Biomedical subjects

E Oosterwijk

Publications and source records attributed to E Oosterwijk.

At least 37 records · Page 2Linked to original sources

PubMed1999

Intratumoral distribution of two consecutive injections of chimeric antibody G250 in primary renal cell carcinoma: implications for fractionated dose radioimmunotherapy.

Tumor uptake of the chimeric G250 (cG250) monoclonal antibody (mAb) in patients with primary renal cell carcinoma (RCC) is among the highest reported in solid tumors. However, as observed in other tumor types, the intratumoral distribution of the antibody is highly heterogeneous, which may limit the efficacy of radioimmunotherapy. A number of highly dynamic physiological factors have been postulated that may contribute to heterogeneous tumor uptake of antibodies. Their impact on tumor uptake of antibodies may vary from one tumor region to another as well as from one day to the next. Here, we report on a clinical study that was designed to investigate whether the pattern of mAb cG250 uptake within RCC tumors is altered with subsequent injections. Ten patients with a clinical diagnosis of primary RCC were studied. Nine days before surgery, patients received 125I-cG250 (5 mg of cG250, 50 microCi of 125I), followed by a second injection of 131I-cG250 (5 mg of cG250, 3.5 mCi of 131I) 4 days later. Postsurgery, the tumor was cut into (1-cm) thick slices. Slices were imaged on a gamma camera, and the slice with the most pronounced heterogeneity in 131I-cG250 distribution was selected and cut into 1-cm3 cubes. Each cube was analyzed for 121I-cG250 and 131I-cG250 uptake, and the 131I/125I ratio was determined. For each tumor slice, the distribution patterns of both isotopes were reconstructed and compared with each other. All tumors analyzed showed a heterogeneous distribution of both isotopes throughout the tumor slice; focal uptake in some areas of a tumor reached very high levels (up to 0.19% injected dose/g), whereas other tumorous areas of the same slice showed much lower uptake (as low as 0.0047% injected dose/g). Remarkably, in all tumors, the distribution pattern of both injections was identical: without exception, in all samples analyzed (n = 692), the uptake of 125I-cG250 was similar to 131I-cG250 uptake. Overall, the 131I/125I ratio was 1.64+/-0.31 (mean+/-SD). The constant 131I/125I ratios, observed in all tumor samples investigated, indicate that the tumor parameters governing cG250 mAb uptake were not altered significantly within the time period studied. In addition, the results of this study suggest that multiple radiolabeled antibody injections, administered within short time periods, will target the same areas within a tumor and, thus, will not solve the problem of heterogeneous tumor uptake of antibody.

Adult↗

PubMed1999

MN/CA IX/G250 as a potential target for immunotherapy of renal cell carcinomas.

The monoclonal antibody G250 (mAbG250) raised against a human renal cell carcinoma (RCC) has been shown to react with a large number of RCCs. Recently, G250 antigen was isolated and found to be homologous to the MN/CA9 gene originally identified in HeLa cells. To determine whether G250 antigen (MN/CA IX/G250) could be a potential therapeutic target and a tumour marker, a total of 147 cases of RCC were investigated immunohistochemically as well as by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. In addition, total RNAs extracted from patients' peripheral blood samples were analysed for MN/CA9/G250 mRNA signals. Immunohistochemistry demonstrated strong expression in 128/147 (87.1%) of RCCs, in contrast to the lack of expression observed in normal tissues. RT-PCR analyses of frozen specimens resulted in the clear detection of MN/CA9/G250 mRNA signals in 137/147 (93.2%), and despite subtle differences the results were almost identical to those for immunohistochemistry. Although high-grade and -stage tumours exhibited significantly lower expression than low-grade and -stage tumours, a large proportion of tumours expressed MN/G250 protein as well as mRNA. RT-PCR analysis of patients' blood samples revealed the presence of circulating MN/CA9/G250 expressing cells. These findings suggest that this antigen may be a potential therapeutic target as well as diagnostic marker for RCCs.

