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D J Ruiter

Publications and source records attributed to D J Ruiter.

At least 127 records · Page 7Linked to original sources
PubMed1995

Vascular permeability factor expression influences tumor angiogenesis in human melanoma lines xenografted to nude mice.

We studied the expression of the angiogenic factor vascular permeability factor) (VPF, also called vascular endothelial growth factor), in human melanoma cells in vitro and in vivo. Melanoma lines that develop tumors with a low metastatic potential in nude mice were found to have low expression levels of VPF in vitro, and the VPF expression levels in melanoma lines that yield highly metastatic xenografts were high. However, in vivo the correlation between VPF mRNA levels and the frequency of metastasis was lost; in all xenografts equally high levels of VPF mRNA were found, independent of the parental cell line. Hence, in vivo VPF gene expression was upregulated in the low expressing lines. The external factor responsible for this induction may be hypoxia, given that we found that low oxygen tension caused a (reversible) increase in the VPF mRNA levels in otherwise low expressing melanoma lines in vitro. A melanoma line with an inducible VPF expression was engineered into a line with a constitutive VPF expression. In the xenografts from this line a change in the vascular architecture was seen, indicating that the pattern or the level of VPF expression is important for tumor angiogenesis in melanoma xenografts.

Alternative Splicing↗
PubMed1995

Role of integrins as signal transducing cell adhesion molecules in human cutaneous melanoma.

Tumour progression involves a series of sequential steps leading to metastasis. For several of these steps, tumour cells must be equipped with the appropriate adhesive phenotype. Contact with adjacent cells in the primary tumour must be reduced, and invasion and metastasis require adhesive interactions with ECM components. A group of adhesion molecules called integrins is involved in many of these interactions. Integrins are heterodimeric transmembrane molecules that link the cell to the cytoskeleton. They mediate adhesion to ECM components and to other cells. They may be present in an active or inactive conformation, and in addition to adhesive events, they transfer signals into the cell inducing changes in gene expression. Both functions implicate integrins in tumour progression, and their role in cancer has been the subject of many studies over the past 5 years. Several studies of human cutaneous melanoma have demonstrated that the expression of integrins correlates with tumour progression in vivo. Furthermore, integrin expression and function in melanoma cell lines have been found to correlate with invasive or metastatic potential. Finally, evidence from experimental studies in vitro and in vivo shows that integrins have a role in melanoma tumorigenesis, invasion, angiogenesis and metastasis. Integrins might be used as prognostic markers for clinical outcome and they may be useful therapeutic targets in melanoma.

Amino Acid Sequence↗
PubMed1994

Covalent dimerization of vascular permeability factor/vascular endothelial growth factor is essential for its biological activity. Evidence from Cys to Ser mutations.

Vascular permeability factor, or vascular endothelial growth factor (VPF/VEGF) is an important factor in the regulation of vascular growth and vascular permeability. VPF is a secreted, dimeric protein and has 8 cysteine residues conserved with platelet-derived growth factor (PDGF). To study the role of some of these cysteine residues in maintaining the structure and function of VPF, we replaced the codons for the second, third, fourth, and fifth cysteine by serine codons, and expressed the mutant proteins in a mammalian expression system. Cysteine residues 2 and 4 in VPF were found to be directly involved in anti-parallel interchain disulfide bonds, as in PDGF. VPF mutants lacking one of these cysteins were severely impaired in their S-linked dimerization, while upon coexpression of both mutants the ability to form dimers was restored. The VPF mutants lacking cysteine residue 2 or 4 also competed poorly for receptor binding of labeled VPF and had low biological activity, but these defects were also complemented by coexpressing the two mutants, indicating that for efficient receptor binding and activation VPF needs to be a covalent dimer, unlike PDGF-BB. Furthermore, cysteine residue 5 was found to be essential for VPF dimerization and activity, while the mutant lacking cysteine residue 3 was only mildly affected in its ability to dimerize and had partial biological activity.

