GTGeorge Tsirakis

George Tsirakis

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George Tsirakis has a total of 50 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Open Access

    Bone Marrow Mast Cell Density Correlates with Circulating Biomarkers of Bone Disease in Multiple Myeloma

    by Rodanthi Vyzoukaki, Maria Devetzoglou, Constantina A. Pappa, Andreas N. Antonakis, Samer Masud, Anastasia Papadopoulou, George Tsirakis, Michael G. Alexandrakis

    Aims: There is increased mast cell density (MCD) in multiple myeloma (MM) bone marrow (BM) that is correlated with advanced disease stage. Mast cells (MCs) produce various mediators promoting MM growth and bone metabolism. The aim of this study was to evaluate whether BM MCD correlates with markers of bone metabolism, such as circulating levels of osteoprotegerin (OPG), soluble receptor activator of nuclear factor-κB ligand (sRANKL), osteopontin (OPN) and macrophage inflammatory protein-1 alpha (MIP-1 alpha). Study Design: This is a cross-sectional study. Place and Duration of Study: Department of Medicine, University of Crete, Department and Laboratory of Haematology, University Hospital of Heraklion, Department of Haematology and Internal Medicine, Venizelion Hospital of Heraklion, Department of Haematology, General Hospital of Chania, between January 2010 and December 2014. Methodology: All parameters were analyzed by ELISA. We studied 56 active MM patients (32 males, 24 females) and 20 healthy controls. According to ISS 14 patients were in stage I, 22 in stage II and 20 in stage III. MCs were highlighted in BM immunohistochemically, using monoclonal antibody to MC tryptase. Results: All values were higher in active MM patients compared to healthy subjects (pConclusion: MCs are increased in MM BM and participate in many aspects of the disease. They may release various cytokines increasing myeloma growth and also may participate in the skeletal disease of MM rendering them as potential targets for therapy.

  • Interleukin-10 Induces Both Plasma Cell Proliferation and Angiogenesis in Multiple Myeloma

    by Michael G. Alexandrakis, Nektaria Goulidaki, Constantina A. Pappa, Anna Boula, Fotios Psarakis, Ioannis Neonakis, George Tsirakis

    In multiple myeloma the angiogenic process is enhanced by various mediators. Among them interleukin-10 (IL-10), secreted mainly by myeloma-associated macrophages seems to participate in myeloma progression with variable manners. The aim of the study was to measure serum levels of IL-10 in various stages of MM patients and to correlate them with various angiogenic cytokines, such as vascular endothelial growth factor and angiopoietin-2 and with known proliferation parameters, such as serum levels of B-cell activating factor and bone marrow infiltration by myeloma plasma cells, in order to explore their clinical significance. We measured serum levels of the above parameters by ELISA in 54 newly diagnosed MM patients. All of them were higher in MM patients and were increasing in parallel with disease progression. Furthermore, IL-10 correlated positively with both angiogenic cytokines and proliferation markers. This correlation of IL-10 with both angiogenic cytokines and markers of disease activity implicates that they all have an important role in MM pathogenesis and progression.


  • Circulating levels of soluble Fas ligand reflect disease progression in multiple myeloma

    by Michael G. Alexandrakis, Constantina A. Pappa, Anna Kolovou, Stavroula Kyriakaki, Rodanthi Vyzoukaki, Maria Devetzoglou, George Tsirakis

    Multiple myeloma (MM) plasma cells are apoptosis resistant. The system of Fas with its ligand (Fas-L) participates actively in the extrinsic apoptotic system. In oncology, its role is controversial, since it has been reported both to suppress and promote tumor growth. The aim of this study was to measure serum levels of soluble Fas-L (sFas-L) in patients with active MM and to correlate them with markers of disease activity. We studied 57 patients with active MM, along with 22 healthy controls. We measured serum levels of sFas-L and interleukin-6 (IL-6) by enzyme-linked immunosorbent assays, as well of beta-2 microglobulin (B2M), C-reactive protein (CRP) and lactate dehydrogenase (LDH). We also measured the degree of bone marrow infiltration. All parameters were increased in patients, compared with controls (p < 0.001 for all cases) and also in parallel with disease stage (p < 0.001 for all cases). Positive correlations were noted between serum levels of sFas-L with IL-6, infiltration (p < 0.001 for both cases) and LDH (p < 0.04), but not with CRP and B2M. We suggest that the system of Fas/Fas-L participates actively in MM progression in a complex manner and that serum levels of sFas-L may reflect disease progression. Further studies are needed to determine its usefulness as a marker of disease activity.


