Decreased expression of SorCS1 in colorectal cancer: An independent predictor of poor prognosis.

Previously, we identified that sortilin related VPS10 domain containing receptor 1 (SorCS1) was hypermethylated in colorectal cancer (CRC) tissues. Here, we aimed to investigate the association between CRC and SorCS1. DNA methylation was determined by methylation-specific polymerase chain reaction (MSP) or quantitative real-time methylation analysis (MethyLight). Colorectal cancer tissue specimens from 239 patients that had undergone surgical treatment were evaluated using immunohistochemistry (IHC) analysis for the expression of SorCS1 and correlated with clinicopathological variables and prognosis. We found that SorCS1 was hypermethylated in CRC cell lines and 67.5% (27/40) CRC tumor tissues. The loss of SorCS1 mRNA (p<0.001) and protein expression (p=0.033) were highly correlated with promoter methylation. In addition, SorCS1 expression was significantly increased in younger patients (p=0.006), low CEA level (p<0.001) and pT1-2 stage (p=0.005). Survival analysis revealed that decreased expression of SorCS1 was an independent factor for predicting the increased risk of recurrence (p=0.024) and poor overall survival (p=0.006). Subgroup analysis for CEA level, pT and pN classifications showed that SorCS1 retained its stratified significance only in patients with low CEA level, pT3-4 tumors and pN1-2 lymph node status. Our findings suggest that SorCS1 is epigenetically inactivated in a substantial fraction of CRC, and its expression may be a promising prognostic factor in CRC patients.