Binding, Competitive↗
PubMed1994

DNA in situ hybridization as a diagnostic tool in the discrimination of melanoma and Spitz naevus.

As the clinical and histological differential diagnosis between Spitz naevus and cutaneous melanoma may be very difficult, we have investigated whether DNA in situ hybridization maybe helpful in resolving this problem. To this end, routinely-processed paraffin sections of 15 typical Spitz naevi, 15 typical nodular melanomas, and five cases originally misdiagnosed as Spitz naevi but which later metastasized and were reclassified as melanoma were analysed using a method previously described (De Wit et al., J Invest Dermatol 1992; 98: 450-458). Microscopical semi-quantitative evaluation revealed that the number of nuclei with supernumerary aberrations of the centromere region of chromosome 1, suggestive of aneuploidy, was significantly different in Spitz naevi and nodular melanoma. The mean number of aberrant nuclei per high power field was 0.41 and 4.01, respectively (P = 0.0001). On applying the results of the typical lesions to the equivocal, originally misdiagnosed lesions, three out of five could be identified as melanoma. These results suggest that the application of DNA in situ hybridization may contribute to the positive identification of histologically equivocal pigmented lesions. The advantages of this technique are that it is cheap, requires little tissue, and can be applied on routinely-processed paraffin sections.

Adolescent↗
PubMed1994

Intratumoral PEG-interleukin-2 therapy in patients with locoregionally recurrent head and neck squamous-cell carcinoma.

BACKGROUND: An enhanced efficacy of local as compared to systemic administration of interleukin-2 (IL-2) has been demonstrated in several experimental tumors. We previously reported that guinea pigs with palpable tumors and regional micrometastases could be cured by intratumoral injections of polyethylene glycol-modified IL-2 (PEG-IL-2). In the present study this treatment schedule was applied in a clinical situation. PATIENTS AND METHODS: Nineteen patients with 11 local and 11 regional recurrences of head and neck squamous cell carcinoma (HNSCC) were treated with intratumoral injections of 200,000 U of PEG-IL-2 3 times weekly in courses of 4 weeks. RESULTS: Treatment was given on an out-patient basis, and was well tolerated. Temporary regional swelling and redness developed in 10 patients, and in 9 of them systemic eosinophilia was documented. Median duration of treatment was 4 weeks (range 2-14 weeks). Seventeen patients were evaluable for response. One complete response (CR; 6%; duration 91 weeks), and 6 stable diseases (SDs; duration 8-57+ weeks) were recorded. The CR and the 3 best SDs (23, 40, 57+ weeks) occurred in patients with a single regional tumor recurrence of relatively small size. During treatment, all 4 developed locoregional edema and redness, and high levels of circulating eosinophils. Median survival was 23 weeks for all patients, and 45+ weeks for the patients with SD. CONCLUSION: Intratumoral injection of PEG-IL-2 in patients with HNSCC is feasible. This treatment appears beneficial for highly selected patients. The objective response rate is insufficient to justify wide clinical application.

Aged↗
PubMed1994

Swimming and the risk of cutaneous melanoma.

Recreational exposure to the sun may not explain fully current trends in melanoma incidence. The hypothesis was examined whether carcinogens in water play a role in the development of cutaneous melanoma. In a case-control study, 128 melanoma patients and 168 patients with other types of malignancy completed a detailed questionnaire on aquatic leisure time activities. All relative risk estimates were adjusted for age, gender, educational level, pigmentation characteristics, and exposure to sun habits. Regular swimming during the summer months in swimming pools and in open waters such as rivers and seas before the age of 15 years, was associated with odds ratios of 2.20 (95% confidence interval (CI), 1.05-4.62) and 2.41 (95% CI, 1.04-5.58), respectively, compared with no swimming at all or swimming in relatively unpolluted waters, such as lakes and fens. Melanoma patients learned to swim at a younger age; compared with those who never learned to swim or who learned to swim after the age of 12 years, the odds ratio was 1.87 (95% CI, 0.91-3.78) for those who learned to swim at ages 9-12 years, and 2.22 (95% CI, 1.16-4.26) for those who learned to swim before 9 years of age. Compared with persons who had no swimming certificates, an odds ratio of 1.25 (95% CI, 0.71-2.23) was found for persons with one or two certificates, and an odds ratio of 2.96 (95% CI, 1.25-6.96) for persons with three or more certificates. The positive association between a history of swimming and melanoma risk suggests that carcinogenic agents in water, possibly chlorination by products, play a role in melanoma aetiology.

