STAT6 and STAT1 Pathway Activation in Circulating Lymphocytes and Monocytes as Predictor of Treatment Response in Rheumatoid Arthritis

Objective

To find novel predictors of treatment response to disease-modifying antirheumatic drugs (DMARDs), we studied activation of STAT (signal transducers and activators of transcription) 6 and 1 in circulating leukocytes of patients with rheumatoid arthritis (RA).

Methods

19 patients with untreated recent-onset RA, 16 patients with chronic RA irresponsive to synthetic DMARDs and 37 healthy volunteers provided blood samples for whole blood flow cytometric determination of intracellular STAT6 and STAT1 phosphorylation, expressed as relative fluorescence units, in response to IL-4 and IFN-γ, respectively. Phosphorylation was restudied and treatment response (according to European League Against Rheumatism) determined after 1-year treatment with synthetic DMARDs in recent-onset RA and with biological DMARD in synthetic DMARD-irresponsive RA. Estimation-based exact logistic regression was used to investigate relation of baseline variables to treatment response. 95% confidence intervals of means were estimated by bias-corrected bootstrapping and the significance between baseline and follow-up values was calculated by permutation test.

Results

At baseline, levels of phosphorylated STAT6 (pSTAT6) induced by IL-4 in monocytes were higher in those who achieved good treatment response to synthetic DMARDs than in those who did not among patients with untreated RA (OR 2.74, 95% CI 1.05 to 9.47), and IFN-γ -stimulated lymphocyte pSTAT1 levels were higher in those who achieved good treatment response to a biological drug than in those who did not among patients with chronic RA (OR 3.91, 95% CI 1.12 to 20.68). During follow-up, in recent-onset RA patients with good treatment response to synthetic DMARDS, the lymphocyte pSTAT6 levels decreased (p = 0.011), and, consequently, the ratio of pSTAT1/pSTAT6 in lymphocytes increased (p = 0.042).

Conclusion

Cytokine-stimulated STAT6 and STAT1 phosphorylation in circulating leukocytes was associated with treatment response to DMARDs in this pilot study. The result, if confirmed in larger studies, may aid in developing personalized medicine in RA.

Activated Phosphorylated STAT1 Levels as a Biologically Relevant Immune Signal in Schizophrenia

OBJECTIVE

Activation of STAT1 is directly downstream of the cytokine receptors that signal from specific proinflammatory cytokines known to be dysregulated in schizophrenia (SZ), such as IFNγ, IL6, IL2 and IL10, as well as hypoxia, viral/bacterial infections and peptide growth factors. If the increased cytokine protein levels repeatedly observed in SZ have biological consequences, then the measurement of pSTAT1 is a logical step forward.

METHODS

Peripheral blood mononuclear cells (PBMCs) from controls (n = 13) and subjects with SZ (n = 22) were extracted using the Ficoll method. Participants with SZ were diagnosed using the SCID, clinical symptomatology was measured using the Positive and Negative Syndrome Scale (PANSS), and cognitive functioning was measured using the MATRICS Consensus Cognitive Battery. Levels of activated STAT1 (Y701), i.e. phosphorylated STAT1 (pSTAT1), were measured by a commercially available ELISA in nuclear extracts from PBMCs.

RESULTS

There was a significant bimodal distribution in the sample, with an SZ subgroup expressing significantly greater levels of activated pSTAT1 than the remainder of the participants. In this subgroup, levels of pSTAT1 were significantly higher than in the control group, as well as significantly higher than in the remainder of the SZ subjects. Furthermore, this subsample of patients manifested significantly poorer cognitive performance on several measures of the MATRICS.

DISCUSSION

pSTAT1 levels may provide a measure of the biological relevance of widely reported elevations in levels of cytokines in SZ over the past several decades. Activation of kinase cascades can be used to partition or disassemble the composite immune signal in patients living with SZ.

