Effective knockdown of PLK1 with siPLK1-NP leads to G2/M cell cycle arrest and reduced viability of three TNBC cell lines (BT549, MDA-MB-231, and LM2-4luc+/H2N). (A) Expression levels of PLK1 mRNA after treated with either siSCR- or siPLK1-NP for 24 h, as measured by qPCR, and normalized to GAPDH expression. (B) Protein expression of PLK1 after 48 h, as assessed by western blot with Actin as the loading control. (C) Cell viability after 72 h. (D) Cell cycle analysis after 24 h treatment with siSCR-, siPLK1-NP, or 10 nM of BI2536. All with siRNA dose of 50 nM. All data are presented as mean ± SD from 3 independent experiments.