We analyzed the expression of Bcl-2 and

Twist1 in a cohort of 97 cases of hepatocellular carcinoma with detailed clinical and pathologic information (Supporting Tables s2, s3). Comparisons were made between RAD001 order the metastasis and nonmetastasis groups, as well as between the VM and non-VM groups. The results indicated that the Bcl-2 and Twist1 nuclei were positive, and that both had statistical significance (Tables s4, s5). The results showed that there was a correlation between the positive Bcl-2 and Twist1 nuclei, and that there was a statistical significance (Fig. 7A). Based on the analysis, the cytoplasmic expression of Bcl-2, Twist1, and Twist2 had no significant correlation with metastasis or VM formation. Correlation analyses were carried out for the relative proteins VE-cadherin, E-cadherin, MMP2, MMP9, HIF-1a, and VEGF. The results showed the correlation of HIF-1a, VEGF, VE-cadherin, and MMP9 with the nuclear expression of Bcl-2 and Twist1 (Fig. 7B). The Kaplan-Meier survival analysis suggested that the positive Bcl-2 nucleus, Twist1 nucleus, VE-cadherin, and MMP9 were correlated learn more with poor survival of these patients. Their survival time was also shorter than that of the negative group. The other indicators were not statistically

significant (Fig. 7C). Tumor cells can respond differently to various microenvironments, such as apoptosis, senescence, MCE and plasticity.20 The key factor in a microenvironment is hypoxia. Hypoxia can induce the up-regulation of HIF-1 in tumor cells, activate numerous signal transduction pathways,

promote tumor cell proliferation, induce EMT occurrence, or secrete VEGF. Consequently, a single tumor cell or tumor cell populations are forced to adapt to the changes caused by hypoxia.21-23 Tumor cells obtain blood for relieving hypoxia using a secretion factor or by simulating angiogenesis. Among them, tumor metastasis and VM formation are involved in tumor cells losing their epithelial adhesion molecules and obtaining a mesenchymal phenotype (as vimentin, N-cadherin, or VE-cadherin).19, 24-27 Our preliminary work19 has proven that VM exists in hepatocellular carcinoma, and that VM formation is correlated with the EMT-regulating factor Twist1. These findings indicate that VM formation may possibly be a part of EMT.25 Therefore, we named this process epithelial-endothelial transition (EET). The EET of tumor cells under a specific condition can be used for early vascular structuring to obtain the original blood source. Tumor cells are further remodeled or differentiated into endothelial cell-like tumor cells to participate in the construction of tumor microcirculation.28, 29 Hypoxia can directly induce the up-regulation of HIF-1. HIF can further combine with the promoter of Twist1 to promote its transcript expression, and further induce the occurrence of EMT.