We also knockdown the expression of CapZβ in 4T1 mouse breast cancer cells by shRNA (Fig. 4D) and showed CapZβ knockdown markedly inhibited MHV (a β-coronavirus) infection of 4T1 cells, manifested by the lower expression of nonstructural protein 9 (NSP9) (Fig. 4E) and lower dsRNA staining (Fig. 4F) in MHV-infected CapZβ-knockdown cells when compared to infected control cells. This evidence concerns the gene CAPZB and breast cancer.