Ex vivo stimulation of renal tubular p-aminohippurate transport by dexamethasone and triiodothyronine in human renal cell carcinoma

This paper is the third of a long-term planned series of papers dealing with ex vivo investigations of drug transport in human kidney. The aims of this study are (a) to investigate whether or not human renal cell carcinoma (RCC) can actively accumulate p-aminohippurate (PAH) and (b) to test the response of RCC on dexamethasone or triiodothyronine (T3) using tissue slices ex vivo. By this approach, the accumulation capacity of RCC should be stimulated as a prerequisite for an increased uptake of anti-tumour drugs. Tissue slices of RCC samples of 30 patients were incubated for 24 h in Williams medium E containing 0.01–50 μM dexamethasone or T3. Thereafter, slices were placed in PAH-containing Cross–Taggart medium, and PAH uptake into kidney tissue was measured for 2h under standardised conditions as described previously. In intact human renal cortical slices, PAH uptake capacity, expressed as slice to medium ratio (Q _S/M), was about 2.8 ± 0.16 after 24 h of incubation and increased significantly in dexamethasone-containing medium in a concentration-dependent manner, up to ∼150%, whereas T3 did not influence PAH accumulation. On the other hand, in RCC the PAH accumulation capacity was completely abolished (Q _S/M∼1). However, after administration of dexamethasone, the accumulated amount of PAH increased significantly in RCC tissue in a concentration-dependent manner, up to ∼190%. T3 was without effect in RCC, too. Surprisingly, the dexamethasone-mediated stimulation could be differentiated into responders and non-responders, with maximal effects at different concentrations for each patient. Nevertheless, the maximal transport rates remained low in RCC, even under hormone influence. In conclusion, a moderate stimulation of tubular transport capacity can be shown ex vivo in human RCC. This phenomenon is only of a relatively low degree compared with intact renal tissue. However, in principle, the response of RCC on dexamethasone could form a basis for further therapeutic strategies to overcome multi-drug resistance in RCC patients. For this purpose, additional experiments analysing the expression of transporters of the ABC cassette-type are in progress. Received: 25 April 2000 / Accepted: 27 July 2000     

In vitro stimulation of renal tubular p-aminohippurate transport by dexamethasone in rat kidneys and in intact kidney tissue of patients suffering from renal cell carcinoma

The aim of this study was to test whether or not the accumulation of p-aminohippurate (PAH) can be increased in intact human renal cortical slices obtained from tumor-bearing kidneys of patients suffering from renal cell carcinoma (RCC). Tissue slices were incubated for 24 h in Williams medium E containing 0.01–50 μM dexamethasone. Thereafter slices were placed in PAH-containing Cross-Taggart medium and PAH uptake into kidney tissue was measured for 2 h. In both rat and human renal tissue slices, PAH uptake capacity increased significantly in a concentration-dependent manner after 24 h of incubation in dexamethasone-containing medium (rat, 136%; man, 156%). The stimulatory effect was already significant after 12 h of incubation. In additional experiments it was shown that incubation in triiodothyronine (T₃)-containing medium has different effects: in man, T₃ does not influence the PAH accumulation capacity of renal cortical slices whereas in rats PAH accumulation is significantly lower after 24 h of incubation with T₃. Thus stimulation of tubular transport capacity can be performed in vitro in human renal cortical slices. Discrepancies between the effects of dexamethasone and T₃ indicate different modes of action of the two hormones at the cellular level. Received: 4 August 1997 / Accepted: 28 October 1997     

Tubular PAH transport capacity in human kidney tissue and in renal cell carcinoma: correlation with various clinical and morphological parameters of the tumor

In vitro accumulation ofp-aminohippurate (PAH) was investigated in intact human renal cortical slices of normal kidney tissue and in tissue slices of renal cell carcinoma (RCC). The technique used was established in preliminary experiments on rat kidney tissue slices. In principle, the accumulation capacity is comparable in renal tissue slices of both species (slice to medium accumulation ratios between 4 and 8). In man sex differences in accumulation capacity do not exist. But, as shown in detail for rats, accumulation capacity drops with age. Tissue slices of RCC are unable to accumulate PAH actively; slice to medium ratio reaches about 1 and indicates passive PAH uptake only. Surprisingly, in tumors of stage pTl PAH uptake is lowest, perhaps as a sign of PAH transport out of the cells. There is no difference between peripheral and central parts of RCC. Age and sex are without influence on PAH uptake in RCC tissue slices. Interestingly, the accumulation capacity of intact tissue of kidneys infested with RCC also depends on the severity of the tumor (stage, diameter), but not on grading and formation of metastases.     

