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: Toinvestigate the expression of SMO protein in colon cancer and its association with clinicopathological parametersand postoperative liver metastasis, immunohistochemistry was performed with paraffin-embedded specimensof 96 cases. Relationships between SMO protein expression and clinicopathological parameters, postoperativeliver metastasis were analyzed.
Results: IHC examination showed that SMO protein expression was significantlyincreased in colon cancer tissues compared to normal colon tissues (P = 0.042), positively related to lymph nodemetastases (P = 0.018) and higher T stages (P = 0.026). Postoperative live metastasis-free survival was significantlylonger in the low SMO expression group than in those with high SMO expression (48.7±8.02 months vs 28.0±6.86months, P=0.036). Multivariate analysis showed SMO expression level to be an independent prognostic factorfor 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 biomarkerfor postoperative liver metastasis, and SMO might play an important role in colon cancer progression.