Antigens, Neoplasm↗

PubMed1999

In vivo and in vitro characterizations of three 99mTc-labeled monoclonal antibody G250 preparations.

UNLABELLED: In previous clinical studies, excellent visualization of tumor lesions has been observed with 131I-labeled monoclonal antibody (mAb) G250 in patients with renal cell carcinoma (RCC). In several cases, 131I-cG250 immunoscintigraphy disclosed tumor lesions that were not visualized by radiography or CT. To improve image quality, we aimed to develop a 99mTc-labeled mAb G250 preparation for radioimmunodetection of RCC. We studied in vitro stability, biodistribution and imaging potential of three 99mTc-labeled G250 preparations in nude mice with subcutaneous RCC xenografts.125I-G250 and the nonspecific mAb 131I-MN14 were used as control antibodies. METHODS: The mAb G250 was labeled with 99mTc according to three methods using: (a) S-hydrazinonicotinamide (HYNIC), (b) S-benzoylmercaptoacetyltriglycine (MAG3) and (c) a direct labeling method (Schwarz method). The stability of all preparations was tested in serum at 37 degrees C during 48 h. In addition, diethylenetriamine pentaacetic acid, cysteine and glutathione challenge assays were performed. RESULTS: All preparations showed good stability in serum during the 48-h incubation period. 99mTc-G250 (Schwarz) showed release of the radiolabel at a 100-fold or higher molar excess of cysteine and at a 10,000-fold or higher molar excess of glutathione. 99mTc-MAG3-G250 showed release of the radiolabel at a 10,000-fold molar excess of cysteine. 99mTc-HYNIC-G250 was stable under all conditions. Tumors were clearly visualized with all preparations. 99mTc-G250 (Schwarz) showed significantly lower blood levels (3.8 %ID/g) compared with all other preparations (11.2, 13.4 and 13.4 %ID/g for 99mTc-HYNIC-G250, 99mTc-MAG3-G250 and 125I-G250, respectively, 48 h postinjection). At 48-h postinjection, mean tumor uptake was very high with all mAb G250 preparations: 92.4 (99mTc-HYNIC-G250), 125.9 (99mTc-MAG3-G250), 29.4 (99mTc-G250 Schwarz) and 75.4 (125I-G250) %ID/g. Mean tumor uptake of the nonspecific 131I-MN14 mAb was 6.6 %ID/g. CONCLUSION: In this study, 99mTc-HYNIC-G250 showed excellent in vitro stability and tumor targeting. Moreover, this preparation could be labeled with high efficiency (>95%) at room temperature within 15 min. Therefore, 99mTc-HYNIC-G250 seems to be an ideal candidate for radioimmunodetection of RCC.

Animals↗

PubMed1999

Phase I radioimmunotherapy of metastatic renal cell carcinoma with 131I-labeled chimeric monoclonal antibody G250.

Clinical tumor targeting studies with chimeric monoclonal antibody G250 (cG250) in renal cell carcinoma (RCC) patients indicated the potential use of this antibody for radioimmunotherapy. Here we report on a phase I activity dose escalation study to determine the safety, the maximum tolerable dose (MTD), and the possible therapeutic potential of 131I-labeled cG250 in patients with progressive metastatic RCC. All patients (n = 12) received a diagnostic i.v. infusion of 5 mg of cG250 labeled with 222 MBq of 131I. If accumulation of the antibody in metastatic lesions was observed, patients were hospitalized and a second, therapeutic, i.v. infusion of 5 mg of cG250 labeled with a high dose of 131I was administered (n = 8). Three patients per dose level were entered, starting at 1665 MBq/m2. If no dose-limiting toxicity occurred, the study continued at the next dose level (555 MBq/m2 increase). Most patients experienced mild nausea without vomiting. No other complaints were reported during hospitalization. In two of two patients who received a dose of 2775 MBq/m2, grade IV hematological toxicity was observed, which was defined as dose limiting. Thus, the MTD was set at 2220 MBq/m2. In one patient (2220 MBq/m2), stable disease (lasting 3-6 months) was achieved, whereas another patient (2220 MBq/m2) showed a partial response that is ongoing (>9 months). The minor responses observed in this phase I trial in patients with an advanced stage of RCC are encouraging and warrant further study in a phase II setting at the MTD to determine the efficacy of radioimmunotherapy for metastatic RCC.

