The Potential of Osteopontin as a Therapeutic Target for Human Colorectal Cancer

Objective Osteopontin (OPN), a phosphorylated glycoprotein, is involved in tumor progression and metastasis. Previously, we have reported that high OPN mRNA expression level possessed clinicopathological or prognostic significance in human colorectal cancer (CRC). The aim of this study is to investigate whether OPN can serve as a novel molecular target for CRC therapy. Material and Methods Western Blot assay was performed to detect the expression of OPN protein in 18 CRC and corresponding nontumor colon tissue samples. RNA interference (RNAi) was employed to knockdown endogenous OPN expression in CRC cell line (LoVo). MTT, colony formation, and tumorigenicity assays were performed to analyze the effect of OPN downregulation on the in vitro and in vivo proliferation of CRC cells. Wound healing and Matrigel invasion assays were performed to analyze the effect of OPN downregulation on migration and invasion of CRC cells. A clonogenic cell survival assay after radiation was performed to analyze the effect of OPN downregulation on the radiosensitivity of CRC cells. Results The relative level of OPN protein expression in CRC tissues was significantly higher than that in corresponding nontumor colon tissues ( P