Sulindac (400 ppm) was administered in the drinking water on a daily basis for 3 months to L2D1+/p53+/– mice (n = 8) and wild-type littermate mice (n = 8), starting when mice were 4 months old. (a) Dysplasia scores were calculated after the mice were sacrificed at the age of 8 months. UE, upper esophagus; LE, lower esophagus. Micrographs show immunohistochemical staining for COX-2 in the esophagus (b and c) and prostaglandin receptor EP2 in the tongue (d and e) in sulindac-treated (c and e) and -untreated (b and d) L2D1+/p53+/– mice, respectively. Magnification ×400.