circ-ERBB2 facilitated TNBC growth in vivo. (A) Tumor volume of mice injected with MDA-MB-231 cells carrying sh-circ-ERBB2 or sh-NC. (B) Tumor images of mice injected with MDA-MB-231 cells carrying sh-circ-ERBB2 or sh-NC. (C) Tumor weight of mice injected with MDA-MB-231 cells carrying sh-circ-ERBB2 or sh-NC. (D to G) The expression of circ-ERBB2, miR-136-5p, and PDK4 protein in mouse tumor tissues in the sh-circ-ERBB2 and sh-NC groups was assessed by qRT-PCR or Western blotting. (H) The protein levels of PCNA, cleaved caspase 3, and MMP9 in tumor tissues of the sh-circ-ERBB2 and sh-NC groups were evaluated by Western blotting. *, P < 0.05.