Influence of microenvironments on microcirculation patterns and tumor invasion-related protein expression in melanoma

This study aimed to investigate the influence of different microenvironments on melanoma microcirculation patterns, invasiveness and metastatic behavior. Sixty C57BL/6J mice were randomly divided into two groups with 30 mice per group. Melanoma B16 cells were injected into the subretinal space and groin area of mice synchronously. The number of each type of microcirculation pattern was counted. Invasion and metastasis were observed. Epithelial cell kinase (EphA2), matrix metalloproteinase (MMP)-2 and -9 expression and their mRNA levels were detected by immunohistochemical staining and real-time PCR and compared between the two groups. Five invasions and six lung metastases were found in the subretinal group while no invasion and metastasis were found in the groin group. The number of vasculogenic mimicry (VM) was significantly higher in the subretinal group (P=0.000). However, no significant difference in the numbers of mosaic and endothelium-dependent vessels was observed between the two groups (P=0.076 and 0.146, respectively). EphA2, MMP-2 and MMP-9 expression was significantly higher in the subretinal group. The mRNA levels of EphA2, MMP-2 and MMP-9 were slightly higher in the subretinal tumors (P=0.002, 0.001 and 0.001, respectively). In conclusion, this experimental paradigm can be a powerful one in which to investigate tumor-microenvironment interactions in melanoma. Tumor cells in the intraocular microenvironment had increased EphA2 expression which induced the formation of VM channels. Moreover, expression of MMP-2 and -9 in tumor tissue was increased to enhance the invasiveness and metastatic behavior.