Effects of the pyrimido-pyrimidine derivative RX-RA 85 on metastatic tumor cell-vascular endothelial cell interactions

Abstract

An important step in the metastatic process is the interaction of blood-borne malignant cells with the vascular endothelium. Among the agents that may interfere with this process are pyrimido-pyrimidines, such as RX-RA 85, developed originally as an antiplatelet agent. Using an endothelial cell momolayer attachment assay we have investigated the effects of RX-RA 85 on tumor cell and endothelial cell properties. Exposure of bovine aortic endothelial cells for 3 h to greater than 4 micrograms/ml RX-RA 85 produced toxic effects, resulting in vacuole formation, retraction and finally rounding up of the cells. Endothelial cells derived from different sources behaved dissimilarly; human brain, human meninges, mouse brain, mouse lung and rat lung endothelial cells were less sensitive to drug treatment than bovine aortic endothelial cells. RX-RA 85 treatment of bovine aortic endothelial cells increased B16-F1 melanoma cell adhesion. When B16-F1 cells were exposed to 4-8 micrograms/ml RX-RA 85, increased adhesion to the subendothelial matrix occurred, whereas exposure to higher drug concentrations (8-16 micrograms/ml RX-RA 85) decreased adhesion. Indirect immunofluorescence staining of cytoskeletal structures in B16-F1 cells adhering to and spreading on matrix revealed that the differential effects of RX-RA 85 on the organization of microtubules and microfilaments might explain the dose-dependent differences in adhesion kinetics.

Differential Adhesion of Metastatic Rat Mammary Carcinoma Cells to Organ-Derived Microvessel Endothelial Cells and Subendothelial Matrix

“…We did not find differences in endothelial adhe sive properties when the endothelial cells were grown under various conditions. Al though BAE cells can be modified in their adhesive characteristics by manipulating their cholesterol content [28] or simply by washing the endothelial cell monolayer be fore the assay with buffer [29], we did not observe changes in adhesion in the present study using 13762NF cells.…”

“…Since endothelial cells can change during in vitro growth in their morphology and bio chemistry [27,28], adhesion [28][29][30], ex pression of cell surface glycoproteins [16,17], and extracellular matrix [30], we exam ined the effects of different endothelial cell culture conditions on the adhesion assay. We did not find differences in endothelial adhe sive properties when the endothelial cells were grown under various conditions.…”

Effect of dipyridamole on invasion of five types of malignant cells in organ culture

“…We ignore the molecular basis of these effects. Reportedly, these substances at the same time diminished the number of stress fibers, the organization of microfilaments in the peripheral cell cortex and the extent to which ruffling zones were present [11]. The anti-thrombotic effect of DPD is ascribed to synergistic modification of several biochemical pathways [9]: inhibition of platelet cAMP-phosphodiesterase; potentiation of adenosine inhibition of platelet function by blocking reuptake of adenosine by vascular and blood cells; stimulation of prostacyclin production and potentiation of its antiaggregatory activity.…”

Effects of RA 233 treatment on the adhesive, invasive and metastatic properties of 13762NF rat mammary tumor cells

“…13762NF cells were radiolabeled as described elsewhere [16,24,33] with 0"25 mCi Na[SlCr]O4 (Carrier-free, New England Nuclear, Boston, MA, U.S.A.) per 100mm dish for 3h in DME:F12 containing 5 per cent FBS. In some experiments, tumor cells were incubated for 14-18h with the indicated RA 233 concentrations.…”

“…We have shown that pyrimido-pyrimidines, which can affect growth and cytoskeletal organization of tumor cells [25], interfere with metastatic tumor cellvascular endothelial cell interactions [24] and the growth-promoting activity of epidermal growth factor (EGF) in EGF-responsive tumor cell clones [20]. The pyrimido-pyrimidines, and especially the drug RA 233, have been tested for inhibition of metastasis formation in a number of animal systems with conflicting results [1,14,18,28,40,41].…”