Role of microRNA in spinal metastatic cancer angiogenesis

Spine is the third common body site for tumor metastasis via blood-borne transmission. MicroRNA (miR) can regulate tumor progression via affecting hypoxia inducible factor-1 alpha (HIF-1 alpha) and vascular epithelial growth factor (VEGF). This study generated VX2 tumor bearing rabbits, on which tumor cells were isolated and were transfected with miR-18a, in order to analyze the role of miR-18a in spinal metastatic tumor's angiogenesis process. VX2 tumor bearing rabbits were prepared and isolated for tumor cells, which were prepared for single cell suspension. Tumor cells were transfected with miR-18a mimics or inhibitors, and were tested by RT-PCR. MTT assay was used to detect proliferation ability of tumor cells after transfection. Immunohistochemistry (IHC) staining was used to quantify the expression of CD31, Ki67 and micro-vessels in spinal metastatic tumors. The expression of VEGF and HIF-1 alpha were determined by Western blotting. Compared to control group, those cells transfected with miR-18a mimics had elevated miR-18a expression. Those cells had lower proliferation ability starting from 96 hours after transfection (P<0.05). The positive rates of CD31, Ki67 and micro-vessel number were 60%, 50% and 62.36 +/- 10.22, respectively. All of those parameters were significantly lower than control group (P<0.05). Protein levels of HIF-1 alpha and VEGF were decreased in miR-18a transfected tumor cells (P<0.05 compared to control cells). MiR-18a over-expression decreased cell proliferation ability, decreased level of CD31, Ki, and micro-vessel regeneration, and inhibited HIF-1 alpha and VEGF expression for blocking angiogenesis.