  • Circulating Levels of Soluble Angiogenic Factors in Multiple Myeloma: Correlation with Parameters of Disease Activity and Prognosis

    by Michael G. Alexandrakis, George Tsirakis

    Abstract: The progression of multiple myeloma depends on bone marrow microenvironment that can offer favorable conditions for its growth. Among the most important features of the disease is the alteration of bone marrow microenvironment, including dysregulation of various molecules with consequent increased angiogenic potential, extended bone disease, resistance to any likely therapy and furthermore direct growth of myeloma clone. Angiogenesis, as can be estimated by immunohistochemical staining of blood vessels, i.e. microvascular density, is a hallmark in the progress of many malignancies, including multiple myeloma. Many pro-angiogenic molecules participate in the process, being aberrantly or over-expressed by myeloma and other cells of bone marrow. Those molecules, possessing multiple properties, may circulate in peripheral blood and therefore could be measured. Here we present an overview of the most important molecules that participate, directly and indirectly, in the angiogenic process of multiple myeloma and try to evaluate their role, as factors of disease activity and moreover of prognosis. Furthermore, many of circulating angiogenic molecules have been constituted possible targets for therapeutic interventions. All this provided information contributes to a better comprehension of the complex pathophysiology of multiple myeloma.


  • Open Access

    Relationship between Circulating BAFF Serum Levels with Proliferating Markers in Patients with Multiple Myeloma

    by Michael G. Alexandrakis, Parascevi Roussou, Constantina A. Pappa, Ippokratis Messaritakis, Athina Xekalou, Nektaria Goulidaki, Anna Boula, George Tsirakis

    In multiple myeloma, there are many factors influencing the growth of the malignant clone in direct and indirect manners. BAFF is a growth factor for myeloma cells. The aim of the study was to measure its circulating levels in 54 pretreatment patients, along with serum levels of other proliferation markers, such as interleukins-6, -10, and -15, CRP, and beta-2 microglobulin, as well as bone marrow plasma cell infiltration and expression of Ki-67 PI, in various stages of the disease and after effective treatment in 28 of them. Serum levels of the previously mentioned factors were measured by ELISA, whereas bone marrow plasma cell infiltration and Ki-67 expression were estimated immunohistochemically. All measured parameters were higher in pretreated myeloma patients compared to healthy population and were also increasing with the progression of the disease. They all also decreased after effective therapy. Furthermore, all pretreatment values correlated to each other. BAFF seems to be an important growth factor for myeloma plasma cells. Measuring its serum levels, along with the previously mentioned cytokines, may provide important information regarding the degree of myeloma cells’ proliferation. Therefore, they all could be used as markers of proliferation and disease activity.


  • Serum levels of angiopoietin-2 are associated with the growth of multiple myeloma

    by Constantina A Pappa, George Tsirakis, Panagiotis Samiotakis, Maria Tsigaridaki, Athanasios Alegakis, Nectaria Goulidaki, Michael G Alexandrakis

    Angiopoietins and their receptor, Tie-2, have crucial role in angiogenesis. We measured serum levels of angiopoietin-2 (Ang-2), soluble Tie-2, and factors of burden and prognosis in myeloma (LDH, CRP, beta-2 microglobulin, and interleukin-6) in 55 newly diagnosed patients, with 30 of them in plateau phase, in order to note correlations among them. Levels of Ang-2 were higher in patients in advanced stage of disease, decreased in plateau phase, and correlated with all other factors. Circulating Ang-2 in myeloma patients significantly correlated to factors of disease burden and prognosis, and therefore measuring its levels may be important for the valuation of the disease.


  • Emerging roles of endoglin/CD105 and angiogenic cytokines for disease development and progression in multiple myeloma patients

    by Ca Pappa, Mg Alexandrakis, A Boula, Fe Psarakis, A Kolovou, V Bantouna, E Stavroulaki, G Tsirakis

    Angiogenesis is an essential process for the expansion of multiple myeloma (MM), in which many angiogenic factors participate. Endoglin (CD105) is a transforming growth factor-β co-receptor, being mainly expressed in angiogenic endothelial cells and has been used as a marker of tumor angiogenesis, having prognostic potential. The aim of the study was to evaluate serum levels of soluble CD105 (sCD105) in MM patients, both during diagnosis and after effective conventional chemotherapy, in the plateau phase, and to correlate them with the clinical stage of the disease, as well as with the known angiogenic factors vascular endothelial growth factor, angiogenin and interleukin-18 (IL-18). Serum levels of the aforementioned factors were measured, by enzyme-linked immunosorbent assay, in 56 newly diagnosed MM patients, in 35 of them who entered plateau phase and in 24 healthy controls. Bone marrow aspirations were also performed in all patients to determine plasma cell infiltration. All measured cytokines were higher in MM patients compared with controls and with advancing disease stage (p < 0.001 for all cases). Furthermore, the values of all factors decreased significantly in the plateau phase (p < 0.001 for all cases). Serum levels of sCD105 correlated with the other angiogenic cytokines, whereas only serum levels of angiogenin had prognostic value for the survival. In conclusion, CD105 and the angiogenic cytokines vascular endothelial growth factor, angiogenin and IL-18, seem to have emerging roles both in angiogenesis and tumor growth in MM. Copyright © 2013 John Wiley & Sons, Ltd.


