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D J Ruiter

Publications and source records attributed to D J Ruiter.

At least 109 records · Page 6Linked to original sources
PubMed1996

Relevance of ultraviolet-induced N-ras oncogene point mutations in development of primary human cutaneous melanoma.

Intermittent or recreational exposure to sunlight is thought to contribute to development of human cutaneous melanoma. We investigated the incidence of ras oncogene mutation in human cutaneous melanoma in connection to sun-exposed body sites in the patient, using a large series of DNA samples derived from paraffin-embedded material as well as from fresh tumor samples and cell lines. We first show that, of the ras family, predominantly N-ras is activated (15%), whereas rarely H-ras or K-ras are mutated. The occurrence of N-ras mutations correlates with continuous exposure to sunlight of the primary tumor site. Of all tumors initiated on chronically sun-exposed body sites, 26% contained mutated N-ras, in contrast to 0% of sun-protected melanomas. Melanoma lesions obtained from patients from North or Central Europe contained fewer N-ras mutations (12%) as compared with patients from Australia (24%). Mutations were specifically associated with nodular melanoma and to a lesser extent with lentigo malignant melanoma. N-ras mutations did not correlate with metastasis or survival parameters. This study identifies a subset of cutaneous melanomas that contain in the primary lesion ultraviolet-induced N-ras mutations, which are maintained through further progression.

Base Sequence↗
PubMed1995

Requirement for the synergy site for cell adhesion to fibronectin depends on the activation state of integrin alpha 5 beta 1.

We investigated the influence of the activation state of integrin alpha 5 beta 1 on its dependence on the PHSRN synergy site for binding to RGD in fibronectin. K562 and MV3 cells lacked alpha v beta 3 expression and adhered to fibronectin through alpha 5 beta 1. Mel57 cells adhered through alpha v beta 3 and alpha 5 beta 1. A recombinant fibronectin polypeptide, containing five type III repeats from the central cell binding domain 3Fn6-10, and a mutated polypeptide lacking the synergy site were equally effective in promoting Mel57 adhesion. For K562 and MV3, the mutated polypeptide was not or poorly active compared to the control polypeptide. Expression of alpha v beta 3 in MV3 induced strong adhesion to the mutated polypeptide. TS2/16 stimulatory beta 1-integrin antibodies or Mn2+ induced alpha 5 beta 1-mediated adhesion of K562 and MV3 to GRGDSP. In the presence of TS2/16 or Mn2+, alpha 5 beta 1-mediated MV3 adhesion to the mutated polypeptide was equally strong as adhesion to the control polypeptide. Mn2+ or TS2/16 induced weak K562 binding to the mutated polypeptide, and in the presence of a combination of phorbol 12-myristate 13-acetate, Mn2+, and TS2/16, alpha 5 beta 1-mediated K562 adhesion to the mutated and control polypeptide was equally strong. Our findings demonstrate that requirement for the PHSRN synergy site for alpha 5 beta 1-mediated adhesion to RGD in fibronectin depends on the activation state of the integrin.

Amino Acid Sequence↗
PubMed1995

Expression of CD44 splice variants in human cutaneous melanoma and melanoma cell lines is related to tumor progression and metastatic potential.

Expression of CD44, particularly of certain splice variants, has been linked to tumor progression and metastasis formation in a number of different animal and human cancers. Because human cutaneous melanoma is among the most aggressive human cancers, we explored expression of CD44 isoforms (CD44v) in lesions of melanocytic tumor progression. In addition, by RT-PCR and FACS analysis we assessed CD44v RNA species and cell surface expression of CD44v in cultured melanocytes isolated from human foreskin and in a panel of 2 non-, 2 sporadically and 2 highly metastatic human melanoma cell lines. We observed that all melanocytic lesions examined showed strong uniform expression of standard CD44 (CD44s) epitopes. We did not detect CD44v6 expression in the melanocytic lesions. However, CD44 isoforms containing v5 or v10 were differentially expressed. V5 was expressed in 16%, 0%, 20%, 67% and 58% of common nevi, atypical nevi, early primary melanomas (< or = 1.5 mm), advanced primary melanomas (> 1.5 mm) and metastases, respectively, and hence was related to tumor progression. In contrast, CD44v10 was expressed in all common nevi, whereas part of the atypical nevi and most primary melanomas and metastases lacked v10. CD44v RNA patterns were closely similar in cultured melanocytes and all melanoma cell lines. Melanocytes expressed high levels of CD44s but no CD44v, whereas all melanoma cell lines expressed CD44v at the surface. Interestingly, expression of v5 was strongly increased in the highly metastatic cell lines. Our results suggest a role for CD44 variant domains, particularly v5 and v10, in human melanocytic tumor progression.

