Igor Tsaur

Goethe-Universität Frankfurt am Main, Frankfurt, Hesse, Germany

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Publications (53)116.82 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Sequential application of target drugs is standard procedure after renal cell carcinoma (RCC) patients develop resistance. To optimize the sequence, antitumour effects of the mTOR inhibitor RAD001 or the tyrosine kinase inhibitor (TKI) sorafenib on RCC cells with acquired resistance to the TKI sunitinib was evaluated. RCC cells were exposed to 1 μM sunitinib for 24 hrs (as control) and for 8 weeks (to induce resistance) and then switched to RAD001 (5 nM) or sorafenib (5 μM) for a further 8 weeks. Tumour cell growth, cell cycle progression, cell cycle regulating proteins and intracellular signalling were then investigated. Short-term application of sunitinib (24 hrs) induced cell growth blockade with accumulation in the G2/M phase. RCC cells became resistant to sunitinib after 8 weeks, demonstrated by accelerated cell growth along with enhanced cdk1, cdk2, loss of p27, activation of Akt, Rictor and Raptor. Switching to sorafenib only slightly reduced growth of the sunitinib resistant RCC cells and molecular analysis indicated distinct cross-resistance. In contrast, full response was achieved when the cancer cells were treated with RAD001. p19 and p27 strongly increased, phosphorylated Akt, Rictor and Raptor decreased and the tumour cells accumulated in G0/G1. It is concluded that an mTOR-inhibitor for second-line therapy could be the strategy of choice after first-line sunitinib failure. © 2014 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.
    Journal of Cellular and Molecular Medicine 12/2014; · 4.75 Impact Factor
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    ABSTRACT: Prostate specific antigen is not reliable in diagnosing prostate cancer (PCa), making the identification of novel, precise diagnostic biomarkers important. Since chemokines are associated with more aggressive disease and poor prognosis in diverse malignancies, we aimed to investigate the diagnostic relevance of chemokines in PCa. Preoperative and early postoperative serum samples were obtained from 39 consecutive PCa patients undergoing radical prostatectomy. Serum from 15 healthy volunteers served as controls. Concentrations of CXCL12, CXCL13, CX3CL1, CCL2, CCL5, and CCL20 were measured in serum by Luminex. The expression activity of CXCR3, CXCR4, CXCR5, CXCR7, CXCL12, CXCL13, CX3CR1, CXCL1, CCR2, CCR5, CCR6, CCR7, CCL2, and CCL5 mRNA was assessed in tumor and adjacent normal tissue of prostatectomy specimens by quantitative real-time polymerase chain reaction. The associations of these chemokines with clinical and histological parameters were tested. The gene expression activity of CCL2 and CCR6 was significantly higher in tumor tissue compared to adjacent normal tissue. CCL2 was also significantly higher in the blood samples of PCa patients, compared to controls. CCL5, CCL20, and CX3CL1 were lower in patient serum, compared to controls. CCR2 tissue mRNA was negatively correlated with the Gleason score and grading. Chemokines are significantly modified during tumorigenesis of PCa, and CCL2 is a promising diagnostic biomarker.
    Cancer research and treatment : official journal of Korean Cancer Association. 10/2014;
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    ABSTRACT: Chemokines undergo alterations during neoplasia. However, knowledge about their functional significance in prostate cancer (PCa) progression is still sparse. Since chemokine (C-C motif) ligand 2 (CCL2) is significantly up-regulated in patients with PCa, aim of the current study was to assess whether CCL2 contributes to invasive behavior of prostate cancer cells in vitro.
    World Journal of Urology 09/2014; · 2.89 Impact Factor
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    ABSTRACT: Targeted therapies have improved therapeutic options of treating renal cell carcinoma (RCC). However, drug response is temporary due to resistance development.
    Molecular cancer. 06/2014; 13(1):152.
