Absence of p21WAF1 expression correlated with sensitivity to TSA and IFNα combination therapy. A. MCF-7, MDA-MB-468, H460, Calu-6, DU-145, LNCaP, HT-29 and Caco-2 cells were treated with control, 0.02 μM TSA, 500 IU/ml IFNα, or TSA and IFNα for 24 hours. Whole cell protein was extracted and subjected to immunoblot with an anti- p21WAF1 antibody, and, an anti-actin antibody as a loading control. B. MCF-7 cells were transfected with control scrambled or p21WAF1 siRNA for 8 hours, followed by treatment with control, 0.02 μM TSA and/or 500 IU/ml IFNα for 72 hours. The effect of the siRNAs on p21WAF1 gene and protein expression was analysed by semi-quantitative RT-PCR with the house-keeping gene β-2-microglobulin (β2M) as a loading control or by immunoblot, with actin as a loading control. C. Cell viability was examined by the Alamar blue assay, measured as optical density (OD) units of absorbance, and expressed as percentage of absorbance for drug-treated samples over control-treated samples (% viable cells). ** p < 0.01.