Expression of genes that inhibit tumorigenesis, such as tumor necrosis factor, alpha-induced protein 1, suppression of tumorigenicity 7 and thrombospondin 1, was down-regulated in fat line chickens, while the expression of genes promoting tumor formation, including ret proto-oncogene and turban tumor syndrome, was up-regulated. This evidence concerns the gene TNFAIP1 and neoplasm.