Base Sequence↗
PubMed1995

T lymphocyte adhesion to human brain pericytes is mediated via very late antigen-4/vascular cell adhesion molecule-1 interactions.

T cell adhesion to the brain microvascular endothelium and subsequent migration into the brain parenchyma is one of the major events in the development of multiple sclerosis (MS). Interactions of the T cell integrin very late antigen-4 (VLA-4) with its receptor, vascular cell adhesion molecule-1 (VCAM-1) have been described to be of crucial importance for the development of MS. We investigated the expression of these adhesion molecules in MS brain tissue by immunohistochemical analysis, and studied their functional involvement in an in vitro T cell adhesion assay. A number of other adhesion molecules were studied for comparison. In cryosections of several MS brains, expression of VCAM-1 was demonstrated not only on the endothelium of vessels surrounding MS plaques, but also in perivascular positions, suggesting expression by pericytes. T cells adhered to both cell types in vitro. Both LFA-1/intercellular adhesion molecule-1 and VLA-4/VCAM-1 interactions were equally involved in the adhesion of T cells to TNF-alpha-stimulated endothelial cells. However, adhesion of T cells to TNF-alpha-stimulated pericytes was clearly dominated by VLA-4/VCAM-1 interactions. These results indicate that pericytes, next to endothelial cells, may play an important role in regulating T cell infiltration into the central nervous system.

Brain↗
PubMed1995

Alpha v-integrins in human melanoma: gain of alpha v beta 3 and loss of alpha v beta 5 are related to tumor progression in situ but not to metastatic capacity of cell lines in nude mice.

We investigated the expression of alpha v-integrins in different stages of human cutaneous melanocytic tumor progression. We observed that alpha v beta 5 was the alpha v-integrin expressed in all common nevocellular nevi, in 78% of dysplastic nevi, in 63% of early primary melanomas, in 43% of advanced primary melanomas, and in 33% of melanoma metastases. Hence, loss of alpha v beta 5 expression was related to melanocytic tumor progression. In line with earlier reports, alpha v beta 3 was exclusively detected in advanced primary melanomas and metastases (24% and 50% respectively). Staining with anti-alpha v monoclonal antibodies (MAbs) in lesions where both alpha v beta 3 and alpha v beta 5 were absent showed that alternative alpha v-integrins were expressed in advanced primary melanomas and metastases. By FACS analysis, we determined expression of alpha v beta 5 and alpha v beta 3 in 4 human melanoma cell lines with different metastatic capacities after s.c. inoculation into nude mice. One of the non-metastatic and both highly metastatic cell lines expressed alpha v beta 5 at their surface. Surprisingly, alpha v beta 3 was detected exclusively in the non-metastatic cell lines. Absence of alpha v beta 3 in the highly metastatic cell lines was confirmed by lack of immunoprecipitation from 35S-methionine-labeled cells and by absence of immunohistochemical staining on primary and metastatic xenograft lesions. Our findings indicate that alpha v beta 5 expression is often lost in advanced stages of melanocytic tumor progression in situ, while alpha v beta 3 is acquired, but that a decrease in alpha v beta 5 and an increase in alpha v beta 3 expression are not necessarily related to the metastatic behavior of human melanoma cells in nude mice.

Animals↗
PubMed1995

Glycoconjugate profile and CD44 expression in human melanoma cell lines with different metastatic capacity.

