Cloning and apoptosis-inducing activities of canine and feline TRAIL

The apoptosis process is crucial to various biological processes including embryo development and organism homeostasis. Inducing apoptosis of cancer cells has become a very attractive field for cancer therapy in the recent years. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; also called Apo2L, TNFSF10, CD253, or TL2) is a member of tumor necrosis factor family. Preclinical studies showed that human TRAIL induced apoptosis of various tumor cell lines, whereas nontransformed normal cell lines were not affected. We have cloned both canine and feline TRAIL full-length genes by using Rapid Amplification of cDNA Ends-PCR technology. Truncated soluble versions of the canine and feline TRAIL genes were also constructed. The degree of identity between canine TRAIL protein and the human, mouse, chicken, porcine, and rat homologues is 81.3%, 61.7%, 54.3%, 82.9%, and 63.2%, respectively. The degree of identity between the feline TRAIL protein and the human, mouse, chicken, porcine, and rat homologues is 84.2%, 64.2%, 54.4%, 86.8% and 65.7%, respectively. The identity between the canine and feline TRAIL proteins is 93.2%. The canine and feline soluble TRAIL proteins were expressed in both mammalian and bacterial expression systems. Western immunoblot assays with TRAIL-specific antibody confirmed the identity of expressed protein. Both canine and feline TRAIL proteins were shown to specifically induce apoptosis and inhibit cell growth of cancer cells at a level comparable with their human counterpart.