Adult↗

PubMed1998

Two-step radio-immunotargeting of renal-cell carcinoma xenografts in nude mice with anti-renal-cell-carcinoma X anti-DTPA bispecific monoclonal antibodies.

The specificity of antibodies offers unique opportunities to target tumors with radionuclides. However, due to the slow clearance of radiolabeled antibody, relatively high back-ground is observed in non-target organs. Pre-targeting protocols using bispecific monoclonal antibodies (bsMAbs) and radiolabeled chelates may overcome this problem. We have evaluated the anti-renal-cell-carcinoma (RCC) X anti-DTPA bsMAb G250 x DTIn1 for 2-step targeting of RCC tumors in nude mice. Tumor uptake of 111In-DTPA was similar up to a 3-day interval between bsMAb and 111In-DTPA injections and decreased thereafter. The effect of G250 x DTIn1 protein dose was studied. High tumor uptake was seen at 1 to 4 micrograms, whereas at higher doses uptake decreased. Tumor was saturated with 15 micrograms bsMAb. At the saturating bsMAb dose the 111In-DTPA amount was varied. High tumor uptake was observed at a 10-fold molar excess 111In-DTPA, whereas at higher excess uptake decreased. After priming with 15 micrograms bsMAb and targeting with a 10-fold molar excess 111In-DTPA, the biodistribution of 111In-DTPA was studied for 1 to 48 hr after injection. Good tumor retention of 111In-DTPA was observed, while the radiolabel cleared rapidly from the blood. Consequently, tumor-to-blood ratios increased with time to 500 at 24 hr after injection. In conclusion, RCC xenografts can be targeted efficiently using G250 x DTIn1 and 111In-DTPA. However, this requires careful tuning of bsMAb protein dose and 111In-DTPA dose. Using the optimal protein dose and 111In-DTPA dose, high 111In-DTPA tumor uptake and tumor-to-blood ratios can be obtained, thus providing good perspectives for diagnostic and therapeutic use in humans.

Animals↗

PubMed1998

Immunohistochemical analysis of intratumoral heterogeneity of [131I]cG250 antibody uptake in primary renal cell carcinomas.

In previous studies, highly heterogeneous uptake of 131I-labelled chimeric monoclonal antibody G250 ([131I]cG250) in primary renal cell carcinomas has been observed (intratumoral differences > factor 100). In this study, we investigated a possible correlation between intratumoral antibody uptake and four immunohistochemically determined parameters: G250 antigen expression, blood vessel density, neovascularization and percentage of viable tumour cells. Whole tumour slices of four different tumours were cut into 1-cm3 cubes, and in each cube the [131I]cG250 uptake was determined. The correlation between [131I]cG250 uptake and each individual parameter was determined in a multiple regression analysis. Additionally, the data were reanalysed after introducing arbitrary cut-off values for each parameter. If a sample showed expression of a parameter above the introduced threshold value, this sample fulfilled one condition. Subsequently, the Pearson correlation coefficients were calculated from [131I]cG250 uptake and the number of fulfilled conditions (0-3). All tumour samples with high [131I]cG250 uptake [> 0.1% of the injected dose per gram (ID g(-1))] showed high antigen expression (> 50%). However, not all samples with high antigen expression displayed high uptake. A statistically significant correlation between [131I]cG250 uptake and antigen expression was found (beta = 0.44, 0.69 and 0.74) in three out of four tumours analysed. Of the other determined parameters, no consistent correlation with [131I]cG250 uptake was found; only the percentage of viable tumour cells correlated significantly in two out of four tumours (beta = 0.80 and 0.26). Calculation of the Pearson correlation coefficients showed a statistically significant correlation between [131I]cG250 uptake and an increased number of fulfilled conditions in all tumours, indicating that each of the individual parameters contribute to the uptake of [131I]cG250. These observations indicate that high antigen expression is a prerequisite for high antibody uptake. However, regional differences in antibody uptake within a tumour cannot be explained by antigen expression alone.

