Downregulation of circITCH promotes osteosarcoma development and resistance to doxorubicin via the miR-524/RASSF6 axis.

Zhou, Wei; Liu, Yuan; Wu, Xuejian

BACKGROUND Osteosarcoma (OS) is a malignant bone cancer, in which circular RNAs (circRNAs) acting as important modulators. Here, we aimed to explore the functional role of circRNA itchy E3 ubiquitin protein ligase (circITCH) in the development and doxorubicin (DXR) resistance of OS and the possible mechanistic pathway. METHODS Quantitative real-time PCR or western blot assays were exploited to analyze the expression of circITCH, miR-524 and Ras association domain family member 6 (RASSF6). Cell viability and half-maximal inhibitory concentration (IC50) value of DXR were monitored by Cell Counting Kit-8 assay. Cell migration, invasion and apoptosis were determined via transwell assay and flow cytometry. The target interaction among circITCH, miR-524 and RASSF6 was validated by dual-luciferase reporter assay and RNA immunoprecipitation assay. A xenograft model of MG-63/DXR cells stably expressing circITCH in nude mice was established for assessing the role of circITCH in vivo. RESULTS Downregulation of circITCH and RASSF6, as well as the upregulation of miR-524 were revealed in OS by study of 40 paired OS tissue and normal tissue samples. Overexpression of circITCH lowered the cell viability, IC50 value of DXR, migration and invasion, while facilitated apoptosis of OS cells. CircITCH sponged miR-524 to upregulate RASSF6, causing OS progression inhibition and DXR resistance reduction. Additionally, circITCH upregulation reduced tumor growth in vivo. CONCLUSIONS Transduction with circITCH represses OS progression and promotes DXR sensitivity by the miR-524/RASSF6 axis, providing a new perspective for therapeutic intervention.