Fig. 1

CircDIDO1 is identified as a circRNA downregulated in GC. a) GEO datasets (GSE83521 and GSE89143) were downloaded for integrated analyses of differentially expressed circRNAs. The common downregulated circRNAs were listed as indicated. b) The annotated region in DIDO1 gene for the formation of circDIDO1 was shown. The exact sequence of back splicing site in circDIDO1 was confirmed by sequencing. c) PCR detection of circDIDO1 and linear transcript of DIDO1 by divergent and convergent primers in cDNA and gDNA of GC cells. d) The stability of circDIDO1 and DIDO1 mRNA was detected by RNase R degradation assay. Data are shown as means ± SD (n = 3, **P < 0.01). e) The distribution of circDIDO1 in GC cells was examined by RNA-FISH with a specific probe. Cell nuclei were counterstained with DAPI. Scale bars = 25 μm. f) The expression levels of circDIDO1 in GC cells (SGC-7901, HGC-27, MGC-803, AGS, and MKN-45) and normal gastric mucosa epithelial cells (GES-1). Data are shown as means ± SD (n = 3, **P < 0.01). g) The expression levels of circDIDO1 in tumor and matched non-tumor tissues from 102 GC patients were analyzed by qRT-PCR. h) The association between circDIDO1 expression level and overall survival time was analyze by Kaplan–Meier plot. Log-rank tests were used to determine statistical significance