Hypoxia-induced vasculogenic mimicry formation via VE-cadherin regulation by Bcl-2

Vasculogenic mimicry (VM) refers to the unique ability of highly aggressive tumor cells to mimic the pattern of embryonic vasculogenic networks. Hypoxia plays a pivotal role in the formation of VM. Hypoxia-induced Bcl-2 overexpression is observed in many types of tumors including melanoma, in which it is associated with tumorigenicity and angiogenesis. VE-cadherin, the major endothelial adhesion molecule controlling cellular junctions and blood vessel formation, is also overexpressed in melanoma. Despite these connections, whether hypoxia induces VM formation via VE-cadherin regulation by Bcl-2 is not confirmed. We used human melanoma cells to upregulate or knockdown the expression of Bcl-2 to investigate the possible molecular mechanism of VM formation under hypoxia. Bcl-2 overexpression increased VE-cadherin expression and VM formation under normoxia, whereas Bcl-2 siRNA significantly decreased VE-cadherin expression and VM formation under hypoxia. We then demonstrated that Bcl-2 regulated VE-cadherin transcription activity by Western blot, three-dimensional cultures, reporter gene assay, and clinical analysis. Therefore, Bcl-2-dependent VE-cadherin overexpression may be an important mechanism by which hypoxia induces VM.