Antibodies, Monoclonal↗

PubMed1998

Tumor retention of 186Re-MAG3, 111In-DTPA and 125I labeled monoclonal antibody G250 in nude mice with renal cell carcinoma xenografts.

UNLABELLED: In radioimmunotherapy of solid tumors substantial gain might be achieved by carefully selecting the radionuclide and the linker connecting it to the antibody. In contrast to 131I, radiometals such as 90Y and 111In may be retained in the tumor cell after internalization of the antibody, thereby enhancing the radiation dose to the tumor. The physical properties of 186Re with 1.08 MeV beta-emission (71%) and 137 keV gamma-emission (10%) seem ideal for radioimmunotherapy. In this study we investigated in nude mice with s.c. renal cell carcinoma xenografts the biodistribution and the retention in the tumor of 186Re-MAG3 labeled monoclonal antibody (mAb) G250 as compared to 111In-DTPA-G250, to 125I-G250 and to 131I-MN14 (non-specific control mAb). Radiolabeled antibody preparations were i.v. injected. Seventy two hours p.i. the biodistribution of the radiolabel was determined. Blood levels of all mAb G250 preparations were remarkably low (mean: 2.38, 1.40 and 1.43% ID/g for 125I, 111In and 186Re respectively) whereas blood levels of mAb MN14 were significantly higher (mean: 12.3% ID/g), indicating tumor processing of mAb G250. Retention of 111In in the tumor was significantly higher than of 186Re and 125I whereas retention in the tumor of 186Re and 125I did not differ significantly. CONCLUSION: In contrast to other radiometals such as 111In and 90Y, 186Re is not retained in the tumor cell. Therefore 186Re has no additional advantage for radioimmunotherapy with respect to retention in the tumor.

Animals↗

PubMed1998

Detection of DNA amplification in human renal cell carcinoma cell lines using restriction landmark genomic scanning.

Gene amplification, which has often been observed in various human cancers, appears to be associated with the development and progression of malignant phenotypes. However, in renal cell carcinoma (RCC), conventional analytic methods requiring specific primers and probes have revealed infrequent amplification of known oncogenes. We attempted to determine if gene amplification was truly uncommon in RCC. The genomic DNAs extracted from 5 human RCC cell lines were examined by restriction landmark genomic scanning (RLGS), a two-dimensional gel analysis which allows evaluation of approximately 2,000 radiolabelled DNA fragments. By this method, we detected 24 distinct spots commonly amplified in at least 2 RCC cell lines compared to normal kidneys. Comparing the present results with chromosomal assigned-RLGS, approximately one half of these DNA fragments proved to be located on chromosome 2, 5 or 7. Our data suggest that amplification of unknown genes is likely to occur in RCC cell lines.

Carcinoma, Renal Cell↗

PubMed1998

Expression of cadherin-6 as a novel diagnostic tool to predict prognosis of patients with E-cadherin-absent renal cell carcinoma.