Changes in glycoconjugate production have been reported for tumor cells. In this study, we investigated the glycoconjugate expression pattern in normal human melanocytes and in a panel of 6 human melanoma cell lines with different metastatic capacity after s.c. inoculation into nude mice. Glycoconjugates were labeled in vitro with [35S] sulphate and [3H] glucosamine, purified from cells and culture medium by column chromatography and identified by treatment with specific glycosidases. Characterization of the purified glycoconjugate fractions as well as alcian-blue staining of xenograft lesions revealed that hyaluronic acid (HA) is the main glycoconjugate produced by all cell lines. Highly metastatic cell lines expressed higher levels of HA than melanocytes and than weakly metastatic or non-metastatic cell lines. In addition, a shift in dominance from chondroitin-sulphate proteoglycan to heparan-sulphate proteoglycan was observed with increasing metastatic capacity. We also studied the expression and binding activity of the HA receptor CD44. Immunoprecipitation experiments indicated high CD44 synthesis only in highly metastatic cell lines, but FACS analysis demonstrated approximately the same surface expression in melanocytes as in all cell lines. Adhesion assays to immobilized HA showed that CD44 can be present in an inactive or an active conformation. Our data suggest that a combination of increased HA production and the expression of CD44 on the cell surface may be associated with high metastatic potential of human melanoma cell lines in nude mice.

Animals↗
PubMed1995

Components of the plasminogen activation system in uveal melanoma--a clinico-pathological study.

In tumour development, proteases such as plasminogen activators (PAs) play a role in degradation of the extracellular matrix and other tissue barriers. Recently, we demonstrated that plasminogen activators, their inhibitors, and urokinase receptor emerge in late stages of cutaneous melanocytic tumour progression. In this study we investigated the expression and distribution of the various components of the PA system and the presence of PA enzyme activity in 45 freshly frozen primary uveal melanoma with known follow-up (14 spindle and 31 non-spindle type) and in metastases (n = 5). Tissue-type PA (t-PA) was found in endothelium of blood vessels and in tumour cells in almost all lesions, and was markedly present at the invasive front (towards the sclera and Bruch's membrane), but no correlation with tumour-related death could be established. Urokinase PA (u-PA) was expressed focally, by only five non-spindle cell melanomas but in all metastases. u-PA expression correlated with occurrence of metastasis. u-PA receptor (u-PAR) was present in one-third of all the tumours examined. Plasminogen activator inhibitors (PAI-1 and PAI-2) were found only focally in approximately 10 per cent of the lesions. Staining of t-PA, u-PA, and PAI was observed in all the metastases. We conclude that in uveal melanoma, u-PA expression may be associated with metastatic disease and accordingly with a poor prognosis. Further research on a larger group of tumours with known follow-up is needed to establish whether u-PA positivity is of additional prognostic value in uveal melanoma.

Biomarkers, Tumor↗
PubMed1995

VWF release and platelet aggregation in human melanoma after perfusion with TNF alpha.

Twenty-nine stage IIIA/B melanoma patients treated by isolated limb perfusion (ILP) with a high dose of recombinant human tumour necrosis factor alpha (rHuTNF alpha), interferon gamma (IFN gamma), and melphalan were histologically documented with emphasis on therapy-induced changes of the tumour vasculature. Sequential biopsies were taken at various intervals before and after the treatment to compare the morphological change. In order to visualize microvascular changes, immunostaining was performed for von Willebrand factor (VWF), type IV collagen, alpha-smooth muscle actin, endothelial antigen PAL-E, tissue factor, CD41 (thrombocyte marker), and fibrin. In biopsies prior to perfusion, necrosis, haemorrhage, and fibrin thrombi were not found. Within 3 h following triple combination therapy, a change in the distribution of VWF staining occurred, from a discrete endothelial pattern in the untreated lesions to a fuzzy perivascular and subepidermal pattern in the treated lesions. Within 24 h, this was accompanied by intravascular thrombocyte aggregation and erythrostasis, in the absence of tissue factor and fibrin deposits. These findings indicate that the thrombocyte aggregation observed is not caused by local procoagulant activity, but is rather the result of the therapy-associated vascular damage or haemostasis. Although it is difficult to derive the dynamics of this process from static images, we assume that TNF alpha induced endothelial cell damage, leading to VWF release. Release VWF may play a role in the adhesion between thrombocytes and the damaged endothelium or the denuded subendothelium. As a consequence, the blood flow is impaired, leading to congestion and oedema, compatible with an early stage of haemorrhagic infarction.

