Boris Feldkoren - Academia.edu (original) (raw)

Papers by Boris Feldkoren

The Journal of Urology, 2014

ABSTRACT INTRODUCTION AND OBJECTIVES: Signal transduction through transforming growth factor-beta... more ABSTRACT INTRODUCTION AND OBJECTIVES: Signal transduction through transforming growth factor-beta 1 (TGF-b1) pathway affects epithelial to mesenchymal transition (EMT), partly by modulation of ECadherin expression. Concurrent impact of extracellular matrix driven activation of integrin signaling on evolution of EMT has not been well characterized. We assess cumulative effect and molecular mechanisms of TGF-b1 and integrin signal transduction on E-Cadherin expression in renal cell cancer (RCC). METHODS: TGF-b1 driven alteration of EMT specific markers was confirmed in an established in-vitro model of RCC. Global changes in expression of cell surface integrins were evaluated by microarray and confirmed by RT-PCR. Arginylglycylaspartic acid (RGD), in addition to TGF-b1, was utilized to mimic integrin signaling and evaluate cumulative effects on markers of EMT. Silencing of potential mediators of cumulative action of RGD and TGF-b1 was carried out by small interfering RNA and confirmed by Western blotting or RT-PCR. RESULTS: After stimulation of RCC cells with TGF-b1, a threefold increased expression of integrin aVb3 was identified by microarray and confirmed by RT-PCR. Pre-treatment of cells with RGD in addition to TGF-b1 demonstrated a significantly higher effect on expression of markers of EMT (E-cadherin and Snail-1) than either ligand alone. SiRNA mediated silencing of FAK and PINCH, independently and conclusively abrogated the cumulative effect of RGD and TGF-b1 on markers of EMT. CONCLUSIONS: We have identified a novel mechanism through which extracellular matrix event transduction by integrins further augments TGF-b1 related effects on the well established markers of EMT. Molecular machinery involved in integrin/TGF-b1 interplay serves as an attractive therapeutic target in RCC.

Journal of Steroid Biochemistry and Molecular Biology, 2001

Our aim was to investigate the effect of a single testosterone (T) injection on the androgen rece... more Our aim was to investigate the effect of a single testosterone (T) injection on the androgen receptor (AR) in rat skeletal muscle (SM) cytosol. The properties of AR were studied in order to establish the protocol for differential determination of free and hormone-occupied AR in SM cytosols from non-hormone-deficient animals. Using the developed ligand-exchange protocol, we demonstrated that injection of T (1 mg/kg) caused alternating changes of the total AR binding. The binding minimum (23% of the control) was measured 1 h after the injection. It was followed by pronounced and lasting elevation of the AR binding. In the control cytosols, AR complexes constituted 25% of the total receptor content. Changes of their relative content immediately after T administration were consistent with rapid nuclear translocation of the AR. Inhibition of protein synthesis by cycloheximide (CHI) injection demonstrated that delayed and lasting increase of the AR binding after T injection partially depended on the stimulated protein synthesis. Altogether, the obtained evidence supports the assumption that the AR mediates elevation of its own gene expression in SM upon administration of T. : S 0 9 6 0 -0 7 6 0 ( 0 1 ) 0 0 1 2 5 -X

Medicine & Science in Sports & Exercise, 1979

ABSTRACT

Anabolic steroids are synthetic derivatives of testosterone and are characterized by their abilit... more Anabolic steroids are synthetic derivatives of testosterone and are characterized by their ability to cause nitrogen retention and positive protein metabolism, thereby leading to increased protein synthesis and muscle mass. There are disagreements in the literature in regards to the interaction of anabolic steroids with the androgen receptor (AR) as revealed by competitive ligand binding assays in vitro using cytosolic preparations from prostate and skeletal muscle. By use of tissue extracts, it has been shown that some anabolic steroids have binding affinities for the AR that are higher than that of the natural androgen testosterone, while others such as stanozolol and methanedienone have significantly lower affinities as compared with testosterone. In this study we show that stanozolol and methanedienone are low affinity ligands of the rat recombinant AR as revealed by a ligand binding assay in vitro, however, based on a cell-based AR-dependent transactivation assay, they are potent activators of the AR. We also show that a single injection of stanozolol and methanedienone causes a rapid cytosolic depletion of AR in rat skeletal muscle. Based on these results, we conclude that anabolic steroids with low affinity to AR in vitro, can in fact in vivo act on the AR to cause biological responses.

