HDAC inhibitor–mediated induction of TK transcript in EBV⁺ lymphoma cells. Three million P3HR1 cells in 3 mL of RPMI 1640 medium were exposed to individual HDAC inhibitors for 48 hours. HDAC inhibitors used include short-chain fatty acids (butyrate and valproate), cyclic tetrapeptide (apicidin), cyclic depsipeptide (parent largazole and analogs A and B), benzamide (MS275), and hydroxamic acids (oxamflatin, LBH589, SAHA, PXD101, and Scriptaid). Inhibitor concentrations were determined empirically so that cytotoxicity remained minimal. Total RNA extraction, reverse transcription, and real-time PCR analysis were performed as described in “Analysis of lytic gene expression.” Real-time PCR was performed in triplicate on each HDAC inhibitor–treated sample for both TK mRNA and β-actin mRNA, and these values were used to determine respective ΔCt and the fold induction. RNA from P3HR1 cells treated with 1.0 and 2.5mM sodium butyrate were used as internal controls in each experiment (not shown for each inhibitor). Each assay was repeated 3 times and error bars in each individual figure represent SDs.