Expression of DKK1 in Endometrial Endometrioid Carcinoma and Its Correlation with Wnt/β-catenin Signalling Pathway

OBJECTIVES: Endometrial cancer is the most prevalent form of cancer affecting female reproductive organs. The most common histologic type, endometrioid carcinoma, accounts for 75–80% of all endometrial cancer cases. Studies on DKK1 expression profiles and their inhibitory role in the Wnt signalling pathway in the genesis and development of endometrial carcinoma are scarce. This study aimed to investigate DKK1 expression in endometrial carcinoma and its correlation with the Wnt/β-catenin pathway. METHODS: A total of 160 formalin-fixed paraffin-embedded samples were included in this study (50 cases of endometrial atypical hyperplasia, 50 cases of endometrioid endometrial carcinoma, 30 cases of proliferative endometrium and 30 cases of secretory endometrium). The expression patterns of DKK1, E-cadherin, β-catenin and c-Myc in endometrial atypical hyperplasia and carcinoma were investigated and compared with that of proliferative and secretory endometrium. Immunohistochemistry and analysis were performed from July 2018 to June 2020. RESULTS: A decreasing pattern of immunopositivity for DKK1, E-cadherin and β-catenin from proliferative/secretory endometrium to endometrial atypical hyperplasia and endometrioid carcinoma was found. Increasing c-Myc immunopositivity was noted from proliferative/secretory endometrium to endometrial atypical hyperplasia and endometrioid carcinoma. Moreover, decreasing DKK1 immunopositivity was well correlated with E-cadherin, β-catenin and c-Myc immunopositivity. CONCLUSION: Decreasing DKK1 positivity from benign endometrium to endometrioid carcinoma suggests a negative regulatory function of DKK1 in endometrioid carcinoma. DKK1 is downregulated in the Wnt signalling pathway in endometrioid endometrial carcinoma. Therefore, DKK1 is promising as a biomarker for screening endometrioid carcinoma. Future studies should examine the reactivation of the DKK1 gene, which may be a valuable strategy for antagonising the Wnt signalling pathway.