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    ABSTRACT: Inhibitors of the mammalian target of rapamycin (mTOR) have improved the treatment of renal cell carcinoma (RCC). However, chronic drug exposure may trigger resistance, limiting the utility of these agents. The metastatic behavior of RCC cells, susceptible (RCC(par)) or resistant (RCC(res)) to the mTOR inhibitor temsirolimus, was investigated. Adhesion to vascular endothelium or immobilized collagen and fibronectin was quantified. Chemotactic motility was evaluated with a modified Boyden chamber assay. Integrin α and β subtype receptors were analyzed by flow cytometry and Western blot analysis. The physiological relevance of the integrins was then determined by blocking studies and small interfering RNA knockdown. Adhesion to endothelial cells and to fibronectin (not to collagen) and chemotaxis were enhanced in RCC(res) compared to RCC(par). RCC(res) detached from fibronectin and motile activity further increased under retreatment with low-dosed temsirolimus. α5 integrin was diminished inside the cell and at the cell surface, whereas the β3 subtype was reduced intracellularly but elevated at the plasma membrane. In RCC(par), blocking α5 surface receptors enhanced RCC-collagen but reduced RCC-fibronectin interaction, whereas the opposite was true for RCC(res). Chemotaxis of RCC(par) but not of RCC(res) was strongly diminished by the α5 antibody. Blocking β3 significantly lowered chemotaxis with stronger effects on RCC(res), compared to RCC(par). Importantly, β3 knockdown reduced chemotaxis of RCC(par) but upregulated the motile behavior of RCC(res). Temsirolimus resistance is characterized by quantitative alterations of integrin α5 and β3 expression, coupled to functional changes of the integrin molecules, and forces a switch from RCC adhesion to RCC migration.
    Neoplasia (New York, N.Y.) 04/2014; 16(4):291-300. · 5.48 Impact Factor
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    ABSTRACT: Molecular tumour targeting has significantly improved anti-cancer protocols. Still, the addition of molecular targeting to the treatment regime has not led to a curative breakthrough. Combined mammalian target of Rapamycin (mTOR) and histone deacetylase (HDAC) inhibition has been shown not only to enhance anti-tumour potential, but also to prevent resistance development seen under mono-drug therapy. This investigation was designed to evaluate whether cross-communication exists between mTOR signalling and epigenetic events regulated by HDAC. DU-145 prostate cancer cells were treated with insulin-like growth factor (IGF) to activate the Akt-mTOR cascade or with the HDAC-inhibitor valproic acid (VPA) to induce histone H3 and H4 acetylation (aH3, aH4). Subsequently, mTOR, Rictor, Raptor, p70s6k, Akt (all: total and phosphorylated), H3 and H4 (total and acetylated) were analysed by western blotting. Both techniques revealed a link between mTOR and the epigenetic machinery. IGF activated mTOR, Rictor, Raptor, p70s6k and Akt, but also enhanced aH3 and aH4. Inversely, IGFr blockade and knock-down blocked the Akt-mTOR axis, but simultaneously diminished aH3 and aH4. VPA treatment up-regulated histone acetylation, but also activated mTOR-Akt signalling. HDAC1 and 2 knock-down revealed that the interaction with the mTOR system is initiated by histone H3 acetylation. HDAC-mTOR communication, therefore, is apparent whereby tumour-promoting (Akt/mTORhigh, aH3/aH4low) and tumour-suppressing signals (Akt/mTORlow, aH3/aH4high) are activated in parallel. Combined use of an HDAC- and mTOR inhibitor might then diminish pro-tumour effects triggered by the HDAC- (Akt/mTORhigh) or mTOR inhibitor (aH3/aH4low) alone.
    Journal of Cellular and Molecular Medicine 04/2014; · 4.75 Impact Factor
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    ABSTRACT: The prevention of postprostatectomy incontinence has always been a challenge for urologists. Improved understanding of male continence and changes in pelvic anatomy after radical prostatectomy and the implementation of new surgical techniques raised hope of reduced incontinence rates. Despite using the full potential of continence-sparing techniques and atraumatic robot-assisted surgery, postprostatectomy incontinence still occurs in 5-20 % of cases. Recently published data showed a trend of improved early return to continence using anterior suspension or posterior reconstruction in robot-assisted prostatectomy. Postprostatectomy incontinence has a negative impact on quality of life and causes high costs of treatment. Therefore, further research in the amelioration of postoperative continence is mandatory.