In many carcinomas, E-cadherin is considered to be a prognostic marker for patient survivals, and its decreased expression is associated with metastatic disease. Among renal cell carcinomas (RCCs), however, only 20% of tumors express E-cadherin, whereas a much higher percentage express other cadherins, e.g., N-cadherin and cadherin-6 (T. Shimazui et al, Cancer Res., 56: 3234-3237, 1996). Among these cadherins expressed in RCCs, cadherin-6 has been identified as a major cadherin in the renal proximal tubules and in the tumors themselves. Hence, we have investigated the relationship between prognosis and cadherin-6 expression in tumor cells in 43 patients with RCC. Expression of cadherin-6, E-cadherin, and alpha-catenin was detected immunohistochemically and evaluated microscopically as normal, heterogeneous, or absent. Normal, heterogeneous, and absent expression of cadherin-6 were observed in 19, 16, and 8 of 43 cases, respectively. Coexpression of E-cadherin and cadherin-6 was detected in only 10 cases. Among 30 tumors in which E-cadherin expression was absent, 24 expressed cadherin-6. In addition, the expression pattern of alpha-catenin correlated more highly with that of cadherin-6 than it did with E-cadherin (P = 0.0003 versus 0.025). In survival analyses, aberrant expression of cadherin-6 correlated with poor survivals both among all patients (P = 0.0009) and in those with E-cadherin-absent RCC (P = 0.0008). These results suggest that cadherin-6 is a major cadherin playing an essential role in cell-cell adhesion in E-cadherin-absent RCC.

Adolescent↗

PubMed1998

Phase I/II radioimmunotherapy trial with iodine-131-labeled monoclonal antibody G250 in metastatic renal cell carcinoma.

This Phase I/II radioimmunotherapy study was carried out to determine the maximum tolerated dose (MTD) and therapeutic potential of 131I-G250. Thirty-three patients with measurable metastatic renal cell carcinoma were treated. Groups of at least three patients received escalating amounts of 1311I (30, 45, 60, 75, and 90 mCi/m2) labeled to 10 mg of mouse monoclonal antibody G250, administered as a single i.v. infusion. Fifteen patients were studied at the MTD of activity. No patient had received prior significant radiotherapy; one had received prior G250. Whole-body scintigrams and single-photon emission computed tomography images were obtained in all patients. There was targeting of radioactivity to all known tumor sites that were > or =2 cm. Reversible liver function test abnormalities were observed in the majority of patients (27 of 33 patients). There was no correlation between the amount of 131I administered or hepatic absorbed radiation dose (median, 0.073 Gy/mCi) and the extent or nature of hepatic toxicity. Two of the first six patients at 90 mCi/m2 had grade > or =3 thrombocytopenia; the MTD was determined to be 90 mCi/m2 131I. Hematological toxicity was correlated with whole-body absorbed radiation dose. All patients developed human antimouse antibodies within 4 weeks posttherapy; retreatment was, therefore, not possible. Seventeen of 33 evaluable patients had stable disease. There were no major responses. On the basis of external imaging, 131I-labeled mouse monoclonal antibody G250 showed excellent localization to all tumors that were > or =2 cm. Seventeen of 33 patients had stable disease, with tumor shrinkage observed in two patients. Antibody immunogenicity restricted therapy to a single infusion. Studies with a nonimmunogenic G250 antibody are warranted.

Adult↗

PubMed1997

The effect of antibody protein dose of anti-renal cell carcinoma monoclonal antibodies in nude mice with renal cell carcinoma xenografts.

