TSA and IFNα exerted co-operative cytotoxic effects in cancer cell lines from a range of different tissue origins, but not in normal non-malignant cells. A. Neuroblastoma [BE(2)-C], breast (MCF-7 and MDA-MB-468), lung (H460 and Calu-6), prostate (DU-145 and LNCaP), and colon (HT-29 and Caco-2) cancer cells were treated with control (Cont), 0.02 μM TSA and/or 500 IU/ml IFNα for 72 hours. Cell viability was examined using the Alamar blue assay, measured as optical density (OD) units of absorbance, and expressed as the absorbance of treated over control samples (ie., % viable cells). ** p < 0.01, *** p < 0.001. B. MRC-5 cells were treated with control, 0.02 μM TSA and/or 500 IU/ml IFNα for 72 hours, and cell viability was assessed as above. Moreover, histone protein was extracted and subject to immunoblot analysis with anti-acetylated histone H3 antibody, after 6 hour exposure to control, TSA and/or IFNα.