Comparison of characteristics of mouse immortalized normal endothelial cells, MS1 and primary cultured endothelial cells.

Tumor blood vessels support the progression of tumors by providing nutrition and oxygen required for growth. By acting as gatekeepers, they allow the metastasis of tumors to secondary locations. An important strategy in cancer therapy has been to target tumor blood vessels consequently inhibiting tumor angiogenesis. To date, antiangiogenic therapy being employed for cancer treatment have yielded profoundly good results. However, it has been shown that current antiangiogenic drugs have several problems, such as adverse side effects and drug resistance. Tumor endothelial cells (TEC), which line the inner layer of blood vessels of the tumor stromal tissue, are the main targets of the antiangiogenic therapies. TEC have been reported to differ significantly from endothelial cells resident in normal blood vessels. These differences provide a window through which TEC can be targeted solely with little or no impact on normal endothelial cells (NEC). Currently, as part of new antiangiogenic drug discovery processes, cell-based screening is being performed using thousands of small chemical compounds. For the success of such screening purposes, there is a need to obtain the right kind of cells and in adequate quantities. Primary–cultured endothelial cells isolated from murine / human blood vessels are the preferred choice. However, maintenance of the primary-cultured endothelial cells is costly and overtime these cells become senescent and perish. As a result, MS1, SV40 immortalized islet-derived endothelial cells, have been used in place of the primary-cultured cells. MS1 is commercially available with comparatively cheaper cell culture requirements. 　In this study, we compared the characteristics of MS1 and primary-cultured endothelial cells ; NEC and TEC to investigate the possibility of using MS1 cells for chemical screening in search of a new antiangiogenic drug. MS1 cells proliferate faster compared to TEC and upregulated the mRNA expressions of CD133 and Sca-1 genes. However, mRNA expression of most of the other genes, which were upregulated in TEC compared to NEC, were also expressed at lower levels in the MS1 cells. Furthermore, MS1 migrated at a slower rate and did not form tubes on matrigel, as opposed to the function of TEC. In conclusion, MS1 did not completely resemble NEC, nor TEC in function and gene expression. It is suggested that for chemical screening, primary-cultured TEC and the corresponding NEC would be a more ideal choice of cells

Development of Immortalized Human Tumor Endothelial Cells from Renal Cancer

Tumor angiogenesis research and antiangiogenic drug development make use of cultured endothelial cells (ECs) including the human microvascular ECs among others. However, it has been reported that tumor ECs (TECs) are different from normal ECs (NECs). To functionally validate antiangiogenic drugs, cultured TECs are indispensable tools, but are not commercially available. Primary human TECs are available only in small quantities from surgical specimens and have a short life span in vitro due to their cellular senescence. We established immortalized human TECs (h-imTECs) and their normal counterparts (h-imNECs) by infection with lentivirus producing simian virus 40 large T antigen and human telomerase reverse transcriptase to overcome the replication barriers. These ECs exhibited an extended life span and retained their characteristic endothelial morphology, expression of endothelial marker, and ability of tube formation. Furthermore, h-imTECs showed their specific characteristics as TECs, such as increased proliferation and upregulation of TEC markers. Treatment with bevacizumab, an antiangiogenic drug, dramatically decreased h-imTEC survival, whereas the same treatment failed to alter immortalized NEC survival. Hence, these h-imTECs could be a valuable tool for drug screening to develop novel therapeutic agents specific to TECs or functional biological assays in tumor angiogenesis research