A pilot study of vasculogenic mimicry immunohistochemical expression in intraocular melanoma model

Vasculogenic mimicry (VM) has been recognized as a new form of angiogenesis. However, some previous studies have demonstrated the absence of VM channel in a uveal melanoma xenograft mice model. This study investigated the pattern and distribution of microcirculation in an intraocular animal model. C57Bl/6 mice were randomly divided into 3 groups used for the blood supply models of malignant melanoma. The right eyes of the mice received subretinal injections with B16 melanoma cells and the left eyes were the control. One experimental group mice was randomly sacrificed at days 3, 7 and 14 to evaluate the tumor size and microcirculation by immunostaining with anti-CD34 antibodies, PAS staining and electronic microscopy (EM). Activated-carbon tracing was used to confirm whether the VM structure connected to the host blood circulation at day 14. We observed 3 types of microcirculation patterns in this model. The tracer was used to confirm whether VM structure connected to the host blood circulation. The distribution of VM and MV was not uniform and appeared in patches. As the area of tumor tissue expands, the number of endothelium increases and that of VM decreases. The number of endothelium-dependent vessels correlated with the tumor size (r=0.805, P=0.000), while the number of VM was inversely correlated (r=0.47, P=0.03). The EM results validated the presence of 3 patterns. In conclusion, VM along with endothelium-dependent vessels and MV sustained the blood supply. Tumor cells can obtain oxygen and nutriment through VM and MV besides endothelium-dependent vessels. VM may be a way to adapt to rapid tumor growth and invasiveness.