Dickkopf-related Protein 2 Induces G0/G1 Arrest And Apoptosis Through Suppressing Wnt/Β-catenin Signaling And Is Frequently Methylated In Breast Cancer

OBJECTIVEDickkopf-related protein 2(DKK2)is an antagonist of the Wnt/β-catenin signaling pathway,and downregulation of DKK2 has been reported in a wide range of cancers.We detect the expression and methylation status of DKK2 in breast cancer.Forthermore,the biological functions of DKK2 in breast cancer were also studied.METHODSRT-PCR and real-time PCR were used to examine the expression of DKK2 in breast tumor cell lines and tissues,normal adults tissues.Methylation status of DKK2 was detected by MSP.The biological functions of DKK2 in breast cancer were detected colony through formation assay,CCK8 viability assay,flow cytometry cell cycle,AO/EB examined apoptosis analyses,transwell migration and Wound healing assays,Microtube formation and conditioned medium assays,along with in vivo tumorigenicity assay.The expression levels of DKK2 in breast cancer tissues was evaluated by immunohistochemistry analyses.The expression of DKK2,Wnt/β-catenin signaling pathways and EMT related factor were examined by Western blot analysis and Indirect immunofluorescence determinations.RESULTSDKK2 was frequently silenced in breast cancer cell lines(8/8).DKK2 promoter methylation was detected in 77.8% of breast cell lines and in 86.7% of breast tumor samples;however,it was rarely detected in normal breast tissues(19%).Ectopic expression of DKK2 changed breast tumor cell morphology,inhibited cell proliferation and colony formation by inducing G0/G1 cell cycle arrest and cell apoptosis,and suppressed breast cancer migration by reversing the epithelial-mesenchymal transition and downregulating stem cell markers.Moreover,restored expression of DKK2 disrupted human umbilical vein endothelial cell microtube formation.In vivo,the growth of MDA-MB-231 cells in nude mice was markedly decreased after stable expression of DKK2.DKK2 suppressed canonical Wnt/β-catenin signaling by mediating β-catenin activity,while decreasing the abundance of active β-catenin.CONCLUSIONSOur findings demonstrated that DKK2 can function as a tumor suppressor of angiopoietic cell proliferation and can induce apoptosis through regulating Wnt signaling during breast tumorigenesis.Thus,DKK2 could be a potential tumor marker and future therapeutic target in the prognosis and treatment of breast cancer.