effects of inhibition of IL-6 on cell survival were studied in LNCaP-IL6+ cells, a model system for advanced prostate cancer, which produce IL-6. We show that the autocrine IL-6 loop is responsible for resistance to apoptosis and increased cellular levels of myeloid cell leukemia-1 (Mcl-1) protein, an antiapoptotic member of the Bcl-2 family. Treatment of cells with a chimeric anti-IL-6 antibody (CNTO 328) led to the induction of apoptosis and downregulation of Mcl-1 protein levels. Specific knockdown of Mcl-1 gene expression by small interfering RNA also yielded an increase in apoptosis of LNCaP-IL-6+ cells. Vice versa, inactivation of IL-6 autocrine loop had no influence on apoptosis levels in the absence of Mcl-1, thus suggesting this molecule as a mediator of the survival action of IL-6. Mcl-1 protein regulation by the endogenous cytokine directly involved the extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase pathway. Our data support the concept of anti-IL-6 targeted therapy in therapy-resistant prostate cancer.

Functional role of phosphatidylinositol 3-kinase/Akt pathway on cell growth and lytic cycle of Epstein-Barr virus in the Burkitt's lymphoma cell line, P3HR-1

The phosphatidylinositol 3-kinase (PI3-K)/Akt pathway is involved in various malignancies, but the role of PI3-K/Akt pathway in Epstein-Barr virus (EBV) infected Burkitt's lymphoma (BL) cells remains unclear. To elucidate therapeutic targets for BL, this study investigates the effect of PI3-K/Akt pathway in: EBV-positive BL cell lines Raji, P3HR-1, Akata and Daudi; and EBV-negative BL cell lines Ramos and BJAB. Results of analyses indicate that Akt was constitutively phosphorylated in BJAB, P3HR-1, Akata, and Daudi but not in Ramos and Raji cells. We characterized Akt phosphorylation on cell growth and EBV lytic cycle in P3HR-1 cells, which were phosphorylated most intensively. The Akt was equally phosphorylated in cells cultured with and without fetal bovine serum for a few days. Akt phosphorylation and cell growth were inhibited by PI3-K specific inhibitor LY294002 in a dose-dependent manner. LY294002 markedly down regulated expression of EBV lytic gene BRLF1 protein Rta, BMRF1 protein EA-D, but not BZLF1 protein ZEBRA. The inhibitor reduced viral capsid antigen (VCA) positive cells. Down regulation of Rta by LY294002 occurred at the transcriptional level. These results demonstrate that PI3-K/Akt pathway is activated constitutively in P3HR-1 cells; it promotes cell growth and the lytic cycle cascade downstream of ZEBRA.

Systemic Inflammatory Response, Prostate-Specific Antigen and Survival in Patients with Metastatic Prostate Cancer

BACKGROUND

It is increasingly recognised that, in cancer patients, disease progression is dependent on a complex interaction of the tumour and the host inflammatory response and that the systemic inflammatory response, as evidenced by an elevated C-reactive protein (CRP) concentration, may be a useful prognostic factor.

MATERIALS AND METHODS

The prognostic value of CRP compared with prostate-specific antigen (PSA) was examined in 62 patients with metastatic prostate cancer receiving androgen-deprivation therapy.

RESULTS

In all, 41 (66%) of patients died, 38 (61%) of their disease. On univariate survival analysis, PSA (p < 0.05) and CRP (p < 0.05) were significant predictors of cancer-specific survival. On multivariate analysis, both PSA (HR 1.96, 95% CI 1.00-3.83, p = 0.049) and CR (HR 1.97, 95% CI 0.99-3.92, p = 0.052) were independent predictors of cancer-specific survival. PSA concentrations were significantly correlated with those of CRP (r(s) = 0.46, p < 0.001).

CONCLUSION

The results of the present study suggest that, in patients with metastatic prostate cancer, the presence of an elevated CRP concentration predicts poor outcome, independent of PSA.

