Noxa induction triggered GSIXII-induced apoptosis. (A) Breast cancer cells were first transfected by siRNA targeting Bim, Puma, or Noxa, or control siRNA (siCt), and then treated or not with GSIXII for 48 hours and analyzed with flow cytometry after Apo2.7 immunostaining. Represented data are the means of positive cells ± SEM, from three independent experiments. SiRNA effects were compared with corresponding controls. (B) Expression of Noxa protein was assessed with immunoblot after 48 hours of treatment of GSIXII, 15 μM, in indicated breast cancer cell lines. (C) Noxa mRNA is induced by a GSIXII treatment. Quantitative PCR was performed on cell lines after 48 hours of treatment with mock (white) or GSIXII (black) and quantified as arbitrary units (au) compared with the mock-treated condition. Represented data are the means of positive cells ± SEM, from three independent experiments.