Adolescent↗
PubMed1994

Anti-endothelial cell antibodies in sera of patients with autoimmune diseases: comparison between ELISA and FACS analysis.

In some patients suffering from rheumatoid arthritis (RA), vasculitis is a clear clinical manifestation, mentioned as rheumatoid vasculitis (RV). Autoantibodies directed against endothelial cells (AEA) have been implicated in the pathogenesis of this disorder, and it has been suggested in a number of studies that testing for AEA should be included in diagnosing RV. To test this hypothesis, we have evaluated the presence of AEA in sera of patients suffering from various autoimmune diseases, employing an ELISA with fixed cultured endothelial cells (EC). In all the groups of patients ELISA-positive sera were present. A significant difference in percentage of positivity was found between the RA and RV group (P < 0.05). In addition, our results indicated that not only antibodies directed against antigens on the EC membrane were detected, but also antibodies directed against intracellular components like DNA, histones and cytoskeletal components. Therefore, we also tested all these patient sera on unfixed intact EC using indirect immunofluorescence followed by FACS analysis. Whereas in the total patient population 34 out of 65 patients were AEA-positive as determined in the ELISA, only seven patients were weakly positive when examined by flow cytometry. We conclude that: (i) an ELISA on fixed EC does not specifically detect AEA. A positive test result is, however, to some extent correlated with the occurrence of vasculitis, and may therefore be helpful in diagnosing this disease; (ii) FACS analysis is a more suitable method than ELISA to measure the presence of membrane-specific AEA in patient sera; (iii) specific IgG-AEA are less common in patients suffering from autoimmune disorders than was assumed previously.

Adult↗
PubMed1994

Emergence of alpha 5 beta 1 fibronectin- and alpha v beta 3 vitronectin-receptor expression in melanocytic tumour progression.

Cell adhesion is crucial in the process of tumour progression. As integrins are important receptor molecules involved in cell adhesion, we studied the distribution of the alpha 1-6, alpha v, alpha IIb, beta 1, beta 3, and beta 4 integrin subunits in tissue sections of common naevocellular naevi (n = 22), dysplastic naevi (16), thin (24) and thick primary cutaneous melanomas (28), and melanoma metastases (25). We found correlated expression of alpha 1/alpha 2, of alpha 4/alpha 5/beta 3, and of alpha 6/beta 4. Decrease of alpha 6 and beta 4, and increase of alpha 4 and alpha v were found to be correlated with melanoma progression. Furthermore, expression of alpha 5 and beta 3 was detected only in primary melanoma and melanoma metastasis. Our findings indicate that during melanoma progression alterations in integrin expression occur, the most striking being emergence of alpha 5 beta 1 fibronectin and alpha v beta 3 vitonectin receptor.

Biopsy↗
PubMed1994

Quantitative immunohistological analysis of the microvasculature in untreated human glioblastoma multiforme. Computer-assisted image analysis of whole-tumor sections.