    Der Urologe 02/2014; · 0.46 Impact Factor
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    ABSTRACT: Inhibitors of the mammalian target of rapamycin (mTOR) have improved the treatment of renal cell carcinoma (RCC). However, chronic drug exposure may trigger resistance, limiting the utility of these agents. The metastatic behavior of RCC cells, susceptible (RCCpar) or resistant (RCCres) to the mTOR inhibitor temsirolimus, was investigated. Adhesion to vascular endothelium or immobilized collagen and fibronectin was quantified. Chemotactic motility was evaluated with a modified Boyden chamber assay. Integrin α and β subtype receptors were analyzed by flow cytometry and Western blot analysis. The physiological relevance of the integrins was then determined by blocking studies and small interfering RNA knockdown. Adhesion to endothelial cells and to fibronectin (not to collagen) and chemotaxis were enhanced in RCCres compared to RCCpar. RCCres detached from fibronectin and motile activity further increased under retreatment with low-dosed temsirolimus. α5 integrin was diminished inside the cell and at the cell surface, whereas the β3 subtype was reduced intracellularly but elevated at the plasma membrane. In RCCpar, blocking α5 surface receptors enhanced RCC-collagen but reduced RCC-fibronectin interaction, whereas the opposite was true for RCCres. Chemotaxis of RCCpar but not of RCCres was strongly diminished by the α5 antibody. Blocking β3 significantly lowered chemotaxis with stronger effects on RCCres, compared to RCCpar. Importantly, β3 knockdown reduced chemotaxis of RCCpar but upregulated the motile behavior of RCCres. Temsirolimus resistance is characterized by quantitative alterations of integrin α5 and β3 expression, coupled to functional changes of the integrin molecules, and forces a switch from RCC adhesion to RCC migration.
    Neoplasia. 01/2014; 16(4):291–300.
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    ABSTRACT: Die Vermeidung der Postprostatektomieinkontinenz (PPI) ist seit jeher eine Herausforderung für den operierenden Urologen. Die zurückliegenden Fortschritte im Verständnis der Anatomie und Physiologie des Kontinenzmechanismus des Mannes und das Etablieren neuer operativer Techniken ließen auf eine Verbesserung der Kontinenzraten hoffen. Unter Ausschöpfen kontinenzerhaltender Operationstechniken und schonendem robotisch assistiertem Zugang tritt dennoch in 5–20 % der Fälle Inkontinenz auf. Unlängst konnte jedoch in mehreren Publikationen ein Trend zur verbesserten Frühinkontinenz bei robotisch assistiertem Vorgehen mit anteriorer oder posteriorer Rekonstruktion beschrieben werden. Angesichts des negativen Einflusses der PPI auf die Lebensqualität und der Therapiekosten ist weitere Forschung zur Verbesserung des Kontinenzerhalts geboten.
