scholarly journals Role of interleukin-10 and interleukin-24 in the pathogenesis of В-cell chronic lymphocytic leukemia

2018 ◽  
pp. 56-61
Author(s):  
Т.Н. Жевак ◽  
Н.П. Чеснокова ◽  
Т.В. Шелехова ◽  
О.Е. Царева ◽  
И.А. Будник ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Serum Level ◽  
B Cell ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
Disease Stage ◽  
Enzyme Linked Immunosorbent Assay ◽  
Control Group ◽  
Patient Groups ◽  
Cell Chronic Lymphocytic Leukemia

Цель. Изучить закономерности изменения экспрессии интерлейкина-10 и интерлейкина-24, обладающих иммуномодулирующим эффектом, при развитии B-клеточного хронического лимфолейкоза. С учетом этого выявить информативные прогностические критерии развития гемобластоза и/или нового подхода к терапии заболевания. Методы. У 120 больных с разными стадиями В-клеточного хронического лимфолейкоза методом твердофазного иммуноферментного анализа исследована динамика уровней интерлейкина-10 и интерлейкина-24 в сыворотке крови. Результаты. Обнаружено закономерное повышение содержания интерлейкина-10 и интерлейкина-24 в сыворотке крови пациентов уже на начальной стадии B-клеточного хронического лимфолейкоза и сохранение их достоверно высоких уровней на последующих стадиях заболевания. Заключение. Обнаруженный нами факт повышения содержания интерлейкина-10 в сыворотке крови пациентов с В-клеточным хроническим лимфолейкозом является фактором риска снижения противоопухолевой защиты организма вследствие подавления им механизмов клеточного иммунитета и способности ингибировать апоптоз малигнизированных клеток. Напротив, повышение экспрессии интерлейкина-24, обладающего проапоптотической активностью и стимулирующего дифференцировку клеток, может способствовать повышению эффективности механизмов противоопухолевой резистентности организма. Устранение дисбаланса продукции и/или содержания указанных цитокинов в сыворотке крови может создать условия повышения эффективности терапии пациентов с В-клеточным хроническим лимфолейкозом. Aim. To study serum levels of immunosuppressive cytokines (interleukin (IL)-10 and IL-24) in patients with B-cell chronic lymphocytic leukemia for assessment of the disease progression and elaboration of a new treatment strategy. Methods. 120 patients with B-cell chronic lymphocytic leukemia were enrolled in the study and divided into four groups according to the disease stage (Rai stage I-IV). Control group included 30 healthy volunteers. Concentrations of IL-10 and IL-24 were measured in serum using the enzyme-linked immunosorbent assay (ELISA). Results. Serum levels of IL-10 and IL-24 levels were significantly increased in all patient groups compared to the control. No difference in the cytokines levels between the patient groups was observed. Conclusion. In patients with B-cell chronic lymphocytic leukemia, the increased serum level of IL-10 might impair the antitumor defence by inhibiting the cell immune response and preventing apoptosis of malignant lymphocytes. On the other hand, the increased serum level of IL-24 might oppose these effects by promoting cellular differentiation and inducing apoptosis in malignant cells. Therefore, correction of IL-10/IL-24 imbalance may be a beneficial therapeutic strategy for patients with B-cell chronic lymphocytic leukemia.

scholarly journals Serum Levels of IL-6 Type Cytokines and Soluble IL-6 Receptors in Active B-Cell Chronic Lymphocytic Leukemia and in Cladribine Induced Remission

1999 ◽  
Vol 8 (6) ◽  
pp. 277-286 ◽  
Author(s):  
T. Robak ◽  
A. Wierzbowska ◽  
M. Błasińska-Morawiec ◽  
A. Korycka ◽  
J. Z. Błoński
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Serum Level ◽  
B Cell ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
Enzyme Linked Immunosorbent Assay ◽  
Control Group ◽  
Healthy Controls ◽  
Serum Concentrations ◽  
Cell Chronic Lymphocytic Leukemia