Chemotherapy, Cancer, Regional Perfusion↗
PubMed1995

Analysis of N-ras mutations in human cutaneous melanoma: tumor heterogeneity detected by polymerase chain reaction/single-stranded conformation polymorphism analysis.

Determination of the activation state of oncogenes as well as tumor suppressor genes is a main subject of interest in the analysis of the mechanism of tumor initiation. In human melanoma, the c-myc and N-ras oncogenes have been found to be activated in approximately 50% and 15% of the analyzed material, respectively. These studies have mostly been done on fresh tumor material or cell lines. Only in a few cases has an attempt been made to look at tumor heterogeneity or clonality with respect to the activation of oncogenes. We have adjusted the polymerase chain reaction (PCR)/single-stranded conformation polymorphism analysis (SSCP) technique to screen paraffin-embedded melanoma material for the presence of N-ras mutations and found genetic defects at particular progression stages. In one melanoma of the skin, we were able to sublocalize an N-ras mutation in the intraepidermal tumor part, that was absent in the part deeply invading the dermal layer. We conclude that a thorough investigation of N-ras activation in human melanoma should include analysis of histologically different parts of the tumor.

Base Sequence↗
PubMed1995

Properties of metastasizing and nonmetastasizing human melanoma cells.

Dissemination of tumor cells includes several steps, such as: (a) detachment of tumor cells from the primary tumor, (b) traversement of the basement membrane, and (c) migration into the extracellular matrix. In these processes, at least two important categories of proteins are involved: proteases and adhesion molecules. In this contribution we describe the expression and function of components of the plasminogen activator (PA) system (proteases) and of integrins (cell-matrix adhesion molecules) in a panel of four human melanoma cell lines with different invasive and metastatic capacity. Regarding the components of the PA system, we found differences in expression of urokinase-type PA (uPA) and type 1 and 2 PA inhibitors (PAI-1 and -2) between metastasizing and nonmetastasizing cell lines. Both components were exclusively expressed in the highly invasive and metastatic cell lines. Interestingly, studies on the expression of PA components in fresh human melanocytic lesions, showed expression of these components exclusively in advanced primary melanomas and melanoma metastases. Regarding integrin expression we found elevated levels of VLA-2 and VLA-6 in the highly invasive and metastatic cell lines compared with normal cultured melanocytes and nonmetastatic melanoma cell lines. In addition, increased adhesion of the highly metastatic cell lines to laminin (LM) and collagen (COLL) was observed. Furthermore, reduced adhesion of normal melanocytes and nonmetastatic melanoma cells to LM and CO was mainly due to the fact that the integrins involved in adhesion to these matrix components were present in an inactive state. Finally, differences were observed in expression of integrins involved in adhesion to fibronectin.

Amino Acid Sequence↗
PubMed1995

A lysosomal marker for activated microglial cells involved in Alzheimer classic senile plaques.

One of the major histopathological lesions in brains of patients with dementia of the Alzheimer type (DAT) is the senile plaque. Although previous studies have shown that senile plaques are often accompanied by microglial cells, the role of these cells in DAT pathology is still unclear. In an immunohistochemical and immunoelectron microscopical analysis of DAT and control brain tissues we addressed this issue using two monoclonal antibodies (mAbs KP1 and 25F9) directed against lysosomal antigens in monocytes and macrophages. Whereas KP1 stained lysosomes in both resting and activated microglial cells, 25F9-staining was predominantly found in lysosomes of activated microglial cells in classic senile plaques. The number and size of 25F9-positive lysosomes in activated microglial cells was increased compared to 25F9-staining in unaffected areas in DAT and control sections. We conclude that mAb 25F9 is a unique and useful lysosomal marker, with a higher specificity than other known markers, for activated microglial cells associated with classic, but not with diffuse, senile plaques.

