Expression of Smoothened Protein in Colon Cancer and its Prognostic Value for Postoperative Liver Metastasis

Backgrouds: The hedgehog (Hh) signaling pathway is composed of patched (PTCH) and smoothened (SMO), two transmembrane proteins, and downstream glioma-associated oncogene homolog (Gli) transcription factors. Hh signaling plays a pathological role in the occurrence and development of various cancers. Methods: To investigate the expression of SMO protein in colon cancer and its association with clinicopathological parameters and postoperative liver metastasis, immunohistochemistry was performed with paraffin-embedded specimens of 96 cases. Relationships between SMO protein expression and clinicopathological parameters, postoperative liver metastasis were analyzed. Results: IHC examination showed that SMO protein expression was significantly increased in colon cancer tissues compared to normal colon tissues (P = 0.042), positively related to lymph node metastases (P = 0.018) and higher T stages (P = 0.026). Postoperative live metastasis-free survival was significantly longer in the low SMO expression group than in those with high SMO expression (48.7 +/- 8.02 months vs 28.0 +/- 6.86 months, P=0.036). Multivariate analysis showed SMO expression level to be an independent prognostic factor for postoperative live metastasis-free survival (95% confidence interval [CI] = 1.46-2.82, P = 0.008). Conclusions: Our results suggest that in patients with colon cancer, the SMO expression level is an independent biomarker for postoperative liver metastasis, and SMO might play an important role in colon cancer progression.