We have investigated the serum concentrations of interleukin-6 (IL-6) and two IL-6 family cytokines-oncostatin M (OSM) and leukemia inhibitory factor (LIF)-in 63 patients with B-cell chronic lymphocytic leukemia (B-CLL) and 17 healthy controls using the enzyme-linked immunosorbent assay (ELISA) method. Simultaneously, we measured the serum levels of the soluble forms of two subunits of the IL-6 receptor complex-ligand binding glycoprotein 80 (sIL-6R) and glycoprotein 130 (sgp130). The cytokines and receptors were evaluated in 25 untreated patients and 38 patients treated with cladribine (2-CdA), as well as in 17 healthy controls. We have correlated the serum levels of these proteins with Rai's clinical stage of the disease, the response to 2-CdA treatment and some hematological parameters. We have also evaluated the correlation of the IL-6 serum level with the concentration of OSM and IL-6 soluble receptors. IL-6 was measurable in 62/63 (98.4%), OSM in 20/25 (80%) of untreated and 14/38 (37.8%) of the treated patients. sIL-6R and sgp130 were detectable in all 63 patients and LIF in none of the CLL patients. IL-6 serum level in untreated patients was not significantly different as compared to its concentration in the control group (P>0.05). However, in the patients treated with 2-CdA the IL-6 level was significantly lower (P<0.02), and the lowest concentration was found in the patients with complete remission (CR; median 1.4 pg/ml; P<0.02). The concentration of sIL-6R was significantly higher in untreated (median 61.8 ng/ml) and treated (median 50.1 ng/ml) CLL patients when compared to normal persons (median 41.2 ng/ml; P=0.04; P<0.001, respectively). There was no difference between the sIL-6R levels in the patients with CR and the healthy controls. In non-responders sIL-6R concentration was the highest and similar to its level in the untreated patients. OSM level was higher in the untreated patients (median 1.8 pg/ml) than in the normal controls (median 0.0 pg/ml; P<0.001) and in the CR patients (median 0.0 pg/ml; P<0.03). The serum concentration of sgp130 was similar in the untreated (median 480 pg/ml) and treated (median 470 pg/ml) patients, as well as in the healthy persons (median 420 pg/ml; P>0.05). We have found significant positive correlation between the levels of sIL6R and the lymphocytes count in CLL patients (Ρ=0.423; P<0.001). In addition, sIL-6R and OSM serum concentrations correlated also with CLL Rai stage. In conclusion, the serum level of IL-6, OSM and sIL-6R, but not LIF and sgp130, are useful indicators of CLL activity.

Characteristics and Outcome of B-Cell Chronic Lymphocytic Leukemia in HCV-Positive Patients.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4986-4986
Author(s):  
Stefano Molica ◽  
Rosanna Mirabelli ◽  
Demetrio Misuraca ◽  
Caterina Battaglia
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Monoclonal Gammopathy ◽  
Absolute Lymphocyte Count ◽  
Serum Levels ◽  
Autoimmune Disorders ◽  
Lymphocytic Leukemia ◽  
Severe Infections ◽  
Hodgkin's Lymphomas ◽  
Cell Chronic Lymphocytic Leukemia

Abstract HCV-associated B-cell non-Hodgkin’s lymphomas (NHL) show distinctive clinico-pathological features such as older age, liver damage, presence of monoclonal gammopathy, increased incidence of autoimmune disorders, extranodal localizations and restricted histological subtypes. As far as B-cell chronic lymphocytic leukemia (CLL) is concerned, information dealing with either characteristics or outcome of HCV-associated CLL are limited. With this background we compared clinico-hematological features and outcome of 34 HCV-positive patients diagnosed at our institution as having immunologically typical B-cell CLL (i.e., CD5+/CD23+/CD79b-/SmIg dim) with 161 unselected CLL HCV-negative patients followed-up in the last 10 years. The two groups were alike with respect to main clinico-hematological features such as age (P=0.780), sex (P=0.650), absolute lymphocyte count (P=0.788), platelet count (P=0.362), haemoglobin level (P=0.704), β2-microglobulin (P=0.192), Binet stage distribution (P=0.224) and lymphocyte doubling time (LDT)(P= 0.620). As expected either ALT or AST serum levels at the time of CLL diagnosis were significantly higher in HCV-positive patients in comparison to HCV-negative ones (P&lt;0.0001 for both). In contrast, no difference was found in the incidence of monoclonal gammopathy between HCV-positive and HCV-negative patients (10.3% versus 7.7%; P=0.708). The same applied for autoimmune disorders which were homogeneously distributed in the two subgroups (P=0.711) and accounted, more frequently, for autoimmune emolytic anemia (AEA)(HCV-negative subgroup, 5.5%; HCV-positive subgroup, 9.0%). The proportion of severe infections registered did not reflect the HCV-status (HCV-negative subgroup, 9.6%; HCV-positive subgroup 6.4%; P= 0.510). Also second tumours were equally distributed among HCV-positive and HCV-negative subgroups (10% versus 6.8%; P=0.655). Survival curves projected at 10 years did not show any statistical in terms overall survival (Hazard Risk, 0.690; 95% CI: 0.216–1.304; P=0.167). Finally, the short term hepatic toxicity of chemotherapy did not increase among HCV-positive patients (P=0.671). In conclusion, HCV-positive patients with B-cell CLL do not differ from other patients both for presentation and clinical outcome. The need to activate specific protocols of antiviral therapy appears less urgent in comparison to NHL, however, younger CLL patients HCV-positive who are eligible for therapies at higher immunosuppressive potential (i.e., chemo-immunotherapy) should be taken in special consideration.