Amphotericin B and sodium deoxycholate induced impairment of renal p-aminohippurate accumulation (PAH) and effect on lipid peroxidation in the rat kidney.

The influence of amphotericin B on PAH transport as well as on lipid peroxidation in rat renal cortical slices was studied in vitro and ex vivo. In vitro, renal cortical slices were incubated with different amphotericin B (AmB) concentrations (2-60 micrograms/mL) or with the corresponding vehicle concentrations of sodium deoxycholate (NaDo) (1.64-49.2 micrograms/mL) and time dependently (15-30-60 min) with 30 micrograms/mL AmB or 24.6 micrograms/mL NaDo. Ex vivo, PAH transport of renal cortical slices was investigated following a 3-day intravenous AmB administration with 3 mg/kg per day or 2.46 mg/kg/day NaDo, respectively. In vitro AmB as well as NaDo decreased PAH transport dose and time dependently. At the highest AmB concentration of 60 micrograms/mL, PAH uptake decreased to 17.6%. The corresponding NaDo concentration (49.2 micrograms/mL) decreased PAH uptake to 33.3%. Time dependently AmB decreased PAH uptake to 25% after 60 min. NaDo caused a decrease to 69%. Administration of AmB for 3 days resulted in a PAH decline to 81%; NaDO decreased PAH uptake to 77%. In vitro as well as in vivo, AmB or its vehicle did not induce lipid peroxidation in renal cortical tissue. In summary, the results show that AmB and its vehicle, NaDo, decrease PAH uptake by renal cortical cells, reflecting a direct effect of AmB on tubular function. The impairment of the PAH transport is not due to enhanced lipid peroxidation.     

Correlation of renal organic anion and cation transport with blood pressure in SHR.

In 1974, we found that sera from SHR suppressed renal PAH transport (PSEBM 145:97, 1974). Since a "natriuretic factor" depresses PAH as well as Na transport, we proposed that "natriuretic factor" was elevated in SHR. Our current investigation amplifies the previous study. On a given day, one spontaneously hypertensive rat (SHR) and one rat from a normotensive strain [Wistar Kyoto (WKY) or Sprague-Dawley (SD]) were examined together. SHR sera compared to WKY/SD sera significantly depress PAH (organic anion) and TEA (organic cation) uptake by rat renal slices. The ability of SHR sera to depress uptake correlated significantly with the BP: the sera with the greatest depressive influence on renal PAH and TEA uptake came from the SHR with the highest BP (PAH r = 0.89, p less than 0.0001; TEA = r = 0.76, p less than 0.01). Subsequent separation of serum on Sephadex 25 localized the factor to the same fraction as "natriuretic hormone". A similar correlation was found between the ability of the fraction to depress the 2 transports and the height of the BP. The serum factor did not inhibit ATPase activity. In contrast to the serum effects, renal slices removed from SHR showed increased rather than decreased PAH and TEA transport which significantly correlated with the BP. The slices with the highest uptakes came from the SHR with the highest BP. The high uptake of organic ions by the SHR renal slices could be an adaptive response to the serum factor or vice versa. We postulate that a serum factor which depresses PAH and TEA transport and is not "ouabain-like" may play a role in the BP elevation of SHR.     