BACKGROUND: Antibodies preferentially can direct radionuclides to solid tumors. However, antibody uptake in tumors is often highly heterogeneous. This heterogeneity may be overcome by increasing antibody protein dose. METHODS: The biodistribution of increasing protein doses of radioiodinated antirenal cell carcinoma (RCC) monoclonal antibodies (MoAbs) G250 and RC 38 was studied in mice with NU-12 or SK-RC-52 RCC xenografts. In addition, MoAb affinity constants and antigen densities (Scatchard analysis) and MoAb processing (internalization) were determined in vitro. RESULTS: The relative uptake of G250 in NU-12 tumors was very high at low protein doses (125% injected dose/g [%ID/g]), but decreased at higher doses, suggesting tumor saturation. Indeed, saturation of G250 antigen occurred at 3 microg protein. In this model, 9200 G250 determinants per NU-12 cell could be targeted, which is only 6.1% of the 150,000 G250 determinants per NU-12 cell as determined in vitro. The RC 38 uptake in NU-12 tumors remained constant up to the 10 microg dose level (40% ID/g) and decreased at higher doses. RC 38 antigens were saturated at 25 microg of RC 38. With RC 38, 15% of the available RC 38 antigens per NU-12 tumor cell were targeted. In contrast, G250 uptake in SK-RC-52 tumors was very low at low antibody dose (4% ID/g at 1 microg) and increased with increasing protein dose. These differences in G250 biodistribution might be related to differences in the processing of G250 by the tumor cells. CONCLUSIONS: Our studies show that some RCC tumors can be saturated with anti-RCC MoAbs at low (25 microg) to very low (3 microg) protein doses. At nonsaturated doses relatively high tumor uptake can be achieved. Surprisingly, in NU-12 tumors only 6.1% and 15% of the available antigenic sites were targeted at the saturating dose levels with G250 and RC 38, respectively.

Animals↗

PubMed1997

Decreased expression of alpha-catenin is associated with poor prognosis of patients with localized renal cell carcinoma.

During the progression of many cancers, cell-cell adhesion molecules, e.g., E-cadherin (EC), may be down-regulated. In a number of carcinomas, EC has been described as an independent prognostic variable. We have studied the expression of adhesion molecules participating in cadherin-catenin complexes in renal cell carcinoma (RCC) specimens. Expression of EC, catenins and p120cas protein was examined in frozen tissue of 90 RCC specimens by immunohistochemistry, and these molecules were evaluated for their significance as prognostic markers. Staining was scored as normal (homogeneously positive at cell-cell borders) or abnormal (heterogeneous or absent). A significant correlation between poor survival and decreased expression of alpha-, beta- or gamma-catenin was observed, whereas no association between survival and EC or p120cas expression was seen. Cox's proportional hazard regression analysis showed that in patients with pT1-3N0M0 disease, reduced alpha-catenin expression correlated with poor survival, suggesting that alpha-catenin expression might be an independent prognostic indicator for patients of this group.

Adolescent↗

PubMed1997

Targeting of renal cell carcinoma with iodine-131-labeled chimeric monoclonal antibody G250.

PURPOSE: Pharmacokinetics, biodistribution, immunogenicity, and imaging characteristics of iodine 131 (131I)-labeled chimeric monoclonal antibody (mAb) G250 (cG250) were studied in patients with renal cell carcinoma (RCC) to determine the therapeutic potential of this antibody. PATIENTS AND METHODS: Sixteen patients with RCC received a single intravenous (IV) infusion of 6 mCi 131I-labeled cG250. Five protein dose levels were investigated (2 to 50 mg). Planar scintigraphic images were acquired, and normal tissue biopsies and tumor samples were obtained of surgery (7 days postinjection). The immunogenicity of cG250 was investigated using a sandwich enzyme-linked immunosorbent assay (ELISA) and dosimetric analysis was performed. RESULTS: In all patients with antigen-positive tumors (n = 13), the primary tumors and all known metastases were clearly visualized. Overall uptake, expressed as the percentage of the injected dose (%ID), in the primary tumors ranged from 2.4 to 9.0. Focally, 131I-cG250 uptake as high as 0.52% ID/g was observed. However, intratumoral uptake was highly heterogeneous. 131I-cG250 uptake in nontumorous tissues remained low. Dosimetric analysis showed that up to .48 Gy/mCi was guided to the primary tumors. Selected "hot areas" within these tumors received up to .72 Gy/mCi. A bone metastasis received .23 Gy/mCi and regional lymph node metastases received .20 Gy/mCi. Minimal human antichimeric antibody (HACA) levels were detected in two of 16 patients. CONCLUSION: 131I-cG250 tumor uptake is among the highest reported in clinical studies with antitumor antibodies in solid tumors. Since tumor-sterilizing levels may be guided to the tumor when high doses 131I-cG250 are administered (> 100 mCi) and cG250 appears to be immunosilent, cG250 is a promising vehicle for radioimmunotherapy in RCC.