Because histologically prominent microvascular proliferation is frequently present in glioblastoma multiforme, it has been hypothesized that this neoplasm is particularly dependent on neovascularization for its continued growth and that antiangiogenic therapy might be especially useful. To quantify the histological aspects of microvascular proliferation in glioma, a feasible and reproducible method was developed for computer-assisted image analysis of the visualized microvasculature in glial tissue. This method was used to compare several vascular parameters in histological whole-tumor sections of untreated human glioblastoma multiforme with those in histologically normal cerebral cortex and white matter. There was a significant increase in mean number, area, and perimeter of blood vessels per microscopic field in glioblastoma multiforme compared to normal cerebral white matter. In a substantial number of tumor fields, however, the vascular density was in the same range as that of normal cerebral white matter. The striking heterogeneity of the microvasculature within glioblastoma multiforme was illustrated by the significantly higher standard deviation for the vascular parameters in tumor tissue. The results of this study suggest that many regions of glioblastomas multiforme are not overtly angiogenesis dependent and may be difficult to treat by antiangiogenic therapy alone.

Adult↗
PubMed1994

Studies on functional and structural role of urokinase receptor and other components of the plasminogen activation system in malignancy.

Using immunohistochemistry and in-situ hybridization, we studied the expression of the components of the plasminogen activation system during progression to malignant melanoma with fresh melanocytic lesions. Expression of these components is confined to late stages of melanoma. t-PA expression is limited to rare cases of metastatic melanoma. The other components are frequently expressed concomitantly in the same tumour. Urokinase (u-PA) is expressed in stromal cells and only in tumour cells at invasive foci, urokinase receptor (u-PAR) in tumour cells, plasminogen activator inhibitor type I (PAI-1) in the intratumoral extracellular matrix and plasminogen activator inhibitor type II (PAI-2) in tumour cells and stromal cells. In order to investigate the role of u-PAR as a prognostic marker, we have developed an assay for quantitation of the receptor. As a first step towards structural investigations, we have determined the disulfide cross-links of the first domain of uPAR.

Biomarkers, Tumor↗
PubMed1994

Accumulation of intercellular adhesion molecule-1 in senile plaques in brain tissue of patients with Alzheimer's disease.

The still unsolved pathogenesis of Alzheimer's disease (AD) has been the subject of extensive speculation. Some years ago, a local acute phase reaction involving production of interleukin-1 (IL-1) and IL-6 was proposed as the triggering event in AD. Since it has been reported that these cytokines induce expression of intercellular adhesion molecule-1 (ICAM-1), we analyzed AD brain tissue cryosections for the presence of ICAM-1 by immunostaining and for ICAM-2 expression as a control. In senile plaques a marked diffuse or granular staining for the ICAM-1 domains 1, 4, and 5 was observed, whereas ICAM-2 expression was observed in microglial cells. Immunoprecipitation analysis demonstrated the presence of a 85 kd ICAM-1 molecule in AD frontal cortex. Our findings indicate that ICAM-1 accumulates in senile plaques as a complete 5-domain molecule at a relatively early stage of senile plaque formation. Our results are in support of a cytokine-mediated pathogenesis of senile plaque formation.

Adolescent↗
PubMed1994

Measurement of tissue factor messenger RNA levels in human endothelial cells by a quantitative RT-PCR assay.

We have developed a sensitive and quantitative RT-PCR assay for the determination of tissue factor (TF) mRNA levels in human cells. An in vitro synthesized internal standard RNA was used to correct for differences in reverse transcription or amplification of various RNA samples. The PCR products were quantitated by hybridization. The sensitivity was such that less than 0.2 microgram of total endothelial RNA sufficed to measure its TF mRNA content. The RT-PCR assay was used to determine TF mRNA levels in endothelial cells treated with a factor from human melanoma cells and/or TNF. In this way the amount of TF mRNA could be induced to a level that was at least 80-fold higher than that in non-induced cells. This increase was in the same order of magnitude as the induction of measured TF activity.

Base Sequence↗
PubMed1994

Plasminogen activators, their inhibitors, and urokinase receptor emerge in late stages of melanocytic tumor progression.