Reduced levels of CCL2 and CXCL10 in systemic lupus erythematosus patients under treatment with prednisone, mycophenolate mofetil, or hydroxychloroquine, except in a high STAT1 subset

INTRODUCTION

Our recent data showed that signal transducers and activators of transcription 1 (STAT1), adenosine deaminase acting on RNA (ADAR), C-C motif chemokine ligand 2 (CCL2), and C-X-C motif chemokine 10 (CXCL10) were significantly elevated in a systemic lupus erythematosus (SLE) cohort compared to healthy donors. High and low STAT1 subsets were identified in SLE patient visits. The present study analyzed the correlation of common treatments used in SLE with the levels of these biomarkers.

METHODS

Peripheral blood leukocytes were collected from 65 healthy donors and 103 SLE patients, of whom 60 had samples from two or more visits. Total RNA was isolated and analyzed for the expression of mRNA and microRNA using Taqman real-time polymerase chain reaction (PCR) assays. Relative expression of interferon signature genes, CCL2, and CXCL10 were determined by the ΔΔCT method. Results were correlated with therapy using prednisone, mycophenolate mofetil, and hydroxychloroquine and analyzed by Wilcoxon/Kruskal-Wallis test and Fisher's exact test.

RESULTS

CCL2 and CXCL10 were significantly higher in untreated patients compared to treated patients, however, in high STAT1 patient visits there is no significant difference between treated and untreated patients' visits. When comparing linear regression fits of interferon (IFN) score with CCL2 and CXCL10, untreated patients and high STAT1 patients displayed significantly higher slopes compared to treated patients. There was no significant difference between the slopes of high STAT1 and untreated patients indicating that CCL2 and CXCL10 were correlated with type-I IFN in high STAT1 patients similar to that in untreated patients. CCL2 and CXCL10 levels in the high STAT1 subset remained high in treated patient visits compared to those of the low STAT1 subset.

CONCLUSIONS

Among the biomarkers analyzed, only CCL2 and CXCL10 showed significantly reduced levels in treated compared to untreated SLE patients. STAT1, CCL2, and CXCL10 are potentially useful indicators of therapeutic action in SLE patients. Further work is needed to determine whether high STAT1 levels convey resistance to therapies commonly used to treat SLE and whether STAT1 inhibitors may have therapeutic implication for these patients.

Elevated signal transducers and activators of transcription 1 correlates with increased C-C motif chemokine ligand 2 and C-X-C motif chemokine 10 levels in peripheral blood of patients with systemic lupus erythematosus

INTRODUCTION

The present study examines the levels of recently reported biomarkers, adenosine deaminase acting on RNA (ADAR), C-C motif chemokine ligand 2 (CCL2), C-X-C motif chemokine 10 (CXCL10), signal transducers and activators of transcription 1 (STAT1), and miR-146a in systemic lupus erythematosus (SLE) patients over multiple visits.

METHODS

Peripheral blood leukocytes were collected from 65 healthy donors and 103 SLE patients, 60 of whom had samples from 2 or more visits. Total RNA was isolated and analyzed for the expression of mRNA and microRNA using Taqman real time PCR assays. Relative expression of I-IFN signature genes, chemokines, and miR-146a were determined by the ΔΔCT method. Results were correlated with clinical data and analyzed by Wilcoxon/Kruskal-Wallis test and Fisher's exact test.

RESULTS

Levels of ADAR, CCL2, CXCL10, and STAT1 in SLE were significantly elevated compared with the healthy controls (P <0.0001). ADAR, CCL2, and CXCL10 showed significant correlation with IFN score in both healthy donors (P <0.0033) and SLE patients (P <0.0001). In SLE patients, miR-146a level was not significantly different from healthy controls nor correlated to the IFN score. Two STAT1 populations were identified: a low STAT1 and a high STAT1 group. High STAT1 patient visits displayed higher (P ≤0.0020) levels of CCL2 and CXCL10 than the low STAT1 patient visits. STAT1 levels correlated with IFN score in low STAT1 group but not in high STAT1 group. More importantly, high STAT1 levels appeared as an enhancer of CCL2 and CXCL10 as indicated by the significantly stronger correlation of CCL2 and CXCL10 with IFN score in high STAT1 patient visits relative to low STAT1 patient visits.

