SHISA3, an antagonist of the Wnt/β-catenin signaling, is epigenetically silenced and its ectopic expression suppresses growth in breast cancer

Breast cancer (BC) is the foremost cause of cancer related deaths in women globally. Currently there is a scarcity of reliable biomarkers for its early stage diagnosis and theranostics monitoring. Altered DNA methylation patterns leading to the silencing of tumor suppressor genes are considered as an important mechanism underlying tumor development and progression in various cancer types, including BC. Very recently, epigenetic silencing ofSHISA3, an antagonist of beta-catenin, has been reported in various types of tumor. However, the role ofSHISA3in BC has not been investigated yet. Therefore, we aimed at evaluating the contribution ofSHISA3in BC causation by analyzing its expression and methylation levels in BC cell lines (MDA-MB231, MCF-7 and BT-474) and in 103 paired BC tissue samples. TheSHISA3expression and methylation status was determined by qPCR and methylation specific PCR (MSP) respectively. The role ofSHISA3in BC tumorigenesis was evaluated by proliferation and migration assays after ectopic expression ofSHISA3. The association betweenSHISA3hypermethylation and clinicopathological parameters of BC patients was also studied. The downregulation ofSHISA3expression was found in three BC cell lines used and in all BC tissue samples. However,SHISA3promoter region was hypermethylated in 61% (63/103) tumorous tissues in comparison to the 18% of their matched normal tissues. The 5-aza-2'-deoxycytidine treatment restoredSHISA3expression by reversing promoter hypermethylation in both MDA-MB231 and MCF-7 cells. Furthermore, ectopic expression ofSHISA3significantly reduced the proliferation and migration ability of these cells. Taken together, our findings for the first time reveal epigenetic silencing and tumor suppressing role ofSHISA3in BC. Henceforth, this study has identifiedSHISA3as potentially powerful target for the development of new therapies against BC, as well as novel diagnostic and therapy response monitoring approaches.