Serum BAFF (B-Cell Activating Factor of the TNF Family) Compared with Immunoglobulin Heavy-Chain Mutation Status, ZAP-70 and CD38 as a Predictor of Time to First Treatment in Early B-Cell Chronic Lymphocytic Leukemia.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3093-3093
Author(s):  
Stefano Molica ◽  
Gaetano Vitelli ◽  
Giovanna Cutrona ◽  
Giovanna Digiesi ◽  
Rosanna Mirabelli ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Heavy Chain ◽  
Immunoglobulin Heavy Chain ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
B Cell Activating Factor ◽  
Mutational Status ◽  
Time To First Treatment ◽  
Cell Chronic Lymphocytic Leukemia

Abstract We analyzed the correlation between well-established biological parameters of prognostic relevance in B-cell chronic lymphocytic leukemia [CLL] (i.e, mutational status of the immunoglobulin heavy chain variable region [IgVH], ZAP-70- and CD38-expression) and serum levels of BAFF (B-cell activating factor of the TNF family) by evaluating the impact of these variables on the time to first treatment [TFT] in a series of 69 previously untreated Binet stage A B-cell CLL patients. By using a commercial ELISA (R & D Systems, USA) we found that higher levels of BAFF characterized more frequently patients with Rai stage 0 (P=0.008) and mutated IgVH (P=0.03). In contrast, peripheral blood lymphocytosis (P=0.06), serum β2-m (P=0.159), LDH (P=0.333) and percentage of ZAP-70-positive (P=0.242) or CD38-positive B-CLL cells (P=0.142) did not reflect circulating levels of BAFF. The relationship among various bio-pathological parameters, analyzed by the multiple correspondence analysis (MCA), showed two different clinico-biological profiles. The first, characterized by higher BAFF serum levels (i.e., > 336 ng/mL), presence of mutation in the IgVH, low percentage of CD38-positive B-CLL cells (< 30%) and low LDH was associated with a stable pattern of disease generally not requiring therapy. The second, defined by lower BAFF levels, absence of mutation in the IgVH, high percentage of CD38- positive B-CLL cells and high LDH was associated with a more progressive pattern of disease and a shorter TFT. After a median follow-up time of 35 months (range, 2–120 months) 26 (37.6%) out of 69 patients experienced a need for chemotherapy. Kaplan-Meier estimates of patientsTFT, plotted after searching the best cut-off for BAFF (i.e., 336 ng/mL), demonstrated that low BAFF concentration was associated with a shorter TFT (median TFT 36 months) while median was not reached by patients with BAFF levels higher than 336 ng/mL (P<0.0001). Along with lower serum levels of BAFF (Hazard Ratio [HR], 0.19; P<0.0001), the univariate Cox proportional hazard model identified absence of mutation in IgVH (HR, 0.17; P<0.0001), CD38-positivity (HR, 3.32; P=0.01) and lower platelet count (HR, 0.19; P=0.03) as predictor of shorter TFT. Finally, in multivariate analysis only mutational status of IgVH (HR, 0.25; P=0.007) and serum concentration of BAFF (HR, 034; P=0.04) affected significantly TFT. Our results indicate that in early B-cell CLL clinico-biological profile including among other parameters BAFF may provide a useful insight into the complex interrelationship of prognostic variables and semplify their interpretation. The possible presence of BAFF isoform in B-CLL could peraphs account for the unexpected correlation between low soluble BAFF levels and poor clinical outcome in patients with early disease.

