ABSTRACT
<p><b>OBJECTIVE</b>To observe in vitro changes of endothelial cells after confrontation with tumor cells.</p><p><b>METHODS</b>Dynobeads were used to isolate the endothelial cells from the rat lung. Mouse dendritic cell sarcoma cells (DCS), human gastric carcinoma cells (BGC-823) and mouse lung adenocarcinoma cells (LA795) were added to the endothelial cells when the latter was at the confluence phase. Phase contrast microscope, scanning electro-microscope, immunohistochemistry, transwell and fluorescence dye transfer were used to detect morphological and functional changes of the endothelial cells.</p><p><b>RESULTS</b>Endothelial cells may look like cobble stones or long spindle shaped. Direct contact of tumor cells with endothelial cells induced round vascular-like space formation between confluent endothelial cells. Tumor cells were often found at the newly appeared spaces. Tumor cell conditioned medium could support the growth and promote the locomotion of endothelial cells through transwell. It was observed that luciffer yellow was directly transported from tumor cells to endothelial cells.</p><p><b>CONCLUSIONS</b>Tumor cells can directly induce morphological and functional changes in endothelial cells. Direct intercellular communication between tumor cells and endothelial cells is present.</p>