circPLIN2 promotes clear cell renal cell carcinoma progression by binding IGF2BP proteins and miR-199a-3p

Recent evidence has indicated that circular RNAs (circRNAs), a novel type of regulatory RNA, play important roles in the development and progression of various cancers. However, the potential regulatory roles and molecular mechanisms of circRNAs in clear cell renal cell carcinoma (ccRCC) remain largely unclear. Here, we explored circRNA expression profiles in 10 paired samples of RCC (including cancer tissues and surrounding tissues) from the Gene Expression Omnibus (GEO) datasets GSE124453 and GSE108735. We initially identified hsa_circ_0086457, designated circPLIN2, derived from exons 4 to 5 of the PLIN2 gene. We observed that circPLIN2 was preferentially located in the cytoplasm and was more stable than its linear counterpart PLIN2. circPLIN2 was significantly upregulated in ccRCC cells and tissues, and its overexpression was correlated with higher clinical stage and worse prognosis for ccRCC patients. Moreover, gain- and loss-of-function assays indicated that circPLIN2 promoted ccRCC cell proliferation, migration, and invasion in vitro and ccRCC tumor growth and metastasis in vivo. Mechanistically, circPLIN2 not only increased the stability of the c-Myc and MARCKSL1 mRNAs by binding to the KH domains of IGF2BP proteins but also competitively sponged miR-199a-3p to abolish the repressive effect of miR-199a-3p on ZEB1 expression, which ultimately resulted in ccRCC tumorigenesis and progression. Collectively, our results suggest that circPLIN2 may represent a promising diagnostic and prognostic biomarker and a potential therapeutic target for ccRCC patients.