Inhibition of gluconeogenesis and <Emphasis Type="Italic">p</Emphasis>-aminohipuric acid accumulation in rat renal cortical slices by ionic and nonionic contrast media

Background. Renal dysfunction is a well-recognized complication induced by contrast media (CM). Nonionic CM have been introduced into clinical use to replace conventional ionic CM in an effort to reduce toxicity. However, the nephrotoxic effects of nonionic CM have not been fully evaluated. We previously determined the activities of N-acetyl--d-glucosaminidase and -glutamyltransferase released from rat and human renal slices incubated with contrast media. Dose-dependent enzyme release from renal slices was observed, but there was no statistical difference in the increase of enzyme activities between ionic and nonionic CM. The present experiment was conducted to compare the effects of ionic and nonionic CM on the metabolic function of rat renal slices.Methods. Rat renal cortical slices were incubated with ionic CM (diatrizoate, iothalamate) and nonionic CM (iopamidol, iohexol) at 37°C for 90min. To examine the dose–response effects of CM on gluconeogenesis and p-aminohipuric acid (PAH) accumulation in the rat renal slices, slices were incubated with 30, 60, and 90mgI/ml of CM. The inhibitory effects of nonionic CM on gluconeogenesis and PAH accumulation were compared with those of ionic CM in an independent experiment, in which slices were incubated with CM at a concentration of 60mgI/ml. In addition, rat renal slices were incubated with mannitol instead of CM to investigate the effects of osmotic pressure on gluconeogenesis and PAH accumulation.Results. A dose-dependent reduction of gluconeogenesis in rat renal slices was demonstrated by both ionic CM and nonionic CM. The inhibition of PAH accumulation was dose-dependent with nonionic CM, but not with ionic CM. Gluconeogenesis and PAH accumulation within the renal slices were both inhibited according to the increase in osmotic pressure produced by mannitol. The reduction in gluconeogenesis and PAH accumulation within the rat renal slices incubated with 60mgI/ml of nonionic CM were significantly less than those resulting from the same concentration of ionic CM.Conclusions. Nonionic CM is less nephrotoxic than ionic CM with regard to gluconeogenesis and PAH accumulation in rat renal slices. These differences in nephrotoxic effect between ionic and nonionic CM may in part be attributable to differences in osmotic pressure.     

In vitro sensitivity testing of human renal cell carcinoma with cytostatic agents and interferon alpha-2a

Summary Samples of 38 human renal cell carcinomas (RCC) were subjected to routine histopathological examination but also to in vitro sensitivity testing with mitomycin C, vinblastine and interferon Alpha-2a at various concentrations corresponding to serum titers recommended to be effective in vivo, employing a monolayer assay. Extending earlier in vitro studies, both tumor cell kill rates (TCKR) and proliferation rates (PR) were assessed. Following in vitro preparation the tumor cell cultures were simultaneously exposed to the anticancer drugs listed above. The proliferation rates were determined immunocytochemically using the monoclonal antibody Ki-67. Nine (23.7%) of the tumors investigated revealed temporary and limited response with respect to either TCKR or PR. Improvement of this percentage could only be obtained by increasing drug concentration to titers with toxicity intolerable for in vivo administration. The in vivo data presented correspond to clinical temporary and limited remissions in patients with metastatic RCC ranging up to 25%.     

Effect of cyclosporine A on accumulation of tetraethylammonium and p-aminohippurate, and on lipid peroxidation in rat renal microsomes and cortical slices

The effect of cyclosporine A (CsA) on lipid peroxidation (LPO) was assessed in renal cortical slices and renal microsomes. Cortical slices were incubated with 1500 micrograms/ml CsA and microsomes with 0.5-20 micrograms/ml under identical conditions (pH 7.4, 37 degrees C) for 3 hours, and LPO monitored by the formation of malondialdehyde (MDA). CsA at concentrations of 3 micrograms/ml and higher caused a significant increase MDA in microsomes and renal cortical slices showed a time dependent release of MDA into the incubation medium. The influence of CsA on tetraethammonium (TEA) and p-aminohippurate (PAH) accumulation in renal cortical slices was investigated for up to 3 hours with concentration of CsA from 10 to 1000 micrograms/ml. CsA caused a time- and concentration-dependent decrease of TEA accumulation and higher concentrations of CsA decreased PAH accumulation in renal cortical slices. The results add further evidence to the suggestion that lipid peroxidation participate in CsA-induced impairment of kidney function.     

