A novel circular RNA, circXPO1, promotes lung adenocarcinoma progression by interacting with IGF2BP1

Studies have demonstrated that noncoding RNAs play important roles in various types of cancer; however, noncoding RNAs derived from regions of genomic alterations have rarely been explored, especially for circular RNAs (circRNA). Previously, we found several circRNAs were upregulated in lung adenocarcinoma (LUAD) tumor tissues by RNA sequencing. Here, we characterized a novel circRNA, circXPO1, in LUAD, which is derived from a well-established cancer therapeutic target, XPO1. circXPO1, is formed by back-splicing of exon 3 and exon 4 of XPO1 gene. circXPO1 was highly expressed in LUAD tissues compared with paired adjacent non-tumor tissues, and high circXPO1 expression correlated with worse overall survival. circXPO1 expression was positively correlated with the XPO1 gene copy number. Mechanically, circXPO1 could bind with IGF2BP1 and enhance CTNNB1 mRNA stability, and subsequently promote LUAD progression. In a LUAD patient-derived xenograft model, intratumoural injection of cholesterol-conjugated siRNA specifically targeting circXPO1 efficiently suppressed tumor growth. To summary, these results suggest that circXPO1 is critical for LUAD progression and may serve as a biomarker for poor prognosis and a therapeutic target. On the other hand, the functional roles of noncoding transcripts derived from coding genes should be re-evaluated.