Aged↗

PubMed1997

Rapid imaging of experimental infection with technetium-99m-DTPA after anti-DTPA monoclonal antibody priming.

UNLABELLED: Antibodies accumulate nonspecifically in infectious foci due to the locally increased vascular permeability. This study describes a method of infection imaging in which 99mTc-DTPA (diethylenetriaminepentaacetic acid) is trapped at the target by a previously administered anti-DTPA monoclonal antibody. DTIn1. METHODS: Rats with Staphylococcus aureus-infected calf muscle were injected intravenously with DTIn1. Two to 24 hr after the DTIn1 injection, 99mTc-DTPA was injected intravenously. In separate experiments, excess DTIn1 was cleared from the circulation 2 hr after injection with bovine serum albumin (BSA)-DTPA-In, galactosylated BSA-DTPA-In, goat antimouse IgG or avidin. Additionally, the effect of DTIn1 dose on 99mTc-DTPA abscess uptake was determined in a three-step protocol. The distribution of the radiolabels was studied by gamma counting of dissected tissue and gamma camera imaging. RESULTS: Priming with DTIn1 resulted in specific retention of 99mTc-DTPA in the abscess. Such 99mTc-DTPA abscess uptake was not dependent on the interval between the DTIn1 and the 99mTc-DTPA injection: Optimal 99mTc-DTPA abscess uptake was already achieved within a 2-hr time span between the DTIn1 and DTPA injections. However, relatively high 99mTc-DTPA background was observed due to slowly clearing DTIn1-99mTc-DTPA complexes. Background reduction with various agents had a prominent effect on DTIn1 as well as 99mTc-DTPA biodistribution. The best reduction was obtained using BSA-DTPA-In. Optimal 99mTc-DTPA abscess uptake in the three-step protocol was obtained at higher DTIn1 doses (> 100 micrograms). CONCLUSION: Infectious foci in a rat model can be imaged earlier with extremely low background levels after priming with DTIn1, followed by BSA-DTPA-In and imaging with 99mTc-DTPA, as compared with directly labeled IgG.

Abscess↗

PubMed1996

Complex cadherin expression in renal cell carcinoma.

E-cadherin is an intercellular adhesion protein expressed by most epithelia. Decreased expression of E-cadherin correlates with tumor aggressiveness in most carcinomas. In renal cell carcinoma (RCC), however, this correlation is not well established and the prevalence of negative tumors is higher than in other carcinomas. Our immunofluorescence study of alpha-catenin expression in 20 RCC cell lines revealed a typical honeycomb staining pattern in all of the lines, whereas only six expressed E-cadherin. This suggested that other cadherins are expressed in RCC lines. Indeed, immunoprecipitation with an anti-alpha-catenin antibody resulted in coprecipitation of proteins of Mr 125,000-135,000. Using Western blot, these proteins react with a pan-cadherin antibody. To identify these cadherin related proteins, RT-PCR using degenerated primers and sequence comparisons was carried out. We then assessed the expression of the identified cadherins. N-cadherin mRNA was present in all cell lines; and cadherin 6 mRNA was seen in 16 lines. Cadherin 11 (mRNA) and E-cadherin (protein) were expressed in five and six lines, respectively. A cadherin 4 transcript was observed in only one line, whereas no P-cadherin protein could be detected. Expression of the four main cadherins was also found in normal kidney (two samples tested) and RCC specimens (four samples). Thus, RCC and normal kidney express a complex set of cadherins.

Cadherins↗

PubMed1996

Aminopeptidase a is a constituent of activated pericytes in angiogenesis.

