FRZB knockdown upregulates β-catenin activity and enhances cell aggressiveness in gastric cancer

Abstract

Studies have shown that FRZB correlates with gastric tumorigenicity and may play role in regulating the Wnt/β-catenin signaling pathway. In the present study, we investigated the correlation between FRZB and the Wnt/β-catenin signaling pathway using gastric cancer tissues and an FRZB.knockdown gastric cancer cell line model. The protein levels of FRZB and β-catenin were examined using immunohistochemical staining. FRZB-specific shRNAs were used to generate FRZB.knockdown MKN45 gastric cancer cells. Cell proliferation assay, suspending culture and Annexin.V/PI double staining analysis were used to investigate the role of FRZB knockdown in cell growth. In.vitro migration/invasion assays were performed. The expression of Wnt/β-catenin downstream targets was analyzed by RT-PCR. FRZB mRNA levels showed negative correlation with β-catenin levels in paired non-tumor and tumor tissues. FRZB protein levels were negatively correlated with β-catenin levels analyzed by IHC staining. Furthermore, high FRZB protein levels were correlated with membrane localization of β-catenin. FRZB knockdown increased gastric cancer cell growth in monolayer and soft agar culture; it increased cell aggregates in suspending culture and rendered less apoptosis which indicated increased anti-anoikis growth. FRZB knockdown increased cell migration and invasion and increased the expression of Wnt/β-catenin downstream targets such as MMP7 and cyclin D1. Our studies revealed that FRZB levels were correlated with β-catenin subcellular localization. Knockdown of FRZB in gastric cancer cells increased cell growth and migration/invasion which was also accompanied by activation of Wnt/β-catenin downstream targets. FRZB knockdown may upregulate the Wnt/β-catenin pathway and promote aggressiveness in gastric cancer.