Fig. 1

CircCD44 was upregulated in triple-negative breast cancers (TNBCs). A Schematic graph of the scanning strategy. Five paired normal tissues and TNBCs were included and subjected to circRNA sequencing to identify the dysregulated circRNAs, as we previously reported [13]. B Heatmap of candidate RNA sequences in TNBCs and paired normal tissues. Blue, downregulated circRNAs; red, upregulated circRNAs. C Schematic diagram of circCD44 formation from CircBase; validation strategy for circCD44 and Sanger sequencing of the junction of circCD44. D Left: FISH detection of circCD44 using a junction-specific probe in the indicated shRNA-transfected MDA-MB-231 cells; scale bar: 20 μm. Right: qRT–PCR analysis of circCD44 in different cell fractions. GAPDH and Malat1 were used as positive controls for the cytoplasm and nuclei. E qRT–PCR analysis of CD44 and circCD44 using random primers or oligo dT primers. F Relative RNA level of circCD44 in 36 TNBCs and 27 non-TNBCs and paired normal tissues. All RNA levels were normalized to the paired normal tissue of TNBC; ***, P < 0.001, NS, non-significant. G Relative circCD44 level in breast cancer cell lines and normal breast epithelial cells; ***, P < 0.001. H Thirty-six TNBC patients were divided into two groups with a cutoff of the mean level of circCD44 detected by qRT–PCR in the whole cohort. Kaplan–Meier survival analysis was then applied. Data are representative of at least 2–3 experiments with similar results