The therapeutic potential of TRAIL receptor signalling in cancer cells

In tumour cells, activation of the apoptotic machinery by death receptor ligands of the tumour necrosis factor (TNF) receptor superfamily of cytokines represents a novel therapeutic strategy. However, systemic treatment of tumours with TNF-alpha and CD95 ligand may produce severe toxic effects. The tumour necrosis-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family capable of inducing apoptosis in a wide variety of cancer cells upon binding to pro-apoptotic receptors, while having no effect on the majority of normal human cells tested. Interestingly, preclinical studies in mice and nonhuman primates showed no systemic cytotoxicity upon injection of either recombinant TRAIL or agonistic TRAIL-receptor antibodies. Furthermore, these treatments have been shown to effectively suppress the growth of a range of tumour xenografts. Although unwanted effects of some TRAIL preparations have been reported in normal cells, the use of TRAIL receptor agonists could represent a suitable approach in cancer therapy. Here, we shall review our current understanding of apoptotic and non-apoptotic TRAIL signalling, the therapeutic potential of TRAIL-based approaches in cancer treatment, and the results of phase 1 and 2 clinical trials with recombinant TRAIL or agonistic TRAIL receptor antibodies, either as monotherapy or in combination with other chemotherapeutic agents.