Aged↗
PubMed1995

An addition to the controversy on sunlight exposure and melanoma risk: a meta-analytical approach.

Case control studies on the association between sunlight exposure and melanoma risk show considerable differences in design; this could be responsible for the variation in study results. In an attempt to resolve the controversy between study results, the results of 25 publications on case control studies were evaluated using meta-analytical techniques. Comparison of odds ratios between subgroups of studies revealed that the range of odds ratios was far greater for hospital-based studies than for population-based studies. For the latter type of studies, the odds ratios were homogeneous and the pooled odds ratios were 1.57 (95% confidence interval [CI], 1.29-1.91) for intermittent sunlight exposure and 0.73 (95% CI, 0.60-0.89) for chronic exposure. However, among other problems, the lack of standardized measures for sunlight exposure warrants cautious interpretation of these results. It is concluded that evidence to support the intermittent sunlight theory is still far from complete.

Case-Control Studies↗
PubMed1995

Expression of endoglin in psoriatic involved and uninvolved skin.

Endoglin is a glycoprotein with TGF-beta binding capacity and is predominantly expressed on endothelial cells. In psoriasis, TGF-beta has appeared to play a role in the extravasation of peripheral blood mononuclear cells via the endothelium. In order to find out more about the role of endoglin in psoriasis, immunohistochemical staining with PN-E2, a novel anti-endoglin, and of PAL-E, recognizing vascular endothelium, was carried out in psoriatic involved, psoriatic uninvolved and normal skin. The expression of the antigens was assessed semi-quantitatively using a five-point scale. In psoriatic involved skin, a high endoglin expression was found. In psoriatic uninvolved skin, however, we found that endoglin expression was significantly decreased compared with normal skin. The relevance of these findings to the pathogenesis of psoriasis is discussed.

Adolescent↗
PubMed1995

Early and extensive contribution of pericytes/vascular smooth muscle cells to microvascular proliferation in glioblastoma multiforme: an immuno-light and immuno-electron microscopic study.

Although florid microvascular proliferation (MVP) in glioblastoma multiforme (GBM) has long been considered as proliferation of endothelial cells (EC), recent immuno-light microscopic studies demonstrated many alpha-smooth muscle actin (alpha-sm actin)-positive cells in this MVP, suggesting a major contribution of pericytes and/or vascular smooth muscle cells (VSMC). Under certain culture conditions, however, alpha-sm actin expression has also been described in EC. In order to further investigate to what extent pericytes/VSMC participate in MVP in GBM, we performed an immunohistochemical study at both the light and electron microscopic levels with anti-alpha-sm actin, with an antibody against EC (EN-4) and with an antibody recently described to react with "activated" pericytes in conditions with neovascularization (anti-high molecular weight-melanoma associated antigen). In this detailed study of MVP in GBM, two distinct cell types could be recognized on the basis of a consistent ultrastructural localization and immunophenotype: EC and pericytes/VSMC; no transitional forms were found between these two cell types. The contribution of pericytes/VSMC to MVP in GBM was extensive and already present in many delicate tumor capillaries, suggesting not only an essential but also an early role of these cells in this type of tumor angiogenesis.

Antigens, Neoplasm↗
PubMed1995

The role of vascular permeability factor and basic fibroblast growth factor in tumor angiogenesis.

In the last decade a considerable amount of research has been dedicated to studying the process of angiogenesis. In the field of tumor biology angiogenesis is a relevant subject of investigation as well, since newly formed blood vessels are required for the growth of tumors and provide an exit route for metastasizing tumor cells. In this review we discuss some aspects of tumor angiogenesis with emphasis on the role that growth factors bFGF and VPF play in this process. A number of biochemical characteristics and biological properties of the two factors and their receptors are reviewed, and the expression of bFGF and VPF in both normal tissues and in tumors is discussed. Finally, we speculate on the use of bFGF and VPF expression as a diagnostic parameter and on possible clinical applications.

Animals↗