Tyro3, Axl Ve Mer (TAM) Receptors On Surfaces of Mononuclear Cells in Patients with B-Cell Chronic Lymphocytic Leukemia

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4588-4588
Author(s):  
Dilvin Guney ◽  
Aysin Tulunay ◽  
Funda Pepedil ◽  
Isik Kaygusuz ◽  
Cafer Adiguzel ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Mononuclear Cells ◽  
Conflicts Of Interest ◽  
Gradient Centrifugation ◽  
Lymphocytic Leukemia ◽  
Control Group ◽  
Ligand Molecule ◽  
Tam Receptors ◽  
Cell Chronic Lymphocytic Leukemia

Abstract Abstract 4588 Background: Tyro 3 (Sky), Axl, and Mer receptors are members of the family of tyrosine kinases and Gas6 is their ligand molecule. In some types of cancer, upregulation of Axl/Gas6 indicated a worse prognosis, but an opposite situation was observed in renal “cell” carcinoma. This contradiction may suggest that Axl/Gas6 pathway varies depending on the type of cancer. The objective of this study is to investigate TAM receptors on surfaces of mononuclear cells in patients with B-Cell chronic lymphocytic leukemia (B-Cell-CLL). Material & Methods: B-Cell-CLL patients (grade 0–1, according to the classification of RAI), who were not on a drug treatment, were recruited in this study (n= 20; 9 female, 11 male). Their ages were 44 to 74 (mean: 63), and the control group consisted of 13 healthy volunteers (5 female, 8 male), whose age range is 20–89 (mean: 36). Mononuclear cells were isolated by density gradient centrifugation, and then surface TAM receptors were detected by flow cytometry. Mononuclear cell were stained with the primary antibodies against Tyro3, Axl and Mer. Results: The percentage of the surface TAM receptors on mononuclear cells from the patient group (25–75% interquartile range): Tyro 3= 25.50 (4.2– 45.62); Axl= 17/55 (5.57– 36.32), and Mer= 19.90 (1.92– 37.55). In the control group the following values were obtained: Tyro 3= 2.60 (1.35–3.25); Axl= 0.9 (0.4–2.6), and Mer= 2.50 (0.35–3.65). The percentage of three of them was significantly higher in the B-Cell-CLL group than those in the control group (P<0.01). Conclusion: In conclusion, this preliminary study showed that TAM receptors on surfaces of mononuclear cells are higher in patients with B-Cell-CLL patients than the control group. Gas6/TAM signaling may play a potential role in the pathogenesis of B Cell-CLL. Further studies are required to elucidate the actual role of Gas6/TAM signaling in B-Cell-CLL. Gas6/TAM signaling might be a new strategic goal for the treatment of B-Cell-CLL. Disclosures: No relevant conflicts of interest to declare.

Serum BAFF (B-CELL Activating Factor Of The TNF Family) predicts time to First Treatment in Early B-CELL Chronic Lymphocytic Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4158-4158
Author(s):  
Stefano Molica ◽  
Gaetano Vitelli ◽  
Giovanna Cutrona ◽  
Giovanna Digiesi ◽  
Rosanna Mirabelli ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Serum Concentration ◽  
B Cell ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
B Cell Activating Factor ◽  
Mutational Status ◽  
Time To First Treatment ◽  
The Impact ◽  
Cell Chronic Lymphocytic Leukemia

Abstract We analyzed the correlation between well-established biological parameters of prognostic relevance in B-cell chronic lymphocytic leukemia [CLL] (i.e, mutational status of the immunoglobulin heavy chain variable region [IgVH], ZAP-70− and CD38− expression) and serum levels of BAFF (B-cell activating factor of the TNF family) by evaluating the impact of these variables on the time to first treatment [TFT] in a series of 125 previously untreated Binet stage A B-cell CLL patients. By using a commercial ELISA (R & D Systems, USA) we found that higher levels of BAFF characterized more frequently females (P=0.01), patients with Rai stage 0 (P=0.03), mutated IgVH disease (P=0.008) and low ZAP-70 expression (P=0.04). In contrast, age (P=0.35), peripheral blood lymphocytosis (PBL)(P=0.09), hemoglobin (Hb) level (P=0.64), platelet (PLT) count (P=0.12), serum β2-m (P=0.49), LDH (P=0.85) and percentage of CD38-positive B-CLL cells (P=0.63) did not reflect circulating levels of BAFF. We used an optimal cut-point search to determine how to best split soluble BAFF data. Maximally selected log-rank statistics plots identified a BAFF serum concentration of 311 ng/mL as the best cut-off (P&lt;0.0001). Accordingly, patients who had BAFF levels higher than 311 ng/mL experienced a longer TFT (median 108 months) in comparison to patients whose BAFF levels were lower than 311 ng/mL (median 30 months; P&lt;0.0001). Along with serum concentration of BAFF, the univariate Cox proportional hazard model identified Rai substage I–II (P=0.003), lower PLT count (P=0.04), higher PBL count (P=0.01), increased LDH (P=0.01), ZAP-70 expression &gt; 20% (P=0.02) and absence of mutation of IgVH (P&lt;0.0001) as predictor of shorter TFT. In multivariate analysis only soluble BAFF (Hazard ratio [HR], 6.13; CI 95%, 2.31–16.25) and mutational status of IgVH, (HR= 2.99; CI 95% 1.33–6.76, P=0.008) maintained their discriminating power. The effects of BAFF on TFT were masked by mutational status of IgVH in patients with unmutated IgVH. However, serum levels of BAFF and mutational status of IgVH had a joint effect on TFT in patients with mutated IgVH which translates into a segregation of patients with mutated IgVH in two groups with different TFT according to BAFF levels (HR= 8.9; P&lt;0.0001). Our results indicate that in early B-cell CLL biological profile including among other parameters soluble BAFF may provide a useful insight into the complex interrelationship of prognostic variables. Furthermore, BAFF along with mutational status of IgVH can be adequately used to predict clinical behaviour of patients with low biological risk.