Monoclonal antibodies in human renal cell carcinoma and their use in radioimmune localization and therapy of tumor xenografts

A series of monoclonal antibodies (Mabs) to human renal cell carcinoma (RCC) material was developed. Two Mabs (D5D and A6H) that showed especially restrictive reactivities were radiolabeled with iodine 131 and tested in nude mice bearing human tumor xenografts for their ability to specifically localize RCC. Extensive studies of tissue radioactive uptake indicated that these Mabs could specifically localize RCC tumors with some mice achieving high tumor:blood ratios ranging from 15 to 60. Scintigraphic scanning revealed specific and consistent detection of RCC xenografts. Finally, preliminary results indicate that larger intravenous doses of radiolabeled RCC Mabs were effective as radioimmune therapy in inhibiting RCC xenograft growth. Mabs can be produced that are highly restrictive to human RCC and may be useful clinically for radioimmunoscintigraphy or therapy.     

Experimental study of renal disorder caused by oxaliplatin in rat renal cortical slices

Background Oxaliplatin is a newly developed antitumor platinum complex that is known to have low nephrotoxicity. The inhibitory effects of oxaliplatin on several tubular functions were compared with those of cisplatin and carboplatin, using a renal cortical slice system.Methods and results Rat renal cortical slices were incubated with 0.25mM to 2.0mM of oxaliplatin, cisplatin, on carboplatin at 37°C for 120min. Para-amino hippuric acid (PAH) accumulation, gluconeogenesis, and ATP content in the rat renal slices were determined. PAH accumulation was not inhibited by carboplatin, but it was signific-antly inhibited by oxaliplatin and cisplatin. Inhibition of PAH accumulation by cisplatin was greater than that by oxaliplatin. Gluconeogenesis was not decreased by carboplatin, but it was suppressed by oxaliplatin and cisplatin in a dose-dependent manner. The decrease in gluconeogenesis induced by oxaliplatin was significantly greater than that induced by cisplatin. ATP content in the renal slices was decreased by oxaliplatin, cisplatin, and carboplatin to almost the same extent. As an in vivo experiment, 21.6mmole/kg of oxaliplatin, cisplatin, or carboplatin was injected into rats; then blood urea nitrogen (BUN) and serum creatinine were determined on day 4. Significantly elevated levels of BUN and serum creatinine were observed only in the rats injected with cisplatin.Conclusions Oxaliplatin did not cause nephrotoxicity in the in vivo study; however, the nephrotoxic pattern of oxaliplatin observed in the renal cortical-slice system resembled that of cisplatin. The reason why oxaliplatin is less nephrotoxic than cisplatin in vivo could not be fully elucidated in the present experiment using the renal cortical-slice system.     

Gene therapy using cationic multilamellar liposomes containing human interferon-beta gene against renal cell carcinoma

The anticancer activity of cationic multilamellar liposomes containing human IFN-beta gene (IAB-1) against renal cell carcinoma (RCC) was examined. Concentrations of IFN-beta protein were measured by an enzyme-linked immunosorbent assay. The cytotoxic activity of IAB-1 against RCC cells and normal renal proximal tubule endothelial cells (RPTEC5899) was examined by the microculture tetrazolium dye assay. For the in vivo study, the NC65 RCC cell line was inoculated into severe combined immunodeficiency mouse. The RCC cells treated with IAB-1 secreted significant amounts of IFN-beta protein. Significant in vitro cytotoxic activity of IAB-1 against RCC cells was observed. In contrast, treatment of RCC cells with recombinant IFN-beta protein resulted in less cytotoxicity. No significant cytotoxicity was seen in RPTEC5899 cells. Apoptosis was observed in RCC cells treated with IAB-1. The size of NC65 RCC cancers transfected with IAB-1 in mice was significantly smaller than that receiving injection of empty liposomes or recombinant IFN-beta protein. These findings show that IAB-1 may have significant antitumor activity against RCC, and suggest its potential clinical application for gene therapy against RCC.     