The Journal of Urology, 2014

ABSTRACT INTRODUCTION AND OBJECTIVES: Signal transduction through transforming growth factor-beta... more ABSTRACT INTRODUCTION AND OBJECTIVES: Signal transduction through transforming growth factor-beta 1 (TGF-b1) pathway affects epithelial to mesenchymal transition (EMT), partly by modulation of ECadherin expression. Concurrent impact of extracellular matrix driven activation of integrin signaling on evolution of EMT has not been well characterized. We assess cumulative effect and molecular mechanisms of TGF-b1 and integrin signal transduction on E-Cadherin expression in renal cell cancer (RCC). METHODS: TGF-b1 driven alteration of EMT specific markers was confirmed in an established in-vitro model of RCC. Global changes in expression of cell surface integrins were evaluated by microarray and confirmed by RT-PCR. Arginylglycylaspartic acid (RGD), in addition to TGF-b1, was utilized to mimic integrin signaling and evaluate cumulative effects on markers of EMT. Silencing of potential mediators of cumulative action of RGD and TGF-b1 was carried out by small interfering RNA and confirmed by Western blotting or RT-PCR. RESULTS: After stimulation of RCC cells with TGF-b1, a threefold increased expression of integrin aVb3 was identified by microarray and confirmed by RT-PCR. Pre-treatment of cells with RGD in addition to TGF-b1 demonstrated a significantly higher effect on expression of markers of EMT (E-cadherin and Snail-1) than either ligand alone. SiRNA mediated silencing of FAK and PINCH, independently and conclusively abrogated the cumulative effect of RGD and TGF-b1 on markers of EMT. CONCLUSIONS: We have identified a novel mechanism through which extracellular matrix event transduction by integrins further augments TGF-b1 related effects on the well established markers of EMT. Molecular machinery involved in integrin/TGF-b1 interplay serves as an attractive therapeutic target in RCC.

Journal of Steroid Biochemistry and Molecular Biology, 2001

Our aim was to investigate the effect of a single testosterone (T) injection on the androgen rece... more Our aim was to investigate the effect of a single testosterone (T) injection on the androgen receptor (AR) in rat skeletal muscle (SM) cytosol. The properties of AR were studied in order to establish the protocol for differential determination of free and hormone-occupied AR in SM cytosols from non-hormone-deficient animals. Using the developed ligand-exchange protocol, we demonstrated that injection of T (1 mg/kg) caused alternating changes of the total AR binding. The binding minimum (23% of the control) was measured 1 h after the injection. It was followed by pronounced and lasting elevation of the AR binding. In the control cytosols, AR complexes constituted 25% of the total receptor content. Changes of their relative content immediately after T administration were consistent with rapid nuclear translocation of the AR. Inhibition of protein synthesis by cycloheximide (CHI) injection demonstrated that delayed and lasting increase of the AR binding after T injection partially depended on the stimulated protein synthesis. Altogether, the obtained evidence supports the assumption that the AR mediates elevation of its own gene expression in SM upon administration of T. : S 0 9 6 0 -0 7 6 0 ( 0 1 ) 0 0 1 2 5 -X

Medicine & Science in Sports & Exercise, 1979

ABSTRACT

Anabolic steroids are synthetic derivatives of testosterone and are characterized by their abilit... more Anabolic steroids are synthetic derivatives of testosterone and are characterized by their ability to cause nitrogen retention and positive protein metabolism, thereby leading to increased protein synthesis and muscle mass. There are disagreements in the literature in regards to the interaction of anabolic steroids with the androgen receptor (AR) as revealed by competitive ligand binding assays in vitro using cytosolic preparations from prostate and skeletal muscle. By use of tissue extracts, it has been shown that some anabolic steroids have binding affinities for the AR that are higher than that of the natural androgen testosterone, while others such as stanozolol and methanedienone have significantly lower affinities as compared with testosterone. In this study we show that stanozolol and methanedienone are low affinity ligands of the rat recombinant AR as revealed by a ligand binding assay in vitro, however, based on a cell-based AR-dependent transactivation assay, they are potent activators of the AR. We also show that a single injection of stanozolol and methanedienone causes a rapid cytosolic depletion of AR in rat skeletal muscle. Based on these results, we conclude that anabolic steroids with low affinity to AR in vitro, can in fact in vivo act on the AR to cause biological responses.