As we did before,13 (link) FaDu cells were collected for protein extraction 48 hours after siRNA transfection or 72 hours after cisplatin treatment. The FaDu cell lysates were lysed with 2× sodium dodecyl sulfate (SDS) sample buffer (100 mM Tris-HCl [pH 6.8], 10 mM ethylenediaminetetraacetic acid, 4% SDS, 10% glycine). After protein quantification with Bicinchoninic Acid kit (Bio-Rad Laboratories Inc., Hercules, CA, USA), 20 µg proteins were loaded, separated on a 10% SDS-PAGE gel, and transferred to a polyvinylidene fluoride membrane. After blocking with 5% non-fat milk for 1 hour at room temperature, the membranes were incubated with anti-TCN1 (1:1,000, Abcam), anti-PARP (1:1,000), anti-cleaved-caspase 3 (1:500), and anti-GAPDH (1:300) overnight at 4°C. The membranes were then washed with TBST three times for 5 minutes each time. Then the membranes were incubated with a horseradish peroxidase-conjugated secondary antibody at room temperature for 1 hour. After washing three times, the signals were detected using ECL kit (Bio-Rad Laboratories Inc.). Each experiment was repeated three times.