Redistribution of epidermal growth factor immunoreactivity in renal tissue after nephrotoxin-induced tubular injury

Tubular necrosis elicits a process of renal tissue repair characterized by an increase of cell turnover in tubular epithelium. The present study was undertaken to examine the distribution of epidermal growth factor (EGF) and/or of its larger precursor proEGF in the kidney undergoing tubular regeneration. Sprague-Dawley rats were exposed to various drugs (aminoglycosides or platinum-based anticancer agents) known to induce tubular necrosis. The proliferative response resulting from renal tissue damage was measured by the incorporation of [3H]thymidine into DNA of renal cells. EGF immunoreactivity was evidenced by immunocytochemical staining, using anti-EGF antibody and immunogold-silver staining. Concomitantly with the increase of cell proliferation resulting from tubular injury, a redistribution of EGF immunoreactivity was observed in renal tissue (from the inner stripe of outer medulla towards renal cortex). Amazingly, EGF was detected in proximal tubules of nephrotoxin-treated rats whereas, in the kidneys of control animals, it was almost exclusively found in distal tubules and collecting ducts. Insofar as the administration of exogenous EGF has recently been shown to enhance renal tubular regeneration after ischaemic injury [Humes et al: J Clin Invest 1989; 84:1757-1761], our observations lend further support to the concept that EGF might be involved in renal tissue repair.     

Effects of medium pH on p-aminohippurate transport in rat kidney fragments.

Addition of many oxidizable substrates to medium often enhances p-aminohippurate (PAH) transport by incubating renal tissue. Since the oxidation of various substrates by rat kidney tissue may change medium pH and this pH change has not been considered by many in conclusions, we followed the effects of medium pH on the magnitude and kinetics of in vitro PAH transport. Two previous studies employing rat kidney slices reported different optimal medium pH for PAH accumulation, i.e. pH 6.5 and pH 8.0. By repeating these studies over a wide range of medium pH, we confirmed the presence of enhanced steady state accumulation relative to pH 7.4 at two separate pH ranges, one at pH 6.7--6.9 (+ 15%), and the other at pH 7.7--7.9 (+ 22%). PAH influx, as measured by early tissue accumulation, was not different at pH 7.4 and 7.8; while at pH 6.8, it actually decreased. It was only later in the incubation that accumulation was greater at pH 6.8 and 7.8. Probably due to the small stimulation in steady state accumulation at either pH, we could not discern, by the methodology currently available, if this was secondary to augmented influx, decreased efflux, or a combination of both in the latter part of incubation. We conclude that the contribution secondary to medium pH changes must be considered when evaluating the effects of various substrates on PAH accumulation by kidney slices.     

Short-term regulation of basolateral organic anion uptake in proximal tubular OK cells: EGF acts via MAPK,PLA(2), and COX1

The organic anion transport system of the kidney is of major importance for the excretion of a variety of endogenous compounds, drugs, and potentially toxic substances. The basolateral uptake into proximal tubular cells is mediated by a tertiary active transport system. Epidermal growth factor (EGF) leads to an increase in the basolateral uptake rate of the model substrate para-aminohippuric acid (PAH) in opossum kidney (OK) cells. This stimulation is mediated by successive activation of the mitogen-activated protein kinases,mitogen-activated/extracellular signal-regulated kinase kinase (MEK) and extracellular regulated kinase isoforms 1 and 2 (ERK1/2). This study investigates the regulatory network of EGF action on PAH uptake downstream ERK1/2 in more detail. EGF stimulation of the basolateral uptake rate of [(14)C]PAH was abolished by the phospholipase A(2) inhibitor AACOCF3.[(14)C]PAH uptake was enhanced by arachidonic acid. Furthermore, EGF led to an increase in arachidonic acid release and to the generation of prostaglandins. AACOCF3 did not influence EGF-induced ERK1/2 activation, indicating that ERK1/2 is upstream of PLA(2). In addition, EGF stimulated the influx of extracellular Ca(2+). However, Ca(2+)-influx was not required for the stimulatory action of EGF on [(14)C]PAH uptake. Inhibitors of COX and lipoxygenases reduced [(14)C]PAH uptake dose-dependently, whereas inhibition of cytochrome P450 did not. In the presence of indomethacin, EGF had no stimulatory effect on [(14)C]PAH uptake. The inhibitory effect of indomethacin was not due to competitive action on PAH uptake. Furthermore, prostaglandin E(2) (PGE(2)) increased basolateral [(14)C]PAH uptake rate dose-dependently, and this increase was also observed in the presence of indomethacin. Selective inhibition of COX2 by indomethacin amid or indomethacin n-heptyl ester did not inhibit [(14)C]PAH uptake, whereas selective inhibition of COX1 dose-dependently inhibited [(14)C]PAH uptake. This and previous data lead to the conclusion that EGF successively activates MEK, ERK1/2, and PLA(2), leading to an increased release of arachidonic acid. Subsequently, arachidonic acid is metabolized to prostaglandins via COX1, which then mediate EGF-induced stimulation of basolateral organic anion uptake rate.     