Monoclonal antibody (MAb) RC38 recognizes a human renal antigen of 160 kD recently identified as human aminopeptidase A (APA; EC 3.4.11.7). This ectoenzyme is able to hydrolyse selectively N-terminal glutamyl and aspartyl residues from oligopeptides. By enzyme histochemistry, APA activity has also been localized in the microvessels of all organs in animals and man. The purpose of this study was to investigate the distribution of human APA as recognized by MAb RC38 in the microvasculature of normal human tissues and pathological conditions associated with neovascularization. Unexpectedly, in normal tissues vascular staining with MAb RC38 was generally weak and often absent, while in tumours, granulation tissue, and chronic synovitis, marked microvascular staining was demonstrated. By immuno-electron microscopy, the antigen was found on the cell membrane of activated pericytes and their processes in the tumour vasculature. RC38 expression could not be detected on cultured human endothelial cells or pericytes. These observations suggest that pericyte expression of a subtype of APA (as recognized by MAb RC38) is markedly enhanced in the vasculature of tumours and wound healing tissue as compared with normal resting tissues. This provides further evidence of the altered state of pericytes in these conditions. Pericyte APA may be involved in the metabolism of biologically active oligopeptides during neovascularization, supporting a regulatory role of pericytes in this process. In addition, MAb RC38 may be useful as a marker of pericyte activation in tissue sections.

Aminopeptidases↗

PubMed1996

Anti-renal-cell carcinoma chimeric antibody G250 facilitates antibody-dependent cellular cytotoxicity with in vitro and in vivo interleukin-2-activated effectors.

Renal cell carcinoma (RCC) is relatively resistant to chemotherapy and radiotherapy, whereas treatment with biologics has achieved limited success. Although monoclonal antibodies able to recognize human RCC have been identified, most induce little complement-dependent cytotoxicity or antibody-dependent cellular cytotoxicity (ADCC), and thus are of limited potential as therapeutic modalities in their natural conformation. We evaluated a human/ mouse chimeric derivative of the previously described G250 murine monoclonal antibody (mAb), reactive with RCC, to identify a reagent for potential immunotherapy. This chimeric antibody (ch-G250) is composed of the murine variable region from the G250 mAb, which recognizes a tumor-associated antigen expressed on 95% of primary and 86% of metastatic renal cell carcinomas. The constant region of the ch-G250 is comprised of the human IgG1 isotype domains. This chimeric antibody does not bind to normal renal tissue or other normal human tissues, with the exception of gastric mucosal cells and large bile-duct epithelium. Clinical radiolocalization studies have demonstrated the relative tumor-targeting potential of this radiolabeled antibody. This ch-G250 antibody facilitated potent ADCC against several RCC lines when using in vitro and in vivo interleukin-2 (IL-2)-activated peripheral blood mononuclear cells obtained from healthy control donors and patients with cancer, respectively. This lymphocyte-mediated ADCC was specific for RCC cells recognized by the ch-G250 antibody. Using flow cytometry, we found that the level of ADCC was directly related to the degree of binding of ch-G250 to the renal cell target. These in vitro data suggest that this antibody may improve efficacy of IL-2 therapy by targeting cytokine-activated effector cells directly to the tumor and facilitating in vivo ADCC. Clinical studies combining this chimeric antibody with IL-2 treatment will be needed to test the antitumor effects of this ADCC effect in vivo.

Animals↗

PubMed1996

Molecular prognostic factor in renal cell carcinoma.

Renal cell carcinoma (RCC) is characterized by an unpredictable clinical course. Therefore, prognostic factors are urgently needed. So far, clinical staging is the most powerful predictor of the progression of RCC. A better understanding of cell biological and molecular changes associated with the development of this disease is urgently needed. Recently, application of a number of these have been tested. Whereas some do not seem to have prognostic value over the available classical prognostic markers, quantitative nuclear morphometric measurement and assessment of cadherin-mediated adhesion complexes (catenin immunohistochemistry) have opened new prospectives.

Biomarkers, Tumor↗