cytochalasin-b and Astrocytoma

Brain tumor dispersal far from bulk tumor contributes to and, in some instances, dominates disease progression. Three methods were used to characterize brain tumor cell motility in vivo and in vitro: 1) 2 weeks after implantation in rat cerebral cortex, single C6 cells labeled with a fluorescent tag had migrated to brain sites greater than 16 mm distant from bulk tumor; 2) time-lapse videomicroscopy of human brain tumor cells revealed motility of 12.5 microns/hr. Ruffling leading edges and pseudopod formation were most elaborate in more malignant cells; 3) an in vitro assay was devised to quantitatively evaluate motility from a region of high cell density to one of lower cell density. Human brain tumor cells were plated in the center of a petri dish, washed, and refed, establishing a 2-cm circular zone of cells in the dish center. Motility was determined by counting cells daily at predetermined distances from the central zone perimeter. Cells were found 1 cm from the perimeter by 24 hours and 3 cm from the perimeter by 4 days. Increasing serum concentration increased motility; however, neither fibronectin nor arrest of cells in the G0 phase by hydroxyurea altered motility. The addition of cytochalasin B to block cytoskeletal assembly prevented cell motility. Motility increased with increased malignancy. Subpopulations of cells were created by clonal amplification of cells that had migrated most rapidly to the dish periphery. Although morphologically indistinguishable when compared to the original cell line from which they were derived, these subpopulations demonstrated significantly increased motility.

Topics: Amidines; Animals; Astrocytoma; Brain Neoplasms; Cell Movement; Clone Cells; Cytochalasin B; Fibronectins; Fluorescent Dyes; Glioma; Humans; Hydroxyurea; Image Processing, Computer-Assisted; Interphase; Microscopy, Video; Neoplasm Transplantation; Pseudopodia; Rats; Rats, Sprague-Dawley; Tumor Cells, Cultured

Cell-substratum adhesion strengths have been quantified using fibroblasts and glioma cells binding to two extracellular matrix proteins, fibronectin and tenascin. A centrifugal force-based adhesion assay was used for the adhesive strength measurements, and the corresponding morphology of the adhesions was visualized by interference reflection microscopy. The initial adhesions as measured at 4 degrees C were on the order of 10(-5)dynes/cell and did not involve the cytoskeleton. Adhesion to fibronectin after 15 min at 37 degrees C were more than an order of magnitude stronger; the strengthening response required cytoskeletal involvement. By contrast to the marked strengthening of adhesion to FN, adhesion to TN was unchanged or weakened after 15 min at 37 degrees C. The absolute strength of adhesion achieved varied according to protein and cell type. When a mixed substratum of fibronectin and tenascin was tested, the presence of tenascin was found to reduce the level of the strengthening of cell adhesion normally observed at 37 degrees C on a substratum of fibronectin alone. Parallel analysis of corresponding interference reflection micrographs showed that differences in the area of cell surface within 10-15 nm of the substratum correlated closely with each of the changes in adhesion observed: after incubation for 15 min on fibronectin at 37 degrees C, glioma cells increased their surface area within close contact to the substrate by integral to 125-fold. Cells on tenascin did not increase their surface area of contact. The increased surface area of contact and the inhibitory activity of cytochalasin b suggest that the adhesive "strengthening" in the 15 min after initial binding brings additional adhesion molecules into the adhesive site and couples the actin cytoskeleton to the adhesion complex.

Topics: Animals; Astrocytoma; Cell Adhesion; Cell Adhesion Molecules, Neuronal; Cell Line; Cytochalasin B; Fibroblasts; Fibronectins; Glioma; Humans; Kinetics; Neoplasm Proteins; Tenascin

Tissue culture monolayers of seven human intracranial tumours comprising 2 astrocytomas, 3 meningiomas, 1 secondary squamous cell carcinoma and 1 secondary adenocarcinoma were examined by a double immunofluorescent staining technique to demonstrate Concanavalin A (Con A) surface receptors and cytoplasmic actin in the same cell. Tumour cells, treated with fluoresceinisothiocyanate-labelled Con A (FITC-Con A) showed staining in cell margins or in a random distribution over the cell surface. Incubating the cells with FITC-Con A at 37 degrees for increasing periods of time resulted first in staining of clusters and later of perinuclear globules. Cells, pretreated with 4% paraformaldehyde at 4 degrees for 10 min or with cytochalasin B at 37 degrees for 30 min showed staining restricted to cell margins. In the cytochalasin B-treated cells, the peripheral staining was in the form of coarse clusters. Double fluorochrome studies showed that the anti-actin antibody (AAA) staining occurred in sites closely related to those stained by FITC-Con A both in untreated as well as in cytochalasin B-treated cells. The findings suggest that Con A receptors, as an example of a stable cell membrane determinant in human tumour cells, are associated with actin and that their mobility on the cell surface is dependent on an intact cytoplasmic actin system.

Topics: Actins; Adenocarcinoma; Astrocytoma; Brain Neoplasms; Carcinoma, Squamous Cell; Colchicine; Cytochalasin B; Cytoplasm; Fluorescent Antibody Technique; Humans; In Vitro Techniques; Meningioma; Receptors, Concanavalin A; Receptors, Drug