Msi-1 is a Predictor of Survival and a Novel Therapeutic Target in Colon Cancer

Musashi1 (Msi-1), a neural RNA-binding protein, plays an important role in regulating cell differentiation in precursor cells. Recently, aberrant expression of Msi-1 has been detected in several malignancies. However, its role in the progression of colon cancer is largely unknown. We used Western blotting to examine Msi-1 protein expression in 8 cases of primary colon cancer lesions and paired normal colonic mucosa. Msi-1 expression and clinicopathological significance were determined by immunohistochemical staining in a tissue microarray (TMA) containing 203 cases of primary colon cancer paired with noncancerous tissue and 66 lymph node metastasis (LNM) tissues. RNAi was used to analyze the biological function of Msi-1 in vitro. LNM tissue exhibited a striking increase in Msi-1 expression when compared with primary colon cancer and adjacent normal mucosa (87.9% vs. 64.5% vs. 16.7%, P < .001). Overexpression of Msi-1 was associated with higher clinical stage, T stage, lymph node metastasis, presence of distant metastasis, and Ki-67 positivity. Msi-1 served as an independent prognostic marker whose expression levels correlated with poorer metastasis-free survival (MFS) (HR 5.4; P < .001) and poorer overall survival (OS) (HR 3.8; P < .001). Msi-1 silencing significantly inhibited proliferation ability and attenuated the migration and invasion activity of colon cancer cells. Our study provides the basis to explore the use of Msi-1 as a novel prognostic biomarker in colon cancer patients. Aberrant overexpression of Msi-1 during metastasis of colon cancer also suggests that it is a potential therapeutic target.