CONCLUSION

Our data indicate a novel role for STAT1 in the pathogenesis of SLE as an expression enhancer of CCL2 and CXCL10 in SLE patients with high levels of STAT1. Future study is needed to examine the exact role of STAT1 in the etiology of SLE.

Normal breast tissue implanted into athymic nude mice identifies biomarkers of the effects of human pregnancy levels of estrogen

We have generated a novel model system for the study of estrogen intervention in normal breast tissue. Nulliparous human breast tissue was implanted into immunocompromised nude mice and treated with high-dose estrogen to simulate the effects of pregnancy. Treatment of mice with human mid-pregnancy levels of 17beta-estradiol for a period of 4 weeks was followed by 4 weeks of withdrawal to mimic involution. Gene expression in the xenograft tissue was then analyzed by real-time reverse transcription-PCR to identify differences between treated and control tissues. Ten genes previously identified as altered by pregnancy in rodent models were found to be differentially expressed in human breast tissue with a > or =1.8-fold up-regulation of CDC42, TGFbeta3, DCN, KRT14, LTF, and AREG and a > or =0.7-fold down-regulation of STAT1, CTGF, IGF1, and VAMP1. Immunohistochemical analysis of archival paraffin-embedded adult premenopausal human breast tissue specimens identified a significantly lower level of expression of STAT1 (P < 0.05, Mann-Whitney U test) in parous compared with age-matched nulliparous tissue (median of 24% compared with 42% epithelial cells positive). We conclude that many of the pregnancy-induced breast cancer-protective changes observed in rodent models also occur in human breast tissue following intervention using human pregnancy levels of estrogen and that STAT1 expression is a potential biomarker of parity-induced breast cancer protection in the human breast.

A novel modification of a flow cytometric assay of phosphorylated STAT1 in whole blood lymphocytes for rapid detection of interferon-α signal in vivo

Phosphorylation of signal transducer and activator of transcription factor 1 (STAT1) is a key response in the type I interferon (IFN) signal cascade. We developed a novel flow cytometric assay for phosphotyrosine-STAT1 (p-STAT1) to rapidly monitor in vivo IFN signaling. Mouse blood stimulated with mouse IFN-alpha was hemolyzed with lysis buffer in place of lymphocyte purification, permeabilized with methanol, and stained with an Alexa Fluor 488-conjugated anti-p-STAT1 antibody. The cells were also stained with phycoerythrin (PE)-conjugated anti-CD45 antibody for eliminating debris (CD45-negative) from leukocytes (CD45-positive), and with PE covalently linked to cyanin 5-conjugated anti-Gr-1 antibody for separating lymphocytes (Gr-1-negative) and granulocytes (Gr-1-positive). When whole blood was treated with IFN-alpha, the Alexa Fluor 488 intensity of lymphocytes increased, reaching a peak within 1 h, and this increase was statistically significant at IFN-alpha concentrations of 100 U/mL and higher. When IFN-alpha was administered intravenously to mice, the Alexa Fluor 488 intensity of blood lymphocytes was increased, reaching a peak in 1 h and returning to baseline at 18 h, and this increase was dose-dependent, with statistically significant increases seen at doses of 1,000 U/body and higher. The kinetics and dose-responses of p-STAT1 levels in the spleen, lung, and liver were similar to those in blood lymphocytes. This new flow cytometric assay of p-STAT1 in peripheral blood leukocytes will be useful for examining IFN-alpha signaling and for monitoring tissue response to IFN-alpha in vivo.

