Biglycan up-regulated vascular endothelial growth factor (VEGF) expression and promoted angiogenesis in colon cancer

Biglycan is an important component of the extracellular matrix, which belongs to the small leucine-rich proteoglycan family. Recent studies have shown that biglycan expression is elevated in many tumor tissues and implies poor prognosis, such as colon cancer. However, the molecular mechanism of biglycan in colon cancer has not been investigated. The present study aimed to investigate the effects of biglycan on vascular endothelial growth factor (VEGF) expression in colon cancer cells and on tumor angiogenesis in vivo. Biglycan overexpression vectors were constructed, and the stable biglycan overexpression in human colon cancer cell lines (HCT116 cells) was established by G418 screening. The stable cell clones were subsequently used to initiate tumor xenografts in nude mice. Our results showed that biglycan overexpression notably up-regulated the levels of VEGF in colon cancer cells, which was further confirmed by immunohistochemistry analysis in the xenograft colon tumors. Moreover, high levels of biglycan promoted angiogenesis and colon tumor growth, as evidenced by the increased cell viability, colon tumor size, and weight, as well as the CD34 expression. Additionally, we found that the extracellular signal-regulated kinase (ERK) signaling pathway was activated by biglycan in colon cancer cells. The ERK inhibitor PD98059 dramatically reversed the increased expression of VEGF induced by biglycan. Taken together, our results indicated that biglycan up-regulated VEGF expression in colon cancer cells and promoted tumor angiogenesis. Biglycan-mediated VEGF regulation may correlate with the activation of the ERK signaling pathway. Therefore, biglycan may be a promising target for anti-angiogenic therapy for cancer.