  • Open Access

    Anemia in Heart Failure Patients

    by Michael G. Alexandrakis, George Tsirakis

    Heart failure is a very common disease, with severe morbidity and mortality, and a frequent reason of hospitalization. Anemia and a concurrent renal impairment are two major risk factors contributing to the severity of the outcome and consist of the cardio renal anemia syndrome. Anemia in heart failure is complex and multifactorial. Hemodilution, absolute or functional iron deficiency, activation of the inflammatory cascade, and impaired erythropoietin production and activity are some pathophysiological mechanisms involved in anemia of the heart failure. Furthermore other concomitant causes of anemia, such as myelodysplastic syndrome and chemotherapy, may worsen the outcome. Based on the pathophysiology of cardiac anemia, there are several therapeutic options that may improve hemoglobin levels, tissues’ oxygenation, and probably the outcome. These include administration of iron, erythropoiesis-stimulating agents, and blood transfusions but still the evidence provided for their use remains limited.


  • Serum concentrations and clinical significance of soluble CD40 ligand in patients with multiple myeloma

    by G. Tsirakis, C. A. Pappa, F. E. Psarakis, M. Fragioudaki, C. Tsioutis, E. Stavroulaki, A. Boula, M. G. Alexandrakis

    Multiple myeloma (MM) is a disease of plasma cells that express the CD40 receptor. Binding of the CD40 by its natural ligand, CD40 ligand (CD40L), produces growth arrest and/or apoptosis in MM. To evaluate serum levels of soluble CD40L (sCD40L) in MM patients and to correlate them with markers of disease activity and angiogenesis, such as vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), interleukin-6 (IL-6), proliferation marker Ki-67 proliferation index (Ki-67 PI) and bone marrow plasma cell infiltration, fifty-eight MM patients were studied in diagnosis and 43 of them after completion of treatment. Serum levels of sCD40L, VEGF, HGF and IL-6 were measured by ELISA, whereas Ki-67 PI and bone marrow plasma cell infiltration were measured by immunohistochemistry. Pre-treatment levels of sCD40L in MM patients were higher compared to controls and to their levels after effective treatment. Treatment regimen did not affect the degree of reduction of sCD40L levels, whereas patient in partial remission had increased levels compared to those with better response. Significant differences were found among disease stages. There were also positive correlations between CD40L with HGF, VEGF, IL-6 and Ki-67 PI. Elevated serum sCD40L is found in patients with advanced MM stage and can be reduced after effective treatment. Increased levels of this mediator are correlated with angiogenic cytokines, providing evidences that CD40L/CD40 interactions play a significant role in the mechanisms of angiogenesis in MM patients.


  • Role of platelet‐derived growth factor‐AB in tumour growth and angiogenesis in relation with other angiogenic cytokines in multiple myeloma

    by George Tsirakis, Constantina A. Pappa, Peggy Kanellou, Maria A. Stratinaki, Athina Xekalou, Fotios E. Psarakis, George Sakellaris, Athanasios Alegakis, Efstathios N. Stathopoulos, Michael G. Alexandrakis

    Angiogenesis is a complex process essential for the growth, invasion, and metastasis of various malignant tumours, including multiple myeloma (MM). Various angiogenic cytokines have been implicated in the angiogenic process. Among them, platelet‐derived growth factor‐AB (PDGF‐AB) has been reported to be a potent stimulator of angiogenesis in many solid tumours and haematological malignancies, including MM. The aim of the study was to investigate the relationship between PDGF‐AB, microvascular density (MVD), and various angiogenic cytokines, such as basic fibroblast growth factor (b‐FGF), angiogenin (ANG), and interleukin‐6 (IL‐6), in MM patients. Forty‐seven MM patients before treatment, 22 of whom were in plateau phase, were studied. We determined the serum levels of the aforementioned cytokines and MVD in bone marrow biopsies before and after treatment. Mean serum values of PDGF‐AB, b‐FGF, ANG, and MVD were significantly higher in patients compared with controls and with increasing disease stage. Significant positive correlations were observed between serum PDGF‐AB, ANG, and IL‐6 levels and MVD. Furthermore, we found significant positive correlations between PDGF‐AB and b‐FGF, IL‐6, ANG, and β2 microglobulin. We also found that patients with high MVD had statistically significantly higher serum levels of PDGF‐AB when a median MVD value of 7.7 was used as the cutoff point. Furthermore, a significant difference was found in serum levels of PDGF‐AB between pre‐ and post‐treatment patients. Finally, survival time was significantly higher in the low MVD group versus the high MVD group (76 vs 51 months). Our results showed that there is a strong positive correlation between PDGF‐AB and the studied angiogenic cytokines and MVD. It seems that PDGF‐AB plays a role in the complex network of cytokines inducing bone marrow neovascularization in patients with MM. Copyright © 2011 John Wiley & Sons, Ltd.