Inhibition of interleukin-6 with CNTO328, an anti-interleukin-6 monoclonal antibody, inhibits conversion of androgen-dependent prostate cancer to an androgen-independent phenotype in orchiectomized mice

Initially, prostate cancer is androgen dependent. However, most cases progress to an androgen-independent state through unknown mechanisms. Interleukin-6 (IL-6) has been associated with prostate cancer progression including activation of the androgen receptor (AR). To determine if IL-6 plays a role in the conversion of prostate cancer from androgen dependent to androgen independent, we established androgen-dependent LuCaP 35 human prostate cancer xenografts in nude mice, castrated the mice, and blocked IL-6 activity using a neutralizing antibody (CNT0328) for a period of 18 weeks. IL-6 inhibition increased survival of mice and inhibited tumor growth, as reflected by decreased tumor volume and prostate-specific antigen levels, compared with that in mice receiving isotype control antibody. To test the effect of IL-6 inhibition on the conversion from androgen dependent to androgen independent, tumor cells from the treated mice were assessed for their androgen dependence both in vitro and by implanting them into sham-operated or orchiectomized mice. Tumor cells derived from the isotype-treated animals converted to androgen-independent state, whereas tumor cells from the anti-IL-6 antibody-treated mice were still androgen dependent in vitro and in vivo. Although there was no difference in AR levels between the androgen-independent and androgen-dependent tumors, IL-6 inhibition promoted both apoptosis and inhibited cell proliferation in tumors and blocked the orchiectomy-induced expression of histone acetylases, p300 and CBP, which are AR cofactors. These data show that IL-6 contributes to the development of androgen independence in prostate cancer and suggest that it mediates this effect, in part, through modulation of p300 and CBP.

Endocrine regulation of prostate cancer growth

Prostate cancer is one of the most frequently diagnosed malignant neoplasms in the Western world. The focus of this article is on regulation of proliferation, apoptosis, angiogenesis and differentiation by steroid and peptide hormones. Steroid hormones, in particular androgens and estrogens, exert their effects through respective receptors. The androgen receptor is functional in all stages of the disease and it can be activated in a ligand-dependent and -independent manner. In prostate cancer, expression of some androgen receptor coactivators increases during tumor progression. Interleukins and transforming growth factor-β are multifunctional regulators of prostate growth and proliferation. Signal transduction cascades of fibroblast growth factors and insulin-like growth factors are responsible for increased survival and angiogenesis in prostate cancer. In clinical specimens obtained from prostate cancer, there is an increased phosphorylation of mitogen-activated protein kinase and Akt kinase, whose action in the regulation of cell survival is redundant.

Interleukin-6 regulation of prostate cancer cell growth

Interleukin-6 (IL-6) is involved in regulation of immune reaction and cell growth and differentiation. It causes multifunctional responses ranging from inhibition of proliferation to promotion of cell survival. IL-6 effects may depend on experimental conditions such as passage numbers and serum composition. IL-6 signals in target tissues through the receptor that is composed of the ligand-binding and signal-transducing subunits. IL-6 is expressed in benign and malignant prostate tissue and the levels of the cytokine and its receptor increase during prostate carcinogenesis. IL-6 is considered a positive growth factor for most prostate cells. The only exemption seems to be the LNCaP cell line, in which IL-6 causes growth arrest and induces differentiation function. In contrast, IL-6 acts as an autocrine growth factor in the subline LNCaP-IL-6+ established after chronic treatment with IL-6. IL-6 is a candidate for targeted therapy in prostate cancer because of its association with morbidity. Activation of signaling pathways of Janus kinase/signal transducers and activators of transcription factors, mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase has been reported in various prostate cancer cell lines. IL-6 and the related cytokine oncostatin M induce activation of the androgen receptor (AR) in the absence of androgen. IL-6 is also involved in regulation of vascular endothelial growth factor expression as well as neuroendocrine differentiation in prostate. Anti-IL-6 antibodies showed an inhibitory effect on the PC-3 xenograft. However, the development of this therapy in prostate cancer is in early stages.

