Detection of early DJ-stent encrustation by sonographic twinkling-artifacts - a pilot study.

INTRODUCTION: Ureter obstruction caused by a retro-peritoneal tumor is treated by inserting an indwelling ureter splint (DJ-stent). Indwelling duration is limited by cumulative crystalline deposits into the splint, eventually causing the repeated impairment of urine flow. Deciding when a DJ-stent must be replaced is important since belated removal can be accompanied by severe complications. X-ray or conventional sonography do not allow satisfactory evaluation of early incrustation, therefore, the use of sonographic twinkling artifacts (TA) to provide accurate stent surveillance was investigated. MATERIAL AND METHODS: 26 patients with indwelling ureter splints carrying a high risk of developing tumor lysis syndrome (TLS), which is often accompanied by early splint incrustation, were investigated utilizing TA the day after DJ-stent implantation and weekly thereafter. Serum creatinine, uric acid, and urine pH were measured at all TA exams. RESULTS: Early incrustation of the ureter splint was detected by TA in all patients 1-4 weeks after implantation. Incrustation occurred sooner with increased uric acid levels, and high creatinine or acidic urine accelerated early implant incrustation. CONCLUSIONS: TA can be used to monitor early crystalline deposits in implanted ureter splints, before they can be detected by conventional sonography or X-ray imaging and before complications occur.

Altered expression of beta1 integrins in renal carcinoma cell lines exposed to the differentiation inducer valproic acid.

Renal cell carcinoma (RCC) is the most common malignant tumor of the kidney. Adhesion receptors of the beta1 integrin family are assumed to be involved in carcinogenesis, but it is not clear how they contribute to RCC progression. In an in vitro model, we evaluated growth and adhesion capacity of Caki-I and KTC-26 kidney carcinoma cell lines compared to normal renal proximal tubular epithelial cells (PTC). alpha1-alpha6beta1 integrin subunits in malignant and non-malignant cells were evaluated by Western blotting and RT-PCR, integrin surface expression was measured by flow cytometry and confocal microscopy. Additionally, tumor cells were allowed to re-differentiate in the presence of valproic acid (VPA) and dynamic alterations of the integrin profile were analyzed. Caki-I and KTC-26 were characterized by accelerated proliferation and adhesion to an endothelial cell monolayer, compared to PTC cells. The integrin beta1 repertoire in RCC cell lines was significantly different from that detected in PTC, and included down-regulated alpha2 and alpha6, but up-regulated alpha1, alpha3 and alpha5 proteins. VPA application reduced tumor malignancy which was evidenced by reduced cell growth and adhesion capacity. The reduction in tumor malignancy was paralleled by the integrin expression profile of renal tumor cells 'matching' the pattern seen in PTC. We assume that a sensitive integrin balance exists in normal renal epithelial cells, and that dysregulation of the 'physiological' receptor equipment drives these cells towards malignancy. VPA acted on all investigated integrin subtypes and restored the receptor pattern typical for non-malignant cells. Therefore, VPA may represent a novel therapeutic option in RCC treatment.

c-Met responsiveness of isolated hepatocytes evaluated in an in vitro de-differentiation model.

Hepatocyte growth factor (HGF) accelerates tissue regeneration and ameliorates tissue fibrosis through its ligand c-Met receptor tyrosine kinase. Hence, HGF is currently discussed as an attractive therapeutic candidate for fatal liver diseases. However, it remains unclear whether c-Met of de-differentiated hepatocytes adequately responds to HGF in an impaired liver. Therefore, we investigated c-Met expression and c-Met responsiveness to HGF in an experimental de-differentiation cell culture system. Primary rat hepatocytes were seeded on a two-dimensional collagen matrix or embedded within a three dimensional collagen gel to guarantee intact cell geometry. Cells were cultivated in a growth factor enriched extracellular milieu (de-differentiation medium), or in a chemically defined differentiation medium, representing physiologically intact hepatocytes. c-Met surface expression was determined by flow cytometry. Receptor localisation was examined by confocal microscopy, c-Met and phosphorylated c-Met protein were determined by western blotting. Hepatocyte-specific asialoglycoprotein receptor (ASGPr) was examined to control the differentiation status of the cells. Growth factor enriched milieu induced a rapid loss of ASGPr with a significant increase of c-Met surface level and a decrease in c-Met protein level. Surprisingly, the increased amount of c-Met surface expression was associated with its loss of responsiveness to HGF. The addition of bile acids into the culture medium had significantly delayed the process of de-differentiation and restrained the drastic elevation of c-Met (tauroursodeoxycholic acid > ursodeoxycholic acid). Application of the three-dimensional hepatocellular architecture stabilized the c-Met surface receptor level and rendered c-Met activation. We have demonstrated that growth factor enriched extracellular milieu and loss of intact liver architecture seems to be accompanied by an up-regulation of c-Met surface level. Our findings suggest that irresponsiveness of c-Met to soluble HGF was possibly caused by an excessive HGF production and receptor over-stimulation. Both events should be considered when establishing an HGF-based therapy for fibrosis/cirrhosis.

Endothelial adhesion of synchronized gastric tumor cells changes during cell cycle transit and correlates with the expression level of CD44 splice variants.

AIM: To study adhesion capacity and CD44 expression of human gastric adenocarcinoma MKN45 cells at different stages of a first cell cycle. METHODS: MKN45 cells were synchronized by aphidicolin and assayed for adhesion to an endothelial cell (HUVEC) monolayer. Surface expression of CD44 and CD44 splice variants on MKN45 cells was evaluated by flow cytometry. Functional relevance of CD44 adhesion receptors was investigated by blocking studies using anti CD44 monoclonal antibodies or by hyaluronan digestion. RESULTS: Adhesion of MKN45 to HUVEC was increased during G2/M transit, after which adhesion returned to baseline levels with cell cycle completion. In parallel, CD44 splice variants CD44v4, CD44v5, and CD44v7 were all up-regulated on MKN45 during cell cycle progression with a maximum effect in G2/M. The function of CD44 surface receptors was assessed with specific receptor blocking monoclonal antibodies or removal of hyaluronan by digestion with hyaluronidase. Both strategies inhibited tumor cell adhesion to HUVEC by nearly 50%, which indicates that MKN45-HUVEC-interaction is CD44 dependent. CONCLUSION: CD44 expression level is linked to the cell cycle in gastrointestinal tumor cells, which in turn leads to cell cycle dependent alterations of their adhesion behaviour to endothelium.