    Der Urologe 01/2014; 53(3). · 0.46 Impact Factor
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    ABSTRACT: The cyanogenic diglucoside amygdalin, derived from Rosaceae kernels, is employed by many patients as an alternative anti-cancer treatment. However, whether amygdalin indeed acts as an anti-tumor agent is not clear. Metastasis blocking properties of amygdalin on bladder cancer cell lines was, therefore, investigated. Amygdalin (10 mg/ml) was applied to UMUC-3, TCCSUP or RT112 bladder cancer cells for 24 h or for 2 weeks. Tumor cell adhesion to vascular endothelium or to immobilized collagen as well as tumor cell migration was examined. Effects of drug treatment on integrin α and β subtypes, on integrin-linked kinase (ILK) and total and activated focal adhesion kinase (FAK) were also determined. Integrin knock-down was carried out to evaluate integrin influence on migration and adhesion. A 24 h or 2 week amygdalin application distinctly reduced tumor cell adhesion and migration of UMUC-3 and RT112 cells. TCCSUP adhesion was also reduced, but migration was elevated under amygdalin. Integrin subtype expression was significantly and specifically altered by amygdalin depending on the cell line. ILK was moderately, and activated FAK strongly, lost in all tumor cell lines in the presence of amygdalin. Knock down of β1 integrin caused a significant decrease in both adhesion and migration of UMUC-3 cells, but a significant increase in TCCSUP adhesion. Knock down of β4 integrin caused a significant decrease in migration of RT112 cells. Since the different actions of amygdalin on the different cell lines was mirrored by β1 or β4 knock down, it is postulated that amygdalin influences adhesion and migratory properties of bladder cancer cells by modulating β1 or β4 integrin expression. The amygdalin induced increase in TCCSUP migratory behavior indicates that any anti-tumor benefits from amygdalin (seen with the other two cell lines) may depend upon the cancer cell type.
    PLoS ONE 01/2014; 9(10):e110244. · 3.53 Impact Factor
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    ABSTRACT: Amygdalin, a natural compound, has been used by many cancer patients as an alternative approach to treat their illness. However, whether or not this substance truly exerts an anti-tumor effect has never been settled. An in vitro study was initiated to investigate the influence of amygdalin (1.25-10 mg/ml) on the growth of a panel of bladder cancer cell lines (UMUC-3, RT112 and TCCSUP). Tumor growth, proliferation, clonal growth and cell cycle progression were investigated. The cell cycle regulating proteins cdk1, cdk2, cdk4, cyclin A, cyclin B, cyclin D1, p19, p27 as well as the mammalian target of rapamycin (mTOR) related signals phosphoAkt, phosphoRaptor and phosphoRictor were examined. Amygdalin dose-dependently reduced growth and proliferation in all three bladder cancer cell lines, reflected in a significant delay in cell cycle progression and G0/G1 arrest. Molecular evaluation revealed diminished phosphoAkt, phosphoRictor and loss of Cdk and cyclin components. Since the most outstanding effects of amygdalin were observed on the cdk2-cyclin A axis, siRNA knock down studies were carried out, revealing a positive correlation between cdk2/cyclin A expression level and tumor growth. Amygdalin, therefore, may block tumor growth by down-modulating cdk2 and cyclin A. In vivo investigation must follow to assess amygdalin's practical value as an anti-tumor drug.
    PLoS ONE 01/2014; 9(8):e105590. · 3.53 Impact Factor
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    ABSTRACT: To reliably compare the results of gene expression studies, the expression of the target gene should be normalized to the expression of a reference gene. For lymph node metastases of prostate cancer, no data on polymerase chain reaction (PCR) normalization have yet been reported. We aimed to determine the most reliable reference gene combination for this purpose in patients with prostate cancer. Ten histologically- positive and ten negative lymph nodes of patients with prostate cancer were analyzed respectively. Expression of six candidate reference genes was comparatively assessed with quantitative Real-time PCR. The most stably-expressed gene combination was determined with geNorm software version 3.4. Hypoxanthine phosphoribosyltransferase-1 (HPRT1) and TATA box binding protein (TPB) were found to be the most stably expressed genes, with their combination having an expression stability value of M=0.17. Gene combination HPRT1 and TPB has the potential to be utilized for normalization in gene profiling assessment of metastatic and non-metastatic pelvic lymph node tissue from patients with prostate cancer.
    Anticancer research 12/2013; 33(12):5243-8. · 1.71 Impact Factor
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    ABSTRACT: Traditional Chinese medicine (TCM) is an ancient holistic medicine based on the doctrine of Tao and Qi. Tao represents an alteration from which the polarity of Yin and Yang arises and Qi is the vitality which circulates through the body. Therapeutic concepts of TCM include acupuncture, herbal therapy, nutrition and Tuina, a form of manual therapy. TCM is now gaining increased acceptance in the Western society as a complementary therapy. Acupuncture and herbal therapy are the main forms of implementation of TCM in urology.
