MicroRNA therapy inhibits hepatoblastoma growth in vivo by targeting β‐catenin and Wnt signaling

Hepatoblastoma (HBL) is the most common pediatric liver cancer. In this malignant neoplasm, beta‐catenin protein accumulates and increases Wnt signaling due to recurrent activating mutations in the catenin‐beta 1 (CTNNB1) gene. Therefore, beta‐catenin is a key therapeutic target in HBL. However, controlling beta‐catenin production with therapeutic molecules has been challenging. New biological studies could provide alternative therapeutic solutions for the treatment of HBL, especially for advanced tumors and metastatic disease. In this study, we identified microRNAs (miRNAs) that target beta‐catenin and block HBL cell proliferation in vitro and tumor growth in vivo. Using our dual‐fluorescence‐FunREG system, we screened a library of 1,712 miRNA mimics and selected candidates inhibiting CTNNB1 expression through interaction with its untranslated regions. After validating the regulatory effect of nine miRNAs on beta‐catenin in HBL cells, we measured their expression in patient samples. Let‐7i‐3p, miR‐449b‐3p, miR‐624‐5p, and miR‐885‐5p were decreased in tumors compared to normal livers. Moreover, they inhibited HBL cell growth and Wnt signaling activity in vitro partly through beta‐catenin down‐regulation. Additionally, miR‐624‐5p induced cell senescence in vitro, blocked experimental HBL growth in vivo, and directly targeted the beta‐catenin 3′‐untranslated region. Conclusion: Our results shed light on how beta‐catenin‐regulating miRNAs control HBL progression through Wnt signaling inactivation. In particular, miR‐624‐5p may constitute a promising candidate for miRNA replacement therapy for HBL patients. (Hepatology Communications 2017;1:168‐183)