Effect of Cyclosporine a on Accumulation of Tetraethylammonium and p-Aminohippurate,and on Lipid Peroxidation in Rat Renal Microsomes and Cortical Slices

The effect of cyclosporine A (CsA) on lipid peroxidation (LPO) was assessed in renal cortical slices and renal microsomes. Cortical slices were incubated with 1500 μg/ml CsA and microsomes with 0.5–20 μg/ml under identical conditions (pH 7.4,37d`C) for 3 hours, and LPO monitored by the formation of malondialdehyde (MDA). CsA at concentrations of 3 μg/ml and higher caused a significant increase MDA in microsomes and renal cortical slices showed a time dependent release of MDA into the incubation medium. The influence of CsA on tetraethammonium (TEA) and p-ami-nohippurate (PAH) accumulation in renal cortical slices was investigated for up to 3 hours with concentration of CsA from 10 to 1000 μg/ml. CsA caused a time-and concentration-dependent decrease of TEA accumulation and higher concentrations of CsA decreased PAH accumulation in renal cortical slices. The results add further evidence to the suggestion that lipid peroxidation participate in CsA-induced impairment of kidney function.     

Slowly progressive, angiotensin II-independent glomerulosclerosis in human (pro)renin receptor-transgenic rats

For defining the pathogenic effects of the (pro)renin receptor-transgenic rat, strains that overexpressed the human receptor were generated. Although transgenic rats were normotensive and euglycemic and had a renal angiotensin II (AngII) level that was comparable to that of wild-type rats, transgenic rats developed proteinuria with aging and significant glomerulosclerosis at 28 wk of age. In kidneys of 28-wk-old transgenic rats, mitogen-activated protein kinases (MAPK) were activated without recognizable tyrosine phosphorylation of the EGF receptor, and expression of TGF-beta1 was enhanced. In vivo infusion of the (pro)renin receptor blocker peptide (formerly handle region decoy peptide) significantly inhibited the development of glomerulosclerosis, proteinuria, MAPK activation, and TGF-beta1 expression in the kidneys, but the angiotensin-converting enzyme inhibitor did not attenuate these changes despite a significant decrease in the renal AngII level. In addition, recombinant rat prorenin stimulated MAPK activation in the human receptor-expressed cultured cells, but human receptor was unable to evoke the enzyme activity of rat prorenin. Thus, human (pro)renin receptor elicits slowly progressive nephropathy by AngII-independent MAPK activation in rats. This study clearly provided in vivo evidence for the AngII-independent MAPK activation by human (pro)renin receptor and induction of glomerulosclerosis with increased TGF-beta1 expression.     

Comparison of fresh tissue incubation assay and the in vivo localization of monoclonal antibodies to renal cell carcinoma

Few in vitro tests currently available are able to accurately predict the in vivo localization of monoclonal antibodies (Mabs) to cancer. We report on a fresh tissue incubation assay (FTIA) and compare the results of this assay to the in vivo localization of renal cell carcinoma (RCC)-reactive Mab A6H and control Mab AFP-22 to RCC and non-RCC xenografts implanted in nude mice. Both the FTIA and in vivo localization study demonstrated highly selective uptake of A6H in RCC but not in non-RCC xenografts. Radioimmunoscintigraphy using A6H clearly visualized RCC xenografts in every attempt, while AFP-22 did not highlight any of the tumor xenografts. The results demonstrate that FTIA may be a useful in vitro assay for selecting Mabs for in vivo application, and that radioimmunoscintigraphy is a potentially useful tool in detecting cancer sites.     

