KCNQ1OT1 affects cell proliferation, invasion, and migration through a miR-34a / Notch3 axis in breast cancer.

ABSTRACT

BACKGROUND: Breast cancer (BC) accounts for a significant share of cancer-related deaths worldwide. Ongoing investigations have shown that long non-coding RNAs (lncRNAs) drive BC progression but their underlying mechanisms remain largely undescribed. LncRNA KCNQ1OT1 was previously identified in BC but its functional significance remained to be fully investigated. METHODS: KCNQ1OT1 and its downstream target genes were analyzed in breast cancer tissues and cell lines using methods including RT-qPCR, immunohistochemistry and Western blotting. The effects of KCNQ1OT1, miR-34a and Notch3 on BC cells were investigated using assays measuring proliferation (CCK-8, colony formation), apoptosis, and migration/invasion (scratch and Transwell assays). MS2-RIP and dual-luciferase reporter assays were used to study RNA interactions. Xenograft studies were employed to define the tumorigenic potential of KCNQ1OT1 in vivo. RESULTS: KCNQ1OT1 expression was up-regulated in BC tissues and high levels were associated with poorer prognosis. ShRNA inhibition of KCNQ1OT1 expression in BC cell lines retarded proliferation, migration and invasion in vitro and tumor growth in vivo. Up-regulation of KCNQ1OT1 was shown to inhibit miR-34a which was associated with blocking the inhibitory effect of miR-34a on BC cell proliferation, migration and invasion. Notch3 was found to be a downstream target of miR-34a with KCNQ1OT1 markedly inducing Notch3 expression in BC. Evidence for KCNQ1OT1/miR-34a/Notch3 axis was further established in clinical BC samples. CONCLUSION: We identified a KCNQ1OT1/miR-34a/Notch3 axis which promotes BC progression through effects on cell proliferation and metastasis that was further associated with poor patient prognosis. These results propose targeting this axis as novel treatment approach for BC.