Biomedical subjects

J G Van den Tweel

Publications and source records attributed to J G Van den Tweel.

7 recordsLinked to original sources

PubMed1997

Fibronectin distribution in human bone marrow stroma: matrix assembly and tumor cell adhesion via alpha5 beta1 integrin.

Tumor cell interactions with fibronectin (FN) are important for the development of secondary tumors inside the bone marrow stroma. We studied and compared the in situ distribution of FN in paraffin-embedded human bone marrow sections and investigated the in vitro regulation of FN assemblage by bone marrow stromal cells (BMSC). Finally, the role of FN in the interaction of BMSC with tumor cells was studied. Fine elongated FN-positive cell extensions, probably of stromal cell origin, were observed as well as a limited amount of extracellular FN deposits in connective tissues around capillaries and sinusoids. In vitro studies, using the confocal laser scanning microscope, showed that BMSC produced a high amount of FN with a characteristic extracellular matrix formation in an extensive network. FN matrix formation was predominantly detected at contact sites between cultured BMSC. In in vitro cultures with low cell concentrations and in vivo with a limited number of stromal cell contacts only limited matrix was found. From previous studies it is known that the alpha5 beta1 integrin is involved in the regulation of FN assembly. Here the role of the alpha5-subunit of this integrin was investigated. By using two different monoclonal antibodies (mAb) against the alpha5-subunit (2H6 and mAb16) the assembly of endogenous FN was completely blocked, indicating that these antibodies are directed against the active epitope. Another mAb (mAb11) against the alpha5-subunit did not affect the FN assemblage. Codistribution analysis of alpha5-subunits, alpha v-subunits, actin, and FN demonstrated that the alpha5 beta1 integrin is associated with FN and not with intracellular actin. Integrins alpha(v) beta1, alpha(v) beta3, and alpha(v) beta5, also ligands of FN, did not colocalize with FN. Codistribution of alpha v with the terminal ends of actin and not with FN indicates that alpha(v)-subunits are mainly directed to vitronectin rather than to FN. The dominant role of alpha5 beta1 in FN interaction is underlined by effective blocking of tumor cell adhesion with BMSC using anti-alpha5, anti-beta1, and anti-FN antibodies. These results emphasize the important role of alpha5 integrin subunit in FN matrix assembly in human BMSC and an exclusive role of alpha5 beta1 in the anchorage and regulation of FN-mediated adhesion processes in the bone marrow.

Actins↗

PubMed1996

beta1-Integrins dominate cell traffic of leukemic cells in human bone-marrow stroma.

Migration patterns of leukemic cells in bone marrow are largely regulated by cell contacts between leukemic cells and stromal cells or extra-cellular matrix. The mechanism of this interaction with bone-marrow stromal cells was studied in a human in vitro model. Migration behavior of erythroleukemia cell line K562, derived from a patient with chronic myeloid leukemia, was compared with that of the erythroleukemia cell line HEL92.1.7 and the promyelocytic leukemia cell line HL60 from acute leukemias. Interaction varied between low binding affinity (K562) to intensive cell interaction (HEL92.1.7) followed by invasion into the stromal cell monolayer. Some of the HL60 cells adhered to stromal cells, while the remainder migrated into the stromal cell monolayer. The role of adhesion molecules in these cell interactions was determined. Distinct expression of beta1-integrins ICAM-1, CD44 and VCAM-1 was detected on the different cell lines. Inhibition studies pointed to a dominant role of VLA-4- and VLA-5-mediated interactions. K562 lacked VLA-4 and a low binding affinity of the VLA-5 on these cells resulted in an absence of binding to the bone-marrow stroma. These results indicate the VLA-5/fibronectin, VLA-4/fibronectin and the VLA-4/VCAM-1 interaction pathways between leukemic cells and bone-marrow stroma.

Bone Marrow↗

PubMed1996

Molecular test for the detection of tumor cells in blood and sentinel nodes of melanoma patients.

