Fig 2: The prognosis of BC patients with high circYY1 expression was poor. (A) A heat map showed the expression of 5 circRNAs (hsa_circ_0033169, hsa_circ_0101187, hsa_circ_0033170, hsa_circ_0033171, hsa_circ_0033172) in 12 randomly BC tissues and corresponding NC tissues. (B) QRT-PCR revealed the expression of these 5 circRNAs in 12 randomly BC tissues and corresponding neighboring NC tissues. (C) Schematic illustration showed that circYY1 (hsa_circ_0101187) was produced from the YY1 gene (exon 2). (D) QRT-PCR presented the expression of circYY1 in 70 paired BC tissues and neighboring normal tissues. (E) Kaplan-Meier curves and Log rank test revealed the survival time of BC patients with high circYY1 expression and low circYY1 expression. (F) Analysis of the expression of circYY1 in BC cells (MCF7, BT549, MDA-MB-231, MDA-MB-468, and T47D) and MCF10A cells by qRT-PCR. (G) After RNase R treatment, the expression of circYY1 and YY1 mRNA in total RNA of BT549 and MDA-MB-231 cells was detected with qRT-PCR. *P < 0.05, **P < 0.01, and ***P < 0.001.

Fig 3: CircYY1 contributed to BC growth in vivo. (A) Tumor volumes in mice were measured every 7 days. (B) Tumor weight was measured 35 days after injection with BT549 cells carrying sh-circYY1 or sh-NC. (C) QRT-PCR analysis of circYY1 and miR-769-3p expression in mice tumor tissues in the sh-circYY1 group and sh-NC group. (D) Western blotting analysis of YY1, PCNA, HK2, and LDHA protein levels in mice tumor tissues in the sh-circYY1 group and sh-NC group. **P < 0.01 and ***P < 0.001.

Fig 4: The circYY1/miR-769-3p/YY1 axis regulated the malignancy and glycolysis of BC cells. (A) QRT-PCR analysis of miR-769-3p expression in BT549 and MDA-MB-231 cells transfected with anti-miR-769-3p or anti-NC. (B) Western blotting analysis of YY1 protein level in BT549 and MDA-MB-231 cells transfected with si-NC, si-circYY1#1, or si-circYY1#1+anti-miR-769-3p. (C) The protein level of YY1 in BT549 and MDA-MB-231 cells transfected with vector or YY1 was analyzed with Western blotting. (D–K) BT549 and MDA-MB-231 cells were transfected with si-NC, si-circYY1#1, si-circYY1#1+anti-miR-769-3p, or si-circYY1#1+YY1. (D–G) The viability, colony formation, migration, and invasion of BT549 and MDA-MB-231 cells were determined by MTT assay (D), colony formation assay (E), or transwell assay (F and G). (H–J) The levels of glucose uptake, lactate production, and ATP release in BT549 and MDA-MB-231 cells were analyzed with a matching kit. (K) Assessment of HK2 and LDHA protein levels in BT549 and MDA-MB-231 cells by Western blotting. **P < 0.01 and ***P < 0.001.