Background
Osteosarcoma (OS) is the most prevalent primary malignant bone neoplasm causing substantial morbidity in adolescents and children [1]. It originates from mesenchymal cells and is characterized by rapid infiltrating growth, early lung metastasis and a high recurrence rate [2]. Studies have shown that the overall 5-year survival rate of patients with localized OS ranges between 65 ~ 75% and is only 20% for those with recurrent and metastatic tumors [3]. Despite advances in OS treatment approaches such as adjuvant chemotherapy and surgical resection, the survival rates have plateaued in the last 3 decades and are less than satisfactory [4]. Indeed, no specific diagnostic and prognostic biomarkers for OS have been found. Consequently, molecular studies aiming to identify promising therapeutic targets for OS are urgently needed. Circular RNAs (circRNAs) regulate various functions in eukaryotic cells [5]. Based on the order of splicing events and different intermediates, two mechanisms exist for the biogenesis of circRNAs: canonical spliceosome induced splicing and noncanonical lariat splicing [6, 7]. Accumulating studies have shown that circRNAs modulate diverse physiological and pathophysiological processes by sponging microRNAs (miRNAs), interacting with RNA binding proteins, and modulating epigenetic, transcriptional, or translational alterations in target genes as well [8–11]. Abnormal circRNA expression has been found to correlate with the pathogenesis of various cancers and to exert essential regulatory effects on gene expression, cell invasion, cell cycle progression, migration, apoptosis, and proliferation [12–14]. Moreover, circRNAs are thought to possess high diagnostic and therapeutic potential given their structural stability, evolutionary conservation, abundance and organ specificity [15, 16]. However, to date, the roles of circRNAs in OS are not clearly known.
This study evaluated the expression profiles of circRNAs in OS tissues using high-throughput sequencing. We found a novel circRNA, designated circ_001722, significantly upregulated in OS tissues and cells. Our experimental results indicated that circ_001722 exerted pro-oncogenic effects on OS proliferation and invasion through circ_001722/miR-204-5p/RUNX2 Axis. This preliminary study revealed that circ_001722 is a potential therapeutic target for OS.