Phase I study of the sequential combination of interleukin-12 and interferon alfa-2b in advanced cancer: evidence for modulation of interferon signaling pathways by interleukin-12

PURPOSE

To evaluate the safety of sequentially administered recombinant (r) human (h) interleukin-12 (IL-12) and interferon alfa-2b (IFN-alpha-2b) in patients with advanced cancer and to determine the effects of endogenously produced IFN-gamma on Janus kinase-signal transducer and activator of transcription (Jak-STAT) signal transduction in patient peripheral-blood mononuclear cells (PBMCs).

PATIENTS AND METHODS

Forty-nine patients with metastatic cancer received rhIL-12 on day 1 and IFN-alpha-2b on days 2 to 6 of either a 14-day (n = 43) or a 7-day treatment cycle (n = 6). rhIL-12 was initially administered subcutaneously at a dose of 100 ng/kg, whereas IFN-alpha-2b was escalated from 1 to 10 million units (MU) in cohorts of three patients (1, 3, 5, 7, or 10 MU). rhIL-12 was subsequently administered intravenously (IV) in escalating doses (100 to 500 ng/kg) to achieve greater IFN-gamma production. Peripheral blood was drawn for measurement of plasma IFN-gamma and the induction of Jak-STAT signal transduction in PBMCs.

RESULTS

No IL-12-or IFN-alpha-related dose-limiting toxicities were observed. There were no responses in 41 assessable patients. Five patients exhibited stable disease lasting 6 months or longer while on therapy. Optimal induction of IFN-gamma by IL-12 occurred after an IV dose of 250 ng/kg. Patient PBMCs exhibited increased levels of STAT1 after IL-12 administration. The peak level of IFN-gamma achieved with IL-12 therapy correlated with the peak level of intracellular STAT1 in patient PBMCs (r = 0.38, P = .021).

CONCLUSION

The combination of rhIL-12 and IFN-alpha-2b can be administered sequentially with minimal toxicity. IV administration of rhIL-12 modulates IFN-alpha-induced Jak-STAT signal transduction in patient PBMCs.

Undetectable phospho-STAT1 in peripheral blood mononuclear cells from patients with chronic hepatitis C who do not respond to interferon-alpha therapy

BACKGROUND

Recent studies have suggested that phosphorylated signal transducers and activators of transcription 1 (STAT1) plays an important role in interferon (IFN)-mediated biological functions, including antiviral activity. Moreover, it has been demonstrated that suppressors of the cytokine signal 1 (SOCS1) negatively regulates IFN activities.

AIMS

To investigate the involvement of phospho-STAT1 in the response to IFN-alpha therapy in patients with chronic hepatitis C and to evaluate the negative regulatory effect of SOCS1 on STAT1 activation.

METHODS

Sixty-five patients with chronic hepatitis C and 25 healthy subjects were enrolled. Twenty-five of the patients had never been treated with IFN-alpha therapy (naive), while the remaining 40 patients had. The IFN-treated patients were divided into sustained responders (SRs) or non-responders (NRs) on the basis of their response to the antiviral therapy. Peripheral blood mononuclear cells (PBMCs) were obtained from each patient and control, and were either stimulated with IFN-alpha or left unstimulated. Total STAT1, phospho-STAT1 and SOCS1 were revealed by means of Western blot.

RESULTS

Total STAT1 was equally expressed in unstimulated and stimulated PBMCs from all patients and controls. One hundred percent of the stimulated PBMCs from healthy controls and SRs, 96% from naive subjects, and 30% from NRs showed detectable phospho-STAT1. By contrast, 70% of the stimulated PBMCs from NRs showed undetectable phospho-STAT1.

CONCLUSIONS

We have demonstrated that phospho-STAT1 proteins in 70% of patients with chronic hepatitis C who do not respond to IFN treatment are undetectable, which suggests that this protein may be involved in the mediation of IFN sensitivity. The down-regulation of the Jak-STAT pathway because of SOCS1 expression may be one of the possible underlying mechanisms involved in resistance to IFN.