SPARCL1 exhibits different expressions in left- and right-sided colon cancer and is downregulated via DNA methylation

Lay abstract The heterogeneity of colorectal cancer is largely based on their primary tumor locations. For example, patients with left-sided colon cancer generally have better prognoses and different treatment strategies in comparison with patients with right-sided colon cancer. Research is required to uncover the mechanisms underlying these differences. The authors showed that the addition of methyl groups (DNA methylation) to DNA encoding SPARCL1 (a protein involved in cell adhesion) could inhibit regular colorectal cell motility. Furthermore, SPARCL1 protein expression was higher and positively correlated with better prognosis specifically in patients with left-sided colon cancer. The present study provides an evidential basis for the different molecular biological features between left-sided and right-sided colon cancer. SPARCL1 is a promising candidate for predicting colon cancer prognosis and potential therapeutic intervention. Further in-depth study of SPARCL1 would be of great value for clinical application. Aim: The authors previously found that SPARCL1 functions to suppress colorectal cancer metastasis. Here, the epigenetic mechanism of SPARCL1 regulation and its relationship with clinicopathological features in colon cancer were investigated. Materials & methods: SPARCL1 expression was evaluated by immunohistochemistry staining in a tissue array containing 271 left-sided colon cancer samples and 257 right-sided colon cancer samples. In vivo and in vitro DNA methylation states were measured by biochemical sulfide potential assay. The transcription and DNA methylation states in cells were altered by siRNA or decitabine treatment, respectively. Cellular motility properties were compared through transwell assay. Results & conclusion: SPARCL1, mediated by its DNA methylation, may arrest colorectal carcinoma motility. Furthermore, SPARCL1 expression is higher and may have a specific prognostic value in left-sided colon cancer.