Purpose: The mammalian Forkhead Box (Fox) transcription factor FOXM1 is implicated in tumorigenesis including mouse intestinal cancer. However, the clinical significance of FOXM1 signaling in human colorectal cancer pathogenesis remains unknown.
Experimental design: We investigated FOXM1 expression in 203 cases of primary colon cancer and matched normal colon tissue specimens and explored the underlying mechanisms of altered FOXM1 expression and the impact of this altered expression on colon cancer growth and metastasis using in vitro and animal models of colon cancer.
Results: We found weak expression of FOXM1 protein in the colon mucosa, whereas we observed strong FOXM1 expression in tumor-cell nuclei of colon cancer and lymph node metastases. A Cox proportional hazards model revealed that FOXM1 expression was an independent prognostic factor in multivariate analysis. Experimentally, overexpression of FOXM1 by gene transfer significantly promoted the growth and metastasis of colon cancer cells in orthotopic mouse models, whereas knockdown of FOXM1 expression by siRNA did the opposite. Promotion of colon tumorigenesis by FOXM1 directly and significantly correlated with activation of urokinase-type plasminogen activator receptor (PLAUR) expression and elevation of invasion and metastasis.
Conclusions: Given the importance of FOXM1 in regulation of the expression of genes key to cancer biology, dysregulated expression and activation of FOXM1 may play important roles in colon cancer progression and metastasis.