ABSTRACT
<p><b>OBJECTIVE</b>To discuss the tumorigenicity of immortalized endothelial cells differentiated from embryonic stem cells.</p><p><b>METHODS</b>The embryoid bodies (EB) formed in vitro from embryonic stem cells, were induced to differentiate into many "round cells" (the precursor of endothelial cells). These "round cells" later formed the vascular tube-like structures. To immortalize these cells, human telomerase reverse transcriptase (hTERT) cDNA was transfected into "round cells" by lipofectin, RT-PCR and immunocytochemistry were used to evaluate the immortalized cells. And the tumorigenicity of these cells were evaluated by being injected into nude mice subcutaneously.</p><p><b>RESULTS</b>95% of these transfected cells expressed Flk-1, CD34 and vWF, and could proliferate in large quantity in vitro (cell number was doubled in 2 days, and increased 12 times in 3 days), and were able to form tubular structures.</p><p><b>CONCLUSIONS</b>These results suggest that hTERT cDNA transfection can immortalize induced endothelial cells and tumorigenicity is found after immortalized cells are injected into nude mice subcutaneously.</p>