si-α1-AT repressed the viability of MDA-MB-231 cells. (A) qRT-PCR was used to measure the mRNA level of α1-AT in normal human breast cell line Hs 578Bst, human breast cancer cell line SKBR3, ZR-75-30 and T47D, and human TNBC cell line MDA-MB-231. * P<0.05; ** P<0.01; *** P<0.001 vs. Hs 578Bst cells. (B) qRT-PCR was performed to assess mRNA level of α1-AT in MDA-MB-231 cells that were transfected with 0.1% PBS (control), α1-AT-siRNA (si-α1-AT), and unspecific scrambled siRNA (NC) plasmids. (C) Western blot was used to measure the protein level of α1-AT. β-actin was used as the control. The gray value was detected and counted by quality one. (D) CCK-8 was performed to measure the cell viability at 12, 24, 48, and 60 hours. * P<0.05; ** P<0.01; *** P<0.001, vs. NC.