    Der Urologe 06/2013; · 0.46 Impact Factor
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    ABSTRACT: More than 80 % of renal cell carcinomas are currently being detected incidentally by ultrasonic imaging and often affect elderly patients with substantial comorbidities. Surgical options cannot be applied in this cohort as routinely as in younger patients, as in some cases the perioperative risk factors may outweigh the risk of tumor-related death. In this context the concept of active surveillance for localized renal cell cancer in elderly patients is becoming increasingly important. The aim of active surveillance is to avoid surgery-related adverse effects and to achieve a controlled observation of tumor behavior with an option of delayed intervention in cases of aggressive clinical tumor features. This review sheds light on the current status of this strategy.
    Der Urologe 04/2013; · 0.46 Impact Factor
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    ABSTRACT: Bladder cancer is a carcinoma of the elderly population. The highest incidence of bladder cancer is between the ages of 70 and 80 years old. Radical cystectomy remains the gold standard for muscle invasive bladder cancer treatment. In this article different aspects of radical cystectomy in elderly patients are reviewed. The Pubmed-MEDLINE database was searched using the following keywords: radical, cystectomy, elderly and age.
    Der Urologe 04/2013; · 0.46 Impact Factor
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    ABSTRACT: Derzeit stellt die multiparametrische Magnetresonanztomographie (MRT) die diagnostisch genaueste Methode zur Darstellung eines Prostatakarzinoms dar. Der Goldstandard zur Prostatabiopsie ist aufgrund der einfachen Anwendung die systematische Biopsie mit dem transrektalen Ultraschall (TRUS). Durch die Kombination können die Vorteile beider Methoden genutzt werden. Mittlerweile befinden sich mehrere Bildgebungssysteme zur fusionsbildgestützten Biopsie in der Erprobung. Erste Daten zeigen höhere Karzinomdetektionsraten als bei der systematischen TRUS-Biopsie. Allerdings stellen die Verformung der Prostata und die intrakorporale Beweglichkeit Herausforderungen dar, die noch nicht abschließend gelöst sind. Der vorliegende Artikel gibt eine Übersicht über den aktuellen Stand der MRT-gestützten Biopsieverfahren und beleuchtet die aktuelle Datenlage.
    Der Urologe 04/2013; 52(4). · 0.46 Impact Factor
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    ABSTRACT: Multiparametric magnetic resonance imaging (MRI) represents the most accurate imaging modality for prostate cancer imaging to date. Transrectal ultrasound (TRUS) is easily applied and therefore remains the gold standard for systematic prostate biopsies. However, the advantages of both modalities can be combined by image fusion. Currently, several image fusion devices are being implemented into clinical routine. First data show an increased detection rate of prostate cancer compared to systematic TRUS biopsies. At present prostatic deformation and intracorporeal movement represent technical challenges yet to be overcome. The present article gives an overview about the status of MRI-based biopsy techniques and highlights the current studies on the topic.
    Der Urologe 03/2013; · 0.46 Impact Factor
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    ABSTRACT: Targeted drugs have significantly improved the therapeutic options for advanced renal cell carcinoma (RCC). However, resistance often develops, negating the benefit of these agents. In the present study, the molecular mechanisms of acquired resistance towards the histone deacetylase (HDAC) inhibitor valproic acid (VPA) in a RCC in vivo model were investigated. NMRI:nu/nu mice were transplanted with Caki-1 RCC cells and then treated with VPA (200 mg/kg/day). Controls remained untreated. Based on tumor growth dynamics, the mice were divided into "responders" and "non-responders" to VPA. Histone H3 and H4 acetylation and expression of cell signaling and cell cycle regulating proteins in the RCC mouse tumors were evaluated by Western blotting. Tumor growth of VPA responders was significantly diminished, whereas that of VPA non-responders even exceeded control values. Cdk1, 2 and 4 proteins were strongly enhanced in the non-responders. Importantly, Akt expression and activity were massively up-regulated in the tumors of the VPA non-responders. Chronic application (12 weeks) of VPA to Caki-1 cells in vitro evoked a distinct elevation of Akt activity and cancer cells no longer responded with cell growth reduction, compared to the short 2 week treatment. We assume that chronic use of an HDAC-inhibitor is associated with (re)-activation of Akt, which may be involved in resistance development. Consequently, combined blockade of both HDAC and Akt may delay or prevent drug resistance in RCC.
