An interplay between extracellular matrix proteins and the cancer cell promotes the multistep process of in vitro vasculogenic mimicry formation.

Cancer vasculogenic mimicry (VM) is the formation of vasculature structures in the absence of endothelial cells. We previously established an in vitro model that facilitates the formation of a lumen-containing and fluid-conducting tubular structures after 4 days cancer cell growth on Matrigel. Herein, we mechanistically characterize this model in breast and ovarian cancer cell lines demonstrating distinct phases of VM formation and the dependence of specific extracellular matrix proteins. We report that VM occurs in four distinct stages. Firstly, alignment, migration then clustering delineate the area of the future tubular structure. Secondly, contraction of aligned structures followed by loss of attachment of some cells and cellular blebbing. Thirdly, a phase of mass proliferation followed by the raising of specific areas of the cancer cell mass above the Matrigel (bridge). Finally, the formation of a cell monolayer closes the tubular structure, forms a glycoprotein-rich luminal lining, then elevates the structure. Only later stages of VM require AKT and FAK signaling. We demonstrate that the lining of the tubular lumen is rich in laminin. Laminin 111 (but not collagen I) must be presence in the extracellular matrix (Matrigel) for VM to occur and integrin β1, but not integrin β3, is required. RNASeq demonstrates that formation is principally post-transcriptional regulation, however, this technique together with siRNA knockdown identified the first and essential biological function for the protein SMIM11A. VM is associated with poor patient survival and thus an understanding of the mechanism of VM may bring to light novel anticancer targets.