Interleukin-6 and oncostatin M stimulation of proliferation of prostate cancer 22Rv1 cells through the signaling pathways of p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase

INTRODUCTION

Interleukin-6 (IL-6) is a pleiotropic regulator of prostate cancer cell growth. Oncostatin M (OSM), an IL-6-type cytokine, affects the growth of prostate cancers in a paracrine and autocrine manner. In order to understand better the mechanisms controlling proliferation and intracellular signaling by these cytokines in advanced prostate carcinoma, we performed studies in 22Rv1 cells derived from the relapsed xenograft CWR22R.

METHODS

Expression of IL-6 and OSM receptors (OSMR-beta) and elements of signal transduction pathways in 22Rv1 cells were investigated by RT-PCR. Proliferation was assessed by cell counting after treatment with either IL-6 or OSM. IL-6 secretion was measured in conditioned medium from 22Rv1 cells by ELISA. Expression and phosphorylation status of signal transducers and activators of transcription factor (STAT) 3, mitogen-activated protein kinases (MAPK) p44/p42 and p38, and protein kinase B (Akt) was investigated by Western blot.

RESULTS

22Rv1 cells express both subunits of the IL-6 receptor (gp80 and gp130) and leukemia inhibitory factor receptor-beta (LIFR-beta) but not OSMR-beta. Their proliferation was stimulated by IL-6 or OSM and the maximal effect was observed at a concentration of 10 ng/ml of either cytokine. Interestingly, neither IL-6 nor OSM induced phosphorylation of STAT3. OSM modestly increased the phosphorylation of p38 and both cytokines exerted an effect on Akt phosphorylation.

CONCLUSIONS

IL-6 and OSM stimulate proliferation of 22Rv1 cells, at least in part through activation of the phosphatidylinositol 3-kinase (PI 3-K) signaling pathway. Our data provide additional evidence for the growth-stimulatory role of IL-6 and related cytokines in advanced prostate cancer and may serve as a basis for the development of novel experimental therapies.

The prognostic significance of plasma interleukin-6 levels in patients with metastatic hormone-refractory prostate cancer: results from cancer and leukemia group B 9480

Interleukin-6 signaling can activate androgen receptor in a ligand-independent manner and may play an important functional role in hormone-refractory prostate cancer (HRCaP) progression and patient survival. Plasma and serum IL-6 levels have been associated with prostate cancer progression in several small studies. In order to evaluate its prognostic significance in metastatic HRCaP patients, we measured IL-6 in plasma collected at baseline from patients in a large cooperative group study [Cancer and Leukemia Group B 9480 (CALGB 9480)].

METHODS

191 patients entered on CALGB 9480 had pretreatment plasma collected and centrally stored. Using a human IL-6 immunoassay, quantitative levels of IL-6 were measured in duplicate on 300 muL samples. The proportional hazard model was used to assess the prognostic significance of IL-6 in predicting overall survival.

RESULTS

Median IL-6 level for the cohort of 191 patients was 4.80 pg/mL. Survival time among patients with IL-6 levels less than or equal to the median was 19 months (95% CI, 17-22) compared with 11 (95% CI, 8-14) months for patients above the median (P = 0.0004). In multivariate analysis, adjusting on performance status, lactate dehydrogenase, and prostate-specific antigen level, the hazard ratio was 1.38 (95% CI, 1.01-1.89; P = 0.043) using the median level as a cut point. Furthermore, a cut point of 13.31 pg/mL revealed robust prognostic significance with a hazard ratio of 2.02 (95% CI, 1.36-2.98; P = 0.0005).

CONCLUSIONS

Plasma IL-6 level has prognostic significance in patients with metastatic HRCaP from CALGB 9480. These findings support using IL-6 levels in prognostic models and support the rationale for IL-6-targeted therapy in patients with HRCaP.