    PLoS ONE 01/2013; 8(1):e53100. · 3.53 Impact Factor
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    ABSTRACT: Regulatory T cells (Treg) expressing the transcription factor forkhead-box protein P3 (Foxp3) have been identified to counteract anti-tumor immune responses during tumor progression. Besides, Foxp3 presentation by cancer cells itself may also allow them to evade from effector T-cell responses, resulting in a survival benefit of the tumor. For colorectal cancer (CRC) the clinical relevance of Foxp3 has not been evaluated in detail. Therefore the aim of this study was to study its impact in colorectal cancer (CRC). Gene and protein analysis of tumor tissues from patients with CRC was performed to quantify the expression of Foxp3 in tumor infiltrating Treg and colon cancer cells. The results were correlated with clinicopathological parameters and patients overall survival. Serial morphological analysis demonstrated Foxp3 to be expressed in cancer cells. High Foxp3 expression of the cancer cells was associated with poor prognosis compared to patients with low Foxp3 expression. In contrast, low and high Foxp3 level in tumor infiltrating Treg cells demonstrated no significant differences in overall patient survival. Our findings strongly suggest that Foxp3 expression mediated by cancer cells rather than by Treg cells contribute to disease progression.
    PLoS ONE 01/2013; 8(1):e53630. · 3.53 Impact Factor
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    ABSTRACT: Pharmacologic options for patients with castration-resistant prostate cancer are limited. It has been suggested that targeting intracellular molecules, which have been altered during neoplastic development, may slow tumor growth. Therefore, the growth-blocking potential of the histone deacetylase-inhibitor LBH589 and the multiple tyrosine kinase-inhibitor TKI258, applied alone or in combination, was investigated in a panel of prostate cancer cell lines. PC-3, DU-145 or LNCaP cells were treated with various concentrations of LBH589 and/or TKI258. Tumor cell growth, cell cycle regulating proteins, HDAC3- and HDAC4-expression and histone H3 and H4 acetylation were then evaluated by MTT assay and Western blotting. LBH589 dose-dependently blocked prostate cancer cell growth. In contrast, TKI258 did not down-regulate tumor cell growth up to a 1,000 nM dosage. LBH589 elevated histone H3 and H4 acetylation. The cell cycle regulators cyclin B, cyclin D1, cdk1 and cdk4 were down-regulated in PC-3, whereas the suppressor proteins p21 and p27 were up-regulated in LNCaP by LBH589. TKI258 up-regulated p27 in PC-3 or p21 in LNCaP and additionally elevated cyclin B, cyclin D1, cdk1 and cdk4 in both cell lines. Presumably, the increase in cyclin and cdk caused by TKI258 counteracts the benefit of p21 or p27 up-regulation, resulting in TKI258 non-responsiveness. The LBH589/TKI258-combination was not superior to the LBH589 single-drug use in terms of growth reduction. Obviously, TKI258 did not enhance the sensitivity of prostate cancer cells towards an HDAC based regimen. Therefore, the LBH589/TKI258-combination probably does not provide an optimum strategy in fighting advanced prostate cancer.
    Investigational New Drugs 07/2012; · 3.50 Impact Factor

Publication Stats

137 Citations
116.82 Total Impact Points

Institutions

  • 2009–2014
    • Goethe-Universität Frankfurt am Main
      • Klinik für Urologie und Kinderurologie
      Frankfurt, Hesse, Germany
  • 2008–2011
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
  • 2010
    • University of Wuerzburg
      • Institute for Pathology
      Würzburg, Bavaria, Germany