Fig. 1

Characterization of circZFR as a circular RNA in response to glucose starvation in LUAD. a Heatmap of differentially expressed circRNAs between LUAD tissues and adjacent nontumor tissues in microarrays. (GSE101586, |log(Fold change)| > 1.5, p < 0.05; GSE1016840, |log (Fold change) | > 1, adjust.p < 0.05). Gene expression in z score-transformed value was shown (left). Pie chart showing dysregulated circRNAs in both microarrays (right). b Expression of candidate circRNAs in response to glucose limitation. Cells were cultured in high (10mM) or low (2.5mM) glucose. c Top 6 hallmark pathways from GSEA enriched in patients with high circZFR expression. d The genomic loci and validation of circZFR by Sanger sequencing. e Divergent and convergent primers were designed and the gene expression with or without RNase R treatment was detected by gel electrophoresis. gDNA, genomic DNA. f circZFR and ZFR mRNA expression in LUAD cell lines and human bronchial epithelioid cells. g Expression of circZFR in 25 paired LUAD samples were detected by RT-PCR. ACTB was used as a loading control. T tumor tissue, N nontumorous tissue. h RNA stability of circZFR and ZFR. i RT-PCR analysis of subcellular fractionation in the A549 cells (left). Confocal microscopy images of circZFR (green) in A549 cells (right). Nuclei was stained with DAPI (blue). Scale bars, 20 μm. Data are shown as mean ± SD. *p < 0.05, **p < 0.01, ***p < 0.001, two-tailed Student’s t test