To further explore whether CASC9 promoted the malignancy of BC cells by regulating the miR-590-3p/SIX1 axis in BC, si-SIX1 (si-NC) and pcDNA-SIX1 (pcDNA3.1) were transfected into MCF7 and MDA-MB231 cells. Here, SIX1 is linked to breast cancer.