In vitro effects of epidermal growth factor (EGF) on growth of urological malignant tumor cells

It is well known that Epidermal Growth Factor (EGF) is a cell-regulating factor for variety of tissues in vitro including normal and malignant cells. Furthermore, Takano et al reported that a decreased expression of EGF receptor in clones of human cancer KB cell line might be one of the pleiotropic properties of multidrug-resistant cells. However, both the influence of EGF on human urological cancer cell lines and the relation between EGF receptors and sensitivities of antitumor drugs on these cell lines have not been fully described. We have studied the effects of EGF on growth of 4 transitional carcinoma cell lines of bladder (TCCaB), 1 squamous cell carcinoma cell line of bladder (SCCaB), 5 renal cell carcinoma cell lines (RCC) and 3 prostatic carcinoma cell lines (CaP), as well as the relationship between the number of EGF receptors and drug sensitivities of these cell lines in vitro against methotrexate, vinblastine, adriamycin, cisplatin and etoposide (VP16). The present results determined by the in vitro colony forming efficiency method showed that exogenous addition of EGF to cell cultures at 0.1 ng/ml stimulated the growth of SCCaB by 169.0%, and at 1 ng/ml inhibited that of RCC by 2.9%-79.0%, relative to control. The more EGF receptors by 125I-EGF binding assay, the higher inhibition of VP16 on the growth of these cell lines. These results suggested that EGF stimulated the growth of SCCaB and inhibited the growth of RCC in vitro, and we found that these phenomena were correlated with neither the number of EGF receptors nor affinities of that receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endoglin (CD105) expression in human renal cell carcinoma

OBJECTIVE: To evaluate the prognostic potential of endoglin (CD105) expression in human renal cell carcinoma (RCC), as endoglin is a cell membrane glycoprotein expressed in tumour-associated vascular endothelium and a marker of angiogenesis; intratumoral microvessel density assessed by endoglin staining has prognostic significance in some neoplasms. PATIENTS AND METHODS: Tumour samples from 210 patients with RCC (168 conventional), diagnosed between 1982 and 1997, were assessed using the tissue microarray technique with immunohistochemical staining for endoglin. The expression of endoglin was related to clinical variables and survival. RESULTS: Of the tumours, 75% expressed endoglin, and in conventional RCC the expression was inversely correlated to the Tumour-Node-Metastasis (TNM) stage (P = 0.008) and nuclear grade (P = 0.01). There was no correlation between endoglin expression and gender, age, tumour size or cell type. Patients with conventional RCC and high endoglin expression had a more favourable prognosis than those with tumours with lower expression (P = 0.04). A multivariate analysis of prognostic factors showed that TNM stage and nuclear grade were independent predictors of prognosis. Endoglin expression did not add further prognostic information. CONCLUSION: These results indicate that endoglin expression is inversely related to stage and grade in RCC, and that it is associated with prognosis.     

Telomerase activity in human renal cell carcinoma

OBJECTIVE: To determine if telomerase activity plays an important role in the progression of renal cell carcinoma (RCC). MATERIALS AND METHODS: Telomerase activity was measured in 53 tissue samples of RCC (52 patients), 11 samples of normal renal tissue and six tissue samples from benign renal disease using a fluorescence-based telomeric repeat amplification protocol. The activity was assessed for associations with clinical and pathological variables of RCC. To examine the influence of telomerase activity on cell immortalization in vitro, primary cultures of RCC cells were produced; the maximum passage number beyond which cell culture could not be continued was compared with the associated telomerase activity. RESULTS: Among the tissue samples of benign renal disease, one from a patient with a hydronephrotic nonfunctioning kidney had detectable telomerase activity, whereas none of the normal renal tissues had. In 32 of the 53 RCC tissue samples (60%), telomerase activity was detectable, varying from 1.8 to 100.0 TPG units, but was not associated with any clinical or pathological variable such as clinical stage, tumour size, grade or pathological subtype. Telomerase activity also had no association with the maximum passage number of primary cell cultures. CONCLUSIONS: Telomerase activity may not be a prognostic marker for RCC. Alternative mechanism(s) which lengthen telomeres should be considered if maintaining telomere length is considered essential to tumour progression.