Degradation of the extracellular matrix and other tissue barriers by proteases like plasminogen activators (PAs) is a prerequisite for neoplastic growth and metastasis. Recently, we reported that highly metastatic behavior of human melanoma cells in nude mice correlates with urokinase-type PA (u-PA) expression and activity and with PA inhibitor type 1 and 2 (PAI-1, PAI-2) expression. Here we report on the occurrence of components of the PA system in the various stages of human melanoma tumor progression in situ. We studied the protein distribution on freshly frozen lesions of common nevocellular nevi (n = 25), dysplastic (= atypical) nevi (n = 16), early primary melanomas (n = 8), advanced primary melanomas (n = 11), and melanoma metastases (n = 17). Tissue-type PA was present in endothelial cells in all lesions, whereas in metastases it could be detected in tumor cells in a minority of the lesions. u-PA, its receptor, PAI-1, and PAI-2 could not be detected in benign and in early stages but appeared frequently in advanced primary melanoma and melanoma metastasis lesions. u-PA was detected in stromal cells and in tumor cells at the invasive front, the u-PA receptor and PAI-2 in tumor cells, and PAI-1 in the extracellular matrix surrounding tumor cells. Localization of the corresponding messenger RNAs and enzyme activities revealed a similar distribution. We conclude that plasminogen activation is a late event in melanoma tumor progression.

Dysplastic Nevus Syndrome↗
PubMed1994

Induction of alpha-smooth muscle actin expression in cultured human brain pericytes by transforming growth factor-beta 1.

Pericytes are cells localized at the abluminal side of the microvascular endothelium and completely enveloped by a basement membrane. Pericytes have close contact with endothelial cells and are probably involved in the regulation of endothelial cell functions. Previous studies suggested a role for pericytes in microvascular proliferation in tumors. To study this cell type, we isolated human brain pericytes from microvessel segments derived from autopsy brain tissue. These cells were characterized in vitro using a panel of monoclonal antibodies. Human brain pericytes were reactive with monoclonal antibodies directed against the high molecular weight-melanoma associated antigen and intercellular adhesion molecule-1, but only a minority of the cells expressed alpha-smooth muscle actin (alpha-SMA, 0 to 10%) or vascular cell adhesion molecule-1 (10 to 50%). In histologically normal human brain microvessels in situ, pericytes consistently lacked staining for these four markers. Tissue with microvascular proliferation, however, showed a marked pericyte staining for both alpha-SMA and high molecular weight-melanoma associated antigen. The expression of alpha-SMA in vitro could be slightly up-regulated by incubation with serum-containing medium. An increase in alpha-SMA expression up to 40% of the total cell population was seen when pericytes were treated with transforming growth factor-beta 1, whereas basic fibroblast growth factor slightly inhibited alpha-SMA expression. Incubation with other factors (platelet-derived growth factor-AA, heparin, interferon-gamma, tumor necrosis factor-alpha) had no effect on the alpha-SMA expression at all. Transforming growth factor-beta 1 thus induces smooth muscle-like differentiation in pericytes in vitro and might play a role in the activation of pericytes during angiogenesis in vivo.

Actins↗
PubMed1993

Expression of calcyclin in human melanocytic lesions.

When comparing two subsequent stages of melanocytic tumor progression we identified calcyclin as a new potential progression marker, the expression of which was correlated with metastatic behavior of various human melanoma cell lines in nude mice. In this study, we describe a good correlation between RNA and protein levels in the xenografts of these cell lines and extended these experiments to a panel of 120 routinely processed human melanocytic cutaneous lesions. Northern blot analysis demonstrated that calcyclin RNA expression was elevated in melanoma metastases as compared to several types of nevocellular nevi. Calcyclin staining using a specific polyclonal antiserum showed a more complex pattern. A stronger staining in a higher percentage of positive cells was observed in thick primary melanoma (> or = 1.5 mm) as compared to thin primary melanoma (< 1.5 mm). Calcyclin expression was also present in a higher percentage of cells showing a stronger staining in melanomas with higher Clark levels (> II) corresponding to the vertical growth phase of primary melanomas. Protein expression in nevocellular nevi was confined to the dermal part and was highest in the lower parts of the dermis. Remarkably, dysplastic nevi (atypical moles), potential precursors of melanoma, did not show any expression at all, either in junctional or dermal parts. Confinement of the expression to the dermal part of nondysplastic nevi and primary melanomas may reflect interactions with the microenvironment of the reticular dermis that occurs with vertical growth.

