Furthermore, the expressions of nm23-H1, MMP9 and MMP2 were detected by western blot, the results showed that MMP9 and MMP2 protein levels were obviously enhanced or reduced and nm23-H1 expression was markedly decreased or increased in BC cells after overexpression or knockdown of circACTN4 (Fig. 4g and h). The gene discussed is MMP9; the disease is breast cancer.