The Molecular and Cellular Processes of Tumor Cell-Mediated Tumor Angiogenesis and Vasculogenesis,

Abstract 3267

It is well known that tumors make blood vessels through endothelial cell-mediated angiogenesis; whereas, increasing data have shown that tumor cell-mediated vasculogenesis plays an important role in tumor neovascularization in a variety of high metastatic malignant tumors, but the mechanisms are largely unknown. We previously established new models for studying the mechanisms of tumor angiogenesis and vasculogenesis (Zhou Q. et al. Method 44(2):190–195, 2008; Zhou Q, et al. Nature: Structure and Molecular Biology 2010, 17:57–62). Using in vitro tube formation system and in vivo mouse tumor xenografts, we have recently tested the vasculogenic capability of 85 tumor cell lines and studied the molecular and cellular processes of tumor cell-mediated tumor neovascularization. Among 62 human tumor cell lines tested, 25 of them were able to directly form capillary-like tubes in vitro and tumor blood vessels in vivo tumor xenografts, while 10 out of 23 mouse tumor cell lines displayed tube-forming and vasculogenic capabilities. Notably, these vasculogenic tumor cells were mostly derived from high metastatic and aggressive tumors, including pre-cancerous stem cells, cancer stem cells, high metastatic tumor cells, and tumor endothelial cells.

Utilizing DNA microarray, tumor tissue array, RT-PCR, western blotting, and immunofluorescient staining, we observed that 15 genes were highly expressed in vasculogenic cancer stem cells and various tumor cells; among them, 4 genes did not expressed in all of the 15 normal human tissues while other 11 genes were only expressed in the testis, but absent in other normal tissues. Additionally, many embryonic angiogenic and vasculogenic genes were overexpressed in the vasculogenic tumor cells, implying that these genes may play an important role in tumor vasculogenesis. Accordingly, we raise a hypothetic model that endogenous and exogenous factors induce tumor cells to express a variety of angiogenic and vasculogenic genes which drive the vasculogenic tumor cells to connect each other and to interact with endothelial cells and various blood cells, resulting in generation of tumor blood vessels.

Furthermore, we explored the role and mechanism of human ovarian cancer Hey1B cell-mediated tumor neovascularization. Herein, for the first time we found that Hey1B cells directly formed capillary tubular structure in vitro independent of any growth factors and functional tumor blood vessels in vivo tumor xenografts. Moreover, we observed that more than 30 angiogenic and vasculogenic genes were overexpressed in the cells and the tumor tissues, including VE-cadherin, FGFR1, VEGFA, HIF1A, Sema4D, plexinB1, EphB2, NOTCH1, ROBO4, Ephrin B2, SFRP1, MAFB, SOX17, WIPF2, MAGEF1, MAGED1, New3, ZFP106, RUNX1, and other 16 poorly annotated genes, while Akt and ERK signaling pathways were found to be over activated in Hey1B cells and the tumor tissues. This valuable information gets new insight into the mechanisms of tumor cell-predominant neovascularization.

Using Hey1B cells as tumor vasculogenic model, we screened anti-tumor vasculogenic small molecules in the traditional Chinese herbal medicinal library and found that lycorine hydrochloride (LH) effectively inhibited Hey1B cell-mediated tube formation in vitro, blood vessel generation and tumor growth in vivo. Molecular mechanism analysis showed that LH markedly inhibited the expression of VE-cadherin, Sema4D, FGFR1, VEGFA, NOTCH1 and SFRP1 genes, and it also blocked Akt and ERK signaling pathways.

Taken together, a varieties of angiogenic and vasculogenic genes are overexpressed in angiogenic and vasculogenic tumor cells, meanwhile, Akt and ERK signaling pathways were activated in the vasculogenic tumor cells tested; and that LH effectively suppresses ovarian cancer neovascularization and tumor growth through inhibition of several key genes and signaling pathways. Therefore, angiogenic and vasculogenic genes and tumor cells are good targets for novel anti-tumor vasculogenesis and anti-tumor drug discovery.