Serum Insulinlike Growth Factor Is Not Elevated in Patients with Early B-Cell Chronic Lymphocytic Leukemia but Is Still a Prognostic Factor for Disease-Progression.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4786-4786
Author(s):  
Stefano Molica ◽  
Gaetano Vitelli ◽  
Rosanna Mirabelli ◽  
Giovanna Digiesu ◽  
Diana Giannarelli ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Growth Factor ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Disease Progression ◽  
Adhesion Molecule ◽  
Serum Levels ◽  
Lymphocytic Leukemia ◽  
Cell Chronic Lymphocytic Leukemia ◽  
Igfbp 3

Abstract Insulin like growth factor 1 (IGF-1) is an important growth and antiapoptotic factor for the cancer cells in several malignancies and in multiple myeloma recent studies support the hypotesis of a role for IGF-1 in disease progression. Clinico-biological relevance of IGF-1 was never studied in B-cell chronic lymphocytic leukemia (CLL). Using a quantitative sandwich immunoassay technique (ELISA)(QUANTIKINE®, Human IGF-1 and IGFBP-3, R & D Systems), we measured the concentration of IGF-1 and its major binding protein IGF-binding protein 3 (IGFBP-3) in serum drawn at the time of diagnosis from 77 Binet stage A CLL patients. Either IGF-1 or IGFBP-3 were significantly decreased compared to healthy age- and sex-matched controls (P&lt;0.0001 for both; Mann-Whitney test). Serum levels of IGF-1 and IGFBP-3 paralleled each other (P=0.002); in contrast, no significant correlation was found between serum levels of IGF-1 and clinico-hematological variables including age (P=0.253), sex (P=0.270), Rai clinical substages (P=0.140), LDH (P=0.956), β2-microglobulin (P=0.368), lymphocyte count (P=0.703) and lymphocyte doubling time [LDT](P=0.233). When correlation were attempted with circulating levels of angiogenic cytokines such as vascular endothelial growth factor (VEGF)(P=0.971), basic fibroblastic growth factor (FGF-2)(P=0.695), angiogenin (P=0.282) or adhesion molecules such as vascular cell adhesion molecule-1 [VCAM-1] (P=0.318), intercellular adhesion molecule-1 [ICAM-1] (P=0.883) and platelet endothelial cell adhesion-1 [PECAM-1] (P=0.772) similar results were found. Serum levels of IGF-1 were further evaluated as a dichotomous variable with respect to progression-free survival (PFS), an endpoint surrogate for overall survival in early B-cell CLL. The best separation of curves was seen with the cutoff point at the 75th percentile of IGF-1 levels (i.e., 93 pg/ml). Median PFS was 63 months in the patient group with low IGF-1, compared to a median PFS of 40 months in the remaining patients (P=0.002; HR, 0.311, 95% C.I, 0.085–0.630). In the multivariate analysis performed including variables significant at univariate analysis [i.e., Rai substage (P=0.002); LDT (P=0.004), IGF-1 (P=0.01)], only Rai substage retained prognostic significance (P=0.006). However, after removing from analysis LDT (only 6 out of 77 had an LDT&lt; 12 months), either IGF-1 or Rai substage entered the model at a significant level ((P=0.03 and P=0.01, respectively). In conclusion, IGF-1 did not correlate with markers of tumor burden or clinical status in CLL thus suggesting that levels of this cytokine do not reflect the intrinsic malignancy of disease. Results of the present study highlight, however, its involvement in mechanisms of disease-progression in early CLL.