Lymph node metastasis dramatically decreases the 5-year survival of melanoma patients. The so-called sentinel node surgery offers a therapeutic approach to resect the first draining lymph node. This technique enables accurate staging of melanoma patients in an early stage of the disease. Detection of a sentinel node metastasis is a strong argument for local lymphadenectomy. To improve the detection of micrometastasis in sentinel nodes of melanoma patients, molecular biological techniques were used. The exclusively melanocyte-specific tyrosinase transcript was amplified by reverse transcription followed by polymerase chain reaction (RT-PCR). In sentinel node examination, the detection of tyrosinase-positive cells by RT-PCR was compared with routine immunohistochemistry. From 16 patients, a total of 28 lymph nodes were tested. The lymph nodes were derived after lymphadenectomy (4 patients) and after sentinel node resection (12 patients with melanoma stage I). By using RT-PCR we could detect 100 tumor cells in a background of 10(8) peripheral blood mononuclear cells. The negative controls were all negative for tyrosinase. Cryostat sections of lymph nodes for mRNA isolation were alternated with sections for immunohistochemistry. By using tyrosinase RT-PCR, we detected 6 additional positive sentinel nodes in patients with melanoma stage I. Furthermore, the tyrosinase RT-PCR enabled us to design a blood test for circulating melanoma cells. Therefore, mRNA was directly isolated from whole blood of 23 blood samples, of which 3 samples were positive for tyrosinase. The present study demonstrates the possibility of a simple and rapid blood test for melanoma patients that has not been available until now. Furthermore, the detection of micrometastasis in sentinel nodes by tyrosinase RT-PCR dramatically increases the accuracy of melanoma staging.

Base Sequence↗

PubMed1995

neu overexpression correlates with extent of disease in large cell ductal carcinoma in situ of the breast.

In a retrospective study of ductal carcinoma in situ (DCIS) of the breast, the expression of the neu oncogene was determined immunohistochemically in 76 women treated by local excision or mastectomy. The histopathological features, including the extent of the lesion, histological subtype, cell type, and number of mitoses, were related to neu overexpression. Immunopositivity was found only in DCIS of large cell type, where it correlated with extent of disease but not with mitotic rate. Our findings, together with previous experimental evidence, suggest that this relationship is a consequence of the effect of the neu protein on cell motility.

Breast Neoplasms↗

PubMed1989

Multifocal rhabdomyoma of the neck. Report of a case studied by fine-needle aspiration, light and electron microscopy, histochemistry, and immunohistochemistry.

A 32-year-old Caucasian man presented with a tumor in the right side of the neck. Preoperative fine-needle aspiration showed large multinucleated cells with abundant granular cytoplasm that were consonant with the features of a granular cell tumor. At surgery, two separate tumors were found. Histologically, the tumor proved to be an adult rhabdomyoma, the 11th such multifocal case reported. The striated muscle origin of this benign tumor was confirmed by immunohistochemical and ultrastructural studies. The tumor cells were desmin-, myoglobin-, and actin-positive. They showed variable numbers of thick and thin filaments, as well as hypertrophic Z-band material. Histochemical studies showed the presence of basophilic muscle cells, vesicular nuclei, ragged red fibers, and diffuse acid phosphatase positivity. These features, together with the absence of actual muscle cell proliferation and the assumption that the mass of the tumor could be explained by the enormous swelling of the muscle cells, lead us to conclude that an adult rhabodomyoma is merely the result of a process of disorderly degeneration and regeneration rather than a real neoplasm or a hamartomatous lesion.

Acid Phosphatase↗

PubMed1977

Macrophage-induced thymic lymphocyte maturation.

Guinea-pig peritoneal macrophages were found to influence the functional maturation of thymic lymphocytes. Autologous thymic lymphocytes obtained from macrophage co-cultures responded to three different mitogens and were reduced in their ability to reassociate spontaneously with macrophages. Neither of these properties were found in thymic lymphocytes that had not been cultured with macrophages. These functional changes appeared to be specific for macrophages since thymic lymphocytes incubated with skin fibroblasts failed to respond to the test mitogens. Furthermore, they were not the result of either the inactivation, by macrophages, of a putative suppressor thymocyte or a soluble macrophage product. In addition to influencing the functional maturation of thymic lymphocytes, macrophages also appeared to play a direct role in inducing the mitogen response of functionally mature cells.

Animals↗

PubMed1974

Genetic aspects of canine mixed leukocyte cultures.

Recent data stress the importance of matching donor and recipient of an organ graft for both the serologically defined (SD) and lymphocyte-defined (LD) determinants. To allow experimental evaluation of the effect of these SD and LD structures in a noninbred experimental animal, mixed leukocyte culture tests were performed between SD identical and nonidentical dogs to clarify the LD system in these animals. The results of these experiments can be summarized as follows: (a) In the dog there is a LD locus distinct from the known SD loci, which in all probability is localized outside the first (SD-1) series locus on the chromosome. (b) The crossing-over frequency between the SD and LD loci on the chromosome is low. (c) Studies in SD identical unrelated dogs and random unrelated dogs show an apparent high linkage disequilibrium between SD and LD loci. (d) The LD system in dogs is polymorphic.

Animals↗