Also, several anti-tumor antibody antigens (e.g., cytokeratin, PCNA, COX-1, COX-2, CEA, AE1/AE3, EGER, ERBB2, Lewis Y, SELENBP1, p53 and Tag 72) that are commonly used as markers for human ovarian cancer are also detected in ovarian carcinomas of hens [6,8,21,23,24,26,28,29]. The gene discussed is PCNA; the disease is ovarian carcinoma.