Mice with tongue tumors (7 days after injection of cancer cells) were cranially irradiated to induce oral mucositis using a RS2000 biological irradiator (Rad Source Technologies) as previously reported (10 (link)). Based on our previous observation that a single 18Gy dose has kinetics and severity of oral mucositis similar to 8Gy x3 fractionated irradiation (10 (link)), we chose 18Gy irradiation to reduce the death rate due to repeated anesthesia for fractionated irradiation to oral tumor-bearing mice that had deteriorating health. Each mouse was anesthetized with 80 mg/kg ketamine, 12 mg/kg xylazine and placed under a lead shield exposing only their head. The day of irradiation was designated day 1. All animals were provided soft food in addition to standard diet. On day 6, when mice began to lose weight due to oral ulcer-associated reduced food intake, mice were divided into 2 groups (of equal weight and tumor size) and treated daily with Tat-Smad7 or vehicle. 125 mg/kg BrdU was administered i.p. two hours before euthanasia. Mice were sacrificed and tongue samples collected on day 10 for pathological evaluation and immunostaining.