To verify whether miR-145 directly acted on ERBB3 to affect HER2-positive breast cancer cells, we divided SKBR3 and BT474 cells into 4 groups: si-ctr, si-circESPTI1, si-circESPTI1 + ERBB3-ctr, and si-circESPTI1 + ERBB3. Here, ERBB2 is linked to breast cancer.