STAT3 Is Constitutively Phosphorylated on Serine 727 Residues, Activates Transcription, and Plays a Major Role in the Pathogenesis of B-Cell Chronic Lymphocytic Leukemia.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1058-1058
Author(s):  
Inbal Hazan-Halevy ◽  
David Harris ◽  
Zhiming Liu ◽  
Alessandra Ferrajoli ◽  
Michael J Keating ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Dna Binding ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Lymphocytic Leukemia ◽  
Disease Stage ◽  
Western Immunoblotting ◽  
Tyrosine Residues ◽  
Cell Chronic Lymphocytic Leukemia ◽  
Constitutive Phosphorylation

Abstract Signal transducer and activator of transcription 3 (STAT3) plays a pivotal role in cellular physiology and organ development. Tyrosine phosphorylation of STAT3 provides cells with survival advantage and induces proliferation, whereas deletion of STAT3 results in embryonic lethality. As might be expected, STAT3 is commonly activated in neoplastic cells. Constitutive phosphorylation of STAT3 on tyrosine 705 residues has been found in a number of solid tumors and hematologic malignancies. A decade ago, Frank et al. (JCI100:3149, 1997) reported that unlike other neoplasms in B-cell chronic lymphocytic leukemia (CLL), STAT3 is constitutively phosphorylated (p) on serine 727 but not on tyrosine residues. This observation prompted us to investigate the role of STAT3 in CLL. We studied peripheral blood (PB) cells from ~100 patients with CLL using Western immunoblotting and found that in all patients, regardless of PB count, disease stage, or treatment status, STAT3 is constitutively phosphorylated on serine 727 but not on tyrosine residues. Serine pSTAT3 was detected in CD19+ but not in CD19− CLL PB-derived cells or in normal PB-derived B-lymphocytes isolated by immunomagnetic beads. Unlike constitutive serine pSTAT3, tyrosine pSTAT3 could be induced by incubating CLL cells with cytokines, such as interleukin (IL)-6, or anti-IgM antibodies. However, expression of cytokine-induced tyrosine pSTAT3 was transient and was no longer detected shortly (2 hours) after removal of the stimulating agent. In contrast, serine pSTAT3 levels remained stable in vitro for up to 72 hours, confirming that serine phosphorylation of STAT3 is constitutive in CLL cells. Because CLL is the only disease in which STAT3 is constitutively phosphorylated exclusively on serine residues and since tyrosine phosphorylation is thought to be required for STAT3 activation, we sought to determine whether serine pSTAST3 is biologically active. First, we isolated cytoplasmic and nuclear extracts and used Western immunoblotting to demonstrate that pSTAT3 is present both in the cytoplasm and the nucleus. Then, we confirmed these findings using confocal microscopy. After confirming that serine pSTAT3 translocates to the nucleus, we asked whether serine pSTAT3 binds to DNA. Using the electrophoretic mobility shift assay we demonstrated that nuclear STAT3 binds to a STAT3-specific DNA probe and that STAT3-DNA binding was eliminated by both anti-STAT3 and anti-serine pSTAT3 antibodies. Furthermore, although induction of tyrosine pSTAT3 by exogenous IL-6 slightly increased STAT3-DNA binding, complete dephosphorylation of tyrosine pSTAT3 by T-cell tyrosine phosphatase did not affect STAT3-DNA binding, suggesting that STAT3-DNA binding does not require tyrosine phosphorylation. Finally, pull-down of STAT3 with biotin-labeled DNA further confirmed that serine pSTAT3 binds to DNA in CLL cells. We then asked whether serine pSTAT3 initiates transcription. To answer this question we infected CLL cells with a lentiviral GFP-STAT3-shRNA and, as control, with GFP-empty vector and calculated changes in RNA levels by relative real-time PCR. In several CLL samples, infection with GFP-STAT3-shRNA induced a ~4-fold time-dependent reduction in the STAT3-regulated genes Bcl2, Pim1, Bcl-xL, Cyclin D1, p21 Waf1, and c-Myc, implying that serine pSTAT3 initiates transcription. Taken together, our data suggest that constitutive phosphorylation of STAT3 on serine 727 residues is a hallmark of CLL and induces activation of proliferation and survival genes. Therefore, STAT3 should be considered a therapeutic target in this disease.

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