Amino Acid Sequence↗
PubMed1993

E-cadherin expression in head and neck squamous-cell carcinoma is associated with clinical outcome.

The cell-cell adhesion molecule E-cadherin has been shown to suppress invasive growth of epithelial cells in vitro, and loss of its expression is thought to be important in invasion and metastatic potential of epithelial tumors in vivo. We retrospectively studied the level of E-cadherin expression in 50 primary head and neck squamous-cell carcinomas (HNSCC) by immunohistochemical methods, on frozen sections, using anti-E-cadherin monoclonal antibody (MAb) 6F9. It concerned patients with different stages of carcinoma of larynx or oral cavity who had been treated with curative intention 30 months or more before. Percentages of membranous stained tumor cells were scored in 1 of 5 categories. Scores were generally low, as in 11/50 lesions < or = 5% cells were stained, and in 19/50 lesions only 6-25% cells showed membranous staining. In 9 lymph-node metastases evaluated, E-cadherin expression was in the same range as in the primary tumors. There was a significant correlation between the level of membranous E-cadherin expression in the primary tumor and the degree of differentiation. No relation was found with tumor size (pT) or regional lymph-node classification (pN). Nevertheless, 29 patients surviving > or = 30 months without evidence of disease had significantly higher levels of membranous E-cadherin expression in their primary tumors than 10 patients with unfavorable clinical course clearly related to recurrent and/or metastatic HNSCC. Moreover, this could only partially be explained by distinctions in differentiation grade between both groups. Our results suggest that membranous E-cadherin expression has prognostic importance in patients with HNSCC.

Adult↗
PubMed1993

Regulation of integrin-mediated adhesion to laminin and collagen in human melanocytes and in non-metastatic and highly metastatic human melanoma cells.

We compared integrin-mediated adhesion to extracellular matrix (ECM) components of cultured human melanocytes and 6 human melanoma cell lines with different metastatic capacities in nude mice. Cultured melanocytes and most melanoma cell lines adhered strongly to fibronectin (FN), whereas only highly metastatic cell lines adhered to laminin (LM), collagen type I (COI) and type IV (COIV). Adhesion to LM and CO could be blocked by anti-alpha 6 and anti-alpha 2 monoclonal antibodies (MAbs) respectively. This observation is consistent with the finding that expression of LM receptor alpha 6 beta 1 and LM/CO receptor alpha 2 beta 1 was low on melanocytes and non- or poorly metastatic cell lines, whereas these integrins were strongly expressed on highly metastatic cell lines. In addition, immunoprecipitation from [35S]-methionine-labeled cells demonstrated increased synthesis of alpha 6, alpha 2 and beta 1 in highly metastatic cell lines and immunohistochemistry showed expression of alpha 6 beta 1 and alpha 2 beta 1 only in xenograft lesions from highly metastatic cell lines. Furthermore, the observation that adhesion of melanocytes and non- or poorly metastatic cell lines could be stimulated with anti beta 1 MAbs demonstrates that these receptors, on these cells, are expressed in an inactive state. Our results suggest that alpha 2 beta 1 and alpha 6 beta 1 play a role in human melanoma metastasis in nude mice and demonstrate that interactions of these integrins with their ligands can be regulated at the level of surface expression and activation state of the receptor.

Animals↗