IGFBP‑rP1‑silencing promotes hypoxia‑induced angiogenic potential of choroidal endothelial cells via the RAF/MEK/ERK signaling pathway.

Insulin‑like growth factor binding protein‑related protein 1 (IGFBP‑rP1) has been reported to have various functions in different cellular contexts. Our previous investigation discovered that IGFBP‑rP1 inhibited retinal angiogenesis in vitro and in vivo by inhibiting the pro‑angiogenic effect of VEGF and downregulating VEGF expression. Recently, IGFBP‑rP1 was confirmed to be downregulated in the aqueous humor of patients with neovascular age‑related macular degeneration compared with controls; however, its specific role remains unknown. The present study applied the technique of gene silencing, reverse transcription‑quantitative PCR, western blotting, cell viability assays, cell motility assays and tube formation assays. Chemical hypoxic conditions and choroidal endothelial (RF/6A) cells were used to explore the effect of IGFBP‑rP1‑silencing on the phenotype activation of RF/6A cells under hypoxic conditions and to elucidate the underlying mechanisms. siRNA achieved IGFBP‑rP1‑silencing in RF/6A cells without cytotoxicity. IGFBP‑rP1‑silencing significantly restored the viability of RF/6A cells in hypoxia and enhanced hypoxia‑induced migration and capillary‑like tube formation of RF/6A cells. Furthermore, IGFBP‑rP1‑silencing significantly upregulated the expression of B‑RAF, phosphorylated (p)‑MEK, p‑ERK and VEGF in RF/6A cells under hypoxic conditions; however, these upregulations were inhibited by exogenous IGFBP‑rP1. These data indicated that silencing IGFBP‑rP1 expression in RF/6A cells effectively promoted the hypoxia‑induced angiogenic potential of choroidal endothelial cells by upregulating RAF/MEK/ERK signaling pathway activation and VEGF expression.